bio-nanotechnology for sustainable environmental · bio-nanotechnology offer new avenues for...

Bio-Nanotechnology for Sustainable Environmental Remediation and Energy Generation

for Sustainable Environmental Remediation and Energy Generation

E. González, E. Forero (Eds.)

2016

Bio-Nanotechnology

Bio-Nano Convergence Network

Academia Colombiana de Ciencias Exactas Físicas y Naturales & Nanoscale Science and Technology Center Copyright © 2016 All rights reserved. No part of this book may be reproduced in any form without written permission from publishers.

Design, diagramation and art by UniversoNano Media Design

ISBN: 978-958-9205-90-7 Printed in Bogotá, Colombia. DISONEX.

Editors of this Book

Edgar E GonzálezGeophysical Institute, Faculty of Engineering, Pontificia Universidad Javeriana, Bogotá, ColombiaNanoscale Science and Technology CenterAcademia Colombiana de Ciencias Exactas Físicas y Naturales

Enrique ForeroAcademia Colombiana de Ciencias Exactas Físicas y NaturalesColegio Máximo de las Academias de ColombiaBogotá, Colombia

Cbionano-Fealac Convergence Networkwww.fealac.orgwww.cbionano.orgContact: María Isabel LoaizaInternacionalization Office COLCIENCIAS, Bogotá, Colombia

TABLE OF CONTENTS

Heavy Metals Contamination

Bio-Nanotechnology: Challenges and Opportunities.......................... 17Edgar González, Ivan Montenegro

Heavy Metal Distribution in Mine Water at Firefly Village, Shikoku, Japan ................................................................................................... 33

Katsuro Anazawa

Arsenic in drinking water: Current situation and technological alternatives for removal....................................................... 39Ma. Teresa Alarcón, Alejandra Martín, Liliana Reynoso, M. Piña-Soberanis

Modelling of Mercury Transport, Fate and Transformation in Continental Surface Water Bodies........................................................... 65Nelson Obregón, Leonardo García, Diana M. Muñoz

Remediation

Nano modified clays, bioclays and bio-leaching for water and sediments remediation .......................................................................... 103

N. Porzionato, L. M. Guz, M. Olivelli, G. A. Curutchet, R. J. Candal

Biotechnological Synthesis of Silver Nanoparticles using Phytopathogenic Fungi and their Microbicidal Effect ..........................135Raquel Villamizar

Ecotoxicology in Nanotechnologies ...................................................... 153Andrea Luna-Acosta

Sustainable Energy

Biorefinery by the hand of the nanotechnology: biodegradable polymers from industrial biomass wate................... 207

José Vega-Baudrit , Michael Hernandez-Miranda, Rodolfo González-Paz, Yendry Corrales-Ureña

Community criteria for integral management of domestic solid waste ........................................................................................................ 249

Alejandro Martinez, Luz E. Muñoz, Erika Nadachowski

Ecotoxicology

Environmental and bioenergetic context of livestock production in the Comarca Lagunera region, Mexico............................................... 215

Luis A. Hernández, José L. González, Juan Estrada

Community action

CO2 from waste to resource: Conceptual evaluation of technological alternatives for its exploitation.................................... 233

Jorge Chavarro

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AUTHORS

Andrea Luna-AcostaDepartment of Ecology and TerritoryFaculty of Environmental and Rural StudiesPontificia Universidad Javeriana

Katsuro AnazawaDepartment of Natural Environmental StudiesGraduate School of Frontier SciencesThe University of Tokyo

A. González-Herrera.Instituto Mexicano de Tecnología del Agua (IMTA)

Alejandra Martín-DomínguezInstituto Mexicano de Tecnología del Agua (IMTA)

Diana M. MuñozGeophysical Institute, Faculty of EngineeringPontificia Universidad Javeriana

Alejandro MartinezCentro de Educación para el Desarrollo Corporación Universitaria Minuto de Dios

Erika NadachowskiSistema general de Areas protegidas, Coorporación Autónoma General del Risaralda CARDER

Edgar E GonzálezGeophysical Institute, Faculty of Engineering, Pontificia Universidad JaverianaNanoscale Science and Technology CenterAcademia Colombiana de Ciencias Exactas Físicas y Naturales

Lucas Martín GuzInstituto de Investigación e Ingeniería Ambiental, CONICETUniversidad Nacional de San Martín

José Vega-BaudritLaboratorio Nacional de Nanotecnología CONARE-CeNAT-LANOTECLaboratorio de Polímeros, POLIUNA, Universidad Nacional

Luis A. HernándezInstituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias. Centro Nacional de Investigación Disciplinaria en Relación Agua-Suelo-Planta-Atmósfera.

José L. González BarriosInstituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias. Centro Nacional de Investigación Disciplinaria en Relación Agua-Suelo-Planta-Atmósfera.

Juan Estrada AvalosInstituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias. Centro Nacional de Investigación Disciplinaria en Relación Agua-Suelo-Planta-Atmósfera.

Luz E. MuñozCorporación Universitaria de Santa Rosa de Cabal

Gustavo Andrés CurutchetInstituto de Investigación e Ingeniería Ambiental, CONICETUniversidad Nacional de San Martín

Iván MontenegroSTI Policy Unit, Colciencias

Jorge ChavarroCentro de Investigaciones CENIGAA

Leonardo GarcíaBasic Science DepartmentUniversidad Jorge Tadeo Lozano,

Liliana Reynoso CuevasCentro de Investigación en Materiales Avanzados, S.C. (CIMAV) Unidad Durango, México

M. Piña-SoberanisInstituto Mexicano de Tecnología del Agua (IMTA)

Ma. Teresa Alarcón-HerreraCentro de Investigación en Materiales Avanzados, S.C. (CIMAV) Unidad Durango, México

Natalia PorzionatoInstituto de Investigación e Ingeniería Ambiental, CONICETUniversidad Nacional de San Martín

Melisa OlivelliInstituto de Investigación e Ingeniería Ambiental, CONICETUniversidad Nacional de San Martín

Roberto Jorge CandalInstituto de Investigación e Ingeniería Ambiental, CONICETUniversidad Nacional de San Martín

Nelson ObregónGeophysical Institute, Faculty of EngineeringPontificia Universidad Javeriana

Raquel VillamizarDepartamento de Microbiología, Facultad de Ciencias BásicasUniversidad de Pamplona

Rodolfo González-Paz Laboratorio Nacional de Nanotecnología CONARE-CeNAT-LANOTECLaboratorio de Polímeros, POLIUNA, Universidad Nacional

Yendry Regina Corrales-UreñaLaboratorio Nacional de Nanotecnología CONARE-CeNAT-LANOTECLaboratorio de Polímeros, POLIUNA, Universidad Nacional

Michael Hernandez-MirandaLaboratorio Nacional de Nanotecnología CONARE-CeNAT-LANOTECLaboratorio de Polímeros, POLIUNA, Universidad Nacional

The Forum for East Asia- Latin American Co-operation (FEALAC) is a conference where twenty (20) countries from Latin America and sixteen (16) from East Asia currently participate. It places its main focus the strengthening of political, cultural, educational, social, economic, scientific and technological relations amongst member countries. Both Colombia and Japan have recently been appointed co-chairs of the Work Group on Science, Technology, Information and Education.

Preliminary work led by the joint action of the Colombian Presidential Agency of International Cooperation (APC), the Administrative Department of Science, Technology and Innovation -COLCIENCIAS-, the Ministry of Foreign Affairs, and the Colombian Association for the Advancement of Science, resulted in the development of Phase 1 within the consolidation of the Network of scientific-technological convergence. As a result of this preliminary work, an outline of the main task was drawn for Phase 2, hence, allowing it to set the Network of Bio-Nano Convergence (Cbionano-FEALAC), which was developed under the institutional coordination and execution of COLCIENCIAS, with the support of the Ministry of Foreign Affairs, APC and ACAC.

As a result of all the activities carried out in phases I and II, the main aspects that guide the development of this initiative were agreed. From international workshops held, the working groups proposed as components to be addressed within the framework of cooperation projects between countries that are part of FEALAC: i) Detection, measurement, monitoring of heavy metals into water; ii) Nanoremediation; iii) Bioremediation; iv) Biorefineries.

Two key areas of convergence were identified once problems concerning the member countries were reviewed: environment and

PREFACE

energy. These areas play an important role in research, innovation and development policies due to their social impact and relevance to member countries.Some initiatives, encouraging open and wide consultation with relevant experts and key members of the community in order to identify the main issues that modern societies within the 21st century have to cope with at a global level, show that there is consensus when considering that issues regarding energy, water and the environment are part of the key challenges that must be addressed urgently and effectively in order to guarantee the planet’s sustainability.

The proposal consists in addressing environmental issues placing the focus on contamination produced by heavy metals in fresh water resources. All countries within FEALAC are to a greater or lesser extent affected by this complex problem, which in addition to causing serious damage to the environment, also compromises food safety and the health of the population exposed to this sort of contaminant.

Hence, in the specific case of contamination produced by arsenic on fresh water for human use in South and East Asia, some 50 million people are exposed to concentrations of arsenic with values higher than those recommended by relevant environmental and health authorities. In Latin America, it is estimated that some 5 million people are exposed to contamination produced by this metal.

Governments of a large number of countries affected by contamination by heavy metals have formulated programs and policies oriented to obtain information and prepare mitigation and remediation plans regarding the presence of heavy metals.

In Colombia, due to the significant problem that contamination by mercury poses at present, the Ministry of Environment and Sustainable Development launched a Unified National Plan providing clear guidelines on transfer of technology, promoting the use of clean technologies, encouraging training, and building awareness on the use of mercury and products containing it, in a drive to minimize its

impact and protect public health and the environment from its effects. On the other hand, the Colombian Nanoscience and Nanotechnology Network has established as one of its priority tasks the need to tackle contamination by heavy metals from the perspective of nanoscale technologies, specifically by means of measurement, monitoring, mitigation and nanoremediation.

Despite the fact that within FEALAC countries there has been a number of initiatives aiming at monitoring, mitigating and remediating heavy metals present in fresh water for human consumption, there is a call to increase cooperation and joint research in an effort to address this serious environmental problem. Some countries lack information regarding the degree of contamination by this sort of contaminant and the size of the population exposed to it in excess of recommended values remains unknown.

Bio-Nanotechnology offer new avenues for detection, measurement, monitoring, and remediation. There is no doubt that progress in detection, measurement and monitoring has been achieved by means of this technology. Within many FEALAC countries there is capacity to develop low-cost, high precision portable processes and systems. From a remediation point of view, one of the most important contributions that have sprung from the revolution that nano-technology entails has been the production of nanomaterials, which involves, in turn, innovative and exceptional properties relevant to the completion of this sort of tasks.

Likewise, bio-refinery offers an important opportunity to live up to energy challenges with a high degree of sustainability and environmental commitment, in tandem with the valuable contributions made by biomaterials when applied - amongst other uses- to heavy metal remediation. It is convenient that remediation tasks as well as energy production are framed in a single holistic context, in which strategies for remediation may be set up in conjunction with energy production, maintaining an optimal balance between results and the impact caused on the environment and living beings in general. This

methodology demands that the toxicological effects and life cycle of processes and nanomaterials used must continuously be assessed.

It is beyond question that by means of the execution of this sort of projects, FEALAC leadership as a forum for the actual economic and political integration of member countries will be strengthened, hence contributing in the development of scientific knowledge and the application of technology, benefiting, as a result, both regions.

The FEALAC-Cbionano International workshop Environment and Energy: Challenges and Opportunities from Bio and Nanotechnology was co-hosted in Bogotá Colombia by the Ministry of Foreign Affairs, Presidential Agency of International Cooperation (APC-Colombia), the Administrative Department of Science, Technology and Innovation –COLCIENCIAS, Colombian Association for the Advancement of Science -ACAC, Pontificia Universidad Javeriana and Universidad de los Andes. The international workshop was attended by 350 researchers in energy and environment, academic authorities, public and private functionaries, entrepreneurs, teachers and advanced students in the area of bio-nanotechnology, among others.

The topics covered in the workshop were: • Detection and measurement of heavy metals in water. • Bio and nanoremediation of heavy metals in water. • Biorefinery, a strategic route to address the energy problem.

This book contains some of the presentations made at the workshop, as well as contributions by experts from FEALAC countries on energy and environment from the opportunities offered by bio-nanotechnology.

“For human societies to achieve a productive, healthful, and sustainable relationship with the natural world, the public and

private sectors must make environmental considerations an integral part of decision making”

The National Academies of Sciences, Engineering, and Medicine

Bio-Nanotechnology: Challenges and opportunitiesEdgar González1, Iván Montenegro2

1Geophysical Institute, Faculty of Engineering, Pontificia Universidad Javeriana. Bogotá D.C., Colombia. Nanoscale Science and Technology Center, Bogotá D.C., Colombia. e-mail: [email protected] Policy Unit, Colciencias, Bogotá D.C., Colombia, e-mail: [email protected]

Taking advantage of the capabilities offered by biology and the enormous potential of nanotechnology, in a convergence context, a promising scenario which adopts the name of bio-

nanotechnology is being constructed. In this scenario, solutions of great impact and sustainability to address the environmental and energy problems can be proposed and developed. In this chapter, we take into consideration the main challenges facing society in the 21st Century and the ways in which biotechnology offers to address them in a context of sustainability, are presented. In addition, the governance of international cooperation in I & D in the areas of energy and environment, are analysed.

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E. González, E. Forero (Eds) Bio-Nanotechnology for Sustainable Environmental Remediation and Energy Generation. ACCEFYN&NanoCiTec, Bogotá, 2016.

Introduction

Nanoscience and nanotechnology are oriented to the study and manipulation of matter and energy at the nanoscale, where fundamental processes and components that support the structure and behaviour of all existing nature take place. When atoms and/or molecules are associated to form entities with close to nanometer dimensions, the physical and chemical behaviour of these entities –called nano-objects- are very sensitive to their composition, shape and size [1]. Properties such as electrical conductivity, elasticity, heat capacity, dispersion and light absorption, within many others, are drastically modified by changes in the aforementioned aspects. This makes the nanoscale behavior of matter a novel approach of great importance for potential applications and uses.

Taking advantage of the capabilities offered by biology and the enormous potential of nanotechnology, in a context of convergence, a promising scenario which adopted the name of bio-nanotechnology is being constructed: “atom-level engineering and manufacturing using biological precedents for guidance” [2]. In this scenario are being developed strategies and scientific and technological tools to address the major challenges facing society in the 21st century. Between the main challenges the environmental problem and energy sustainability are highlighted.

The crisis in water quality as well as the urgent need to develop methodologies and systems with the capacity to produce clean energy that fulfil the criteria of efficiency and sustainability, are some of the problems that can be tackled by bio-nanotechnology. However, to achieve this goal, it is necessary to increase international cooperation and strengthen mobility programs to transfer all this knowledge to new generations.

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The role of bio-nanotechnology in the 2st century

The substantial developments in science and technology that took place during the twentieth century, marked the consolidation of a society based on knowledge, but that is drastically affected by many problems that compromise, among others, environmental, energy, water and agricultural sustainability. As a result, a number of initiatives have been undertaken to face these challenges: • At the request of the National Science Foundation, the National

Academy of Engineering has published a list of the 14 grand challenges for engineering in the 21st century “considered essential for humanity to flourish” [3]. These challenges have been selected on the basis of opinions gathered from experts and from the general public around the world since 2006. These challenges include, among others, the need to make solar energy economical, provide access to clean water, develop carbon sequestration methods, manage the nitrogen cycle, and pass over engineer better medicines.

• The Millennium Project was founded in 1996 by the Smithsonian Institution, Futures Group International and the United Nations University as an independent non-profit global participatory research think-tank of futurists, scholars, business planners, and policy makers who work for international organizations, governments, corporations, NGOs, and universities [4]. Fifteen global challenges have been identified which provide a framework to assess the global and local prospects for humanity. Some of these challenges are: sustainable development and climate change, clean water, energy, science and technology.

• To replace the Millennium Development Goals, the United Nations launched in 2015 the 2030 Agenda for Sustainable

Challenges and opportunities

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Development and the 17 Sustainable Development goals. These goals are integrated and indivisible balancing the three dimensions of sustainable development: economic, social and environmental [5]. In the goals are included essential aspects such as the availability and sustainable management of water and sanitation, sustainable and modern energy for all, sustainably managed forests, to fight against climate change and its impacts, to protect, restore and promote sustainable use of terrestrial ecosystems, to combat desertification, to cease and reverse land degradation, and to halt biodiversity loss.

• The Royal Geographical Society has established a programme to analyse the biggest social, environmental and economic challenges facing the UK in the coming decades. The initiative falls within the context of the 21st Century Challenges. The list of challenges includes: low carbon energy, climate change, sustainability, air pollution, food security and water security, among others [6].

In order to respond to the challenges identified in the different initiatives listed above, emerging technologies such as bio and nanotechnology can play strategic roles. Figure 1 shows the most significant challenges that can be confronted with the use of these technologies. For example, the problem of clean water -which is understood in all initiatives as one of the main challenges-, is being looked at from the point of view of the strengths and opportunities offered by new processes, nanomaterials and devices that will allow the improvement of monitoring, mitigation and remediation activities [7].

The steady population growth, demand for food, industrial development, inadequate waste-water purification and treatment as well as the rise in pollution sources, are some aspects that are

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Figure 2. Some of the challenges that can be assumed from the bio-nanotechnology. Reproduced with permission of NanoCiTec.

creating a true “water crisis”. According to the World Health Organization, 780 million people lack access to safe drinking water. This number is increasing exponentially, opening the way for a severe crisis of survival. The UN warns that, with the current level of consumption, 60 per cent of the world’s population will suffer water shortages by 2050. Adequate water management and implementation of effective sanitation programs to achieve the goals of the 2030 Agenda for Sustainable Development are urgent


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and necessary. With the use of new materials it will be possible to develop portable sensors with high sensitivity and low cost, which will enable the configuration of networks for monitoring and measuring contamination of water bodies [8-9]. This, in turn, will help to determine causes of pollution, mobility of pollutants and the impact on the environment and on living creatures. Furthermore, it will be possible to develop bio-nanostructured membranes and filters to purify contaminated waters efficiently and safely.

By using microorganisms it is possible to create nanostructured systems for wastewater treatment and energy production from degradation of organic matter found in the wastewater. An holistic approach to produce clean energy from environmental sanitation is one of the biggest challenges that must be faced. (Figure 2).

Figure 2. Holistic approach: to produce clean energy from environmental sanitation.

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Information on scale about production of nanomaterials, life cycle, costs and impact on the environment and on living things is still lacking.

Responsible bionanotechnology: an essential challenge

The supply of new materials is growing exponentially, as their use for consumer products. By 2014, a number close to 18000 products with nanotechnology were identified [10]. However, studies on the impact and risks of using nanomaterials are still incipient as it is illustrated in figure 3, where the number of articles published by year is shown.

Figure 3. Trendlines in the number of publications on nanomaterials, risk and exposure. Modified image from [10].

Life cycle assessments, risk factors for living things, and ecotoxicity of bio-nanotechnological products, are some of the main challenges to be considered in the context of emerging technologies to solve environmental and energy issues. Finding answers to these


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questions will ensure the appropriate use of bio-nanotechnologies in order to make sure that the solutions provided now do not become problems to be solved in the future.

Converging technologies

The so-called converging technologies -biotechnology, nanotechnology, information technology and cognitive technologies- have attracted considerable attention because of their importance in consolidating the initiatives that constitute the roadmap of innovation and development on this era. Transcending the use of the concept of interdisciplinarity as a result from a convergence nano-bio-info-cogno (NBIC) [11], these technologies are in the forefront of the efforts to respond to the challenges faced by the agendas of environmental and energy sustainability, food security, education and health, among others. The concept of new technologies in the context of convergence has given rise to a series of debates and studies by different sectors of society seeking transformative solutions that will have a positive impact on the quality of life.

One of the main definitions of unification of NBIC originated in the need to understand the social implications of nanoscience and nanotechnology, derived from several meetings and workshops supported by the National Science Foundation and the National Science and Technology Council of the United States. The meeting, which took place in New York in 2004, turned out in the publication of a book under the name of Managing Nano-Bio-Info-Cogno innovations: Converging Technologies in Society. [12]. In this book, it is stated that emerging technologies will play an important role in the road to progress and development of society as well as in the identification of new business models. The convergence finds its inspiration in the “unity of nature at the nanoscale”, where all sciences find common ground, as well as in

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the significant achievements in the implementation and capacity of manipulation and control of matter at the nanometer scale.

The European Commission, under the Sixth Framework Programme and in the context of the project Converging Technologies and Their Impact on the Social Sciences and Humanities, leads the issue of the role of converging technologies beyond the posture of the new science unit and nanoscale reductionism. According to the report published in 2008, in the heart of the new concept of converging technologies “are relations, synergies or fusions between broad fields of research and development, such as nanoscience and -technology, biotechnology and the life sciences, information and communication technologies, cognitive science and neurotechnologies. Robotics, Artificial Intelligence and other fields of research and development (R&D) are also taken into account in the discussions” [13].

Gobernance of international cooperation in I&D

Environment energy and their applications based on nanotechnology and biotechnology are related to and conceived as global challenges due to the fact that the spreading of these problems has increased the sources and geographic extent of such challenges.

Governance is conceived as the interaction of state and non-state actors in the area of STI cooperation, coordination and policy making. These actors engage in governance as the process of defining principles, rules, regulations and decision-making procedures [14].

With regard to an environmental context and the relationship between science and policy it is useful to take into account epistemic and legal institutions. The former involving functions


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Bio-Nanotechnology

such as research and development, technology transfer aimed at providing solutions to environment problems. Legal institutions are the ones empowered to make legal rules and adopt cooperative policies. Furthermore, the way in which states organize the process of creating shared scientific knowledge pertinent to environmental cooperation is referred to as epistemic cooperation, and the international institutions involved in creating shared scientific knowledge are considered epistemic institutions [15].

Regarding the case of independent epistemic institutions in a context in which states have an incentive to naturally coordinate environmental policies because the costs and benefits are primarily felt domestically, the technology transfer process becomes a key issue in the sense that actors have a clear incentive to adopt commercially viable and environmentally-friendly technologies.

When collective action is necessary to address a global environmental problem, hierarchy is the optimal relationship between legal and epistemic institutions; hierarchy is the best means of ensuring the availability of a scientific record that is credible to the states bargaining in international legal institutions.

The hierarchical degree of the relationship between epistemic and legal institutions depends on asset specificity –the extent to which information has value to multiple regulators–, credibility of the scientific record, and costs of governance [15].

On the other hand, one of the key dimensions of governance is sharing knowledge and intellectual property management. Undoubtedly, the Intellectual Property System, IPS, has encouraged innovation by helping to overcome market failures. In concrete terms, the Intellectual Property Rights, IPR, are not an impediment to the use and dissemination of technologies in so far as apart from being national in scope and limited in

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time, patent holders can decide to license, to whom to do it and under what terms. Nonetheless, the IPR system shows at least some limitations as far as it does not generate enough incentives for innovation because it can create “patent thickets”, blocking patents, and “patent trolls” [16]. A patent thicket can be defined as an overlapping ensemble of patent rights which delay innovation because it requires innovators to reach licensing contracts for multiple patents from multiple sources. Patent- troll firms purchase patents and then they enforce said patents against purported infringers without themselves intending to manufacture the patented product or supply the patented service. In the field of nanotechnology, patent thickets have emerged limiting the sharing and the use of critical knowledge, impeding, in turn, downstream innovation, and preventing the development of more complex technologies due to exorbitant transaction costs. Hence, patenting nanotechnologies actually reduces commercial competition by making the use of some nanotechnologies highly expensive. Furthermore, a number of nanotechnology patents cover basic science in the quantum field, which raises serious doubts about the ownership of science [17].Some lessons learned and some conclusions on governance and international cooperation can be highlighted. In regards to sharing knowledge and IP management, independent epistemic institutions have a wide and specific demand for scientific and technology records and for specialized information related to the use of technology. Actors have a clear incentive to adopt commercially viable and environmentally-friendly technologies, whose content is channelled by means of these institutions. Dependent epistemic institutions contribute to overcome problems of uncertainty and collective actions, because they give developing countries the opportunity to oversee the R&D process and to resolve the uncertainty problems; and the legal institutions resolve the action’s collective problem establishing legal rules binding to all the affected parties.


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Bio-Nanotechnology

Strengthening R&D in nanotechnology, biotechnology, their convergence and their applications could be supported under different governance frameworks of international STI cooperation. Insofar as these knowledge and technology fields are related to energy and environmental remediation actions whose goals and impacts are clearly perceived in every country, ongoing projects or new ones should be better linked to independent epistemic institutions such as universities, and public or private research centers.

Alternatives and complementations to the traditional IPR system are justified, aiming to encourage innovations such as a prize fund approach, a congressional bill introduced in United States Congress, and the WHO Report about health needs in developing countries [16].

A free, open-source technology capacity building and development approach, and an innovative IPS, supported by a sound governance framework, can create a virtuous cycle, since they provide real opportunities of accessing knowledge, which would in turn lead to strengthening scientific and high-end technology skills.

AcknowledgementThanks to Vicerrectoría de Investigaciones, Pontificia Universidad Javeriana (PPTA: 5126).

References

[1] González E. The new era of nanomaterials. J. Nano Sc. Tech. 2013, 1, 84.

[2] Goodsell D. Bionanotechnology Lessons from Nature. Wiley-Liss. Canada, 2004.

[3] http://www.engineeringchallenges.org/

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[4] http://www.millennium-project.org/millennium/challenges.html

[5]https://sustainabledevelopment.un.org/post2015/transformingourworld

[6] https://21stcenturychallenges.org/

[7] Gonzalez, E.; Marrugo, J.; Martinez, V. (Eds.) El problema de Contaminación por mercurio. Oportunidades y capacidades desde la nanotecnología. RedNanoColombia, Bogotá, 2015.

[8] Salinas S.; Mosquera N.; Yate L.; Coy E.; Yamhure G.; González E. Surface Plasmon Resonance Nanosensor for the Detection of Arsenic in Water. Sensors & Transd. 2014, 183, 97.

[9] Reyes C.; Coy E.; Yate L.; González E.; Nanostructured and selective filter to improve detection of arsenic on surface plasmon nanosensores. ACS Sensors 2016, DOI: 10.1021/acssensors.6b00211

[10] González E. Nanomateriales, Riesgos y Sostenibilidad en: La Influencia de internet, genética y nanotecnología en la medicina y el seguro. U. Externado, 2015, ISBN 9789587724035.

[11] Echeverra J. Interdisciplinariedad y convergencia tecnocientífica nano-bio-info-cogno. Sociologías. 2009, 11 (22), 22-53.

[12] Sims, W.; Roco, M. Managing Nano-Bio-Info-Cogno innovations: Converging Technologies in Society. Springer, Netherlands, 2006.

[13] Andler, D.; Barthelmé, S.; et al. Converging Technologies and their impact on the Social Sciences and Humanities (CONTECS) An analysis of critical issues and a suggestion for a future research agenda Final Report. 2008.

[14] OECD. Meeting Global Challenges through Better Governance: International Co-operation in Science, Technology and Innovation. OECD Publishing, 2012.

[15] Meyer T. Epistemic Institutions and Epistemic Cooperation in International Environmental Governance. Transnational Environmental Law, 2013,15, 44.

[16] Stiglitz J.; Greenwald B. Creating a Learning Society: A New Approach to Growth, Development and Social Progress. New York: Kenneth J. Arrow Lecture Series, 2014.

[17] Pearce J. Open-Source Nanotechnology: Solutions to a Modern Intellectual Property Tragedy. Nano Today, 2013, 339-341.


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Heavy metal distribution in mine water

Heavy metalsContamination

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Heavy metal distribution in mine water at Firefly Village, Shikoku, JapanKatsuro ANAZAWA

River water and river sediments were collected from downstream area of an abandoned copper mine. This region is known for its clean water environment, and heavy metal

concentration in downstream water of the mine was as low as the background level of the region. The river sediments, however, contained high concentration of heavy metals. This phenomenon was understood that when mine water with low pH is neutralized by river water with high pH, dissolved heavy metals are precipitated and concentrated in sediments. The thermodynamic simulation showed that a neutralization treatment could possibly perform 80-100 % removal of heavy metals from the aqueous phase.

Department of Natural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo.5-1-5 Kashiwanoha, Kashiwa Chiba 277-8563, Japan.e-mail: [email protected]


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IntroducciónJapan was once a world’s leading mining nation, and now has nearly 5,000 abandoned mines. Among them, mine pollution such as water pollution has occurred at about 450 sites. [1] In many cases, mine owners are missing, and in those cases, responsibilities for pollution are unclear. Occasionally, those abandoned mines are hidden in the mountains, and water pollution sneaks up on the downstream unawares. In this study, water and sediments of a contaminated river by mine water were investigated to understand geochemical behaviors of heavy metals, and to propose a countermeasure to reduce the pollution at a typical mountain village.

Study area and analytical methodsMisato district of Yoshinogawa city in Shikoku Island is recognized as a “firefly village” with clean water environment (Figure 1). In this district, Genji-Botaru (Luciola cruciata), which is designated as a national protected firefly species, are observed in countless numbers from the end of May to early in June. Strangely enough, no firefly is observed along a main river flow in the district. Various reasons for the lopsided geographical distribution of fireflies have been discussed, such as vegetation or toxicity of agricultural chemicals. Among those potential factors, heavy metals emitted from an abandoned copper mine existing at the upper stream area of the river were considered as the most suspicious cause. However, low concentration of heavy metals was found in the river water, which was considered harmless to the environment. [2]

In order to clarify the cause of the firefly locality, geochemical investigation was performed in this district. Water and sediment were collected from the rivers in the district for chemical analysis. Sample collection was performed 4 times between 2002 and 2007,

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and the samples were taken from 16 fixed points with several additional points each time.

Water temperature, pH and electrical conductivity (EC) were determined at the sampling points. Dissolved heavy metals in river water were determined by atomic absorption spectrophotometry (AAS). Heavy metals in sediments were determined by AAS after mixed acid digestion of HF, HClO4 and HNO3. Determination of mercury was performed by cold-vapor AAS.

Results and discussionThe analytical results are almost identical to the previous work. [3] The mine water and the river water contained less than 0.1 mg/dm3 for Cd, Pb, As, Ni, Cr, Co and Mo, and less than 1.0 ng/dm3 for Hg. On the other hand, extraordinary high concentration of Cu and Zn was found in the mine water (sampling point A in Figs. 1, 2) with a magnitude 3-σ above the average concentration in this study area (Figure 2). The heavy metal concentrations in the

Figure 1. Location map of the sampling sites.

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Figure 2. Variation of dissolved copper (Cu) and zinc (Zn) in river water.

downstream river water are almost equivalent to the background level.

For sediments, among 10 heavy metals, only Cu and Zn also showed higher concentration in mining area than the regional background level, with a magnitude of one sigma (>1σ) above the average in the study region. In contrast to the river water case, the concentrations of Cu and Zn in the sediments show the highest values at point H1, not at point A (Figure 3).

Point H1 is the first sampling point downstream of the junction of the mine water flow and the river. This phenomenon was quantitatively understood by stoichiometry considering the volume fraction of the mine water flow and the main river as 17: 83. [3] Dissolved Cu and Zn in the mine water with low pH were precipitated by the mixing with high pH river water and were included into the river sediments. Environmental threat to the

39


fireflies’ survival was provoked not by water pollution, but by high concentration of Cu and Zn in the river sediments.

As a proposal of countermeasure technique to reduce the outflow of heavy metals in the mine water, thermodynamic simulation was performed on the basis of neutralization treatment with calcium carbonates (CaCO3). The possible precipitates by neutralization reaction were assumed to be Cu4(OH)6SO4 for copper, Fe2O3

for iron, MnO2 for manganese and ZnSiO3 for zinc. Under consideration of reaction efficiency at the confluence of the mine water flow and the main river (point H1), 10% amount of solid CaCO3 was assumed to be eluted into river water as Ca2+. Saturation indices of minerals including heavy metals were calculated on the basis of WATEQ4F database. [5] The calculation results showed that a simple neutralization tank with CaCO3 will possibly be capable to perform 77-100 % removal of the heavy metals (Table 1).

Figure 3. Variation of copper (Cu) and zinc (Zn) in sediments

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Table 1. Removal efficiency and the composition change of the heavy metals in the mine water by neutralization treatment (theoretical value1)) [4]

1) [Ca2+][CO32-] = 0.1 Ksp (calcite)2) Dissolution

Metal

Solution Precipitation

Untreatedwater

(mg/dm3)

Treated water

(mg/dm3)

Removal efficiency

(%)

Chemical Formula (ton/yr)

Ca 52.97 91.02 -- CaCO3 -81.02)

Cu 2.64 0.59 77 Cu4(OH)6SO4 3.10

Fe 0.19 0.00 100 Fe2O3 0.23Mn 1.16 0.00 100 MnO2 1.57Zn 3.77 0.04 99 ZnSiO3 6.88

References[1] JOGMEC. Mine Pollution Control. JOGMEC NEWS 2013, 35, 16.

[2] Shinomura Y.; Anazawa K.; Sato M. The relationship between the river environment and the habitat of firefly in Misato, Tokushima Prefecture, West Japan. Environmental information science Extra, Papers on environmental information science. 2005, 297-302.

[3] Anazawa K.; Kaida Y.; Shinomura Y.; Tomiyasu T.; Sakamoto H. Heavy-metal distribution in river waters and sediments around a “firefly village”, Shikoku, Japan: Application of multivariate analysis. Anal. Sci. 2004, 20, 79-84.

[4] Anazawa K.; Shinomura Y.;Tomiyasu T. The behavior of heavy metals in mine water and the proposal of countermeasure technique at “firefly village”, MIsato, Yoshinogawa City, Tokushima Prefecture, Japan. Environmental information science Extra, Papers on environmental information science. 2007, 21, 601-606.

[5] Ball J.; Nordstrom D. User’s manual for WATEQ4F, with revised thermodynamic data base and test cases for calculating speciation of major, trace, and redox elements in natural waters. US Geological Survey Open-File Report: US Geological Survey, 1991, 188.

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Arsenic in drinking water: Current situation and technological alternatives for removal Ma. Teresa Alarcón-Herrera1, Alejandra Martín-Domínguez2 Liliana Reynoso Cuevas1, M. Piña-Soberanis2

A. González-Herrera2.

Arsenic pollution of natural and/or anthropogenic origin represents a global health challenge that affects millions of people around the world, especially in Latin America.

This problem is particularly pernicious because regions polluted with arsenic remain mostly unperceived, the analytic identification of this metalloid in water is not obvious, and the adverse effects to human health are chronic and hard to directly associate. In affected communities, exposure to arsenic can be effectively mitigated by limiting the consumption of arsenic-laden water.

1Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Unidad Durango Victoria 147 nte, Centro Histórico, C.P. 34000, Durango, Dgo., Méxicoe-mail: [email protected] Mexicano de Tecnología del Agua (IMTA). Paseo Cuauhnáhuac 8532, Col. Progreso, C.P. 62550, Jiutepec, Mor. e-mail: [email protected]

E. González, E. Forero (Eds) Bio-Nanotechnology for Sustainable Environmental Remediation and Energy Generation. ACCEFYN&NanoCiTed, Bogotá, 2016.

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IntroductionArsenic is a common element found in the atmosphere, rocks, soil and water. It is moved to the environment through a combination of reactions that include natural processes and several by-products of human activity such as mining waste, fossil fuels, pesticides, herbicides, desiccants, wood preservatives, food cattle additives, semiconductors, pigments, among many others.People can be exposed to arsenic through inhalation and food or water ingestion. In certain areas of the world, the natural geology increases arsenic content in drinking water available to populations. Arsenic is highly toxic in its inorganic form; it is classified as a carcinogenic compound in the IA group (carcinogenic to humans) due to evidence it causes adverse health effects [1].

The long-term health effects of arsenic are the most worrying ones. These are mainly attributed to drinking arsenic-contaminated water, using it in food preparation, or ingesting food irrigated with it. Chronic toxicity produced by the accumulation of arsenic in the body results in skin lesions (e.g. hand and foot hyperkeratosis), myocarditis, diabetes, cardiovascular diseases, and damage to the nervous and respiratory systems.

The permanent intake of contaminated water by arsenic causes the so-called “endemic regional chronic hydroarsenicism” (or HACRE by its initials in Spanish), which is commonplace in various parts of the world. Therefore, the presence of arsenic in surface waters (rivers, lakes, and reservoirs) and groundwater (aquifers) that can be used for human consumption represents a major health risk.

To limit the adverse effects to exposed human populations, international institutions such as the World Health Organization (WHO) and others have established an arsenic concentration limit for drinking water of 10 µg/L. In México, the regulations currently

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Arsenic in drinking water

establish that 25 µg/L is the maximum concentration limit in drinking water (modification to the Mexican official standard, NOM-127-SSA1-1994 [2]). This standard is under review and it is planned to decrease to 10 µg/L in the near future.

Limiting the consumption of arsenic-contaminated water is an effective measure, which can mitigate the exposure of different affected communities. First, it is necessary to identify arsenic exposure by monitoring, measuring, and establishing appropriate remediation actions; these may include the use of alternative sources of groundwater or surface water and/or the use of novel technologies to remove arsenic from water.

The following chapter focuses on the analysis of arsenic in drinking water and the alternative technologies used in Mexico for its remediation through water treatment.

Arsenic in waterArsenic can be found in water in both its organic and inorganic form, but the inorganic one is the most prevalent and it is considerably more toxic. In addition, arsenic occurs in soluble or particulate form. Depending on the local oxidation and reduction conditions, soluble inorganic arsenic subsists in two valence states. For example, arsenic in groundwater (under anoxic conditions) is in arsenite form (As+3) while, in surface water (under aerobic conditions), it is found in an arsenate or pentavalent form (As+5) [3].

Inorganic arsenic is present in water due to the natural dissolution of geologic deposits, industrial discharges, and atmospheric sediments. Because of this, arsenic concentration in the different environmental media has a high variability; however, water remains as its main dispersion pathway.

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Arsenic distribution in superficial waters

The arsenic content in rivers is relative low, generally less than 0.8 µg/L, but it can vary by orders of magnitude as a result of recharge (superficial and underground), geological composition of soil and rocks, weather, mining activity, and urban and industrial waste disposal. In semiarid regions, evaporation favors an increase in arsenic concentration in superficial waters, as well as an increase in water salinity and pH. In fact, this evaporative saturation has caused extremely high arsenic concentrations in places like the Loa River in the north of Chile (190–21,800 μg/L) [4].

In seawater, the average arsenic concentration is relatively low (1.5 to 4 µg/L). Estuaries have a variable arsenic concentration that result from continental waters, contribution of continental deposits, and local variations in salinity and redox gradients. The pluvial water of mining zones has a high arsenic content, usually ranging from 200 to 400 µg/L [5].

Arsenic contamination of geothermal origin in superficial waters and shallow aquifers has been usually reported in geothermal areas all over the world. In Mexico, high arsenic concentrations in geothermic zones has been associated to the Trans-Mexican volcanic belt. The documented cases are mainly in Los Azufres, Michoacan and Los Humeros, Puebla, where reported concentrations are estimated to be 800 µg/L [6].

Arsenic in underground waters

Most aquifers with high arsenic concentrations have been linked to natural geochemical processes. One of the singularities with natural sources of arsenic in underground water is that there isn’t always a direct relationship between high arsenic content in water and high content of arsenic in the aquifer’s constituent materials.There is currently no geological/hydrogeological model for all the

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identified incidents. Water with arsenic has been found in a wide variety of conditions, in oxidant and reductant environments, in over-exploded aquifers, in dry and humid zones or even in superficial and deeply confined aquifers. This variety of situations is defined because of the peculiarity of the circumstances and processes that occur in each one of these cases, i.e., the arsenic presence in each case is the consequence of the specific geochemical environment and hydrogeological conditions.

Unlike anthropogenic pollution, that generates an affection of local character, natural arsenic pollution can affect vast areas. Arsenic concentration in underground waters is fundamentally controlled by water-rock interactions within the aquifer, and concentration values can greatly differ from one environment to other [7]. Taken together, these features tied to arsenic content in aquifers that could be useful for human consumption constitutes a significant health risk.

Worldwide situationNaturally, high arsenic concentrations affect wide areas all over the world. Aside from the problem of arsenic presence in drinking water, underground water with high arsenic levels is commonly used to irrigate diverse crops. This practice has caused the accumulation of arsenic in soils and therefore increased the transfer of metalloids into the food chain [8].

Different studies have identified many areas that contain underground waters with an arsenic content higher than 50 µg/L. The problems most quoted in the literature are, in Asia, Bangladesh, India (West Bengal), Nepal, China, Taiwan, and Vietnam; in America, high arsenic concentrations have been reported in USA, Argentina, Chile, Peru, Bolivia, El Salvador, and Mexico; in Europe, Greece, Hungary, Romania, and Spain. Asia has been

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the continent where most investigations have been carried out, especially in Taiwan and Bangladesh [9, 10].

Situation in Latin America In 2006, at least 4 million of people in Latin America were exposed to arsenic levels that could cause health alterations via the consumption of contaminated water. Rural populations are the most affected ones because of socioeconomic, cultural, and sanitary conditions. In 2008, the Iberoarsen network estimated that 14 million people were at risk of arsenic contamination [10, 11]. The situation has been getting more critical in recent years. The metalloid has been detected in new zones or in zones that had been previously deemed unlikely to be contaminated. Furthermore, population growth has increased both exposure and anthropogenic pollution (mainly by mining industry leachates).

In Argentina, the origin of arsenic in groundwater is mainly due to the volcanic activity of the Andes. Arsenic concentration in groundwater varies within a wide range, from less than 10 µg/L to more than 5000 µg/L. The affected region covers roughly 1.7 million km2 and is considered one of the largest in the world; it includes the provinces of Córdoba, La Pampa, Santiago del Estero, San Luis, Santa Fe, Buenos Aires, Mendoza, San Juan, Chaco, Formosa, Salta, Jujuy and Tucuman [12]. In this region, the rural population (> 1.2 million people) depends on groundwater for their water consumption and for agricultural activities. Arsenic concentration in rural areas at the provinces of Santa Fe and La Pampa exceed 67 µg/L. In Santiago del Estero, which is located in the northeast of the province, arsenic levels in groundwater range from 400 to 600 µg/L. One of the areas most affected by high groundwater arsenic levels is the southeast of the province of Córdoba. The most affected departments are Union, San Justo, Marcos Juarez and Rio Cuarto, where groundwater arsenic concentration ranges from 10 to 4550 µg/L [13, 14].

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The north of Chile is reported as the most affected area and is located largely in the Atacama Desert and part of the Andean mountain range. Reported arsenic concentration in the water range between of 200 to 900 µg/L [4, 9, 10]. In Antofagasta and Calama communities, the population was exposed to high arsenic concentrations in drinking water, until treatment plants for arsenic removal from water were installed in the 70´s . later seawater desalination plants were operating in northern Chile to provide drinking water [10].

In Bolivia, the Lake Poopo basin and the city of Oruro are affected by natural and anthropogenic arsenic in different environments like dust in the air (atmosphere) soils (e.g. in Oruro, where toxic effects were observed in the population) and in surface waters with concentrations ranging from 10 to 2460 µg/L in places devoid of anthropogenic activity. In places with mining activities or environmental liabilities, concentrations range from 600 to 11,140 µg/L [15, 16]. The rivers in the southeastern part of the basin of Lake Poopo have concentrations up to 87 µg/L while the hot springs exhibit concentrations of 65 µg/L. The arsenic content in the south and west of Lake Poopo in water samples from wells (the main source of water for human consumption) have arsenic concentrations up to 299 µg/L. Communities north and northeast of Lake Poopo have reported concentrations up to 964 µg/L [16,17]. An analysis of the water supply wells for human consumption indicates that 90% of this exhibit an arsenic concentration that exceeds the 10 µg/L concentration recommended for human consumption by World Health Organization.

In Paraguay, the reported concentrations are greater than 50 µg/L in the groundwater of the Guarani aquifer, Formación Misiones, and high Paraná [10, 11].

In Peru, arsenic contamination reported in the area of Llo is of

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natural and anthropogenic origin in the surface and groundwater basins of the Andean Region. Arsenic levels have been determined to range between 200 and 400 µg/L in the basins of the Locumba and Rimac rivers [10, 11,18].

In Brazil, arsenic contamination is mainly anthropogenic and is derived from industrial processes related to gold, lead, and zinc mining in the area of Minas of Gerais, Valle Riviera, and the Amazon region [9, 11].

In Uruguay, most water sources available for human supply are from superficial waters. Therefore, the situation is not critical, and concentrations of arsenic in the Mercedes aquifer are on the order of 10-58 µg/L [10, 19].

In Honduras, in the region of Llopango area of Salvador, department of Santa Ana, and the valley of Syria, anthropogenic pollution results from the exploitation of gold and silver ores; in these regions, arsenic concentrations in water are about 50-750 µg/L [10, 11].

In Nicaragua, the volcanic formations in some areas of the country induce the natural contamination of groundwater with arsenic. This occurs in hydrothermally altered and mineralized structures that are primarily the source of arsenic and that are located in tectonic lineaments parallel to Graben of Nicaragua. Natural arsenic contamination in water for human consumption has been identified in the northwestern region (Villanueva, Santa Rosa del Peñon), North Central (Madriz, Nueva Segovia), central (Valle Sebaco) and the Department of Chontales (La Libertad, town Kimuna) [19, 20, 21]. In rural communities like Zapote (Sebaco Valley), Santa Rosa del Peñon, Cerro Mina de Agua, Kimura, Ciudad Dario, San Isidro and Las Pilas, exhibit arsenic concentrations in water up to 1200 µg/L [19, 20].

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In Costa Rica, arsenic concentrations vary between 10 and 200 μg/L in surface waters and aquifers, and these are attributed to active geothermalism in contact with volcanic muds [10, 19]In the Dominican Republic, studies report that arsenic concentrations in the surface water of the Magauca river basin and the Margajita streamare <1-100 and 13-690 μg/L, respectively, and these are mainly associated with the presence of volcanic rocks [10, 19].

In Colombia, arsenic contamination in aquifers results from anthropogenic and/or natural causes. This pollution is associated with gold mining waste and is prevalent in zones of volcanic origin. High levels of arsenic have been reported in soils and sediments from the departments of the south of Tolima, Caldas, Choco, Santander, Nariño la Cordillera Central and Occidental. It is estimated that 5% of the population of Colombia could be at risk of exposure to arsenic by different sources. In regards to agricultural regions (e.g. the Sabana of Bogota), different studies have reported high levels of arsenic in vegetables like lettuce and cabbage [22, 23]. Concentrations of arsenic found in rice are on the order of 0.58 mg/kg, which is twice as much as the maximum recommended by World Health Organization (WHO) of 0.30 mg/kg [22, 23, 24].

Situation in MéxicoThere is currently no official estimate in Mexico of the population exposed to consumption of water contaminated with arsenic. It is estimated that the population exposed to inorganic arsenic via water consumption is approximately 2.0 million, with concentrations ranging in some regions of 30 a 590 µg/L [19, 25, 26].

The presence of arsenic in drinking water supplies has been identified since the sixties in many communities of the Laguna

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region located between the states of Coahuila and Durango. This region has been declared a chronic hydro arsenicism area and it is one of the most researched areas in México. The reported concentrations are variable over time, with peaks of up to 865 µg/L at wells in the villages of Tlahualilo, San Francisco I Madero, and San Pedro [27]. Between the seventies and eighties epidemiological studies showed high incidence of disease states, such as skin lesions and peripheral vascular diseases, which were attributed to arsenic consumption. During the year 1983, an average concentration of arsenic in water of 411 µg/L, and a prevalence of cancerous skin lesions 1.4% was registered in the San Salvador de Arriba municipality of Francisco I. Madero, Coahuila [28].

During 2014, 29 wells in Coahuila and 21 wells in Durango states, all located at the Lagunera region, were analyzed by IMTA and an arsenic concentration in water was found between 25 and 500 μg/L [29].

Since 1990, some of the highest arsenic concentrations in the country have been located in Zimapan, Hidalgo; with values reaching up to 1350 μg/L. In 1993 it was detected that 14% and 7% of the inhabitants of the area suffered from hyperkeratosis ulcers and skin hipercromias respectively. They presented symptoms and signs such as lack of movement in the distal limbs. In 1996 a group of girls in Zimapan presented serious vascular lesions related to chronic arsenic poisoning [25, 30]. To date, the situation has been analyzed and the wells with highest concentration of As have been replaced. Nonetheless, due to the geological and mining waste conditions, constant monitoring and surveillance of the area are required. In the state of Sonora, concentrations between 2 and 305 μg/L have been found in the citites of Hermosillo, Etchojoa, Magdalena and Caborca. In the mountain range of Huautla, As concentration

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is estimated between 500 and 700 μg/L [25, 31].In the state of Chihuahua, 67% of its municipalities had levels of arsenic of over in groundwater wells. The presence of arsenic in several aquifers in the central and southern regions of the state of Chihuahua are of natural origin, mainly due to the geological composition of the area [32]. The southeast region of the state is the most affected areas by the presence of arsenic. Arsenic values of up to 1530 and 780 µg/L have been reported in the municipalities of Jiménez and Meoquí respectively [33, 34].

There is still a great need of assessment and evaluation of multiple wells in Mexico, especially in areas of high hydrogeological risk of contamination. Water contamination with arsenic is a serious problem that requires immediate attention and action. Unfortunately there exists a growth of areas with potential for contamination due to different aspects, including the over-exploitation of aquifers. There exists no systematic evaluation of aquifers in all of the country. It is imperative to include the quantification of inorganic arsenic as a standard parameter for any analysis of water intended for human consumption. Therefore, the institutions responsible for water management to communities should form the best possible interdisciplinary team working to give people quality water, free of contaminants.

Health EffectsArsenic is a toxic element and a carcinogen for humans. The health effects of arsenic consumption are classified as acute and chronic, the latter being caused by the silent and prolonged exposure through consumption of contaminated food and water. Arsenic toxicity depends on the oxidation state, chemical structure, and solubility in the biological environment. The scale of arsenic toxicity decreases in the following order: Arsina > As+3 inorganic > As+3 organic > As+5 inorganic > As+5 organic > arsenical compounds

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and elemental arsenic [35]. Organic arsenic compounds are less harmful to health and are mainly found in seafoods.

The signs and symptoms associated with high levels of prolonged exposure to inorganic arsenic differ highly amongst individuals, population groups, and geographical areas. There isn’t currently a method to distinguish between cases of cancer caused specifically by arsenic and those induced by other factors; a reliable estimate of the magnitude of the problem worldwide is therefore lacking.

Early symptoms of prolonged exposure to high levels of inorganic arsenic are found in the skin, these include skin lesions, calluses on the palms of hands and soles of the feet (hyperkeratosis), hyperpigmentation, and hypopigmentation. Non-cancerous effects have been reported, these include damage to the cardiovascular system, kidney and liver disorders, peripheral neuropathies and developmental encephalopathies, and disruption of the endocrine system related to the development of diabetes [36, 37]. In relation to its carcinogenic effects, a relationship between arsenic in water and an increased presence and mortality from cancers of the bladder, lung, kidney and liver cancer in the exposed population have been identified. Air and occupational exposure to arsenic has been related to the development of bronchogenic cancer.

Prevention and Control

The most important action to be undertaken by communities affected by arsenic pollution is to prevent a prolonged exposure by implementing a secure supply of drinking water for both consumption and food preparation.It is possible to mitigate human exposure by limiting the consumption of arsenic-contaminated water in different affected

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communities by first identifying its presence through measurement and then establishing the appropriate mitigation measures, e.g. the use of alternative sources of groundwater or surface water and/or the use of diverse technologies for removing arsenic from water.

Arsenic removal technologies

There is a wide range of adequate technologies to remove arsenic from water, either intradomiciliary or by centralized systems. The following technologies are among the most studied: coagulation-filtration, coagulation-flocculation-sedimentation-filtration, lime softening, ion exchange, reverse osmosis, nanofiltration, coagulation-microfiltration, coagulation-ultrafiltration, electro-dialysis, capacitive deionization, adsorption on activated alumina or minerals containing iron, adsorption on nanomaterials, electrocoagulation, and distillation. Most of these processes have already been evaluated and validated at both laboratory and field -pilot and full-scale level [38, 39, 40].

The scope of each technology is influenced by diverse variables. For example, the volume of water to be treated, the kind of contaminants present in the water, the availability of trained staff, the feasibility of installing a centralized system with respect to the size and density of urban areas, the user’s economic capacity, the area in which to install the system, and costs associated with operation and maintenance. Additionally, the type and amount of waste generated during these processes is another important element to consider in the selection of the technology. The residue should be handled and properly disposed in order to avoid contamination risks caused mainly by leachates.

The United States, Argentina, Chile, and recently Mexico account for most of the use, in America, of conventional processes. Coagulation technology has been used since 1970 in Chile.

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The membrane processes (Reverse Osmosis, Nano, Micro and Ultrafiltration) and recently direct filtration are the most widely systems used both in Argentina (since 1970) and Mexico (since 1990) [41, 42, 43].

Intradomiciliary SystemsAn intradomiciliary system is the kind of system that is installed inside a housing unit where residents have access to treated water. These systems are also known as equipment used at family level. In general, adsorption based processes are the most readily applicable as intradomiciliary systems, because the user need only pass the water through the filters. However, the main drawback is that the users are responsible for the proper use of the system and its efficiency. There is also the uncertainty of the lifetime of the adsorbent medium, which depends directly on the amount of water passing through it, which in turn depends on the number of inhabitants in each home and their consumption habits.

The duration of a domiciliary filter is calculated relative to a population mean and an average of water consumption (2L/person/day). The population that does not conform to these values will be at risk; on the other hand, the volume of consumption does not take into account the water used to prepare food. When this solution is applied, it must ensure an adequate mechanism to change filters when they are exhausted, and make a proper disposal of arsenic-saturated mediums.

Another drawback of intradomiciliary solutions that use filters is that, normally, these systems have a tendency to be “fouled” over time. Consequently, their use is discontinued as they become impractical because of the water flow decline. The bacteriological aspect of these filters often is not considered, so the bacteria growth inside can affect water quality if appropriate disinfection

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procedures are not taken. To date most filters have been distributed in the Mexican state of Durango at the household level in urban zones; however, this is a temporary and costly measure that does not solve the problem and only masks it.

Centralized systemsCentralized systems also have advantages and disadvantages. On one hand, at drinking-water treatment plants, the quality of water distributed to residents and the waste management are easier and more reliable; however, any failure affects all treated water.Direct filtration (DF) is within the cheapest and easiest methods to operate, basically, an iron-based coagulant and chlorine are added to the pipe at the inlet to the filters. Filtration is carried out in a dual granular medium constituted by sand-anthracite with filtration rates below 7m3/m2/h, and for arsenic concentrations equal or less than 100 µg/L. The advantage of this system, at least in Mexico, is that all the items for construction and operation can be acquired within the country.

The process of coagulation-flocculation-sedimentation-filtration is one of the variants of direct filtration. This process is used when the concentration of arsenic is greater than 100 µg/L [44, 45]. In these cases, the clarification step is required to avoid excessive filter backwash caused by the dosage of coagulant needed to remove the arsenic. This process is the most used in Mexico (Figure 1) for the treatment of drinking water, but it is also an efficient method for removing arsenic [46].

The chemical coagulation stage of both systems can be replaced by electrochemical coagulation. This process, called electrocoagulation, allows for the production of the coagulant of interest (Fe2+ in this case) by applying an electric current to a metallic electrode for its oxidation [47, 48, 49]. The advantage of

Figure 1. Arsenic removal plants installed in different communities in the north of Mexico, using the direct filtration process. (Source Mexican Institute of Water Technology, IMTA).

this process is that the dissolved solids, combined with the cation used for the chemical coagulation, are not added to the water. Thus reducing the amount of sludge produced as waste. The disadvantage in this case is a higher cost than other processes and higher operational complexity and maintenance [50].

The filtration step with sand-anthracite may be replaced by micro or ultra-filtration membranes, both systems allow for better control of the quality of treated water, but they represent higher investment costs than the granular material filters. They also have the disadvantage that the consumables are imported. Additionally, the highly qualified human capital required to operate these technologies is not always easy to find and keep, by water utilities companies in Mexico.

Adsorption on iron-based media, either granular or nanoparticles, is a very efficient way to remove arsenic from water; nevertheless, the main drawback is the same as the membrane processes: these systems have only been tested on a laboratory scale and the experience at pilot level is minimal [51].

Another disadvantage of adsorption processes for arsenic removal


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is the adsorption media. When completely saturated, the media has to be replaced and properly disposed, which also involves additional costs. Often, when the water utility company does not have the financial resources to replace the adsorbent media for new ones, the adsorption system is used as FD by means of coagulant addition. Although in both systems filters are used, the problem of converting an adsorption system to FD is that the filters’ design is not exactly the same and therefore, the FD efficiency will be severely affected because it has to adjust to adsorption columns. The main problem is the different filtration rates and backwash required for both systems.

Regarding the costs and the simplicity of operation of the aforementioned arsenic removal systems, whether membrane, electrochemical, or physical, they cannot compete with direct filtration. This is essentially because the coagulant dose required is low (20-60 mg/L Fe for every mg/L As) and energy consumption can be reduced if gravity filters are used instead of pressure filters. In addition, even in pressure filters pumping requirements are no greater than 1.5 kg/cm2 during filtration.

Reverse osmosis, nanofiltration, and electrodialysis have an additional disadvantage: the disposal of their water reject can only be disposed in the sewer system according with NOM-002-SEMARNAT-1996, which sets the maximum permissible limits of pollutants in wastewater discharges to urban or municipal sewage systems, evaporation lagoons built for this purpose, or discharging them into the sea through submarine issuers. The latter is limited to the drinking water treatment plants available in coastal areas. The processes involving coagulation and/or precipitation have the advantage that the waste generated in the filters’ backwash and the sludge in the clarifiers can be dehydrated. This form allows for the disposal of dry waste; however, waste needs to be disposed of on land free of garbage leachate in order to prevent decrease the


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waste’s pH. This type of waste is not considered hazardous as long as no reductive conditions promote the dissolution of arsenic in water streams crossing the waste deposits.

In Mexico, in the state of Chihuahua, there have been about 600 reverse osmosis plant installations in rural areas to date, with a capacity to remove arsenic of 1,000 to 5,000 liters per day. This is for water that is used only for human consumption [52]. These are small-scale centralized systems that work as commercial bottling plants, but in this case these are not for profit and their aim is to recover the operation costs. Their main drawback is that, more often than not, operators do not have sufficient technical training to detect when the water no longer satisfies the regulations and the indispensable change of membranes and/or filtration materials. Disinfection represents a financial and logistical problem that not all communities can solve. In this case, appropriate coordination with municipal or state governments is an indispensable factor.

Full-scale systems installed at the wellhead in the Comarca Lagunera region, Mexico, to remove arsenic from supply sources with DF systems (Figure 1), were built with federal, state, and municipal resources and are being operated with a treated water cost ranging from $ 0.6-0.8/m3. This cost includes chemical reagents, electrical power for filter backwashing, staff and maintenance [52, 53, 54]. The municipal water utility currently controls these water treatment plants.

This operating cost is the most competitive in Mexico. Moreover, as long as the technology needed to minimize the cost of systems of adsorption and/or membranes is not built in the country FD or conventional clarification (depending on the concentration of As) will continue to be the most viable processes for arsenic removal in countries like Mexico. On the other hand, the correct operation of drinking water treatment systems is one of the major problems

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that must be overcome to guarantee the availability of arsenic free water for the people, as well as constant monitoring of water quality and waste disposal.

Conclusions

Water contamination with arsenic is a serious problem that requires immediate attention and action. Unfortunately, new zones that implicate a potential risk to the population are being detected in Mexico with more frequency and these are mainly due to an overexploitation of aquifers. On the other hand, the little information that users have on this issue, tied to the insufficient monitoring coverage and the costs associated with water purification, are all factors that increase the exposure of the population to this contaminant. Education and community involvement are key factors to ensure effective results in any of the actions to be undertaken.

It is necessary that at least the institutions responsible for water management in each locality understand the risks associated with exposure to high levels of arsenic, either by consumption of arsenic-laden drinking water, through food cooked with contaminated water, or via food crops irrigated with contaminated water (e.g. rice).

The technology exists to remove arsenic. In Mexico, Direct Filtration has proven to be a technically and economically viable process for removing arsenic from water. However, its applicability depends highly on the type of water to be taken in the specific community and it cannot be considered a single solution applicable to all communities. Decision makers should carry out studies to ensure that the selected option is the most convenient from a technical, economic, and social point of view.The main barrier for the mitigate of problems is the lack of

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information, education, and awareness of decision makers and water managers. Also, more research and collaboration between institutions and involved agencies is required before the best options for each specific situation in each community is found.

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Scientific knowledge related to the dynamics of mercury in the environment and precisely in aquatic ecosystems has been focused in understanding the relationships and processes that

control mercury transport, fate and transformation from the different sources of input into aquatic ecosystems to bioavailability processes and bioaccumulation in food chains. Diverse mathematical models of various characteristics have been developed with the purpose of simulating mercury species transport, fate and transformation processes in aquatic ecosystems as tools to approach mercury dynamics in these ecosystems using mathematical expressions, and to use the results to contribute to decision-making related to the management of mercury contamination problems, ecological hazards and human health effects.

Modelling of mercury transport, fate and transformation in continental surface water bodies A case study of the Mojana Region, Colombia

1Geophysical Institute, Faculty of Engineering, Pontificia Universidad JaverianaBogotá, Colombia e-mail: [email protected] Basic Science Department, Universidad Jorge Tadeo Lozano, Bogotá, Colombiae-mail: [email protected]

Nelson Obregón1, Leonardo García2, Diana M. Muñoz1


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Introduction

Mercury is a persistent environmental contaminant that does not degrade. However, it changes in shape and moves through various environmental compartments (air, water, biota, soil and sediment) [2]. This heavy metal is known for its toxicity and negative effects on human health and natural ecosystems [1]. Among the species of organic mercury, methylmercury (MeHg) is considered the most toxic species due to its bioaccumulative and biomagnification capabilities through food chains [4]. The most common form of methylmercury exposition for human beings is through the ingestion of contaminated species, mainly of fish species [5]. The risks to human health due to chronic exposition to methylmercury generate severe socioeconomic consequences for the population [2]. Consequently, in the last few years there has been an increase in the attention to environmental mercury contamination reflected in the global efforts to reduce anthropogenic emissions to the environment and also in research focused in mercury dynamics in the environment, specifically in the quantification of its concentration, mobilization and transformation [2][4][5].

The sources of mercury in the environment include natural sources (e.g., volcanic emissions, discharge from natural mineral sources, forest and soil burning), anthropogenic sources (e.g., gold mining, fossil fuel combustion, industrial waste) and re-emission sources [2]. Regarding aquatic ecosystems, these are commonly contaminated with mercury due to the direct discharge or release produced by anthropogenic activities into water bodies. The most common of these activities are mining and industrial waste discharges combined with indirect sources such as atmospheric deposition, surface run-off, and soil erosion among others [3][10][13]. In water bodies mercury is subject to transport, fate and transformation processes. The latter process is performed through multiple biotic and abiotic transformations such as photochemical

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Modelling mercury transport, fate and transformation

reactions and microbiological activity reductions among which mercury methylation processes are the most significant. So far, methylation processes are not completely known, however, there is scientific evidence which indicates that in water bodies, methylation is produced by aerobic biological activity, particularly in highly productive hydrosystems in ecological terms [35] [43] [48].

Scientific knowledge related to the dynamics of mercury in the environment and precisely in aquatic ecosystems has been focused in understanding the relationships and processes that control mercury transport, fate and transformation from the different sources of input into aquatic ecosystems to bioavailability processes and bioaccumulation in food chains [12]. Diverse mathematical models of various characteristics have been developed with the purpose of simulating mercury species transport, fate and transformation processes in aquatic ecosystems as tools to approach mercury dynamics in these ecosystems using mathematical expressions, and to use the results to contribute to decision-making related to the management of mercury contamination problems, ecological hazards and human health effects [10] [11]. For these reasons, modelling could be a cost-effective way to assess management actions, for instance: the estimation of mercury dynamics in time to determine the risks to the ecosystem and human health, the effectiveness of actions to remediate or passively decontaminate ecosystems, the scope of control and management measures to reduce the sources of polluting loads [10] [11] [17]. However, modelling mercury dynamics in aquatic ecosystems is considered a complex activity [11] [12], due to the amount of processes and factors that govern transport and fate processes (hydrodynamic and sediment transport) and also transformation processes (biogeochemical) to be considered in water bodies. Such complexity is mainly represented in technical, economic and time-consuming efforts [10].

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The Mojana region, located in northern Colombia, is a territory that is classified as a floodplain through the formation of a delta in the confluence of the Cauca, Magdalena and San Jorge Rivers [54]. Such region is known for its biodiversity and for the ecosystem services it provides to the local population, to the Magdalena-Cauca basin and to humanity, especially through its vast system of wetlands which is the most representative ecosystem of the floodplain [54]. However, the sustainability of the natural system of this region is endangered due to mercury contamination, which mainly affects aquatic ecosystems and their ecosystem services. Fishing is one of these. A significant proportion of the local population depends on fishing as a source of food, and fishing has developed into an economic activity of regional significance [52].

Several studies such as Marrugo (2015) [55], Pinedo et al. (2015) [56] and Olivero and Johnson (2002) [4] have shown the critical level of mercury contamination in the region through measurements in different environmental compartments combined with the toxicology effects. The sources of mercury contamination in the Mojana region are directly related and mainly caused by the extensive gold mining activity developed in upstream regions in the basins, including the largest and most intense mining region of the Lower Cauca river basin located in Antioquia and Bolivar departments, which yields an annual average of more than 30 % of the national gold production [50]. As a large proportion of this mining activity is conducted through artisanal and small-scale gold mining processes, known for the use of precarious technology, the absence of knowledge or any regulations or standards and the indiscriminate use of mercury for the gold extraction mining activities which a significant portion it is released into the environment becoming in one of the largest anthropogenic source of polluting loads in the Magdalena – Cauca river basin. Due to transportation phenomena in the different environmental compartments, a considerable portion of these contaminants ends

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up in the aquatic ecosystems of the Mojana region, where they can transform, bioaccumulate and biomagnify in food chains and be exposed to the local population through ecosystem services like fishing [13] [55] [56].

Regarding the mercury contamination problem in the aquatic ecosystems of the Mojana region exposed above, the implementation of a model of transport, fate and transformation of mercury species in aquatic ecosystems could be a valuable tool for managing these environmental and toxicology regional issues and could contribute to the knowledge of this phenomenon’s environmental dynamics. This would allow us to simulate potential contamination scenarios and the efficacy of control or remediation measures, and these results could in turn feed cost-benefit analyses of such measures. Nevertheless, when a modelling project of these characteristics is undertaken it is fundamental to guarantee aspects such as technical capacity, sustainability, computation requirements and institutional commitment, among other factors, due to the complexity of the application of such models [10][12].

Mercury dynamics in continental surface water bodies

Mercury is a metal that is naturally found in the environment, however, anthropogenic activities that have been in development for the last century or so have produced a significant increase in the quantity and distribution of mercury in the atmosphere. Such activities discharge or release mercury directly into aquatic ecosystems (e.g., industrial discharges, mining waste) or indirectly, by discharging or releasing mercury to the atmosphere, to the soil or subsoil through activities like fossil fuel combustion, metal mining, industrial activities, and inadequate disposal of solid waste containing traces of mercury, among others [1].The point or non-point polluting loads released and stored in

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environmental compartments (i.e., air, vegetation, soil or subsoil) can be transported to surface aquatic ecosystems by natural processes like wet or dry atmospheric deposition of mercury, rain, surface and sub-surface run-off, soil erosion processes and the transport of sediment loads and particulate matter linked to mercury species transported into water bodies [2]. The remobilization of mercury is another indirect input source of this metal into aquatic ecosystems. This process encompasses the liberation of mercury species that were previously deposited or accumulated in several environmental compartments and released by human activities such as agriculture, reforestation, mining, dam construction, and sediment dredging or by natural physical biotic processes (hydrological, climatological, geological and biological among others) [3].

In surface water bodies, mercury is subject to various physical, chemical, biological and geological dynamics that will determine its transport, fate and transformation in the aquatic ecosystem. Among such processes, mercury transport and fate are significant due to the hydrodynamic effects of the water body, which is what happens with the advective-dispersive processes that lead the transport of dissolved mercury species and of those linked to suspended matter in the water body. This linking process between mercury species and solid particulate matter is due to the high capacity of mercury to be linked to solid organic or inorganic material, and it is highly significant in mercury dynamics of the aquatic environments as it affects its transport, which is why sediment transport processes (suspended solids, sedimentation and resuspension) are fundamental for the knowledge of the fate of mercury species, and their potential transformation or inactivation processes [2] [4].

After the stages of transport and fate in the aquatic ecosystem, these mercury species are stored in the different compartments of

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the water body and subject to transformation processes through biogeochemical processes that will determine mercury speciation in the water, the bioavailability of mercury species, and also mass exchanges between the phases of the water body (bottom sediments and sediment -water column interface) related to diffusive mass exchange, biodispersion and hyporheic flow [5].

The results of several studies conducted by Gilmour et al. (1992) [6], Benoit et al. (1999) [7], Monperrus et al. (2007) [8] and Drott et al. (2008) [9], stated that mercury transformation processes in the different compartments of the water body are directly related to the microbiological activity of certain types of species found in the water column and the bottom sediments. These biogeochemical transform reactions convert existing mercury into reactive mercury (HgII), elemental mercury (Hg0) and methylmercury (MeHg), and their activity and speciation processes are highly dependent on environmental conditions. These species of mercury interact with the hydrobiological species present in the aquatic ecosystem and produce bioaccumulation processes in the hydrobiological species and biomagnification processes in the food chain. Due to human beings are exposed to contact and ingestion of these species, they represent a public health threat of the communities based in the mercury toxicity properties [4]. Figure 1 outlines the main specific processes of mercury dynamics in surface water bodies.

Characteristics of surface water mercury models of transport, fate and transformation

The mathematical modelling of mercury dynamics in the environment, particularly the models that allow the simulation of the transport, fate and transformation of mercury species in aquatic ecosystems, is a tool that we can use to approach mercury pollution problems in water bodies and determine the hazards that such contamination can represent for the ecological state

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and for the exposed human population [10]. Moreover, these models become fundamental tools in the formulation of plans and actions for the mitigation and control of mercury contamination in aquatic ecosystems. Through the results produced from scenario simulations using these models, represented in mercury species concentrations obtained from the models in the different compartments of simulated water bodies, they provide essential information to guide decision-making processes aimed at managing environmental contamination and the toxicology threat on human health that mercury contamination poses [5].

One of the main applications of mathematical models of mercury transport, fate and transformation in aquatic ecosystems is the evaluation of the risks derived from the contamination of these ecosystems and the remediation possibilities [11]. This is a cost-effective measure in terms of economics and resource investment

Figure 1. Specific mercury processes in surface water bodies.

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that results from the application of a model of these features. A simple and effective measure in many cases, as opposed to other actions related to contamination management such as investment in technology, education, and restrictions to ecosystem services among other aspects [12].

Between the various remediation measures for aquatic ecosystems with mercury pollution problems, it is possible to simulate as a modelling scenario the natural attenuation of the mercury contamination problem trough time. The results obtained from the simulation of this scenario in the mercury species dynamics models in water bodies could allow to the authorities, stakeholders or environmental managers to approach the time scale in which the water achieves its own self depuration plus the final fate of these mercury species as a natural reaction of the ecosystem. Therefore, the application of these models could be a fundamental tool for assessing the viability of remediation actions in mercury-contaminated water bodies [11] [13].

The application of these models to mercury contamination in aquatic ecosystems would also provide information through the construction of prospective scenarios where mercury discharge into the aquatic ecosystem is reduced or increased as an environmental control measure. From the simulation performance results of the effects from these contaminant-variation scenarios, the effectiveness of the measures could be assessed to a certain degree [14].

In the specific case of determining hazards to human health due to mercury contamination in a water body, the models that would allow the simulation of the dynamics of mercury species transformation and bioaccumulation in the water body ichthyic fauna can provide results on bioaccumulated mercury in hydrobiological species and so specify the threat of mercury contamination to the human


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population due to the exposition to contaminated ichthyic species [5]. For the detailed case of transformation models for mercury species that allow the simulation of methylation and demethylation processes combined with the influence of environmental variables in the biogeochemical kinetics that produce methylated species, the results serve as a tool to approach methylation processes, bioavailability of methylated species in the water column, and environmental effects in their transformation kinetics. This information becomes a fundamental tool for the evaluation of mitigation measures for mercury contamination, due to the implications of methylation processes on the exposition of these toxic substances to hydrobiological species and humans [11].

[10] The complexity level of the surface water mercury models of transport, fate and transformation depends on the degree of detail in terms of spatial and temporal dimensions, the morphological characteristics of the aquatic ecosystem to be simulated, and the state or exact destination of the mercury species (biotic community, water body, sedimentation, humans, among others), for these reasons it is important to measure these aspects before developing a modelling project of these characteristics [12]. Additionally, the complexity of the modelling process is also reflected in the large amount of required data about the aquatic ecosystem, such as input data, and for the calibration and validation stages of the model. The reliability of the model and thus the adequacy of the decisions made regarding actions to take in order to face the contamination problem based on the results obtained from the applied models depend on these conditions [15].

Review of surface water mercury models of transport, fate and transformation

The development of these models started around the mid 1960s as a response to the evidence of the negative effects of mercury

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for the environment and its toxic effects in humans [9]. This explains why the main objective of the scientific community in the development of these models to simulate mercury dynamics in surface water bodies is to use them as tools to manage mercury contamination [14]. Thus far, multiple mathematical models with diverse applications and complexity levels have been developed. In general terms it is possible to classify these models in the categories below according to their modelling goal, spatial dimension, and types of simulated processes [10].

a) Models based on the exchange of mercury concentrations between the water-air-sediment interface through the balance of mass among these compartments via simplified processes, i.e., without considering the transport processes of dissolved mercury fractions or mercury linked to particulate suspended matter in the water body [16][17].

b) Models in which mercury is a conservative substance transported in the water column and linked to particulate suspended matter and its fate depends on hydrodynamic processes and also on the transport of sediments in the hydrosystem [18].

c) Models based on the geochemical processes of the mercury cycle in surface water bodies [19] [20].

d) Models based on the bioaccumulation and biomagnification of mercury species in aquatic ecosystem species and their food chain [12].

e) Adapted transport and fate models that allow the simulation of physical processes such as hydrodynamics, sediment transport, and biogeochemical transformations of mercury, using spatial approximations of one-dimensional,

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two-dimensional or three-dimensional models in surface water bodies [21].

Using the classification above, in the following section we will expose the characteristics, scopes, processes and requirements of these models in terms of the simulated processes in surface water bodies, the spatial dimensions of the simulation of the models, as is the case in hydrodynamic processes and sediment transport, biogeochemical processes and bioaccumulation processes.

Simplified mass balance models in well – mixed surface water bodies (zero-dimensional)

The main object of these models is to simulate with a simplified approach the dynamics of mercury in surface lentic hydrosystems, without considering the effects of hydrodynamic and sediment transport, and therefore aquatic systems are regarded as a well-mixed reactors or zero-dimensional systems. Some of these models divide the water bodies into multiple layers between which uniform and time-constant mass exchanges occur [22]. This mass balance approach for mercury modelling cycle is appropriate for small reservoirs, lakes and wetlands where organic and inorganic suspended solids are present and along with minimum variations in terms of inputs or outputs to and from the hydrosystem, polluting loads, and hydrodynamic behavior. Thus, this model is inadequate for highly dynamic aquatic systems such as lotic, large lentic water bodies and coastal areas, where hydrodynamic behavior and sediment transport significantly impact the transport and fate of mercury [23].

Additionally, these models take into account the balance of mercury species in the different compartments through the concept of partition coefficients (KD) that depend on environmental variables of the aquatic ecosystem such as temperature, pH, and

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redox potential among others that indirectly influence the kinetics of mass exchange, which implies the need to determine such environmental variables as input data for this type of models [24].

Among the pioneer models of this type the one developed by Turner and Lindbergh in 1978 [25], it is best known for their simulation processes which describes the dynamics of mercury concentrations in a river-reservoir aquatic system located downstream from the discharge of a chemical product plant. However, this model does not consider the effects of fractions of mercury linking to suspended solids. The results of these models overestimated mercury concentrations downstream from the discharge point of polluting loads [10]. Years later, Fontaine (1984) [28] developed a complete-mix model on the water body, considering three fractions of mercury species (dissolved, particulate and linked to organic substrates) combined with reaction processes, mass exchange between the water column and the bottom sediments controlled by kinetics, sorption processes and geochemical transformations on mercury species [12].

The QWASI (Quantitative Water-Air Sediment Interaction) model developed by Mackay and Diamond on 1989 [27] has the capability of simulating the fate of mercury from the dry and wet atmospheric deposition into the water body, combined with fate processes in the water column, in a completely well-mixed hydrosystem in stationary conditions, as seen in the speciation between dissolved fractions of mercury and those linked to suspended particulate matter, the diffusive mass exchange between water column and sediments, re-suspension and sedimentation [11].

Another model known for its application in various cases that has the capacity of dynamically simulating mercury fate and the mercury cycle in water bodies is the MCM (Mercury Cycling


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Model), developed by Hudson et al. (1994) [28]. This model’s main feature is the segmentation of the water body in multiple compartments, such as lentic hydrosystem, the epilimnion, the hypolimnion, and the bottom sediments, along with four hydrobiological compartments including zooplankton, phytoplankton, and carnivore and non-carnivore fish species. Regarding mercury species, this model simulates the following mercury species: elemental, reactive and methylmercury. With respect to the simulation of the latter species, it has the capacity to simulate reaction rates for methylation and demethylation as a function of the concentration of reactive mercury, sulfate ion, dissolved organic matter and water column temperature [10]. The MCM has been used in different studies, such as the modelling in large lakes in the United States developed by Leonard et al. (1995) [29]and Knightes and Ambrose (2007) [30] where they applied the model in 91 lakes in Vermont and New Hampshire (US), and Kotnik et al. (2002) [31] in the Velenje River in Slovenia.

The SERAFM model developed by Knigthes et al. (2008) [32] is a mercury cycle modelling software extensively spread and applied in multiple cases. This model is based on the balance of mercury species in surface water bodies considered completely mixed or zero-dimensional, along with the segmentation of the system in several layers. It possesses a user-friendly interface developed from databases [10]. The following are among the general features of the SERAFM: categorization of mercury species in elemental, reactive and methylmercury through five phases (solid, inert, phytoplankton, zooplankton, detritus, and dissolved organic matter) and three water body compartments (epilimnion, hypolimnion and bottom sediments), and an equilibrium condition regarding the simulation of sorption processes. The cases in which this model was applied include the research developed by Brown et al. (2007) [33] in artificial wetlands in Nevada (US) and the case developed by Canu et al. (2012) [34] in the Marano-Grado lagoon

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(Italy).

Models based on hydrodynamics and sediment transport

These models simulate the temporal and spatial distribution of mercury point or non-point polluting loads as inputs of hydrosystems, along with the role of sediment transport and fate due to its capacity to link with solid particles dissolved in the water column [15]. The hydrodynamic model and the sediment transport model can jointly simulate the behavior of mercury species released in water bodies that are transported by the water column, in dissolved fractions or linked to suspended solids. Consequently, these models can approach the temporal and spatial distribution of mercury species through the simulation of hydrological, hydraulic and sediment transport dynamics [12].

Normally, this type of hydrodynamic and sediment transport models are appended to a water-quality module through which the changes in the concentrations of the mercury species dissolved in the water column are simulated using the advection-dispersion equation [14]. In a subsequent stage, the results from these models (hydrodynamic, sediment transport and water-quality) are appended to specific modules (sub – models) that simulate the mass exchange and mercury species concentration flow exchanges between the water body phases such as bottom sediments, the water column and the atmosphere [12]. Among the models of this type one of the most important is the MERMC4 model developed by Henry et al. (1995) [35], which is appended as a quality module integrated into the WASP (Water Quality Simulation Program). It is an integrated dynamic quality model for diverse types of hydrosystems through which the hydrodynamic and sediment transport model is appended to the mercury cycle model based on the mathematical formulation of the MCM mentioned in the previous section of this chapter section [36].

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In turn, the WASP software offers modules for modelling mercury transport and fate depending on the water body flow properties. For lotic water bodies there exists the RIVMOD model, which optimizes hydrodynamic processes and fit them to kinetic models for sorption and desorption processes in different compartments of the hydrosystem [36]. The most representative cases conducted using this modelling framework are the mercury transport model developed by Carroll et al. (2000) [37] in the Carson River (Nevada, US), and the model developed by Zagar et al. (2006) [21] in the Soca and Idrijca rivers in Slovenia.

Models based on biogeochemistry and the bioavailability of mercury species

The models based on mercury transformation processes establish the mercury speciation in surface hydrosystems through biogeochemical process, specifically concerning methylation and demethylation mass exchanges between the water body phases (bottom sediments, water-sediment interface and water column), and the bioavailability of mercury species [12]. According to several authors [38] [39] [40], it is estimated that speciation between the different phases of the water body is directly related to the microbiological activity of certain types of particular species developed in the water column and in the accumulated bottom sediments. These biogeochemical reactions transform existing mercury into reactive mercury (HgII), elemental mercury (Hg0) and methylmercury (MeHg), and it depends on environmental conditions such as nutrient availability, traces of metals, temperature and radiation among others. Thus, it is necessary to consider these conditions and simulate them as well in mercury transformation processes. These are regularly simulated as a sub-model that is appended to the general mercury transformation model [38].

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A commonly used methodology in models for the simulation of mercury transformation dynamics in the environment it is to assume equilibrium conditions and estimate the variations among the dominant mercury species in terms of reaction equilibrium coefficients which depend on multiple environmental factors [36][12]. Condition that increases the complexity in the simulation dynamics of these coefficients [17]. However, existing models typically attempt to simplify the simulation of these processes assuming that the concentrations and reaction coefficients are not independent [12]. These mercury biogeochemical transformation models have been developed through time, at present these models allow the calculation of the equilibrium of mercury species in the dissolved, solid and gas states and sediment bound in the different compartments of an aquatic ecosystem (water column, bottom sediments, water-sediment interface, and water-atmosphere interface) [5].

The MINTEQ+ model, developed by Bhavsar et al. (2004) [41] stands out among this type of models due to its applicability and use in multiple cases. It is a detailed geochemical speciation model with chain reactions between the different water column phases and the transfer of mass between the environmental compartments (water, air and sediments) as a dynamic system linked to a hydrodynamic and sediment transport model. This model was applied for modelling heavy metals in various lakes in Canada [41]. Concerning the simulation of mercury methylation and demethylation processes attributed mainly to bacterial metabolic activity, these biological reactions have particular kinetics, which are typically slow and irreversible. The BIOTRANSPEC model developed by Gandhi et al. (2007) [42] it is another representative model that specifically simulates the mercury methylation dynamics through biogeochemical activity allowing the dynamic simulation of methylation and demethylation processes.There are also models that detailedly simulate the methylation

processes by microbiological activity of specific bacteria groups such as iron-reducing and sulfate-reducing, and therefore it is necessary to detail redox and controlled kinetic microbiological degradation reactions in the different phases of the water body [12] [43]. The specific models for simulating this detailed microbiological kinetics are appended or linked to the results and processes of hydrodynamic and sediment transport models and the mass balances between phases of the water column. Among these models, the PHREEQC2, developed by Parkhurst and Appelo (1999) [44] is the most well-known. It is used for exploring the relationships between mercury methylation and the environmental conditions that affect microbiological processes. Additionally, it integrates into software that couple hydraulic one-dimensional modules, mercury speciation and biogeochemical processes modules [12].

In the case of mercury models that simulate the interaction of mercury species with biotic species allowing the modelling of the ecological effects of mercury contamination [10] [5], in general terms, these models allow the simulation of mercury species amounts present in fauna and flora. The most common modelling strategies for this type of models are the use of multiplication factors according to the concentration of mercury species in the water bodies and to the morphologic characteristics of the biotic species, through which mercury concentrations are bioacumulated in the species and biomagnified in the aquatic ecosystem food chain [45]. There are also more detailed approaches to these ecological processes through the modelling of food chains and energy demands of the species through the assessment of their feeding habits, quantities ingested, and metabolism among others [46] [47] [48]. These detailed models allow approaching knowledge of mercury bioaccumulation and biomagnification in fish and other hydrobiological species. However, the application of these models is complex, due to the level of detail of the processes

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and the variables needed data for their calibration.

Data requirements for surface water mercury models of transport, fate and transformation

The data requirements for the implementation of a mercury transport, fate and transformation model depends on its level of complexity in terms of spatial and temporal scale, the complexity of the aquatic system to simulate, the state or destination of the mercury species on the environment to simulate (bottom sediments, food chain, methylation or demethylation) [5][12]. Table 1 includes a brief description of the basic data requirements for the development of surface water mercury models (input and calibration variables and parameters), from the model type classification according to their simulation goal, spatial dimension and processes simulated for each type listed in the previous section.

Regarding the data requirements presented in Table 1 for each type of mercury transport, fate and transformation model, it is possible to identify how the information requirements for the application of the models increases as the complexity of the model in terms of detail degrees of mercury modelling processes, space and time scale, and type of water body among other aspects. These data requirements according to the type of model and their higher level of complexity can be directly connected to a higher level of investment in various resources such as economic, technical, human, space and time, and institutional resources among others [11 ][12][13]. For this reason, when a mercury dynamics modelling project in an aquatic ecosystem it is to be develop, it is recommended to perform a cost-benefit analysis of the resources required among those mentioned for the application of the models and thus find the appropriate model type according to the modelling object and available resources.


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ID Model type

Model type Data requirements

a)

Simulation of mercury concentration exchange between the water-air-sediment interface

• Mercury species concentrations [THg], [MeHg] in air, water and sediment.

• Hydraulic information of flows, volumes or water levels of the water body for space and time coarse scale.

• Mercury atmospheric deposition on annual or monthly scale.

• Hydroclimatological variables: rainfall on monthly or annual scale, wind regimes.

• Features of specific polluting loads: location, average load of mercury species.

b)

Simulation of mercury in the water body as a conservative substance transported in the water column and linked to particulate suspended matter. Its destination depends on hydrodynamic processes and sediment transport.

• Hydrodynamic transport: hydrosystems topology, roughness coefficient, flow discharges and flow velocity in control points.

• Sediment transport: grain-size distribution of suspended and bottom sediments, concentration of total suspended solid fractions (volatile and fixed fractions), dissolved solids and average density of the sediment particles.

• Total mercury concentration [THg] and methylmercury [MeHg] in the water body, specific and tributary streams polluting loads and, suspended sediment and bottom sediment loads.

Table 1. Data requirements for surface water mercury models by model type.

Approaching the mercury contamination problem in continental surface water bodies in Colombia, pointing to the case of the Mojana region

According to the National Study on Water conducted by IDEAM in 2014 [49], it is estimated that in Colombia approximately 205 tons of mercury are released into continental surface water bodies

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c)Simulation of geochemical processes of the mercury cycle in the water body.

• Concentration of total mercury species in the water column and its segmentations (surface, bottom, mid-depth), total mercury [THg], elemental mercury [Hg0] and methylmercury [MeHg] in suspended sediments loads and sediments accumulated and stabilized sediment in the bottom.

• Kinetics rates of biogeochemical transformation processes of mercury species (measured in lab or reference values) in the water column and bottom sediments.

• Presence or absence of sulfur-reducing and iron-reducing bacteria in the water column and bottom sediments.

• Environmental conditions that influence biogeochemical processes in the water column and sediments: temperature, solar radiation, organic mass percentage, dissolved oxygen concentration, nutrient concentrations, and sulfur and iron species concentrations.

d)

Simulation of bioaccumulation and biomagnification of mercury species in aquatic ecosystem species and their food chain.

• Mercury species concentrations in the water column and its segmentation phases (surface, bottom, mid-depth), total mercury [THg], elemental mercury [Hg0] and methylmercury [MeHg] suspended sediments and sediments accumulated in the upper bottom and in stabilized sediment in the lower bottom.

• Mercury species concentrations in plankton species of water bodies (periphyton, phytoplankton and zooplankton).

• Mercury species concentrations in algae and aquatic vegetation tissues.

• Mercury species concentrations in carnivore and non-carnivore ichthyic species tissue and organs.

• Mercury species concentrations in amphibious or terrestrial fauna species which the main food source are the aquatic fauna.


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e)

Simulation of mercury transport and fate that allow the simulation of physical processes such as hydrodynamics, sediment transport and mercury biogeochemical transformations in water bodies using space and time approximations from one-dimensional, two-dimensional and three-dimensional models.

• Appending models and their data requirements (ID model type a) + b) + c) + d).

• Detailed data which depends on the spatial dimension to the water system modelling (1D-2D-3D) and temporal scale (monthly, daily, hourly, sub-daily) series of hydrodynamic data, sediments, mercury species concentrations, environmental conditions, bioaccumulated matter in biotic species.

and surface soils of which 72.5 % correspond to gold mining-related activities. The remaining percentage is attributed to activities or sectors such as ferrous-metal and non-ferrous-metal mining, cement production, and industrial waste among others [13]. In Colombia, gold production is spread among extensive regions of the country. However, the official data for production of gold by department for 2012, published by the Colombian Mining Information System (Sistema de Información Minero Colombiano - SIMCO), indicate that almost 85 % of the national production is focused in three departments: Antioquia accounts for 42 %; Choco is responsible for 37 %; and Bolivar holds 6 % [50]. Additionally, it is estimated that approximately 40 % of the national gold average annual production is concentrated in a region of the Antioquia department known as the Lower Antioquean Cauca, which groups the Segovia, Taraza, Caceres, El Bagre, Zaragoza, Caucasia and Nechí municipalities [51].

It is important to consider that in Colombia, Artisanal and Small Scale Gold Mining (ASGM) activities accounts for approximately 40 % of the total national gold exploitation. In general, ASGM is developed through practices that are inadequate in terms of production, and without regard to environmental impacts, social

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responsibility or the occupational health of the mining workers [13]. The proportion of this type of gold mining activities, which is developed under no regulation or control in productive and environmental terms, can imply that the polluting loads released or poured into the environment derived from the ASGM can be even higher than those previously reported, which further magnifies the environmental mercury contamination problem in the country.

In Colombia, the hydrological basins most impacted by direct mercury discharges associated with gold mining according to the 2014 National Study on Water [49] are: the Magdalena River – Morales arm branch (Bolivar department), the Nechí River and the main stream tributaries of its lower basin (Antioquia department – Lower Cauca region), the main stream tributaries of the Cauca River in its middle and lower basins such as the Taraza River and the Man River (Antioquia department – Lower Cauca region), the main stream tributaries of the middle and lower basins of the San Juan River (Choco department), and the San Jorge River in its lower basin (Cordoba and Sucre departments – Mojana region). Most of these basins, like the Lower Antioquean Cauca region, coincide with intensive gold production activities.

In biophysical terms, the region referred to as Mojana region (Figure 2) is delimited by the river delta formed in the north by the Loba arm branch of the Magdalena River, in the west by the lower basin of the San Jorge River, and in the east by the Cauca River. This river delta forms in its interior and surroundings a floodplain that forms a large system of wetlands and consequently an intricate network of swamps, creeks, lagoons and marshes [52]. In political terms, this region falls under the jurisdiction of eleven municipalities pertaining to four departments; Nechí (Antioquia department), Magangué, Achí, San Jacinto del Cauca (Bolivar department), Ayapel, San Marcos (Cordoba department),


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Guaranda, Majagual, Sucre, Caimito, San Benito Abad (Sucre department). It is important to consider that the Mojana region shares its southeastern border with the Lower Cauca mining region, which is located in the lower-middle basin of the Cauca River, in hydrological terms.

Figure 2. The Mojana region area, hydrosystem and Lower Cauca gold mining production region municipalities.

In the fluvial morphology and hydrological context, the floodplains serve the function of accumulating material produced and transported in its river basins (solids, sediments, detritus, debris, and organic matter among others) [52]. Moreover, they serve to regulate floods in the river basins and promote the mitigation of their effects. Apart from these regulation ecosystem services, that are highly important in a river basin of great size like the Magdalena – Cauca river where is located the Mojana region, these floodplain macro-ecosystems are globally known for their ecological importance in terms of biodiversity and due to the variety of ecosystem services they provide to humanity and mainly to local communities [53].

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As a floodplain in the Magdalena-Cauca river basin, the Mojana region intrinsically provides the ecosystem service of retaining, processing and accumulating solids, nutrients and energy flows generated and transported through its multiple streams [54]. This natural condition is combined with its spatial proximity to the Cauca river upstream territories where mercury polluting loads produced in gold mining are discharged into the environment; i.e., the Lower Antioquean Cauca, the San Lucas mountain range (eastern natural boundary of the Mojana region - Bolivar department), and the Mojana region itself. A large portion of these polluting loads is transported through the lotic water bodies of the basin due to hydrodynamic and sediment transport processes. These water bodies include the Magdalena (Loba arm branch), Cauca, Nechí, Caribona, San Jorge Rivers and also the great wetlands system of the Mojana region, where these streams have a direct connectivity and exchange flows, matter, and temporary or seasonal energy with the Mojana hydrosystem. The mercury loads are transported to the lotic and lentic water bodies of the Mojana region and this becomes the final destination of the mercury species, which can then transform via biogeochemical processes and can bioaccumulate in the hydrobiological species and biomagnify in their food chains.

Research on the quantification of mercury in various environmental compartments of the Mojana region and their environmental and sanitary effects has been conducted approximately since the 1990s [4]. The results from these studies reveal that Mojana regionhas been a mercury contamination problem. As a consequence of those findings, with the development of local, national and global conscience regarding the toxicity of mercury, and after comprehending the magnitude of this environmental and toxicological problem, multiple studies and investigations have been carried out with different objects and scopes, all with the purpose of assess the mercury contamination problem in the

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Mojana region. In general, the scope of these studies falls within the eco-toxicological, environmental and public health fields, and establish mercury and methylmercury concentrations in various environmental compartments such as water, sediments, air and soil combined with biotic species from multiple levels of the food chain such as algae, plankton, aquatic vegetation, ichthyic species, amphibians, terrestrial species, cultivated rice and human urine, hair and blood [55].

The most representative investigations and studies references recommended to deepen the details of the mercury contamination problem in the Mojana region in the compartments mentioned and in local communities are: Marrugo (2015), Una Mirada a impactos del mercurio en Colombia [55]; Olivero-Verbel and Johnson (2002), El lado gris de la minería de oro [4]; and Pinedo et al. (2015), Speciation and bioavailability of mercury impacted by gold mining in Colombia [56]. These publications mainly show results about the various mercury measurements developed in the last few years in the Mojana and neighboring regions in multiple environmental compartments and human communities. Furthermore, they analyze their results in the light of references that point to the environmental problem and the threat to local public health, and they characterize the health effects on the local population that is directly exposed to the contaminated environment.

In general, the results of these studies are a clear evidence of the mercury contamination problem in the aquatic environments of the Mojana region in direct connection with the use of this metal in human activities developed in the Magdalena – Cauca river basin such as gold mining, and the direct or indirect discharge or release of polluting loads into the environment in the surrounding upstream territories of its basin, which contaminate the water bodies of the complex hydrosystem of the Mojana region due

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to mercury transport and fate phenomena. These polluting mercury loads transported and accumulated in the Mojana region hydrosystem subsequently could be transformed into mercury bioavailable species that are biomagnified in the food chains and exposed to the humans, becoming a threat for the health of the local human population.

Data requirements and perspectives for the development of surface water mercury models of transport, fate and transformation in the Mojana region

The application of a model that simulates mercury dynamics in aquatic systems in the hydrosystem of the Mojana region implies much complexity due to the intrinsic features of this great floodplain formed by multiple lotic and lentic surface water bodies added to the connectivity and exchange of flows, matter and permanent or temporary energy with large rivers (Cauca River, the Loba arm branch of the Magdalena River and San Jorge River), and human activity. Thus, its characterization and the modelling of its hydrodynamics and sediment transport processes would require great economic, technical and institutional resources in order to assess the transport and fate of mercury species in the hydrosystem. However, regarding the hydrodynamic model, at present there is a regional hydrodynamic model that was developed by the national institution Fondo Adaptación in 2014 in the context of the project Plan de acción de intervención integral para la reducción del riesgo de inundaciones en la region de la Mojana (Intervention action plan for reducing the risk of floods in the Mojana region) [52]. The model was designed with the purpose of simulating scenarios of flood hazards in the region. Among its main features, it allows the spatial simulation of Mojana region lotic water bodies in one


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dimensional space, and of lentic water bodies and flooding areas in 2-Dimensional space, with spatial resolution of cell size of approximately 400 meters and a sub-daily time scale. The model was developed with the SOBEK software, which is a numerical modelling software package that allows the simulation of various hydrodynamic, biophysical, morphological and ecological processes. It was developed in the 1980s by the Deltares research and technology institute in Delft, Netherlands, and its main advantages include its documentation, support, continuous development and updating process, which incorporates state of the art advances in related fields of hydrodynamics and biophysics [57].

The existence of a hydrodynamic model for the Mojana region hydrosystem with the features mentioned represents a great advantage for undertaking a mercury dynamics modelling project in this aquatic ecosystem. The model could be used to simulate the transport and fate processes of mercury species, integrating a sediment transport model for mercury fractions linked to suspended matter combined with a quality sub-model for simulating the dynamics of mercury species dissolved in the water column. However, it is important to consider the data requirements for the application of this model of transport and fate of mercury species cited in Table 1, ID model type b), summarized as follows: for sediment transport (grain-size distribution of suspended and bottom sediments, concentration of total suspended solid fractions, dissolved solids and average density of the particles), concentrations of mercury species in the water column, specific polluting loads, and suspended sediment and bottom sediment loads. It is important to take into account that the data requirements will be greater if the mercury dynamics modelling project for the Mojana region hydrosystem intends to simulate transformation, bioavailability and bioaccumulation processes (ID model type c), d) and e) according to Table 1).

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Even though various studies and measurements on mercury species in different compartments of the Mojana region water bodies, on hydrobiological species and other environment compartments (air, soil, humans, terrestrial animals), which they have been developed in the past few years, their main goal is to prove the environmental condition of mercury contamination in the region combined with the toxicological effects that imply risks for human health. Consequently, these studies, which have not been specifically developed to provide input data for modelling or for the calibration of the mercury dynamics model, lack the fundamental requirements to be used in a modelling project of the previously mentioned characteristics; i.e., the periodicity of the measurements according to hydrological regimes; the spatial coverage of the measurements according to the spatial scale of simulation of the model; the hydrodynamic, sediment transport and mercury species characterization in the boundary conditions of the model; and the specific polluting loads among other aspects. These requirements restrict the use of the information available produced in existing studies and investigations about the topic for the implementation of a transport and fate model or in more complex terms a transformation and bioaccumulation model in the Mojana region [10][12][36].

These limitations in the available and required data for the development of mercury dynamics modelling projects in the Mojana region point to the need of conducting specific activities to gather this information for the purpose of modelling, as is the case with the formulation of a monitoring plan requiring, at least, the sampling spatial distribution, the periodicity of monitoring campaigns, and mercury species, hydrodynamic, sediment and environmental variables to be sampled and measured, among other aspects, as well as an estimation of the logistics and economic, human and technical resources required for the development of such monitoring plan [12].


Other additional considerations to the data requirements for the implementation of a model like the one described and the implications related to the formulation of a monitoring plan are the economic, technical, human, space and time, institutional and other resources fundamentally represented in the technical capacity to develop the model with highly qualified technicians, investment in specific software and hardware and its corresponding technical support, sustainability of the project in time in economic terms, the institutional commitment and responsibility on the development of these models that represent significant economic investments for institutions or organizations that develop this kind of studies, which is why it is of the utmost importance to conduct a cost-benefit analysis of the various resources required for the application of the models, to specify the type of model that meets the object of the project, and the available resources prior to undertaking a mercury species transport, fate and transformation model in water bodies. However, it is necessary to further detail the present magnitude of the mercury contamination problem in the Mojana region hydrosystem. This would justify the need for undertaking a project with a model of this type, as well as build from existing inputs such as the technical, human and economic resources invested in the development of the hydrodynamic model of the core of eleven municipalities of the Mojana region conducted by the national institution Fondo Adaptación [52]. This would be a crucial step in the implementation of mercury transport, fate and transformation models in this important hydrosystem.

References

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[50] Home page. Sistema de Información Minero Colombiano. http://www.simco.gov.co/ (accesedMarch 20, 2015). Unidad de Planeacion Minero Energetica (UPME) – Bogota D.C. 2015.

[51] Fedesarrollo. Estudio sobre los impactos socio -económicos del sector minero en Colombia: encadenamientos sectoriales. Estudio preparado para la asociación de la minería a gran escala. Bogota, D.C., 2013. 69 pag.

[52] Fondo Adaptación. Plan de acción de intervención integral para la reducción del riesgo de inundaciones en la región de La Mojana. Documento resumen. Bogota, D. C. 2015. 86 pag.

[53] Vilardy, S.; González, J.A. (Eds.). Repensando la Ciénaga: Nuevas miradas y estrategias para la sostenibilidad en la Ciénaga Grande de Santa Marta. Universidad del Magdalena y Universidad Autónoma de Madrid. Santa Marta, Colombia. 2011,228 pag.

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Remediation

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Nano modified clays, bioclays and bio-leaching for water and sediments remediation Natalia Porzionato, Luz M. Guz, Melisa Olivelli Gustavo A. Curutchet, Roberto J. Candal

Water and sediments contamination is one of the more dramatic environmental problems that humanity is facing now. The situation is worst in the undeveloped

countries, with overcrowd cities and deficient water management. Heavy metals, pathogens and recalcitrant organic compounds are between the most dangerous pollutants found in those environments. Versatile and relatively cheap processes for water, waste water and sediments purification should be developed in an attempt to remediate the situation. In this chapter, a few examples of water and sediment contamination in Argentina are presented, as well as remediation alternatives based in the use of nano and bioclays.

Instituto de Investigación e Ingeniería Ambiental, CONICET, Universidad Nacional de San Martín, Campus Miguelete, 25 de mayo y Francia, 1650 San Martín, Provincia de Buenos Aires, Argentina.e-mail: [email protected]


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Introduction

Water contamination is one of the main concerns in the entire world but in particular in undeveloped countries, were environmental control and regulations are lighter than in developed countries, or it application is more difficult due to social or economic constrains [1]. Surface water contamination is mainly consequence of the release of untreated Municipal or industrial effluents to water courses. Municipal effluents, in the cases where industrial effluents are separated from sewage waters, can be relatively easy treated by conventional biological methods. The main problem with sewage waters, beside the enormous volume of water to be treated in big cities, is the presence of the so called emergent contaminants. This group of contaminants include medicines, hormones, and other substances eliminated by human been that cannot be degraded in conventional biological plants. Industrial waste water represents a more complicated problem because some contaminants can be recalcitrant or even toxic to microorganisms. Consequently, conventional bio-treatment may be not enough to eliminate these pollutants. In these cases, different physicochemical methods are typically used which include coagulation/precipitation; oxidation, neutralization, etc. Physicochemical methods can be used alone or coupled with bio treatment and/or adsorption. In the case of coagulation/flocculation and adsorption, the production of solid waste containing concentrated amounts of contaminants can be a problem difficult to solve.

Subsurface water can be contaminated by sewage water, industrial effluents, chemicals and oil spilling. But also there are natural pollutants as arsenic, which may be presented in high concentration in subsurface water. In situ remediation of contaminated subsurface water is a difficult task and is one of the more important and interesting modern challenge for environmental and hydraulic engineers.

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Nano modified clays, bioclays and bio-leaching

When conventional water treatment fails, nanotechnology is one of the modern tools that researchers and engineers can use to resolve complicated problems. Nanomaterials display newest and powerful capacities as adsorbents or catalysts, react faster than regular size materials, can penetrate or migrate to places unavailable for other systems, etc. Newly developed nanomaterials and nano-devices are available or are being studied to resolve pollution problems associated with recalcitrant compounds, metals in water, emergent contaminants, disinfection and even more.

In this chapter some typical examples of different heavily polluted systems in Argentina will be presented as examples of contamination in undeveloped countries, followed by the discussion of different treatment process that involve the use of clays modified in the nanoscale, and bioremediation of metal contaminated sites using native bacteria consortia.

Water contamination in Argentina: a few typical examples

Metal contamination in water and sediments at Reconquista River basin: the case of the José Leon Suarez Channel

The Reconquista is one of the more polluted rivers in the country and is emblematic of environmental problems. This river receives contributions from storm sewers and streams that run across zones of high population density and serious environmental problems (hyper-degraded territories). Many of the tributaries of this basin receive domiciliary and industrial contaminating loads [2]. One of them is the José León Suarez channel (JLSC). This stream runs tubing as a rainwater collector and leaves open at “La Cárcova”

Figure 1. Reconquista River, José León Suarez channel and adjacent neighborhoods. © 2016 Google.

neighborhood situated approximately 4.5 Km. upstream of its drainage at the Reconquista river, as can be seen in Figure 1.

This neighborhood has characteristic of extreme poverty, lack of drinking water services, sewer and energy, and its population is highly exposed to contaminants carried by the channel and those accumulated in the sediments. Figure 2 shows images of drainages discharging in the channel, very close to the houses. Although the JLSC is originated by the confluence of various storm sewers, it pulls high pollution levels as a consequence of irregular loads. However, due to the high water self-purification capacity of these streams, acceptable level of organic contamination (oxygen chemical demand less than 50 mg L-1) reaches the Reconquista River, located only 5 km downstream.

The self-purification rate overcomes the normal degradation rate of

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Figure 2. a) example of drainage that empties into the cannel; b) view of the channel at the border of the neighborhood.

organic matter due to the processes of sedimentation. This process leads to the incorporation of organic matter and other pollutants (as metals) into sediments. The high concentration of organics in the sediments generates a high benthic oxygen demand, setting an anoxic environmental condition suitable for the biocatalyzed formation of sulphides. Under these low redox potential conditions, most of heavy metals might precipitate as poorly soluble sulphides and hydroxides or are adsorbed to the different mineral components of the sediment matrix. The concentration of metals in the sediments corresponding to different points along the JLSC indicated in Figure 3 is shown in Table 1.

Table 1 also displays the concentration of the same metals in the sediments of Roggero Dam (a dam placed at the nascent of Reconquista River), Hidalgo channel (H) (a channel close to JLSC), and in the Reconquista River (R) in an area close to where JLSC and H discharge it waters at Reconquista River. Data presented in

a) b)


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Figure 3. samples sites along the JLSC. Imágenes © 2016 Google Datos del mapa © 2016 Google.

SiteMetal

Copper Chromium Zinc

2 247 8 181

6 350 118 1570

8 220 14 650

9 15 7 330

11 ND ND 800

12 120 56 340

H 115 105 450

R 630 2540 1020

C 6 <0.1 4

Table 1. Metal concentration along the JLSC (see Figure 3). Total content of Cu, Cr, Zn. Comparison with Hidalgo (H), Reconquista (R) and Roggero Dam (C); concentrations in [mg Kg-1]; (ND): no determined.

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the table clearly shows the high level of pollution in the sediments of JLSC, (H) and (R) in comparison with the less polluted area (C). For comparison, Table 2 shows reference levels suggested by the Water National Institute of Argentina.

Metal/Metalloid Level 1 Level 2 Level 3

As 3 9 33

Cd 0.6 0.9 10

Zn 100 271 540

Cu 28 50 110

Cr 26 55 110

Ni 16 35 75

Pb 23 42 250

Table 2. Quality guideline levels in sediments, suggested by INA (Water National Institute). Concentrations in mg Kg-1.No polluted: ≤ Level 1Slightly polluted: Level 1 < Sediment ≤ Level 2Moderately polluted: Level 2 < Sediment ≤ Level 3Very polluted > Level 3

These heavily contaminated sediments are very dangerous because if they are expose to atmospheric oxygen, biocatalized processes can produce an incontrollable leaching of dissolved heavy metal to the water course. This phenomenon happens when the sediments are removed by dragging and piled at the side of the river. Water

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Water contamination by textile dyes

The presence of textile dyes in water is beside an example of landscape contamination, a serious risk for the biota and human being [3-5]. The use of this type of compounds notably increased during the last decades in the entire world [1]. However, due to legislation and strict controls on industrial effluents implemented in Developed Countries, the economic crisis and the need to diminish production costs, a significant fraction of that intensively use textile dyes was relocated to Undeveloped Countries. Figure 4 shows the evolution of dyes consumption during the last decades in different areas of the world.

Figure 4. Evolution of dye consumption during the last decades. Adapted from Hessel et al 2007 [1].

Textile industries in Argentina are concentrated in different areas of the country. In particular, San Martín County has an important concentration of textile factories. The effluents of these industries are discharged in the waters of Reconquista River and other streams with different degrees of treatment [2, 6]. Figure 5 shows an image of the waters of Medrano stream colored in blue due to the presence of textile dyes.

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Figure 5. Medrano stream colored waters (San Martín, Buenos Aires province).

This contaminated waters discharge in the Rio de la Plata, producing important damages in coastal areas close to the river, increases the cost of water purification, affect the biota and hinder the recreational use of the river.Most of the textile companies are medium or small size and need economical alternatives for waste water treatment.

Nano-modified montmorillonite for water decontamination

Clays, and specially laminated clays as bentonites, are useful materials for water treatment due to its high quality as sorbents and supports for catalysts. Besides, clays are usually cheap and abundant materials widely distributed all around the world.

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Clays are composed by tetrahedral layers of silica and octahedral layers of gibbsite. Figure 6a shows schemes of both structures. The central Si(IV) atoms of the tetrahedral can be replaced by Al(III) or Fe(III) atoms, in a phenomenon named isomorphic substitution. As a consequence, the structure acquires negative charge. In the case of the gibbsite layer the same phenomenon occurs with Al(III), which can be isomorphically substituted by Mg(II) or Fe(II). This layer also has a delocalized negative charge.

The tetrahedral and octahedral layers join one which other through the apical oxygen of the tetrahedral layer with the OH of the octahedral layer. Depending on the quantity and distribution of the different layers clays can be classified in different families as 1:1; 2:1 and 2:1:1. The unit formed by one or two tetrahedral layers with one octahedral layer are called sheets and the clays are called bilaminar (1:1, T:O) or three-laminar (2:1, T:O:T). Between each sheet there is an inter-laminar space with intercalated alkaline (Na, K) or alkaline-earth (Ca, Mg) cations, that compensate the intrinsic negative charge of the sheets. Figure 6b shows the scheme of a three-laminar clay, with the interlaminar space and the cations located in this space. These clays are typically called smectites as, for example, montmorillonite (MMT) [7, 8].

Several laminar clays, as montmorillonite, can exchange the interlaminar cations by others inorganic or organic cations. Thanks to these characteristics, MMT is a versatile material that can be used to produce other simple or sophisticated new materials as sorbents, catalyst, polymers modified, etc. The exchange of the interlaminar cations by others with catalytic activity can produce a catalyst [9-14]. The exchange by organic cations (as quaternary ammoniums) can modify the hydrophilicity of MMT, leading to the production of sorbent for organics (as oil, solvents, etc)[15].

The sorption and catalytic properties of modified MMT can

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Figure 6. a) Scheme showing the structure of the octahedral (Gibbsite) and tetrahedral (Silica) and its arrangement in layers.

Figure 6. b) Scheme of a three-laminar clay (2:1) with the interlaminar space. (Modified from [8]).

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be combined to obtain materials that can work as sorbents and catalysts at the same time or sequentially. This type of materials is very promising for environmental remediation. One example is the use of MMT modified with iron oxide nanoparticles for sorption of a cationic dye, followed by oxidation by photo-Fenton process [16].

Fe(III) can be incorporated as iron oxo-hydroxide nanoparticles (FeOx-NP) by the treatment of a suspension of MMT in acetone with FeCl3, followed by lyophilizing. Figure 7 shows images taken by scanning electron microscopy of pure MMT and Fe(III) modified montmorillonite (MMT-Fe). The images clearly show thin flakes of MMT and the FeOx-NP deposited on the MMT-Fe flakes [17].

Figure 7. SEM images of montmorillonite (MMT) and montmorillonite modified with Fe(III) oxo-hydroxide nanoparticles (MMT-Fe). Reprinted from Guz et al. 2014 [17], with permission from Elsevier.

Fe(III) was also located in the interlayer space as determined by X-Ray diffraction analysis (XRD). Figure 8a shows the XRD pattern of MMT and MMT-Fe. The diffraction peak centered at 2θ = 6.51° correspond to and interspace of 13.6 A between sheets in the MMT, while in the case of MMT-Fe the peak shifted to 5.5 A corresponding to an interspace of 16.5 A. These results indicate that FeOx-NP were also located between the sheets increasing the

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interspace.

The presence of FeOx-NP at the surface of the MMT-Flakes also modified the electrophoretic behavior and the surface charge of montmorillonite. As shown in Figure 8b, the Z potential (estimated by measurements of electrophoretic mobility) became notably less negative as pH decreased in the case of MMT-Fe. This phenomenon was consequence of the higher isoelectric point of iron oxide (close to pH 8.0), that modified the overall behavior of MMT-Fe with respect to MMT. These result indicated that the surface charge of MMT-Fe was notably more positive than MMT at pH lower than 6.

Figure 8. a) XRD pattern of MMT and MMT-Fe; b) Z potential vs pH for MMT and MMT-Fe. Reprinted from Guz et al. 2014 [17], with permission from Elsevier.

Adsorption of crystal violet (CV) on MMT was different than on MMT-Fe, as shown in Figure 9. The adsorption isotherms of CV on MMT or MMT-Fe were fitted in terms of a two sites Langmuir model. As can be seen in Table 3, the maximum amount of CV adsorbed by MMT (Qmax1 + Qmax2) was approximately 500 mgdye/gclay, notably higher than for MMT-Fe: 200 mgdye/gclay.These results were consequence of the change in surface charge and the presence of FeOx-NP in the intersapace.

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The analysis of samples of CV adsorbed at MMT and MMT-Fe by Small Angle X-Ray Scattering (SAXS), allowed the precise

Figure 9. Adsorption isotherms of CV on MMT and MMT-Fe. The lines correspond with the fitting using one site or two sites Langmuir models. Reprinted from Guz et al. 2014 [17], with permission from Elsevier.

determination of the interlaminar distance. As shown in Table 4, the presence of CV notably increased the interlaminar space in bothe MMT and MMT-Fe. In the case of MMT the distance increased from 0.29 to 0.49 nm for a CV initial concentration in water in the range 0–150 ppm; however, for concentration higher than 250 ppm the interlaminar space increased to 0.98 nm. This behavior can

R2 Qmax1 Kd1 Qmax2 Kd2

MMT 0.9519 327± 28 0.01± 0.005 174±26 12±6

MMT-Fe 0.9321 104±13 0.08±0.02 87±13 1.4±0.2

Table 3. adsorption constants obtained after fitting the data with two sites Langmuir Model. Qmax: maximum amount of CV adsorbed on MMT or MMT-Fe (mgdye/gclay). Kd: desorption constant (Guz et al 2014, [17]).

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be consequence of dimer formation by CV. The dimeric moieties entered into the interlaminar space increasing the distance even more than in the case of monomeric CV. Similar phenomenon was observed in the case of MMT-Fe. However, in this case the interlaminar distance decreases at low CV concentration due to the exchange with the FeOx species located in the interlaminar space. This result indicated that the Fe(III) species were mobile and could be involved in ion exchange processes.Recalcitrant organic compounds can be totally or partially oxidized by photo Fenton process. Equations 1-5 illustrates the main reactions that take place during Fenton (1-3) and photo-Fenton process (4-5).

[CV]1 0 ppm <150 ppm >250 ppmMMT 0.29 nm 0.49 nm 0.98 nm

MMT-Fe 0.58 nm 0.45 nm 0.96 nm

Table 4. interlaminar space determined by SAXS.

Fe(II) + H2O2 → Fe(III) + HO* + HO- (1)Fe(III) + H2O2 → Fe(III)-OOH2

+ + H+ (2)Fe(III)-OOH2

+ → Fe(II) + HO2 (3)Fe(III) + H2O → Fe(OH)2

+ + H+ (4)Fe(OH)2

+ + hν → Fe(II) + HO* (5)

Hydrogen peroxide (H2O2) is the the typical oxidant used in Fenton and photo Fenton process. Fe(II) catalyze H2O2 decomposition in HO* radicals, which are powerful and no specific oxidants. In the dark the reduction of Fe(III) by H2O2 to regenerate Fe(II) is quite slow and controls the rate of the process. In the presence of light (λ < 400 nm) the product of Fe(III) hydrolysis (reaction (4)) generates Fe(II) and the overall reaction speed up. The optimal pH

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for these reactions is 3.0. Lower pHs decreases reaction rate and at higher pH Fe(III) precipitates.

In the case of MMT-Fe, the FeOx-NP can act as catalyst for Fenton and photo-Fenton process. Figure 10 shows the degradation of CV adsorbed on MMT or MMT-Fe exposed to photo-Fenton treatment CV was completely adsorbed on MMT or MMT-Fe before the oxidation treatment was applied. In the case of MMT without added iron, some activity was observed, due to the catalytic action of the iron naturally present in the clay. After incorporation of Fe(III) or Fe(II) to the system with CV adsorbed on MMT, degradation rate was notably improved. However, the best result was obtained with MMT-Fe. These results indicate that Fe(III) present as FeOx-NP at the surface and inside MMT-Fe acted as an effective catalyst for photo-Fenton process.Figure 11 shows the evolution of total organic carbon in solution

Figure 10. Temporal evolution of CV adsorbed on MMT or MMT-Fe during photo-Fenton treatment. [H2O2] = 50 mM, pH 3, [Fe(II)] y [Fe(III)] = 0.5 mM, MMT y Fe-MMT 3 g/L, [CV] = 0.120 mM, T = 25°C, luz visible: 100 W/m2. Guz L., et al., 2014, [17] with permission from Elsevier.

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(TOC) during photo-Fenton process. At the beginning of the treatment TOC increased due to the release of organic matter to the solution. This phenomenon is consequence of the partial oxidation of the CV adsorbed at the clay, followed by the release of the byproducts to the solution. The organics were further mineralized as the treatment advanced.The results presented above clearly show the feasibility to use

Figure 11. TOC evolution during photo-Fenton treatment. Similar conditions than in Figure 10. Guz L., et al., 2014; [17] with permission from Elsevier.

advanced oxidation, in particular photo-Fenton process, for the destruction of contaminants adsorbed at clays. In this way, the contaminants are not only removed from solution but completely eliminated, avoiding the complex problem of final disposition of dangerous pollutants.

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Bio-modified montmorillonite for water decontaminationMMT is a good adsorbent for positive metal cations thanks to its intrinsic negative charge [18]. Metals cations can replace the cations naturally located in the interlaminar space (typically Na+, Ca2+, etc), but can also be strongly adsorbed at the surface [19-21]. The equilibration is typically reached after few minutes of contact, being this process potentially useful for the treatment of waste waters containing metals (effluents from metallurgy, galvanoplastic companies, etc) [21].

Microbial biomass is also a very useful adsorbent for metals in water. Biomass is intrinsically negative due to the composition of the cellular membranes, which is rich in carboxylic functional groups. Researchers all around the world had demonstrate de feasibility of microbial biomass adsorbents in wastewater treatment [22]. In particular fungi are very interesting because they can growth fast on different surfaces at low cost [23, 24].

This two families of adsorbents have the advantages of being low cost materials with a relatively high adsorption capacity for metals. However, to increase its efficiency, they are used suspended in the wastewater to be treated. The principal drawback is the separation from the liquid phase, this process can be time consuming and expensive, particularly for clays [25]. It was recently demonstrated that the combination of clays with microbial biomass produces biopolymers with better coagulation properties and improved adsorption abilities for metals in water [23]. This is an example of the composition of two materials with synergically improved properties.

Uranium, in the form of highly soluble U(VI), is a dangerous contaminant present in wastewaters produced during preparation

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of nuclear fuels [26, 27]. It was recently demonstrated the feasibility to use adsorption on biopolymers prepared by combination of MMT with fungi as a way to remove U(VI) from water [23]. Biopolymers (BMMT) were prepared by growing biomass in the presence of MMT. Two uranium resistant fungi genus were used: Aphanocladium sp. (Apha sp.) and Acremonium sp. (Acre sp.). Figure 12 shows SEM images of Acre sp. alone, where the typical fibrous structure can be observed, and MMT with 1% of biomass (BMMT), where it can be noted that fungi growth intimately bound to the MMT flakes. Table 5 shows the biomass content of the different BMMT, and the H+ consumption capacity of MMT, Acre sp., Apha sp., and the different BMMT. The increment of the proton consumption capacity of BMMTs, with respect to that of MMT and biomass alone, demonstrates that clay biopolymers have an advantageous structure for chemisorption processes.

Figure 12. SEM images of Acre sp. (left) and BMMT (Acre sp.) composite (right).

Figure 13 shows adsorption isotherms of U(VI) on different adsorbents. As can be seen in the figure, the adsorption curves correlate with a sigmoidal model. This behavior is consequence of the heterogeneity of sites where the adsorbate can bind on the BMMT. Clays have interlayer spaces and external sites, and

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SampleBiomass content

(mg/g MMT)

mmol H+/g

(mmol H+BMMT–

mmol H+MMT)/g biomass

MMT 0.6Acre sp. 1.2 1.2Apha sp. 1.2 1.2BMMT 1% Acre sp. 237 1.2 2.5BMMT 5% Acre sp. 57 0.9 5.2BMMT 1% Apha sp. 257 1.3 2.7BMMT 5% Apha sp. 73 0.95 4.7

Table 5. MMT and BMMT biomass content and H+ exchange capacity (Olivelli et. al., 2013, [23]).

biomass surface functional groups could provide a larger quantity of metal binding sites and greater affinity to the system [23]. The results presented in Figure 13 clearly show that the composite biomaterials displayed improved adsorption capacity for U(VI).

Figure 13. UO22+ adsorbed on BMMT and respective controls. A:

BMMT=MMT+Apha; B: MMT+Acre sp. BMMT in 1% w/v. Reprinted from Olivelli et. al., 2013 [23], with permission from Elsevier

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Bio-remediation of SedimentsThe sediments of the rivers heavily polluted with organic matter are expose to anoxic conditions, as was exemplified above with the cases of Reconquista River and JLS channel. Under these low redox potential conditions, most of heavy metals might precipitate as poorly soluble sulfides and hydroxides or are adsorbed to the different mineral components of the sediment matrix. The anoxic environment maintains metals in a low bioavailable state as long as low redox potential conditions are not altered. However, reduced compounds of sediments such as sulfides tend to oxidize due to redox processes biocatalyzed by sulfur oxidizing bacteria (SOB) when changes in the redox conditions occur [28-30]. This could be caused by exposition to oxygen, either by dredging operations or by drying effects (condition caused by a decrease in the water level). This phenomenon could impact directly on the environment because of the sediment acidification and the heavy metal release into the water column while their bioavailability seems to be incremented [31-36]. These processes have been intensively studied through static assays [37] and dynamic experiments of anaerobic sediments oxidation systems by re-suspension or desiccation [29, 33, 34, 36, 38-40]. The removal of heavy metals from contaminated sediment needs to be a priority as regards safer sediment managing because the risk of metal releasing into ground or surface water (and consequently the incorporation of heavy metal into the food chain).

The oxidation/acidification processes described above have, under controlled conditions, the potentiality of recovering valuable metals from polluted sediments [40, 41, 42]. This set of processes is called bioleaching and was studied as a tool for the remediation of heavy polluted sediments in both agitated batch and in bioheaps systems. The reactions involved in the bioleaching processes could be developed by different mechanisms: acidic

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(interchange reactions or dissolution of acid soluble phases such as carbonates), oxidizing (metals bounded to organic matter or sulphides) or reducing (metals bounded to Fe(III) and Mn(IV) oxides). Most of these mechanisms are based on the biocatalyzed oxidation of the different phases of the sulphur content of the sediment. In these processes, the products (Fe(III), sulfuric acid and polithionates) of acidophilic bacteria metabolism (Acidithio bacillus ferrooxidans and Acidi thiobacillus. thiooxidans) act as reaction agents [28, 43]. The specific mechanisms of sulfide and sulfur oxidation by these species have been extensively studied [44-47]. Beolchini et al. (2015) [48] reviewed the main contributions to the study of bioleaching of sediments and concluded that sediment bioremediation technologies have very site-specific effects. The particular characteristics of each sediment are strongly determinants of the kinetics and efficiency of metal extraction by bioleaching [49-52].

Bioleaching assays were performed on sediments from JLS channel (see Table 1) using stirred batch and bioheaps systems. Experiments in stirred batch were realized using 5, 10 and 15 % (w/v) pulp density (PD) suspended in 0K medium, inoculated with Acidithiobacillus thiooxidans and Acidithiobacillus thiooxidans DSM11478 in a concentration of 1.2×107 cell ml-1, with or without 5% added sulfur. Figure 14 a, shows the percentage of zinc extracted from the sediments and Figure 14 b the evolution of pH. Clearly, PD and sulfur addition have a key rol in zinc extraction and pH evolution, been pH and %Zn extracted intimately related. All systems without added sulfur showed a drop of 1.5 pH unit and an increment of the oxidant-reduction potential (ORP) close to 300 mV in the same time period. Sulfate concentration in these systems (data not shown) rose close to 800 mg L-1 in all conditions, suggesting that acidification is partially due to sulfides oxidation. In these cases, samples with 5% PD showed a final extraction of 40% of total Zn while those with 10 and 15% PD

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showed an extraction of only 20% of total Zn. After the 28th day there was a notable increment in the percentage of extracted zinc. This phenomenon was associated with the drop of pH to values close to 5, that helped to solubilize zinc, being responsible for the increment in zinc extraction.

Figure 14. Bioleaching assay in batch mode with 5, 10 and 15% suspended sediment in 0K medium. (a): Percentage of Zn extracted; (b) reached pH values in systems with and without sulfur added. PD: pulp density, S: sulfur. Reprinted from [53] with permission from ACS.

In systems with added sulfur, a clear relationship between the extracted zinc and pH drop was observed. In systems with the lower sediment pulp density (5%), acidification produced by sulfur biocatalyzed oxidation was faster due to the poorer amount of neutralizing compounds provided by the sediment and because diffusional limitation was not important. These systems came close to a final extraction of 60-80% of initial zinc and reached pH values between 2 and 4. Systems with 10 and 15% PD showed an increment of ORP rise rate, zinc extraction rate and a pH drop at the 28th day.

These results suggest the potentiality of the bioleaching process to extract metals from contaminated sediments amended with elemental sulfur in order to ensure a drop of pH value enough to

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allow metals stabilize in solution. The pulp density and the ratio of added sulfur determine acidification kinetics and the final pH.Given the huge volumes of sediment to be treated, performing a leaching process in stirred batch system could be economically not feasible. An alternative is the application of, bioheap leaching systems.

The bioleaching heap system was compiled into Polyethylene terephthalate (PET) reactors of 12 cm high and 6 cm diameter. A first conditioning step was achieved to improve drainage and aeration. Conditioning was achieved using 5% w/w perlite addition to the sludge. Then elemental sulfur was added (1%, 2% 5% w/w) in the mixture in order to increment the electron source for sulfur oxidizing bacteria. One of the systems was just dusted superficially with 5%w/w sulfur. 100 g (dry weight) of conditioned sediment was used in each system, the bulk density was 280 g l-1. All the systems were inoculated with a mixture of Acidithiobacillus ferrooxidans (DSM 11477) and Acidithiobacillus thiooxidans (DSM 11478) previously suspended in 0K medium. A two stages irrigation methodology was performed; the aim of the first stage or acidification step was promoting the acidification generated by the oxidation of sulfides and elemental sulfur, while in the second step (or washing step) the aim was to drag all the soluble metal that have been released into the microenvironment. In the acidification step all the systems were irrigated with 50 ml of distilled water each 72-h. Before being recycled as irrigation water, leached water was collected and completed with distilled water until 50 ml. Aliquots of irrigation water were taken periodically to monitor pH, Zn and Cu content. Next, in the washing step, systems were washed 500 ml of distilled water.

Figure 15 shows the percentages of copper and zinc extraction, and the final pH reached in different bioheaps. The final pH attained in systems without or with 1% added sulfur remained close to neutral,

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whereas in systems with 2%, 5% sulfur and 5% surface sulfur the final pHs were 4.4, 2.9 and 2.3, respectively. The percentage values of zinc and copper extracted showed great differences between each system and can be associated with the final pH. In systems without and with 1% added sulfur, no net leaching was observed. This phenomenon could be attributed to the pH conditions which were close to neutrality during all the assay. In the others systems a significant leaching of zinc was observed, reaching 71% of efficiency in the case of the system with superficial scattered sulfur and between 36-53% for systems with 5% mixed sulfur. Meanwhile, only for both systems with 5%, a significant leaching of copper was detected. In general, system with 5% surface scattered sulfur showed higher extraction than system with 5% mixed sulfur. The best oxygen availability to perform sulfur oxidation in this system seems to be the main cause of these differences.

Figure 15. Total percentages of copper and zinc of the bioheaps leached out, and final pH of the solutions for each system studied: No sulfur added, 1%, 2%, 5% of sulfur and 5% of superficial sulfur. S: sulphur.


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Conclusions

The fate of pollutants in water strongly depends on the physicochemical and microbiological characteristics of the water course. In the studied case, heavy metals concentrate in the sediments while organics are partially degraded by microbiological activity. The anoxic condition of the sediments leads to the production of stable sulfides, carbonates or reduced metal oxides. The concentration of metals in the more polluted areas is over the acceptable limits. Combination of clays with oxide nanoparticles or biomass produce suitable adsorbents for dyes, metals, etc. The combination of the catalytic properties of iron oxide nanoparticles with the adsorption capacity of clays, produced a material that can be used to separate contaminants from water and to catalytically oxidize the adsorbed pollutant (by photo-Fenton process). Bio-clays display superior adsorption capacity than the separated precursor materials, being useful for the separation of dangerous soluble metal species as U(VI).

Bioleaching processes assisted by acid resistant bacteria is an alternative for the remediation of sediments heavily polluted with metals. This approach allows a controlled release of the metals that, potentially, can be recovered by appropriate chemical treatment.Environmental pollution is a drama that affect all the humanity but hit harder on undeveloped countries. In this chapter we presented different approaches that can be used to mitigate the problem. But the awareness of the people, leaders and authorities, about the environmental and social risk that is facing the Earth is strictly necessary for the well-being of the future generations.

AcknowledgmentsThe Authors gratefully recognize the support given by Universidad

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Nacional de San Martín, Ministerio de Ciencia y Tecnología, Consejo Nacional de Investigaciones Científicas y Técnicas, and Agencia Nacional de Promoción de Ciencia y Tecnología. RJC and GAC are researchers of CONICET.

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[48] Beolchini, F.; Rocchetti, L.; Fonti, V.; Dell’ Anno, A. Consequences of anaerobic biotreatments of contaminated sediments on metal mobility. International Journal of Environmental Science and Technology. 2015, 12 (7), 2143-2152.

[49] Calmano, W.; Hong, J.; Förstner, U. Binding and mobilisation of heavy metals in contaminated sediments affected by pH and redox potential. Water SciTechnol. 1993, 28, 223–35.

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Biotechnological synthesis of silver nanoparticles using phytopathogenic fungi from cocoa

Raquel Villamizar

The objective of this research was to explore the ability of native fungi isolated from cocoa crops, to biosynthesize nanoparticles. Once standardized, the nanoparticles were

characterized such as UV-Vis spectrophotometry and scanning electron microscopy. The microbicidal effect on pathogens of clinical and agro-food interest was also evaluated. As a result it was concluded that living organisms and/or their metabolic products, can be an alternative for clean nanomaterials production with excellent antimicrobial properties.

Universidad de Pamplona, Facultad de Ciencias Básicas, Departamento de Microbiología. Grupo de Investigación en Nanotecnología y Gestión Sostenible (NANOSOST).Km. 1 Vía Bucaramanga, Pamplona Norte de Santander-Colombia.e-mail: [email protected]


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Introduction

According to the inventory of the Project on Emerging Nanotechnologies, silver nanoparticles (AgNP), are located at the bottom of the products generated through this technology . AgNP, have received special attention because of its low volatility, high stability, long and broad antimicrobial activity [1]. At nanoscale dimension, silver presents a considerable number of applications due to their size, shape, aggregation and coupling with different molecular receptors. This characteristic facilitates using them as microbicidal agents able to release silver cations into different types of cell [2] (Figure 1). Actually, AgNP are a promising alternative to fight pathogenic organisms, which have acquired resistance to antibiotics [3] or to eliminate pathogens in different matrices [4].

Figure 1. Silver nanoparticle effect against a bacteria cell.

The main methods used to synthetize silver nanoparticles are based on physical or chemical processes, which generate waste, that in some cases are highly polluting. Therefore, there exists a need for researching about more environmental friendly methods.

In the last 10 years, scientific and technological advances in

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Nanoscience and Nanotechnology in Colombia, have permeated many higher education institutions, including the Universidad de Pamplona, Colombia. The national trend, led by the Network of Nanotechnology is to solve problems with social impacts based on the introduction of inexpensive nanoprocesses and nanomaterials [5].

The research group Nanotechnology and Sustainable Management (NANOSOST) at the Universidad de Pamplona, Norte de Santander, has focused part of their studies on the biotechnological synthesis of silver nanoparticles. The use of living organisms and /or their metabolic products seems to be a clean production strategy of high performance [6].

Filamentous fungi, are eukaryotic, with ubiquitous distribution, easy handling and nutritionally undemanding. They have the ability to become a microfactory of nanoparticles with low cost, high production efficiency and low toxicity [7]. These microorganisms secrete large amounts of bioreactives substances [8] and produce enzymes [9], which can be used as reducing agents in the biological production of AgNP. This biosynthetic capacity is mainly due to their high growth rate and high adaptability to the substrate [10].

Biotechnological synthesis of AgNP mediated by fungi can occur in two ways, “intra- or extracellularly.” In both cases, the reaction occurs thanks to the presence of substances, typically proteinaceous with catalytic activity. This reaction is produced as a defense mechanisms of the microorganisms when they are faced to metal ions, giving as a product small nanoparticles [11].

Filamentous fungi capable of synthesizing nanoparticles have shown the formation of AgNP on the mycelium (intracellular synthesis, Figure 3 A-B). However, the use of this route requires additional processes of cell disruption to separate the

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Figure 2. Methods used in the synthesis of Silver Nanoparticles. Advantages and disadvantages.

nanoparticles from other cellular components, thus increasing process complexity. On the contrary, extracellular synthesis allows the obtention of nanoparticles from aqueous solutions derived from the fungal biomass. A total substrate reduction without waste generation and therefore a 100% efficiency is achieved. Furthermore, colloidal solutions exhibit good dispersion with sizes ranging from 5 to 50 nm [12] (Figure 3C-3D).

Production in the laboratory

Aspergillus flavus is a fungi able to grow and contaminate foods, especially cereals [13]. However, this fungus has also been studied for their ability to biosynthesize silver nanoparticles [9]. Therefore, in this research, A. flavus common pathogenic fungi found in cocoa crops was used to biosynthesize AgNPs. The process contemplated six steps, from obtaining cocoa samples to the characterization of the nanoparticles.

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Figure 3. Biosynthetic routes of AgNP using fungi. A) Fungi biosynthetic capacity B) Mycelial after cell disruption C) Fungi growth on culture media D) Silver Nanoparticles Solution obtained by enzymatic action of fungi.

Sample collection

The pods were sampled in cocoa farms from the Department Norte de Santander. Diseased pods exhibiting symptoms such as deformations, black stains, presence of yellow halos and cream colour powder. The pods in question were packed in plastic paper, labelled and transported in boxes to the laboratory for their processing.

Fungal Isolates

Aspergillus flavus was obtained from ill cocoa pods exhibiting

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Figure 4. Sample collection and in vitro fungi isolating A) Cocoa pod ill B) Isolating process C) Plate on culture media.

the symptoms previously mentionated. By using a mycological ase, spores containing in the upper pod cortex was directly plated on PDA. Media were incubated at 25 °C/5 days. Pure culture was carried out from the heterogeneous growth until obtaining axenic cultures, which were morphologically and molecularly characterized. Figure 4 shows the A. flavus isolating process from ill cocoa pods.

Morphological Characterization

Morphological characterization was performed taking into account aspects such as texture, edge, and mycelium color. Reproductive structure (spores), type of hyphae were observed by coloring them with lactophenol blue. The photographic record was obtained in a Nikon Eclipse 80i phase contrast optical microscope (100 X magnification).

Molecular Characterization

DNA was isolated by using the ultraclean microbial DNA

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Primers β-tub Bt-Lev GTC AAC TCC ATC TCG TCC ATABT-T 2M CAA CTG GGC TAA GGG TCATT

Primers IT S PN3 CCG TTG GTG AAC CAG CGG AGG GAT C

PN16 TCC CTT TCA ACA ATT TCA CG

Table 1. Primer genes β-tubulin and ITS region employed for the characterization of biocontrol fungi isolated from soil cocoa crops.

isolation kit (Mo Bio Laboratories) and prepared according to their specifications. The molecular characterization of the isolated DNA was carried out by employing two molecular markers corresponding to ITS region and the gene β-tubulin. These primers are presented in Table 1. The DNA thus amplified was sequenced by MacroGen and analyzed through the BLAST database.

Biosynthesis of AgNPs by using A. flavus

A. flavus was grown in 250 mL flasks containing malt broth (Oxoid) and prepared according to the specifications. The flasks were incubated in Bioshaker Plus (Molecular Technologies) at 200 rpm/25 °C in darkness. The biomass obtained was collected after 5 days (Figure 5). Subsequently, several washes were applied in order to remove residues of culture medium [9]. Then, the biomass was placed in a flask containing 100 mL of sterile distilled water to create nutritional stress to the fungus and thus obtain secondary metabolites (enzymes/reduction agents) [14]. Fungal solution obtained was filtered with Whatman No. 1 and exposed to a solution of silver nitrate (AgNO3) (Sigma-Aldrich) 1mM pH 6.5 in relation V: V, which was maintained at 25 ° C under constant stirring and darkness until change in colour (Adapted from [15]).

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Figure 5. Fungal Biomass Production in a Batch Bioreactor.

Evaluation of the microbial effect of AgNPs

In culture media

Petri dishes (60 x 15 mm) were prepared with trypticase soy agar (TSA) for bacteria and potato dextrose agar (PDA) for fungi. Each dish was plated with a different type of microorganisms. Escherichia coli were one of the tested strains. This bacterium is commonly associated with outbreaks of gastroenteritis in children [16]. Staphylococcus aureus, was also analyzed. This pathogen is frequently related with outbreaks of toxic infection through food consumption, especially contaminated grain. Finally, the fungus Candida albicans responsible for infections in the genito-urinary women tract [17] was studied. All strains were provided by the type culture center of the Universidad de Pamplona, Colombia.

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The experimental assay consists on determining the inhibition capability of the AgNP on the tested pathogens. For that purpose, a sensidisc was placed on the center of the petri disc and a colloidal solution of the nanoparticles was added. Growth inhibition around the sensidisc was followed during 24 to 96 hours incubating at 37 ° C and 25 ° C, for bacteria and fungi, respectively. Petri dish without AgNP and inoculated with the pathogens was employed as positive control adapted from [18]. All Assays were repeated twice.

Fruit in package

Raw and disinfected tomato and ground-cherry were placed inside polypropylene packaging modified with silver nanoparticles. After that, vacuum to 95% was applied (packing Brand Citalsa) and subsequently fruits were store at room temperature and cooling, with relative humidity of 45% and 55%, respectively. After three days, microbiological analysis of E. coli, aerobic mesophilic bacteria, molds and yeasts were performed [19]. Fruits without cleaning process were used as control.

Results and discussion

Aspergillus was successfully isolated from diseased pods. Macroscopically, it presented a granular and olive green growth. Microscopically, conidiophores, vesicles, matulas, phialides and typical conidia of this fungal species were observed (Figure 6). Molecular characterization allowed confirming the specie A. flavus (RID 7NOVJZ7R01R-NCBI).

The fungus grew favourably in batch culture and enzyme content was obtained. It was exposed to a solution of AgNO3 (0.01 M) and color change was observed after just 24 hours. Figure 7 shows the obtained nanoparticle colloidal solutions.

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Figure 6. Macro and Microscopic Characteristics of A. flavus.

Figure 7. Colloidal Silver Nanoparticles Solution A) enzyme solution obtained from the fungus B). Colloidal solution indicator biosynthesis Silver Nanoparticles.

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The colorimetric result of AgNPs was checked by using UV-Vis (Spectrophotometer Shimadzu) UV-2600 with a sweep from 200 to 900 nm in a time range of 24 to 48. As negative control absorbance 0.001m AgNO3 solution was measured. The UV-Vis allows knowing the plasmon resonance profile as a product of the collective excitation of surface electron cloud present in the nanoparticles. Noble metals like silver have a plasmon resonance in the range of the visible spectrum, resulting in colloidal dispersions of nanoparticles with a range of bright colours [5]. According to several studies, the formation of AgNP can be evidenced by the formation absorbance peak located in a range between 378nm and 420nm. Values tend to increase over time due to aggregation process. Figure 8 shows the characteristic peak obtained at 420 nm, indicating the formation of AgNP using as reducing agent the metabolic products of A. flavus.

Figure 8. UV-Vis spectrum of AgNP biotechnologically synthesized using A. flavus.

The exact mechanism of formation of nanoparticles with fungi is still under study. It is believed, that substrate (usually 1 mM AgNO3) is reduced by enzymatic action of NADH dependent reductases. In addition, proteins and polysaccharides produced

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Figure 9. SEM image of silver nanoparticles.

by fungi would be responsible of the nanoparticles stabilization.

Scanning electron microscopy (Zeiss-EVOHD15) was used to determine size and shape of the biosynthesized nanoparticles. Silver nanoparticles presented spherical shapes, with sizes ranging from 10 nm to 80 nm (figure 9).

The colloidal solution of nanoparticles was dispersed in water for 2 months in the dark (Adapted from [15]). Through this time, it was observed slights changes in colour and the formation of small aggregates. This can be explain by the principle that in a colloidal suspension, van der Waals interactions are presented causing aggregation. As a result, big clusters can appear interfering in the attachment to the cell membrane and therefore reducing the microbicidal activity.

In order to obtain stable solutions, there should be electrical charges on the surface of the particles creating electrostatic repulsion and thus particles remains stable [5]. In the case of our nanoparticles, they present on their surface protein groups of fungal origin, giving stability mainly due to steric interactions.

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Figure 10. Schematic representation of the reduced microbicidal effect of AgNP when cluster formation occurs.

In addition, physical processes like sonication by using ultra sonicates (EImasonic S 15H) were also applied before use.

Figure 11. Inhibitory effect of AgNP on the macroscopic growth of A) C. albicans B) E. coli C) S. aureus. Reproduced with permission from [19].

The inhibitory effect of AgNP on the studied pathogens was confirmed in the petri dish experiments. The results showed that nanoparticles had had a stronger inhibitory effect on C. albicans (30,21 mm) and E. coli (28,42 mm) than S. aureus (20,78 mm) (Figure 11). This phenomenon may be to differences in cell wall composition.

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Once it was proved that AgNP displayed microbicidal effect on bacteria and fungi, assays were performed directly on package used for storage minimally processed fruit. It was observed a significant reduction in counts of aerobic mesophilic bacteria (AM), total coliforms (TC), fecal coliforms (CF), molds and yeasts (M and L) as a result of the use of silver nanoparticles. It can be observed in Figure 12 that nanoparticles cause a reduction from 2 to 4 log units growth in fruits cleaned and disinfected. The most significant effect of inhibiting (4 Log) was observed in fruits disinfected, stored at refrigeration temperatures and modified with AgNP, in contrast with those stored in unmodified packaging without disinfecting.

Figure 12. Inhibition effect of AgNP on storage minimally processed fruits. Reproduced with permission from [19].

Conclusions

The ability of the pathogenic fungus Aspergillus flavus isolated from cocoa crops to biosynthesize silver nanoparticles was shown. The method of biotechnological synthesis allowed obtaining high amount of nanoparticles in short time with excellent phenomenological (size, distribution, stability) and microbicidal properties. These aspects allow us to expect the wide range of

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References[1] Bharathidasan, R.; Panneerselvam A. Biosynthesis and characterization of silver nanoparticles using endophytic fungi Aspergillus concius, Penicillium janthinellum and Phomosis sp. International Journal of Pharmaceutical, Sciences and Research. 2012, 3, 3163-3169.

[2] Valencia, P.; Pridgen, E.; Minsoun, M.; Langer, R.; Farokhzad, O.; Karnik, R. Microfluidic Platform for Combinatorial Synthesis and Optimization of Targeted Nanoparticles for Cancer Therapy. ACS Nano. 2013, 7(12), 10671–10680.

[3] Bindhu, M.R.; Umadevi, M. Antibacterial and catalytic activities of green synthesized silver nanoparticles. Spectrochimica Act Part A: Molecular and Biomolecular Spectroscopy. 2015, 135-274.

[4] Villamizar, R. Nanotecnología al servicio de la conservación arquitectónica, Estrategias basadas en nanotecnología para reducir el crecimiento de hongos en ambientes abitados. Revista nano Ciencia y Tecnología. 2013, 1(1), 8-12.

[5] González, E.; Puntes, V.; Casals E. NANOMATERIALES. Nanopartículas Coloidales. Nanocitec. 2015. Pag. 306. ISBN 978-958-46-6931-5.

[6] www.unipamplona.edu.co/nanosost

[7] Sunkar, S.; Nachiyar, C. Endophytic Fungi Mediated Extracellular Silver Nanoparticles as Effective Antibacterial Agents. International Journal of Pharmacy and Pharmaceutical Sciences. 2013, 3, 99-100.

[8] Li, G.; He, D.; Qian, Y.; Guan, B.; Gao, S.; Cui, Y.; Yokoyama, K.; Li, W. Fungus- Mediated Green Synthesis of Silver Nanoparticles Using Aspergillus terreus. International Journal Meolecular Sciences. 2012, 13, 466-476.

[9] Moharrer, S.; Mohammadi, B.; Azizi, R.; Yargoli, M. Biological synthesis of silver nanoparticles by Aspergillus flavus, isolated from soil af Ahar cooper mine. Indian Journal of Science and Technology. 2012, 5, 2443-2444

[10] Honary, S.; Barabadi, H.; Gharaei-Fathabad, E.; Naghibi, F. Green Synthesis

applications of these nanomaterials, including the biocontrol of pathogenic microorganisms in different matrices. However, further investigation is required, especially regarding to potential cytotoxic effects previous scaling.

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of Silver Nanoparticles Induced by the Fungus Penicillium citrinum. Tropical Journal of Pharmaceutical Research. 2013, 12(1), 7-11.

[11] Ahmad, S.R.; Minaeian, S.; Shahverdi H. R.; Jamalifar H.; Nohi A. A. Rapid synthesis of silver nanoparticles using cultura supernatants of Enterobacteria: A novel biological approach. Process Biochemestry. 2007, 42, 919-923.

[12] Bhainsa, S.D. Extracellular biosynthesis of silver nanoparticles using the fungus Aspergillus fumigatus. Colloid and Surfaces. 2006, 47: 160-164.

[13] Villamizar, R.; Maroto, A.; Rius F. Rapid detection of Aspergillus flavus in rice using biofunctionalized carbon nanotubes field effect transistors. Analytical and Bioanalytical Chemistry. 2010, 399:119-126.

[14] Meareg, G.; Amare, P. Molecular mechanisms of Aspergillus flavus secondary metabolism and development. Fungal Genetics and Biology. 2014, 66, 11-18.

[15] Vigneshwaran, N.; Ashtaputre, N.M.; Varadarajan, P.V.; Nachane, R.P.; Paralikar, K.M.; Balasubramanya, R.H. Biological synthesis of silver nanoparticles using the fungus Aspergillus flavus. Materials Letters. 2007, 61, 1413–1418.

[16] Foster, M. A.; Iqbal, J.; Zhang, C.; McHenry, R.; Cleveland, B.; Herazo, Y.; Fonnesbeck, H.; Payne, D.; Chappell, J.; Halasa, N.; Gómez-Duarte, O. Enteropathogenic and enteroaggregative E. coli in stools of children with acute gastroenteritis in Davidson County, Tennessee. Diagnostic Microbiology and Infectious Disease. 2015, 83, 319-324.

[17] Villamizar, R.; Maroto, A.; Rius, FX. Improved detection of Candida albicans with carbon nanotube field-effect transistors. Biosensors and Bioelectronics. 2009, 136, 451-457.

[18] Nasrollahi, A.; Pourshamsian, Kh.; Mansourkiaee, P. Antifungal activity of silver nanoparticles on some of fungi. International Journal of Nano Dimension. 2011, 1, 233-239.

[19] Villamizar, R.; Monroy, L. Using silver nanoparticles for control pathogenic microorganisms in foods. Alimentech. 2015, 13, 54-59.

Ecotoxicology

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Ecotoxicology in nanotechnologiesAndrea Luna-Acosta

SSeveral chemical compounds are used in human activities such as nanotechnologies, and are released every day in the environment. This chapter will provide an overview of

sublethal and lethal effects that may have this type of compounds on living organisms and humans. It will also be devoted to ERA (Environmental Risk Assessment) and ERM (Environmental Risk Management) processes, which have been developed by environmental agencies, industries and governments in order to detect, reduce and avoid adverse effects of pollutants on ecosystems and their components. This chapter will also show how ecotoxicological tools (biomarkers, bioindicators, bioassays, biomonitoring) are very useful and necessary in this context, with some examples and case studies. There are two ways of reading this chapter. The “rapid way” consists on easily obtaining key information and methodologies of ecotoxicology for nanotechnologies, by reading only the text boxes, figures and tables. The “long way” consists on going deeper on the understanding of the concepts related with ecotoxicological research, by reading the whole chapter.

Department of Ecology and Territory, Faculty of Environmental and Rural Studies (FEAR), Pontificia Universidad Javeriana, Transv. 4 No. 42-00, Bogota, Colombia.e-mail: [email protected]


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Eco….what? Let´s start with some definitions This section will cover definitions of the main terms that will be used in this chapter, starting with a definition for the term “ecotoxicology”. Ecotoxicology was first defined by the French toxicologist René Truhaut, in 1977 [1]. It combines two different disciplines: ecology (“the scientific study of interactions that determine the distribution and abundance of organisms”; [2]) and toxicology (“the study of injurious effects of substances on living organisms”, usually humans; [3]). Ecotoxicology aspires to assess the impact of chemicals on individuals, populations and ecosystems.

It was after World War II (1939-1945) that increasing concern about the impact of toxic chemicals on the environment led toxicology to expand from studies on humans to studies on the environment. It was based on the assumption that if humans can be affected by chemical compounds (as it has been confirmed by multiple case studies), therefore animals, plants and their habitats may also be affected. In this context, the fate of pollutants in the environment is also studied in this field (Figure 1). The fate corresponds to the transport, transformation and breakdown of pollutants in the environment and within the organisms. Therefore, ecotoxicology can be defined as “the study of the harmful effects of chemicals upon ecosystems” [4].

Both terms, contaminants or pollutants, are used for chemicals that are found at levels judged to be above those that would normally be expected. However, pollutant carries the connotation of the potential to cause harm, whereas contaminant is not harmful. Nevertheless, a contaminant can become harmful and therefore, become a pollutant, if noxious effects are observed [4]. Thus, it is preferable to use the term contaminant rather than pollutant, if noxious effects have not yet been observed. The term xenobiotic

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Figure 1. Main goals and objectives of ecotoxicology.

is less commonly used since it has a more general sense, and corresponds to any foreign substance found within a living being [4]. More recently, the term emerging contaminant has been used for chemicals that are not commonly monitored in the environment but have the potential to enter the environment and cause known or suspected adverse effects, e.g. UV filters, pharmaceuticals, etc.

Chemical compounds can be degraded by biological or chemical processes in the environment, but when degradation does not occur, they tend to accumulate, especially in sediments [5]. Factors in the environment, such as temperature, water, salinity, pH, or oxygen concentration, will determine the chemical form of chemical compounds in the environment. These factors will also determine the bioavailability of chemical compounds, which means the actual amount of substance that could exert an effect on the living organism, according to the amount that the

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organism has adsorbed or absorbed. Adsorbed means that the chemical enters the organism dissolved in a liquid or solid, and absorbed that it crosses an external surface to enter the organism. In aquatic ecosystems, chemical compounds can be present in water, sediments or food, and enter in that way into living organisms [6]. Inside the living organism, these compounds can be bioaccumulated (bioconcentrated or bioamplified).

Bioaccumulation means an increase in the concentration of a chemical in a biological organism over time, compared to the chemical’s concentration in the environment. Bioaccumulation occurs because the chemical compound accumulates in the living being and is taken up and stored faster than it is broken down (metabolized) or excreted. Bioconcentration means bioaccumulation of a chemical in a living being when the source of chemical is solely water. Bioamplification corresponds to the increasing concentration of a chemical in the living being at successively higher levels in a food chain [6]. Hydrosoluble compounds (soluble in water) are generally less accumulated in living organisms than liposoluble compounds (soluble in lipids). However, if hydrosoluble compounds, such as many pesticides, are continuously and massively used by humans, living organisms will be constantly exposed to this type of compounds, and a constant exposure to these compounds will potentially cause chronic effects. Lipophilic compounds, such as PAHs (polycyclic aromatic hydrocarbons), PCBs (polychlorobiphenyls), PBDEs (polybromodiphenylethers) and OCPs (organochlorine pesticides), tend to accumulate more easily in living organisms. Biodisponibility and bioaccumulation of contaminants can be correlated to the appearance of noxious effects in the living being, and therefore, bioaccumulation of lipid compounds may cause major noxious effects on main physiological systems such as the endocrine, reproductive, nervous and immune systems, and may cause major ecological impacts [7]. However, it is important to

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keep in mind that a contaminant at very high concentrations in the environment can be harmless while another contaminant at very low concentrations can be very noxious or even lethal. This can be evaluated, for example, by determining the LD50 of the compound. LD50 (abbreviation of lethal dose and 50%) is the dose of substance that is lethal for half (50%) of the animals tested. In general, the smaller the LD50 value, the more toxic the chemical is. It is expressed in milligram (mg) of toxic substance per kilogram (kg) of weight of animal, or parts per million (ppm), and it is recommended to indicate the animal that was tested (rats, rabbits, etc.). In that way, it can be extrapolated to human beings [8]. Occasionally, LD0 (lethal dose for 0% of the animals tested), LD10 (lethal dose for 10% of the animals tested) and LD90 (lethal dose for 90% of the animals tested) are also used. The term LC50 (lethal concentration for 50% of the animals tested) is also often used and is expressed in micrograms (or milligrams) of the material per liter, or ppm, of air or water. The LOAEL (lowest observed adverse effect level) can also be used and corresponds to the lowest dose of a chemical that produce a significant adverse effect [8].

Effects of contaminants vary according to extrinsic factors (chemical nature of the compound, solubility in water, persistence in the environment, chemical similarity with other molecules within the living organism), and to intrinsic factors (capacity of the living organism to transform, metabolize, absorb and/or eliminate this compound). Inside the living organism, these substances can be transformed by detoxification processes, into less toxic molecules that are more easily eliminated. In other cases, these toxic substances are transformed by detoxification processes, into more toxic molecules than the parent molecule (Figure 2). The interaction of these molecules with DNA, proteins or steroids within the organism, may exert indirect physiological effects, especially by affecting defence mechanisms, which induces the development and/or accentuates the existence of diseases [6].


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Because of these interactions within the living organism, chemical contaminants can be carcinogens, teratogens, mutagens, genotoxic substances or endocrine disruptors:• Carcinogenic substances may cause or increase the risk of

cancer. • Teratogenic substances may affect the human embryo or

foetus after the pregnant woman is exposed to the substance, causing physical malformations, problems in the behavioural or emotional development of the child, and decreased

Figure 2. Responses of organisms to deleterious effects to the exposure to pollutants.

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intellectual quotient in the child, or affect pregnancies and cause complications such as preterm labours, spontaneous abortions, or miscarriages.

• Mutagenic substances may induce or increase the frequency of mutations in a living being above the natural background level.

• Genotoxic substances are mutagenic substances that specifically damage the DNA.

• Endocrine disruptors are substances that may interfere with the body’s endocrine system and produce adverse developmental, reproductive, neurological, and immune effects in humans, such as lowered fertility or increased female-to-male birth ratios. In wildlife, it can also induce lowered fertility or the development of imposex or intersex [9]. Imposex corresponds to the development of male sex organs in females. Intersex corresponds to the presence of both male and female cells in a single living being.

These effects can be evaluated through the measurement of bioindicators or biomarker responses. In ecotoxicology, a bioindicator is a living being whose function, population, or status can reveal the presence and/or impact of pollutants in the environment. Bioindicator species effectively indicate the condition of the environment because of their medium tolerance ranges for abiotic environmental conditions and their medium sensitivity to environmental changes [10]. Ubiquitous species have broad tolerance ranges for abiotic environmental conditions and are not very sensitive to environmental changes, while rare species have very narrow tolerances for abiotic environmental conditions and are too sensitive to environmental changes or too infrequently encountered [10]. Therefore, bioindicator species must be in between ubiquitous and rare species. Nevertheless, lethal effects of pollutants are not always observed on bioindicator species, but this does not necessarily


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mean that pollutants are not having a sublethal effect on living organisms. A sublethal effect do not kill but induces a stress in the organism or a stress response at cellular, biochemical and physiological levels. Both acute and chronic stress can induce a failure on physiological homeostasis (i.e. on the balance of essential physiological states), which may cause or contribute to the development of illness. In that case, it will be necessary to wait months, years, or even decades, or that the concentration of the contaminant increases significantly in the environment, to detect effects in bioindicator species. At that point, it may be very difficult to eliminate the stressor or the effect that it has on the environment. Therefore, when effects are not observed at the level of the individual or the population, the effects of contaminants can be evaluated through the measurement of biomarker responses, at a smaller, more sensitive and shorter time scale levels. This may help considerably to prevent irreparable environmental damages.

In medicine, the National Institutes of Health Biomarkers Definitions Working Group defines a biomarker in human beings as “a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention”. PSA (prostate-specific antigen) is an example of biomarker used in medicine as a proxy of prostate size with rapid changes potentially indicating cancer, allowing early diagnosis of dysfunctions on human health. Because of the utility of biomarkers as predictive tools, their scope has extended to other areas such as ecotoxicology.

In ecotoxicology, biomarkers allow early diagnosis of dysfunctions on living organisms, populations and ecosystems, before substantial damage occurs in the environment [11]. They correspond to biological responses in living organisms at molecular, biochemical, cellular, physiological or behavioural levels that allow to highlight and demonstrate the exposure and/or effects of contaminants

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[11,12]. Examples of biomarkers range from the inhibition of AChE (acetylcholinesterase) in the nervous system, an enzyme that if it is inhibited, it may induce changes in the behaviour of living organisms, to the thinning of eggshells in birds. Biomarkers can help to bridge the gap between the laboratory and the field by giving direct evidence of whether or not a particular animal, plant or ecosystem is being affected by pollution. They will often provide more reliable evidence of exposure to pollutants than measurements of the pollutants themselves in the environment, because pollutants are often short-lived and difficult to detect, whereas their effects (detected through biomarker responses) may be much longer-term.

Different extrinsic factors or stressors (climate, physicochemical variables, etc.) in the environment, including chemical contaminants, may exert a stress in the living organisms, and therefore in the environment. According to Van Straalen (2013), “a situation of stress arises when some environmental factor changes and an organism finds itself outside its ecological niche. By definition, the organism cannot grow and reproduce outside its niche, but it may survive temporarily. The stress can be relieved by moving back to the niche, [by using behavioural mechanisms or suppressing the stressor, and during that time by developing a temporary physiological adaptation, which allows survival until the stressor is gone], or by changing the boundaries of the niche (genetic adaptation) [13]”. In this context, responses of biomarkers of environmental stress can be measured and will allow to early assess ecosystem health, and even more if these responses are measured in keystone species. A keystone species is a species that if it is removed from the environment, it will have a disproportionately large effect on its environment relative to its abundance, which means that it will generate a dramatic shift in the ecosystem, affecting many other species, even though that species was a small part of the ecosystem [14].

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These effects can be observed by carrying out bioassays, which correspond to scientific experiments that use a live animal or plant (in vivo) or tissue or cell (in vitro) to determine the effects of a substance on a living organism. In some cases, bioassays will try to “reproduce” natural environmental conditions and this can be done at different scales: • In microcosms: at laboratory scale model ecosystem.• In mesocosms: in an enclosed body of water (pond or flow

through system) of close to natural conditions for running controlled aquatic experimentations.

• In macrocosms: in large model systems.

Active biomonitoring is in between bioassay and biomonitoring. It corresponds to transplantation experiments in the field, in which animals from a clean site are transferred to a contaminated site and vice-versa for long periods of time in order to evaluate their responses in a clean and/or contaminated environment. This type of monitoring is usually combined with chemical monitoring, which corresponds to the assessment of concentrations of chemical compounds (potential contaminants) in water or sediments [6].

Biomarker responses can be measured in bioassays, active biomonitoring and biomonitoring, and are very useful for ERA (Environmental Risk Assessment) and ERM (Environmental Risk Management) processes [15].

ERA is the process that estimates the magnitude and probability of adverse effects of pollutants and other anthropogenic activities on ecosystems and their components, while EIA (Environmental Impact Assessment) is the process that consists on estimating the magnitude of impacts of chemical contaminants in the environment [12]. An assessment is scientifically oriented and consists on evaluating and describing the impacts (with the analysis of data using quantitative techniques and scientific methodologies), while

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management is more politically oriented and consists on choosing among alternatives and determining acceptability of risks (with the examination of solutions to the problem and the establishment and application of regulatory measures, laws and public policies). In that sens ERM is defined as the process of choosing among alternatives and determining acceptability of risks of chemical contaminants in the environment. In this chapter we will consider only ERA and ERM, which should be done before any impact is detected and therefore before carrying out EIAs (Figure 3).

Figure 3. ERA (Environmental Risk Assessment), ERM (Environmental Risk Management) and ecotoxicological tools.

Chemical Contaminants

Several chemical compounds are used on a daily basis in human activities, such as agricultural, farming, mining, industrial and domestic activities. Some examples of these chemical compounds are heavy metal particles including NPs (nanoparticles). These

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compounds are not necessarily immediately toxic for living organisms, but their effect can be sublethal and chronic. They are considered as pollutants in the environment because they have shown to be carcinogenic, teratogenic, mutagenic, genotoxic or endocrine disruptors.

Heavy metals and nanoparticles

As (arsenic), Ba (barium), Be (beryllium), Cd (cadmium), Cr (chromium), Cu (copper), Hg (mercury), Mn (manganese), Ni (nickel), Pb (lead), Se (selenium), Sn (tin), Tl (thallium) and Zn (zinc) are some of the metals called ‘heavy’ because of their high relative atomic mass. These metals persist in nature and can cause damage or death in animals, humans, and plants, even at very low concentrations. For example, the maximum consumption limit recommended for Cd is 5 µg/l in water and 1 µg/kg/day in food, according to international organizations, such as EPA (Environmental Protection Agency), FAO (Food and Agriculture Organization) and WHO (World Health Organization) [16].

All these compounds are natural components of the Earth´s crust. They can enter a water supply by industrial and consumer waste, or even from acidic rain, breaking down soils and releasing heavy metals into streams, lakes, rivers, and groundwater. As trace elements, which means in very small quantities, some heavy metals (e.g. Cu, Se and Zn) are essential to maintain the metabolism of the human body. However, at higher concentrations they can lead to poisoning. Poisoning can result, for instance, from drinking-water contamination (e.g. lead pipes), high ambient air concentrations near emission sources, or intake through the food chain. Other heavy metals (e.g. As, Cd, Hg, Pb) are not essential to maintain the metabolism of the human body and can be toxic or exert noxious effects at low concentrations. Safety levels in food or water have been prescribed for some of them by international organizations

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Table 1. Principal metals used in nanotechnologies and quality standards for humans, to protect public health. Own adaptation based on different international sources. Regulations and recommendations can be expressed as “not-to-exceed” levels, that is, levels of a toxic substance in air, water, soil (not shown in this table), or food that do not exceed a critical value that is usually based on levels that affect animals; they are then adjusted to levels that will help to protect humans. Sometimes these not-to-exceed levels differ among federal organizations because they use different exposure times, animal studies or other factors. EPA: Environmental Protection Agency; FAO: Food and Agriculture Organization; WHO: World Health Organization; OSHA: Occupational Safety and Health Administration; ww: wet weight; ND: standard not determined.

(Table 1). Unfortunately, an important number of pollution accidents and disasters in the world are due to the inappropriate

Institution EPA FAO/WHO

FAO/WHO OSHA WHO

Source Drinking water

Food grade Fish Air£

Humans (organ or

tissue)

mg/l (ppm)

mg/kg ww (ppm)

mg/kg ww (ppm) mg/m3

Longest half-life (days)

Ag (Silver) 0.100 ND ND 0.010 50As (Arsenic) 0.010 0.5 50.0 0.010 3

Au (Gold) ND ND ND ND NDBa (Barium) 2.000 ND ND 0.500 <1

Be (Beryllium) 0.004 ND ND 0.002 450Cd (Cadmium) 0.005 0.5 0.5# 0.005 14 600

Co (Cobalt) ND ND ND 0.100 1 460

Cr (Chromium) 0.100 ND 2.0 0.005 <1Cu (Copper) 1.300 ND ND 0.100 43

Fe (Iron) 2.000 ND ND ND 2 920

MetalsUnits

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Hg (Mercury) 0.002 1.0 0.5* 0.050 70Mn (Manganese) 0.050 ND ND 5.000 40

Ni (Nickel) 0.100 ND ND 1.000 2Pb (Lead) 0.015 2.0 0.3$,& 0.050 3 650

Se (Selenium) 0.050 ND 1.0 0.200 100Sn (Tin) ND 200.0 200.0§ 0.100 100

V (Vanadium) ND ND ND 0.500 10Zn (Zinc) 5.000 ND ND 1.000 280

£ Averaged over an 8-hour work day * 1 ppm for predatory fish (sharks, tuna, sturgeon, horse mackerel, mullet, eel, Atlantic catfish, etc.) $ 0.02 ppm for children in EU (European Union) & 1.5 ppm in shellfish in EU # 2 ppm in shellfish for FAO/WHO and 0.005 in EU § 50 ppm for children in EU

release of heavy metals in the environment, causing noxious effects to the environment but also to human health. Some examples of these impacts will be described in the next section of this chapter.

Heavy metals are dangerous because they tend to bioaccumulate. Bioaccumulation will partly depend on the half-life of the chemical compound. The half-life of a chemical compound corresponds to the decrease of concentrations by half in the environment or in the body of a living being. In humans, half-lives of metals can go from hours (e.g. for Cr) to many decades (e.g. for Cd), depending on the tissue where it accumulates (e.g. blood, kidney, liver, etc.). It is important to note that the time to be completely eliminated from the body is two times longer than the half-life (Table 1).

NPs made from heavy metals are called “metallic NPs”. They are made from different methods, have different applications and could pose different risks for living organisms and ecosystems [17–19]. A more detailed description of NPs will be found in the next text box.

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Nanoparticles

Nanoparticles (NPs), including metallic NPs, are particles between 1 and 100 nanometers in size and are now heavily utilized in biomedical sciences and engineering. They are a focus of interest because of their significant potential in nanotechnology. The term “metallic NPs” is used to describe nanosized metals. This means that they are made from metals such as Au, Ag, Cu, Cd, and Zn. Ag NPs is one of the most widely used nanomaterials (as antimicrobial agent, in textile industries, for water treatment, sunscreen lotions, etc.).

Today these materials can be synthesized and modified with various chemical functional groups which allow them to be conjugated with antibodies, ligands, and drugs of interest, opening a wide range of potential applications in biotechnology, vehicles for gene and drug delivery and diagnostic imaging (magnetic resonance imaging -MRI-, computed tomography -CT-, among others).

Nanomaterials can also be applied in bioremediation, having less toxic effect on microorganisms and improving the microbial activity of the specific waste and toxic material, reducing the overall time consumption and overall cost [17].

However, some of these metals are known to be carcinogenic, teratogenic, mutagenic, genotoxic or endocrine disruptors. In addition, many adverse effects have been associated with chemical synthesis methods due to the presence of some toxic chemicals absorbed on the surface. To try to avoid these effects, ecofriendly alternatives to chemical synthesis methods have been developed with biological methods using microorganisms, enzymes, fungus or plants for NP synthesis, especially Ag NPs.

Nevertheless, as described earlier, metallic nanoparticles present possible dangers, both medically and environmentally [18]. Most of these are due to their properties to be very reactive or catalytic [18]. They are also able to pass through cell membranes

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Biocides and fertilizers

The EPA (Environmental Protection Agency of the USA) defines biocides as “a diverse group of poisonous substances including preservatives, insecticides, disinfectants, and pesticides used for the control of organisms that are harmful to human, animal or plant health, or that cause damage to natural or manufactured products” [20]. While herbicides are chemical substances used to control unwanted plants, pesticides are chemical substances used to control unwanted pests (i.e. insects, nematodes, parasites, gastropods, weeds, mammals or birds that are detrimental to human health or to human agriculture and livestock production). Sale and use of many pesticides, insecticides, herbicides and fungicides have been prohibited in several countries, because of their noxious effects in human health and/or in the environment.

in organisms, and, even if it is unlikely that particles would enter the cell nucleus or other internal cellular components, their interactions with biological systems are relatively unknown.

A chemical compound is noxious if it is not properly disposed so it is important to know the hazards in order to control the risks and ensure proper waste management. Impacts of metals (Table 1) are known and research on metallic NPs has increased in the last decade, although more studies are needed to better assess and understand potential effects of metallic NPs.

The NOAA (National Oceanic and Atmospheric Administration) has also developed SQuiRTs (Screening Quick Reference Tables) that present screening for inorganic and organic contaminants in various environmental media (freshwater, seawater, sediment or soil). The tables can be used to initially identify substances that may threaten aquatic resources of concern. The SQuiRTs also include guidelines for preserving samples and for analytical technique options [19].

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However, some of them are still used illegally. Main biocides used in agriculture, farming or as paints include:

• OCPs (organochlorinated pesticides), such as DDT (dichlorodiphenyltrichloroethane), lindane and dieldrine, are classified as POPs (Persistent Organic Pollutants), because they are toxic, bioaccumulative, mutagenic and teratogenic. Nowadays, it is forbidden to sell DDT in some countries, including Colombia, but its use is still permitted in some countries for malaria control, most of them located in Africa.

• OPs (organophosphate pesticides), such as glyphosate, which have replaced OCPs, and CPs (carbamate pesticides), such as carbofuran, act by inhibiting the activity of proteins but in a non-specific way, which may inhibit the activity of proteins in non-target animals and/or in non-target plants.

• PUs (phenylurea herbicides), such as diuron and isoproturon, are among the most used herbicides in agriculture. Their mode of action is based on inhibiting a process in the photosynthesis of any plant. Some of these herbicides are known to be carcinogenic and endocrine reproductive disruptors.

• TBT (tributylitin) and other organotins, are substances that were present in anti-fouling paints to inhibit growth of aquatic organisms that attach to the vessels’ hulls. Organotins in anti-fouling paints are now forbidden, because they induce imposex (masculinization of females) in aquatic organisms. However, due to its long half-life, TBT can remain in the ecosystem for up to 30 years, and is still used illegally in countries with poor regulation enforcement, such as countries in the Caribbean [21].

Fertilizers contain substances like nitrates and phosphates that,

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when they are in excess in the environment, they are no longer absorbed by plants, and therefore, they are flooded into lakes and oceans through rains and sewage. These substances have proven to become toxic for aquatic life, thereby, increasing excessive growth of algae in water bodies and eventually leading to eutrophication. Eutrophication is the process by which a body of water becomes enriched in dissolved nutrients, such as nitrates and phosphates, that stimulate growth of aquatic plant life. This usually results in a rapid increase or accumulation in the population of algae, typically microscopic, known as algal bloom. When a bloom occurs, it blocks light from reaching the water. This prevents aquatic plants from photosynthesizing, a process which provides oxygen in the water. When oxygen in water becomes too low, the water becomes hypoxic. If hypoxia is bad enough, no organisms can survive and a dead zone is created, as it has been reported in the Gulf of Mexico [22]. This leads to a toxic environment and to death of fish and other aquatic fauna and flora. Indirectly, it contributes to an imbalance in the food chain, as different kinds of fish in water bodies tend to be the main food source of various birds and animals in the environment. Nitrogen and other chemicals in fertilizers can also affect the ground waters and waters that are used for the purpose of drinking, and cause risks like cancer and chronic diseases in humans, especially in children [22].

Fertilizers and pesticides contain heavy metals, such as As, Cd and Pb. Moreover, the emission of substances and chemicals from fertilizers, like CH4 (methane), CO2 (carbon dioxide), NH4

(ammonia), and N2 (nitrogen), has contributed to a great extent in the quantity of greenhouse gases present in the environment. This in turn is leading to global warming and weather changes. In fact, N2O (nitrous oxide), which is a by-product of nitrogen, is the third most significant greenhouse gas, after CO2 and CH4 [23].

PAHs

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PAHs (polycyclic aromatic hydrocarbons) are chemical compounds containing at least two aromatic rings, each compound has five or six carbon atoms. There are two main origins of PAHs. The first main origin is the pyrolytic source via incomplete combustion of organic matter at high temperatures by volcanic eruptions, or by combustion of vehicle fuel, coal or wood, among others. This leads to their emission into the atmosphere. The second main origin is the petrogenic source, due to natural or human release of oil in the environment. Some PAHs, such as naphthalene, anthracene and fluoranthene are listed as priority pollutants by the EPA and have been classified by the WFD (Water Framework Directive of the European Union) as hazardous substances because they are toxic or mutagenic in several animals, following acute or chronic exposures [24].

PCBs and PBDEs

PCBs (polychlorobiphenyls) are dioxins from a large family of organochlorinated compounds of high molecular weight. These POPs are extremely chemically stable, non-flammable, and with low solubility in water. They are widely used because of their insulating properties as dielectrics in processors and condensators, as lubricants in turbines and pumps, or as isolating fluid, among others. Dioxins are a class of persistent organic pollutants, that can attach to fine soil particles or sediment, which are then carried by water downstream and settle in the bottoms of ponds and lakes. Dioxins are known as the most potent synthetic carcinogens ever tested in laboratory animals. A characterization by the National Institute of Standards and Technology of cancer causing potential, evaluated dioxin as over 500,000 times more than As. In addition, the half-life of dioxin in humans is between 11 and 15 years and in sediment it can be more than 100 years [25].

PBDEs (polybromodiphenylethers) are bromated chemical

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products. Some PBDEs are or have been used as flame retardants in plastic products and textiles. Concentrations of PBDEs in some human and marine mammal populations are increasing. PBDEs half-life in humans is between 6 months and 2 years and in sediments is decades or longer [25]. Unfortunately, despite their widespread use and structural similarity to thyroid hormones and PCBs, toxicological evidence remains unavailable.

PPSPs and emerging contaminants

Many PPSPs (pharmaceuticals and personal care products: neutral and acid pharmaceutical products, antibiotics, personal care products such as synthetic perfumes possessing musk or UV filters, veterinary medicines and animal care products) are incompletely eliminated during the wastewater treatment, leading to their presence in aquatic ecosystems. Many of them are considered as endocrine disruptors and recent studies have shown that they induce biomarker responses [e.g. 18]. However, more studies are needed in order to better assess and understand potential impacts of these chemical compounds in the environment.

Coal and plastics

Unburnt coal derives from natural weathering of coal and from human activities including the processing of mined coal, disposal of mining wastes, erosion of stockpiles, and spillage at loading and unloading facilities in ports. When present in marine environments in relatively high quantities, coal has physical effects in organisms (abrasion, smothering, alteration of sediment and stability, reduced availability of light, clogging of respiratory and feeding organs), similar to those of any suspended or deposited sediment. Coal contains PAHs and heavy metals, but their bioavailability appears to be low. However, the presence of contaminants at high concentrations in some coal leachates and the demonstration of biological uptake of coal-derived contaminants in some cases,

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suggests the need of more detailed studies [27].

Similarly, plastics may exert physical and chemical effects on living organisms. Plastics that act as pollutants are categorized into micro-, meso-, or macrodebris, based on their size. In addition to physical effects, plastics contain POPs, which exhibit hormone-like properties (also known as oestrogen-like chemicals), such as BPA (Bisphenol A), DEHP (di-(2-ethylhexyl)phthalate), BBzP (butyl benzyl phthalate) and St (styrene). DEHP, for example, has the potential to cause reproductive and developmental problems and has been strongly linked to asthma and allergies in children, to negative effects on the liver, kidney, spleen, bone formation, and body weight and it may cause certain types of cancer [28]. These type of endocrine disruptors have been found in plastics such as PET (polyethylene terephthalate), PVC (polyvinyl chloride), PS (polystyrene) and PC (polycarbonate). HDPE (high-density polyethylene), LDPE (low-density polyethylene), PP (polypropylene) and bio-based plastics are considered as safer plastics than the others, but researches on risks are ongoing [28].

Main Pollution Accidents and Diseases in the World

Significant issues with chemicals have driven the development of studies in Ecotoxicology. This section will cover a list of major pollution disasters caused by humans, which may help to show why, nowadays, Ecotoxicology has become such an important multidisciplinary scientific field at economic, environmental and social levels.

Associated to mining and industries in the past

• The Four Big Pollution Diseases in Japan are related to the inappropriate release of contaminants in the environment.

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Three of them are related to heavy metals:1) In 1912, the release of Cd into the Jinzü River, due to mining of minerals, caused several fish death, inhibited growth of paddy rice and caused the development of Itai-itai disease with bone deformities, bone fractures, or weak bones in the people eating contaminated rice [29].2) In 1932, a sewage containing Hg was released into Minamata Bay by Chisso’s chemical factory. This caused a neurological disease known as Minamata disease in the people eating fish and shellfish polluted with MeHg (methyl mercury), bringing over 500 fatalities. Symptoms included convulsions, slurred speech, loss of motor functions and uncontrollable limb movements [29].3) In 1965, a second outbreak of Minamata disease was caused by the release of Hg into the Agano River by a chemical plant. Since then, Japan has had the strictest environmental laws in the industrialized world [29].

• In 2008 in the USA, coal fly ash slurry containing heavy metals (As, Ba, Cd, Cr, Cu, Hg, Ni, Pb and Tl) was released into the Emory River, Tennessee, and nearby land and water features. The release was due to a dike failure at the Tennessee Authority Valley (TVA)´s Kingston coal power plant. Although no lethal or sublethal effects were detected, clean-up costs exceeded US $1.2 billion [30].

Examples of pollution accidents and diseases in the past associated to nanoparticles.

No information on pollution accidents and diseases in the past have been associated to NPs. However, metallic NPs are made with heavy metals and the use of engineered nanomaterials is increasing everyday. Exposure to NPs can have a serious impact on human health, living

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Associated to agriculture activities in the past

• From 1955 to 1975 in Vietnam, the U.S. military used Agent Orange as an herbicide and defoliant to kill trees, shrubs and food crops over large areas during the Vietnam War. Unfortunately, it also caused birth defects in humans. The effects of Agent Orange still persist in the form of ecologically and topographically degraded landscapes in different areas of Vietnam [31]. It is suspected that TCDD (tetrachlorodibenzo-p-dioxin), the most potent dioxin and contaminant in Agent Orange, was used to attack the Ukrainian politician Vuktor Yushchenko in 2004, who suffered from acute pancreatitis and changes in his face (chloracne).

• In 1962, scientist Rachel Carson’s book ‘Silent Spring’ showed that the pesticide DDT (dichlorodiphenyltrichloroethane) was decimating bird populations. Synthetic pesticides like DDT swept the globe after the Second World War. It also helped to combat typhus and malaria, but accumulated in the environment. Because of its noxious effects on living organisms including premature human birth, the use of DDT in many nations was subsequently banned and is currently approved only in special cases for control of insect-borne diseases like malaria in Africa.

organisms and ecosystems. First, free NPs can be released into the air or water during production, or during production accidents, or as waste by-product of production, and ultimately, accumulate in the soil, water, or plant life. Second, fixed NPs that are part of a manufactured substance or product, will be recycled or disposed of as waste. However, potential risks of metallic NPs to human health or to the environment are not always assessed, which lead in the future to negative impacts. For these reasons, ERA and ERM of NPs use and disposal are essential nowadays.

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• In 1984 in India, the Bhopal Gas Leak from a pesticide plant caused burning eyes and lungs in their citizens. Thousands died within days. In the years after, pollutants seeping out of the plant site into groundwater caused cancer, growth retardation and dizziness [32].

• In 1986 in Switzerland, a major fire at an agrochemical storehouse called Sandoz, caused the release of agrochemicals containing Hg. The Rhine river turned red at that time, and fish, including the European eel, were killed over a stretch of 100 km [33]. Although the situation subsequently recovered within a couple of years, new procedures for risk and emergency management, including auditing, were introduced in public policies.

Associated to petroleum activities in the past

• In 1968 in Japan and in 1979 in Taiwan, poisoning caused by ingestion of cooking oil contaminated with PCBs (polychlorobiphenyls), caused birth defects in humans, including discoloured skin, deformed nails, and developmental delays [37]. In the processing of edible vegetable oils, the oil is heated under vacuum to near the smoke point and then goes to a deodorization stage that removes trace amounts of odors and flavors, and lightens the color of the oil. In Japan and Taiwan, PCBs were used in the heating medium for deodorization. Due to holes in the pipes, PCBs leaked into the rice bran oil and caused Yusho and Yu-cheng diseases in Japan and Taiwan, respectively. Concern increased when animal studies indicated that PCBs can cause birth defects and liver cancer in high doses [37,38]. In 2008, a dioxin poisoning event caused the 2008 Irish pork crisis in which Irish pork was recalled worldwide.

• In 1986 in Ukraine, the Chernobyl nuclear power plant´s core went into meltdown and caused the biggest radiation

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contamination in human history. It killed 30 people and released 100 times more radiation than the atom bombs dropped on Japan. From 1992 to 2002 in Belarus, Russia and Ukraine more than 4,000 cases of thyroid cancer were diagnosed among children and adolescents, mainly due to contaminated milk. The 19-mile exclusion zone around the plant remains uninhabitable [39].

• In 2000 in Romania, cyanide-contaminated water leaked out from a dam, spewing out 100 tonnes of CN (cyanide). An incredible amount of fish and aquatic plants were killed and up to 100 people were hospitalized after eating contaminated fish [40].

These are only some examples of world´s greatest accidental pollution disasters, and are valuable lessons to be learned from our past, but what about now? Are chemical compounds still affecting the health of humans, animals and plants?

Associated to human activities in the present

Examples of important NP pollution problems nowadays.

Although no human health effects have been ascribed to NPs thus far, early experimental studies indicate that NPs could initiate adverse biological responses that can lead to toxicological outcomes [18]. These considerations have launched the field of nanotoxicology, which is charged with assessing toxicological potential as well as promoting safe design and use of nanomaterials. To properly assess the health hazards of engineered NPs, the whole life cycle of these particles needs to be evaluated, including their fabrication, storage, distribution, application, and potential abuse and disposal. The impact on humans or the environment may vary at different stages of the life cycle, and for this reason, continuous assessment in different organisms, at different life cycles, is needed.

• Nowadays, small-scale or ‘artisanal’ gold miners around the world take silt from basic pits, add Hg to capture gold and heat the mixture to burn off the Hg, leaving the gold behind. However, Hg vapours can cause brain damage and attack the lungs. The UNIDO (United Nations Industrial Development Organization) estimates that some 15 million miners, their families and neighbours are affected [41].

• In Brazil, big mining companies have also been called responsible for one of the worst environmental disasters in Brazil due to dam collapses, unleashing millions of tons of highly toxic mud and mining waste on the Brazilian landscape [42].

• Linfen (China), also known as one of the world´s most polluted cities, coal mines, factories and refineries spew out SOx, coal dust, As and Pb into the air and water supply. Children in the area suffer from Pb poisoning and adults have increasing rates of bronchitis, pneumonia and lung cancer [43].

• In Guatemala, African palm plantations grew 270% from 2003 to 2013, and nowadays, major rivers in the country have been contaminated with pesticides, used to produce African palm oil, affecting humans, producing massive fish die-offs and causing possible damage to 21 varieties of mammals, birds and reptiles; for 1 ton of palm oil produced, between 2.5 tons and 3.8 tons of toxic industrial waste are generated [44].

• In Indonesia, the Citarum River is clogged with plastic junk and fouled by untreated household sewage, solid waste and industrial waste from the over 500 factories that line its banks and now people has stopped fishing in this river [45]. At a bigger scale, the Pacific Garbage Patch, which is twice the size of Texas, is a semi-permanent floating island of plastic trash, circulated by the currents of the North Pacific Gyre. Larger items like fishing nets can entangle and drown sea animals and choke seabirds, while smaller items eventually dissolve and pollute the marine food chain [46].

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• In Nigeria, thousands of separate oil spills during four decades of oil extraction has lead in the Niger Delta to contaminated fish, polluted ground and air, and reduced life expectancy [47].

• In Russia, the Arctic city of Norilsk is now the world’s largest heavy metals smelting complex and the company responsible—Norilsk Nickel—is Russia’s biggest air polluter. Cu, Ni, Pb and other heavy metals taint the soil and water supply while SOx emissions contribute to chronic diseases on the respiratory tract and on the digestive system, and to lung cancer [48].

• In India, the Sukinda Valley contains 97% of India’s chromite ore deposits—used mainly to make chrome plating and stainless steel. Mining processes leave toxic Cr hexavalent in surface and drinking water, soil, and air. Residents suffer from gastrointestinal bleeding, tuberculosis, and asthma. Infertility and birth defects are common and 85% of deaths in mining areas and nearby villages occur due to chromite-mine-related diseases [49].

• In 2013, the World Health Organization estimated that Pb poisoning resulted in 143,000 deaths, and contributed to 600,000 new cases of children with intellectual disabilities, each year [50]. The poisonous Pb released during the recycling process of batteries in countries in the developing world, such as Kenya, or released from leaded gasoline in countries such as Afghanistan, Iraq and North Korea, affects over 12 million people in the developing world, according to the Blacksmith Institute, stunting children’s physical and mental growth [51]. In China, Guiyu is sadly referred to as the “electronic graveyard”, due to its high content of electronic wastes. As a result, 88% of the children in the area suffer from Pb poisoning and there is more than the average rate of miscarriages [52].

• In different regions of the world, power plants and factories often use river or lake water as a coolant, then release the unnaturally warm water back into the environment. Although

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this is not a type of chemical contamination, the increase in temperature—or “thermal shock”—kills fish and other animals, and increases plant growth, reducing oxygen supply in water [53]. The result is often choking algal blooms and dead lakes and rivers.

Even if it seems largely detailed and developed, these are only some of the examples of current issues regarding pollution in the environment. This shows that, although important efforts have been done in public policies, research and public awareness, a high number of health threads are still present in the environment. Efforts on preventing and controlling this type of events must continue.

Appropriate tools to evaluate environmental stress and health of ecosystems In order to understand risks and avoid impacts related to chemical contaminants, this section will describe some of the main tools used in ecotoxicology, which are very useful for ERA and ERM processes.

Biomarkers and bioindicators

Biomarkers are classified as [54]: • Biomarkers of Exposure: reveal that the living being has been

exposed to the contaminant.• Biomarkers of Effect: reveal that the contaminant is having

an effect on the living being.• Biomarkers of Susceptibility: reveal the capacity that has or

acquires the living being in response to the exposure to the contaminant.

Another and more recent way to categorize biomarkers, classified them in only two categories, as [55]:

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• Biomarkers of Defence: reveal that the living being activates a defence response to eliminate the contaminants from its organism.

• Biomarkers of Damage: reveal that the contaminant induces a damage on the living being, which may impair the capacity of the living being for reproduction and even for survival.

Some examples of biomarkers responses studied in living organisms are presented on Table 2.

The energy used by the living organism to activate the response of these biomarkers is called cost of tolerance, because this energy will no longer be used for the basic metabolism, growth or reproduction of the organism (fitness), and therefore may affect these other processes within the organism [56].

The term biomarkers of environmental stress has been recently used because different intrinsic or extrinsic stressors can induce stress and threaten or affect the biota [57]. These stressors are:• Physicochemical factors such as UV radiations, increase

of the sea level, climatic changes, soil erosion, variations in temperature, salinity, dissolved O2, turbidity, etc.

• Biological factors such as interactions between animals (predation, parasitism, competition for space, food or sexual partners), diseases induced by pathogens, etc.

• Anthropogenic factors such as industrialization and deforestation, depletion of natural resources due for example to overfishing, agricultural practices (such as transport or handling), disruption of habitat, contamination by human activities, etc. (Figure 4).

The organism may respond in different ways to these stressors and responses may occur at different levels of biological organization (gene, protein, cell, tissue, organ, etc.) (Figure 4). These responses

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BIOMARKERS OF DEFENCE

BIOMARKERS OF DAMAGE

Core biomarkers*

Detoxification enzymes (EROD, GST) AChE

Detoxification systems (MXDM) VTG, ZRP

Bile FAC Plasmatic AST and ALT

MT Lysosomal membrane stability

Antioxidant defences(SOD, CAT, GPx,

GSSH)

Lipid peroxidation (MDA)

HSP DNA damages, DNA adducts

Others

Genetic polymorphism of detoxicating systems

(cytochrome P-450, GST, etc.)

Molecular markers(cortisol, retinol)

Subcellular and cellular markers

(immunological markers)

Tissular markers(histology and

histopathology)

Physiological markers (LSI, CF)

Table 2. Classification and examples of biomarkers responses studied in living beings. EROD: ethoxyresorufin O-deethylase; GST: glutathione-S-transferase; AChE: acetylcholinesterase; MXDM: mechanism of multixenobiotic defence; VTG: vitellogenin; ZRP: zona radiata proteins; FAC: fluorescent aromatic compounds; AST: aspartate transaminase; ALT: alanine transaminase; MT: metallothionein; SOD: superoxide dismutase; CAT: catalase; GPx: glutathione peroxidase; GSSH: glutathione; MDA: malondialdehyde; HSP: heat shock proteins; LSI: liver somatic index; CF: condition factor.

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are called integrated responses to stressors [58]. In that way, the animal can overcome the threat and maintain its integrity through compensatory and/or adaptive responses (genetic, metabolic and/or behavioural responses). However, if the intensity of the stressor increases, these responses can lose their adaptive value and become non-functional, which may lead to growth inhibition, failure of breeding or reduced resistance to pathogen agents [58]. This means that there is a sequential order of responses to pollutant stress within a biological system. This will depend on the dose of exposure to the chemical compound, i.e. if it is a gradual pollution, with relatively low doses, or if it is an accidental pollution, with relatively high doses (e.g. an oil spill) and/or if the contaminant is extremely toxic. The sequential order of responses will also depend on the period of the exposure to the chemical contaminant, which may vary from minutes to decades. Considering gradual pollutions of contaminants that are not extremely toxic (i.e. most contaminants that are used by human activities), if a contaminant is harmful for the organism, molecular interactions can lead to variations in molecular parameters at relatively short time-periods (hours, days; Figure 4). Later in time (months), these molecular changes can lead to physiological effects. Even later in time (years), individuals, population and ecological performances (e.g. growth, expansion rates, efficiency to use resources, adaptability) may be affected (Figure 4). In the long term (many years, decades), the extinction of populations and even communities (especially if keystone species are affected) may occur, and the structure and functioning of the whole ecosystem can be modified (Figure 4). All these events may also occur at a short period of time if the dose of the contaminant is very high, i.e. in the case of accidental pollutions, or if the contaminant is extremely toxic.

Therefore, different measurements can be done in order to detect effects in the long term or in the short term. These different

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Figure 4. Schematic representation of the sequential responses to contaminant stress within a biological system at different scales with possible effects, ecological significance and in human health. It is important to keep in mind that in the case of an accidental pollution, i.e. if the chemical is present in the environment at high concentrations, or if the chemical is extremely toxic, time scales may be reduced only to months, weeks, days or even hours. Modified from [57, 69].

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measures present advantages and limitations:

1. Population- (bioindicators) and ecosystem-level measures (ecological indicators) assess the effect at an environmental scale, but studies require time scales of years or even decades in order to obtain results and the population needs to be in significant decline in order to detect an impact (Figure 4).

2. Organism-level measures (bioassays) are intermediate in relevance, sensitivity and diagnostic utility, and studies require time scales of months or years. Effects observed at an organism level are always preceded by changes at a suborganism level (genes, proteins, organs, metabolic processes), which can be early detected and a link can be established between these signals and the possible consequences at higher levels of biological organization (Figure 4).

3. Suborganism-level measures (biomarkers) are more diagnostic and sensitive to pollutants than the other level measures and are considered as early-warning signals of distress, since studies can be done at small time scales of minutes, hours or days (Figure 4). However, it is important to keep in mind that it is very difficult to extrapolate results to a whole population or environment. The aim of sub organism-level measures is to discard contaminants that are not potentially dangerous, and make further analysis only on contaminants that may be potentially dangerous in the long term. For this aim, an analogy could be done with medical biomarkers that will help to early detect a disease and discard other diseases, and therefore avoid an irreversible development of this specific disease. It would be more appropriate to carry out studies at the three levels. However, it is generally more difficult, more time consuming and more expensive to take actions when effects are occurring already at the level of a population or an ecosystem. Therefore, another aim of using early-warning signals is to rapidly

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detect potential risks, to avoid reaching that level of impact in the environment.

Bioassays and biomonitoring

An extensive range of ecotoxicological and biodegradation tests are required for the chemical, agrochemical and pharmaceutical industries. The bioassays (Figure 4) often used include:• Bacterial toxicity tests.• Algal growth tests with a variety of species (Scenedesmus

subspicatus, Pseudokirchneriella subcapitata, Navicula pelliculosa, Skeletonema costatum).

• Acute toxicity tests with the aquatic plant Lemna minor.• Acute and reproduction tests in the aquatic invertebrate

Daphnia magna.• Acute toxicity tests with the marine copepod Acartia tonsa,

the marine invertebrate Mysidopsis bahia, the freshwater sediment dwelling species Chironomus riparius or Lumbriculus variegatus or the amphipod Gammarus pulex.

• Oyster embryo larval toxicity test.• Earthworm toxicity tests.• Acute toxicity tests, bioaccumulation, fish growth tests, early

life cycle tests with freshwater and marine fish (rainbow trout Oncorhynchus mykiss, common carp Cyrprinus carpio, gold orfe Leuciscus idus, bluegill sunfish Lepomis macrochirus, fathead minnow Pimephales promelas, Japanese killifish Oryzias latipes, zebra fish Danio rerio, turbot Scophthalmus maximus and sheepshead minnow Cyprinodon variegatus).

The logic behind using some of these species is that if a pollutant is non-toxic to the “most sensitive” species then it would be safe for the rest of the community. Some protocols for these bioassays have been developed or standardized by the US EPA and are available on their website. These bioassays can be used to determine LD50

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(lethal endpoints) or to detect effects rather than death, such as changes in reproduction (e.g. number of eggs laid or young hatched), growth (e.g. biomass or body length) and biochemical or physiological effects (e.g. enzyme synthesis or respiration).

Bioassays are cheap, reliable and easy to perform but there is much debate about their relevance to real environmental conditions. Toxicity testing using single species provides useful information and will almost certainly remain central to the regulation and registration of toxic chemicals but much can be done to expand the scope of toxicity testing. Tests that apply to higher levels of organization should be included, because they of their increased relevance to communities and ecosystems. In this context, bioassays can be carried out at different size scales by using microcosms (small), mesocosms (medium) or macrocosms (large multispecies systems), to more easily extrapolate to ecosystems. Because they are more complex systems, it is seldom possible to produce tests that are as precise and controlled as those carried out in single species. However, despite their limitations these larger-scale tests can provide important insights into the effect of pollutants on whole systems rather than on single species.

In natural systems, organisms are usually exposed to more than one pollutant at the same time. However, regulatory authorities usually assume - unless there is evidence to the contrary - that the toxicity of combinations of chemicals is roughly additive. Fortunately, in many cases, this is quite correct. However, in some cases, toxicity is more than additive, i.e. there is potentiation of toxicity. One particular type of potentiation called synergism occurs when the effect of two or more chemicals combine to have greater impact than expected from their individual concentrations. Some strategies have been developed for this through environmental biomonitoring in situ (in the field) [6]. The aim of biomonitoring is to understand environmental health implications of exposure to

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environmental chemicals, by linking concentrations of chemical contaminants in the field with biomarker responses. Examples of successful ERA and ERM

The general public has learned that chemicals that are not toxic to humans can have deleterious effects on natural resources, which generally have an economic, social or ecological value [59]. It is important to note that a compound with moderate toxicity but very high exposure may cause more damage that a very toxic chemical with very low exposure. ERA has been employed primarily to deal with chemicals and has several advantageous properties in environmental decision-making processes [60]. It provides a quantitative basis for comparing and prioritizing risks as well as a systematic means of improving the understanding of risks. In addition, it estimates clear consistent endpoints. Some successful examples of ERA processes and results are presented in this section.

Decrease of POPs in California

The NOAA (National Oceanic and Atmospheric Administration) in the USA developed the Mussel Watch Program in 1986, with the aim of doing chemical monitoring, i.e. measuring chemical contaminants in water, sediments and mussels every year, and comparing their results with quality environmental standards. Chemical monitoring is very useful since it gives an indication of the presence of a contaminant and helps to assess their fate in the environment. A recent publication by NOAA has shown that the presence of POPs (PAHs, PCBs, etc.) has significantly decreased in the coast of California, after 30 years of starting the Mussel Watch Program, showing the utility of this type of chemical monitoring program in the long term [61].

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It is important to keep in mind that chemical monitoring is important but not sufficient since it cannot give any information of the real impact of the contaminant on the living organism and even less of the potential effects on populations, communities, ecosystems and human health. Thus, monitoring in living organisms or biomonitoring is essential for this type of purposes. Since 1991, the NOAA Bioeffects Program examines the distribution and concentration of chemical contaminants in sediments, but also measures sediment toxicity, and assess the condition of bottom-dwelling biological communities. This information is integrated to develop a comprehensive assessment of the health of the marine habitat.

Recovery of bald eagle populations

Forty years ago, the bald eagle was in danger of extinction throughout most of its range. Habitat destruction and degradation, illegal shooting, and the DDT contamination of its food source, decimated its populations: the number of nesting eagles passed from 100,000 in 1782 to 487 in 1963. The species was in danger of extinction. Bald eagles were poisoned with DDT when they ate contaminated fish, and this interfered with the ability of the birds to produce strong eggshells. The eggs often broke during incubation or otherwise failed to hatch. Measures concerning habitat protection and the banning of DDT in 1972 helped bald eagles make a remarkable recovery. Nowadays, 9,789 nesting pairs of bald eagles have been reported [62].

Removal of Hickey Run from the list of impaired waters

Illegal oil and grease dumping has historically plagued Hickey Run, a tributary of the Anacostia River approximately 1 mile downstream of the Washington, DC–Maryland border. As a result of extensive outreach efforts the major sources of oil and grease were targeted. An 88% reduction in oil and grease occurred from

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1998 to 2002. The Hickey Run is no longer in the list of impaired waters in the USA [62].

Zero lead poisoned children

EPA New England partnered in 2001 with many critical stakeholders to achieve measurable results in reducing childhood Pb poisoning in Boston. Combined partnership efforts between EPA New England and community partners lead to a reduction in blood Pb in children in Boston from 1,123 cases in 2001 to 278 cases in 2009, and results revealed zero lead poisoned children in some zones [62].

Restoration of the Cuyahoga River

The Cuyahoga River was considered one of the most polluted rivers in the USA. The Lake Erie, which the Cuyahoga flows into, was considered as “biologically dead” in the 1960. From 2009 to 2012, a project was developed in the Pleasant Valley of the Mississippi River Basin. Conservation staff worked with farmers on using science to target implementation efforts. These efforts were focused on the identification and implementation of applicable management practices related to water quality improvement: aquatic species have returned, the river itself has become a source of social and cultural value for Cleveland residents, phosphorous loading has been reduced in 37% and Lake Erie now supports the largest fishery of the Great Lakes [62].

It is important to recognize that during all these processes and examples of success stories, chemical monitoring and biomonitoring techniques were applied in order to assess risks and to control the efficiency of environmental risk management practices.

Case studies

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This section will focus on case studies carried out under laboratory-controlled conditions, in outdoor mesocosms or in situ, in order to give some examples of experimental designs that can contribute to the understanding of risks associated to chemical contaminants. It is recommended to read the complete version of all the references cited in this section to have more detailed explanations on the methodology, results and discussions of these studies [63-68].

Laboratory studies

In a set of laboratory experiments, the aim was to evaluate potential risks for estuarine species of using chemical dispersants and therefore bring recommendations on the use of chemical dispersants for oil spill response [63]. To this end, oysters were exposed to different treatments, and physicochemical variables, such as seawater temperature and salinity, were controlled. The first treatment was with clean seawater (control). The second treatment consisted on exposing oysters to oil dispersed with a chemical dispersant. The third treatment consisted on exposing oysters to oil dispersed mechanically (i.e. without dispersant). The fourth treatment consisted on exposing oysters to the dispersant (i.e. without oil). Oysters were exposed to these treatments for 48 hours, and then to clean seawater for 14 days. The whole experiment was replicated three times (Figure 5).

Figure 5. Example of experimental design for a bioassay.

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Results revealed that oysters exposed to oil with a chemical dispersant had concentrations of PAHs in their tissues almost 3 times higher than with mechanically dispersed oil, suggesting that the presence of the dispersant increases the biodisponibility of these compounds. In addition, significant correlations were observed between enzyme activities and PAH body concentrations, which could induce negative effects in immune and detoxification systems in the long-term [63]. Oysters are keystone species of coastal and estuarine ecosystems and therefore if their populations are affected, negative effects could overcome over an entire ecosystem.

These experiments were part of the DISCOBIOL research project. Overall, results of this project revealed that in a natural environment, on a medium or long timescale, biota which have been exposed to oil (with and without dispersant) do exhibit some symptoms which could affect their survival rate in the field even though they do not lead to acute toxicity effects. The recommendations arising from the results of this project are that a NEBA (Net Environmental Benefit Analysis) should be done prior to the use of dispersant, to determine whether its use is expected to minimize the overall damage resulting from oil spill pollution, or at least to define geographical limits where dispersion can be undertaken, based on the water depth and the distance to the shore as well as the presence of sensitive resources.

Similar results were observed in the POLERON research project where similar laboratory experiments were carried out in oysters. In this case, the aim was to analyse risks of exposure in estuarine species of concentrations of diuron (pesticide) that have already been detected in the environment, and of diuron with other molecules, which can be potentially present at the same time in aquatic environments, and therefore to evaluate potential risks of pesticides in estuarine environments. To this

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end, oysters were exposed to clean seawater (control), to an herbicide alone (diuron) or to a mixture of diuron, isoproturon and the pharmaceutical ibuprofen. In vivo exposures were done with relatively high concentrations of contaminants and for short time periods, since in aquatic environments these contaminants can be present at relatively high concentrations but only for short periods of time. Physicochemical variables, such as seawater temperature and salinity were also controlled. Early effects on molecular, biochemical and cellular parameters were detected, suggesting that diuron alone or within a mixture may potentially affect immune defences in oysters [64].

Mesocosm studies

The fate of NPs in invertebrates were studied in mesocosms and will be explained in more detail in the following text box [65,66].

Fate and effects of nanoparticles in invertebrates using mesocosms.The fate and effects of CuO NPs and AgO NPs were examined in clams (Scrobicularia plana) and worms (Hediste diversicolor) [65,66]. Outdoor mesocosms and relatively long periods of exposure (21 days) were selected to mimic environmental conditions (Figure 6). Effects of both soluble or nanoparticulate metal forms were observed on different defence biomarkers (behaviour, antioxidant defence, immune defence and ecotoxicity), but not on damage biomarkers (thobarbituric acid reactive substances, acetylcholinesterase and acid phosphatase). These effects were mainly attributed to the toxicity of the nanoparticulate form, in comparison to the dissolved form of Cu and Ag. Bioaccumulation and effects were more observed in the clam than in the worm. These results suggests that both types of NPs may exert effects in the environment.

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Figure 6 Example of experimental design for a mesocosm study.

This study was part of the NANORETOX research program that used the same sets of nanoparticles in a variety of bioassays (in human cells, mouse cells, mussel cells, zebra fish and invertebrates). Overall, results of this program showed that:•Cu-andCd-ENMs(engineerednanomaterials)wereconsistentlythe most toxic, and SiO2-, TiO2-, and Au-ENMs were among the least frequently toxic.•Zn-andAg-ENMspresentedimportantdifferencesinbehaviour,depending on the test. Thus it was difficult to make a conclusion for these two types of ENMs.•Theparticle sizedidn´thaveaneffect in the rankingof toxicityamong ENMs, based upon composition. For example, Ag-ENMs were always more toxic than Au and SiO2 independently of the size. •MoreresearchonspecifictypesofrisksofMENM(metal-basedengineered nanomaterials) and on properties that increase or diminish the potential for toxicity to both humans and animals is needed. More information on this program and methodologies used to evaluate risks of MENM can be found in the program website (www.nanoretox.org).

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In situ transplantation studies or active biomonitoring

Even more environmentally realistic conditions are transplantation experiments, known also as ABM (active biomonitoring), in which animals from a clean site are transferred to a contaminated site and vice-versa for long periods of time.

In a transplantation study, the aim was to evaluate potential contamination sources and effects in estuarine environments by carrying out active biomonitoring experiments. To this end, juvenile oysters were purchased from an oyster hatchery (near the reference site) and transplanted to a reference site and to different transplantation sites (Figure 7).

Figure 7. Example of experimental design for active biomonitoring.

Results obtained with a transplantation period of 3 months in winter and in summer revealed two distinct groups of contaminants (PAHs and OCPs for the first group, and PCBs and PBDEs for the second group). The group of the two transplantation sites in winter was clearly defined by the levels of PAHs and OCPs, suggesting higher levels of contamination of these chemical compounds on these sites, probably due to local contamination sources. Results also showed that a time period of transplantation of 3 months is sufficient to collect information

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on contaminant accumulation and effects inside the organism [67]. Moreover, tissue contaminant concentrations in this study were correlated to defence and damage biomarker responses, suggesting that the presence of organic chemical contaminants may influence the defence responses in oysters [68]. However, it is important to recognize that in in situ conditions, physicochemical and biological parameters are not controlled and therefore other factors that are not measured in the study, may have also an effect on the measured stress responses.

Overall, the three scales of study (laboratory, mesocosm and in situ) show some advantages and disadvantages and overall, it will depend on the main objectives and duration of the assessment or of the risk management process (Table 3).

Scales of studyControl of

environmental variables

Extrapolation to the wild

Laboratory studies High LowMesocosm studies Low Medium

Table 3. Advantages and disadvantages of carrying out studies at different scales.

Conclusion

Different examples were shown in this chapter to illustrate noxious effects of contaminants in the past and in the present, and challenges for the future. Successful stories were also presented to show the usefulness and applicability of ERA and ERM, by using appropriate ecotoxicological tools. Therefore, ecotoxicological studies can be and should always be considered in ERA and EMR studies in order to have a better knowledge of chemical contaminants that are going to be released in the market or of chemical contaminants that are already in the market and

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that are released in the environment. This will help to develop strategies and avoid noxious effects on plants, animals, humans and ecosystems.

Based on examples and case studies from this chapter, it is highly recommended to analyse risks of nanoparticles at a low level of biological organization (gene, protein, cell, tissue) in order to characterize the types and levels of risks, and also to develop biomonitoring programs to assess potential impacts in the environment. This will help to avoid human health problems and environmental disasters that occurred in the past and to implement appropriate and efficient management practices for synthesis, use and disposal of nanomaterials in the future.

Acknowledgements

The author gratefully acknowledges all the institutions and persons that contributed to the development of the different case studies presented in this study and that are named in the acknowledgments of the published articles and to the co-authors and reviewers of these publications. Special thanks also go to Antoine Verrouil for the constructive comments and feedback for the development and writing of this chapter.

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Biorefinery by the hand of the nanotechnology: biodegradable polymers from industrial biomass wasteJosé Vega-Baudrit , Michael Hernandez-Miranda Rodolfo González-Paz, Yendry Regina Corrales-Ureña

Biorefineries contribute to solve energy, water and environmental problems due to the used of thousands of tons of agricultural biomass residues for production of high value

materials, that from a social point of view could help developing countries to improve their economy. The technological and scientific advances in sciences as nanotechnology have increased the understanding of material properties; helping to find new applications. Examples of materials extracted from Costa Rica biomass waste are presented.

Laboratorio Nacional de Nanotecnología CONARE-CeNAT-LANOTEC, Costa Rica. Edificio Dr. Franklin Chang Diaz, 1.3 km. Norte de la Embajda de EE.UU. Pavas, San José, Costa Rica. Laboratorio de Polímeros, POLIUNA, Universidad Nacional, Costa Rica. e-mail: [email protected]


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Introduction

In Latin American countries, agriculture is one of the major branches of economic activities. Derived from industries which process coffee, bananas, sugar cane and pineapple, a lot of biomass waste is produced every day. For example, in the Costa Rican sugar cane industry approximately 25% of the collected mass is considered as waste [1].

Newcost-effective processes with low environmental impact, improved technologies and new applications have been growing. Since 1990, research and development have been increasing in industries, as well as government policies related to biomass waste convertion [2]. The economy is changing in efficiency, making multiple efforts for full utilization of waste materials. However, water consumption and land use are main factors to be taken care of when an increase of the biomass production is planned [1,3].

Biorefinery is one those processes growing thanks to the enviromental consciousness, and is defined as “the sustainable processing of biomass into a spectrum of marketable products and energy”. Biorefinery facilities are created to produce high value products from biomass waste while preserving natural resources as a side effect by decreasing the consumption of fossile resources and carbon dioxide emissions [4]. This process is focussed in convert the biomass to produce fuels, power, heat, and chemicals. Some examples of biorefineries are: oil, sugar platform biorefinery for bioethanol, syngas and lignin biorefinery (industrial biorefineries)[5]. This is a complex multidisciplinary field of research where nanotechnology can be used for understanding the material properties at the nanoscale level and creating new applications and products in order to develop eco-friendly materials with high value. Polysaccharides (chitosan, chitin, cellulose and derivates), proteins (amino-acids, enzymesand peptides) and polynucleotides

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(polyesters of phosphor acidsand nucleotides) are the most common biopolymers being obtained from agricultural biomass [6].

Costa Rica has a big agricultural industry, which generates large amounts of agro-industrial wastes. The remnants of the production of fruits, such as pineapples, oranges and bananas have been traditionally linked with environmental damage. Cellulose is the main component of several natural fibers such as cotton, flax, hemp, jute, sugar cane and sisal extracted from fruits and wood, among others. This natural polymer represents about one-third of plant tissues and can be restocked by photosynthesis. The principal method used to obtain micro and nanocellulose from fibers as example pineapple peels is by acid hydrolysis [7]. Figure 1 shows the microcellulose and nanocellulose particles synthesized from Costa Rican biomass pineapple peels.

Figure 1. Atomic Force microscopy image from micro and nanocellulose fibers derivated from pineapple peels.

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Seafood and apiculture in Costa Rica are other examples of industries where high value nanostructures materials can be obtained. Seafood companies produce residues of shrimp shells that can be used to produce chitin and chitosan [6]. Chitosan is a natural cationic polysaccharide and is known for suppressing the metabolism of bacteria by interacting with the bacterial cell wall. It is a modified natural polysaccharide comprising copolymers of glucosamine and N-acetyl glucosamine, synthesized by the partial N-deacetylation of chitin, a natural biopolymer derived from crustacean shells such as shrimps [8]. Among water-soluble polymers available, chitosan is one of the most extensively studied materials. It possesses some ideal properties of polymeric carriers in form of nanoparticles: it is biocompatible, biodegradable and nontoxic [9]. Also, chitosan nanoparticles have a lot of advantages such as protecting the drug from degradation prematurely, improving the intracellular penetration and increasing the bioavialability [10]. Moreover, it has been used as stabilized agent for liposomes for the production of adhesives for the release of drugs for wound burn treatment [11]. Figure 2 shows chitosan nanoparticules that were synthesized for analyzing their use in drug delivery, with an average height of 12 nm.

Figure 2. Atomic Force Microscopy height image of chitosan nanoparticles derivated from shrimp shells.

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Propolis is a resin wax, which has a complex composition and a high viscosity. Bees produce it for the construction, repair, insulation and protection of their hive. Since ancient times the propolis is known for its properties and used as antimicrobial, antioxidant, anti-inflammatory, anesthetic, hepatoprotective, immunostimulating. The composition of propolis is complex and varies both qualitative and quantitative, depending on the phytogeographic diversity of harvesting areas. However, there have been more than 180 compounds isolated. Resins, balsams, waxes, volatile oils, pollen and impurities have been identified as its main components. Among them, the flavonoids are active compounds that are consumed in human diet and they have anti-inflammatory and anti-cancer properties [12][13]. Figure 3 shows propolis micro and nanoparticles.

Figure 3. Atomic Force Microscopy height image of propolis nanoparticles derived from bee hives.

In the fishing industry 50% of the whole fish is used for the production of canned food (filet pieces of fish) and the other 50 % is used for producing industrial remnant products such as flour and oil. Of such wastes, 35% is attributed to the head of the fish.

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The composition of fish (amount of protein, carbohydrates, lipids and minerals) varies depending on the species. In general, the content of fish protein is approximately 17-20% [14].

It is estimated that for every ton of a ready-for-commercialization industrialized product, more than another ton is generated in waste. Normally, the residues of heads, tails, scales, skins and bones are used for the production of flour and oil; however, these residues are rich in collagen e.g. skeleton, scales and skin [15 ] ; protein, essential amino acids; fatty acids such as Omega 3: eicosapentaenoic acid (EPA ) and docosahexaenoic (DHA ) [16 ]. These fatty acids are beneficial to human health, and are being used in food formulations, dietary supplements, drugs for neurological disorders, diminution of triglycerides and preventing cardiovascular disease, etc. Therefore, this “waste” is actually a rich source of protein which can be used for extracting collagen that has high commercial value. It can be used in cosmetics and pharmaceuticals as biomaterial due to the low immune response, low antigenicity and low toxicity [17]. It is an alternative for the production of scaffolds [18] and can be used as a material to create particles for drug delivery [19].

Collagen derived gelatin, which is produced from the partial hydrolysis and is used as a material for the production of capsules and tablets coatings; when hydrolyzed, it can be used as a food supplement, commonly in desserts, and other applications such as the production of biodegradable plastics [20]. Figure 4 shows the collagen nanofibers extracted from fish skin. According to the examples taking from Costa Rican biomass waste the production of biopolymers agricultural residues could be factible. However, a lot of effort is still needed for changing the industry perspective; focusing in the use more sustainable products as the biopolymers presented in this study for their product commercialization.

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Figure 4. Atomic Force Microscopy height image of collagen from fish skin.

References[1] Vega, J.; Delgado, K.; Madrigal, S. Biodegradable polyurethanes from sugar cane biowastes. Cellulose Chem. Technol. 2011, 45, 507-514.

[2] Kamm, B.; Gruber, P.; Kamm, M. Wiley- VCH:Wienheim, Germany, 2010; p11.

[3] Gheewala, S.; Bonnet, S.; Prueksakorn , K.; Nilsalab, B. Sustainability Assessment of a Biorefinery Complex in Thailand. Sustainability. 2011, 3, 518-530.

[4] Kelloway, A.; Daoutidis, P. Process synthesis of biorefineries: optimization of biomass conversion to fuels and chemicals. Ind. Eng. Chem. Res. 2014, 53, 5261–5273.

[5] Pandey, A.; Höfer, R.; Larroche, C.; Taherzadeh, M.; Nampoothiri, M. Industrial biorefineries: Industrial Biorefineries and White Biotechnology. Elsevier, 2015; p 3-33.

[6] Benavides, L.; Sibaja, M.; Vega-Baudrit, J. Camacho, M.; Madrigal, S. Estudio cinético de la degradación térmiac de quitina y quitosano de camarón de la espécie “ Heterocarpusvicarius” empleando la técnica termogravimétrica em modo dinâmico. Revista Iberoamericana de polímeros. 2010, 11, 558-573.

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[7] Abdul, H.P.S.; Bhat, A.H.; Ireana, A.F. Green composites from sustainable cellulose nanofibrils: A review. Carbohydrate Polymers. 2012, 87, 963–979.

[8] Wilson, B.; Samanta, M. K.; Santhi, K.; Kumar, K. P. S.; Ramasamy, M.; Suresh, B. Chitosan nanoparticles as a new delivery system for the anti-Alzheimer drug tacrine. Nanomedicine Nanotechnol. Biol. Med. 2010, 6, 144–152.

[9] Elgadir, M. A.; Uddin, M. S. et al. Chitosan nanoparticles: Preparation, size evolution and stability. J. Food Drug Anal. 2015, 23, 619–629.

[10] Kumari, A.; Yadav, S. K.; Yadav, S. C. Biodegradable polymeric nanoparticles based drug delivery systems. Colloids Surf. B Biointerfaces. 2010, 75, 1–18.

[11] Vesículas liposomales estabilizadas com quitosano: estúdio electrocinético. Madrigal, S., Porras, G., Sibaja, M., Vega-Baudrit, J., Vila, A., Molina, F. Revista Iberoamericana de Polímeros. 2010, 11, 46-57.

[12]. Farré, F.; Rasquet, F.; Sanchez, A. El própolis y la salud. Ars Pharmaceutica. 2004, 45, 21-43

[13]. Lee, E.; Kang, G.; Cho, S. Effect of flavonoids on human health: old subjects but new challenges. Recent Pat Biotechnol. 2007, 1,139-50.

[14] Belitz, H.; Grosch, W.; Schieberle, P. Food Chemistry 4th Edition. Springer-Verlag 2009, pag. 617-639. [15] Sikorski, Z.; Scott, D.; Buisson, D. The role of collagen in the quality and processing of fish. Critical reviews in food science and nutrition. 1984, 20, 301–343.

[16] Wang, L.; An, X. et al. Isolation and characterisation of collagens from the skin, scale and bone of deep-sea redfish (Sebastes mentella). Food Chemistry 108 (2008), 616–623. doi: 10.1016/j.foodchem.2007.11.017.

[17] Chen, J.; Li, L. et al. Extraction and characterization of acid-soluble collagen from scales and skin of tilapia (Oreochromis niloticus). Food Science and Technology. 2016, 66, 453–459. doi: 10.1016/j.lwt.2015.10.070.

[18] Glowacki , M. Collagen scaffolds for tissue engineering. Biopolymers. 2008 89, 338-344.

[19] Chen, M.; Huang, Y. et al. Collagen/chitosan film containing biotinylated glycol chitosan nanoparticles for localized drug delivery. Colloids Surf B Biointerfaces. 2015, 128, 339-346.

[20] Quintama, T.; Santos, J.et al. Obtencao de la gelatina de peles de capra Húngara. XI Congresso Brasileiros de Enganharia.COBEQUIC, 2015.

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Environmental and bioenergetic context of livestock production in the Comarca Lagunera region, MexicoLuis A. Hernández, José L. González Barrios Juan Estrada Avalos

S ince the late twentieth century, the agricultural productivity in Mexico was triggered by technological development depicted by the improvement of crops, intensive use of agricultural

machinery, chemical fertilizers, irrigation systems, chemical pest control, disease control and animal health protocols. However, the increase in yields of the different production systems also leads to the intensification of the environmental impacts. Some of these are related to the increase in production of some residues such as cattle manure which contributes 49.45% of total CH4 and N2O emissions from the livestock sector. In this chapter, the environmental risk context and the potential of biogas generation in the Comarca Lagunera region, national main producer of milk, is presented.

Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias. Centro Nacional de Investigación Disciplinaria en Relación Agua-Suelo-Planta-Atmósfera. Margen derecha del canal Sacramento km. 6.5 C.P. 35140. Gómez Palacio, Durango, México. e-mail: [email protected]


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Introduction

Since the late twentieth century, the agricultural productivity in Mexico was triggered by technological development depicted by the improvement of crops, intensive use of agricultural machinery, chemical fertilizers, irrigation systems, chemical pest control, disease control and animal health protocols. In the last 10 years, the agricultural production has increased on average 4.9% per year (± 2.4). Livestock systems have also increased their production, bringing significant economic achievements and increasing the demand of fodder. This sector showed a rise of nearly 200% over the past 10 tears (Figures 1 and 2). Overall, the agricultural sector contributed on the 3.5% of the national Gross Domestic Product (GDP) during 2014 [1, 2].

Livestock activities in 2009 were developed in an area of 110 million hectares, of which, 28% were in the Mexican tropics, 23% in the template zone and 49% in desert or semi-desert areas. Approximately 430 thousand units of specialized production livestock (roughly 13% of the total) are mainly engaged in poultry farming, swine farming and production of milk and beef from cattle, with good standards of quality and safety, enabling them to meet between 70% and 98% of the domestic market, depending of the concerned product, and access to international markets. However, beside them, there is another large segment of approximately 2.9 million units of livestock production in backyards or in extensive grazing systems with low levels of technology and poor access to markets [3].

However, the increase in yields of the different production systems also leads to the intensification of the environmental impacts associated with direct and indirect processes such as water pollution by nitrates, phosphates and pesticides; emission of greenhouse gases (GHG) such as CO2, CH4 and N2O; and soil

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Environmental and bioenergetic context of livestock production

Figure 1. Agricultural production in Mexico in the last 10 years.

Figure 2. Livestock production in Mexico in the last 10 years.

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degradation and pollution [4].

Environmental impacts

Some of the potential impacts linked to production systems are related to the increased production of scraps as manure and wastewater generated from milking cattle and cleaning of stables [5, 6]. On the other hand, cattle manure represents a valuable resource that usually contains all the micro and macro essential elements required for plant growth [7], and its application to cropland increases the soil organic matter and improves several of its traits, like structure, water retention capacity, oxygen content and fertility; it also reduces the soil erosion and nutrients leaching, restores eroded croplands and increases crop yields [8]. Several studies show that the application of animal manure for long periods of time increases the biomass and soil microbial activity [9]. According to Spiehs et al. [11], the use of beef cattle manure as fertilizer significantly increases in 78%, 75% and 130% the total N, organic and microbial biomass in the first 30 cm of the soil profile, respectively; but it could also increase the concentration of Nitrate-N and soluble P in the top soil horizon.

Nevertheless, in some productive units in the country, the most common method of manure management is done by confining, skipping any type of treatment [12], which raises some environmental risks such as: eutrophication of surface water (with impaired water quality, algae growth, damage to fish fauna, etcetera) due to the entry of nutrient and organic substances when ordure or wastewater from livestock production reach the water bodies through discharges, runoffs, or overflows of lagoons; nitrates leaching and possible transference of pathogens to groundwater from facilities where manure is stored or from soils where high doses of untreated manure have been applied; nitrate leaching and transference of pathogens, which are threats for drinking-

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water quality; accumulation of nutrients on the soil if high doses of applied manure can threaten the soil fertility; degradation of natural areas such as wetlands and mangroves; and emissions of greenhouse gases as CH4 and N2O (direct and indirect emissions), as well as other gaseous emissions that include NH3 and hydrogen sulphide [13, 14].

According to the National Emissions Inventory of Greenhouse Gases (Inventario Nacional de Emisiones de Gases de Efecto Invernadero) [15] the average annual GHG emissions by the enteric and manure fermentation from livestock activity in the period 1990-2010 were 44,072 Gg of CO2 eq. (equivalent) which represents 49.45% of the agricultural sector (89,129 Gg of CO2 eq.). The average methane (CH4) emissions for the period were estimated to be 38,164 Gg of CO2 eq., of which, 36.813 Gg of CO2 eq. were originated from enteric fermentation and 1,1105 Gg de CO2 eq. from manure management. The average nitrous oxide (NO2) emissions for the same period were estimated to be 6,153 Gg of CO2 eq. originated from manure management (Figure 3).

Figure 3. Distribution of GHG emissions generated by livestock. Modified from INEGEI [15].

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In search of methodologies for mitigation, factors such as livestock housing, the type of manure collection and storage systems, and the separation of solids and liquids in their processing are practices that should be considered due to their significant impact on ammonia and GHG emissions from such facilities. Most of the options for reducing GHG emissions from stored manure, such as reducing storage time, aeration and stacking, generally aim to reduce the time required for the microbial fermentation process before its application into the soil. These mitigation practices are effective, but their economic viability is uncertain. Semipermeable coverages are valuable for reducing ammonia, CH4 and odors from storage, but are likely to increase N2O emissions when effluents are applied to pasture or crops. Acidification (in areas where soil acidity is not a problem) and cooling are other effective methods for reducing emissions of ammonia and CH4 from the stored manure. Furthermore, composting can efficiently reduce CH4, but may have a variable effect on N2O emissions and increase total losses of ammonia and nitrogen [7].

As a country that has ratified the Kyoto Protocol, Mexico has participated actively in the Clean Development Mechanism (CDM), which in 2009 considered 178 registered projects at the Executive Board of the Inter-Ministerial Commission on Climate Change, from which 142 correspond to projects that aim to reduce methane emissions in the agricultural sector [16]. It is estimated that the total of these projects contributed to the reduction of more than 10 million tons of CO2 eq, placing Mexico in the fifth position worldwide in terms of volume reductions and number of registered projects [17].

Anaerobic digesters as a mitigation strategy

Currently, the recommended mitigation strategy for CH4 emissions from livestock activity is the use of anaerobic digesters

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which also provide opportunities for renewable energy generation and production of bio-fertilizers. According to a study by the Shared Risk Trust (Fideicomiso de Riesgo Compartido, FIRCO) there is nowadays the record of 563 bio-digestion systems related to the methane emission reduction in the agricultural sector in Mexico as stated by the 142 Project Design Documents (PDD) found on the UNFCCC (United Nations Framework Convention on Climate Change) website. Of these PPDs, 54 correspond to the reduction of methane emissions from dairy farms and 88 from swine farms, and each one is in a different stage of the operating cycle of CDM projects. These projects are distributed in the main livestock areas of Mexico, highlighting the states of Sonora, Jalisco, Puebla, Tamaulipas and Veracruz; and generate reductions of almost 3.5 million tons of CO2 eq (until 2009) for this sector [18].The states of Coahuila, Durango, Jalisco, Puebla, Sonora and Tamaulipas have the largest number of projects for mitigation of emissions (76%), while the states of Sonora and Jalisco are those with the largest number of digesters identified from a PDD. Relating these figures to the information of SIAP [19], it is evident that these two states are the main producers of swine in the country. According to FIRCO, the types of digesters that can be found in Mexico are currently lagoon, modular, modular floating covers, ferrocement, of Biobolsa and Reactor. However, the most commonly used technology is the anaerobic lagoon type as it is observed in the 94.2% of the built digesters, the second most used technology is the modular, with 17 biodigesters from total; and Biobolsa is the less used technology, as there are only 3 digesters using this technology.

Regarding the digesters at dairy farms, they are mainly located in the Comarca Lagunera region, located in north-central Mexico (Durango and Coahuila) (Figure 4). This area is the main producer of milk in the country, where technified intensive farming is developed, with specialized cattle (Holstein) for milk production.

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During 2014, the agricultural national inventory reflected the use of almost half a million heads of cattle in the Comarca Lagunera region alone, which represents 18.2% of the national population for that year [2]. Currently in the Comarca Lagunera region, several manure management practices are performed. Such practices include: the stacking of manure in some area of the production unit or its application into the soil after composting or without any treatment. In some farms, manure and other wastes are removed from the feeding and milking areas by water hammer (or flushing) [12], generating a residual liquid of low density and high volume, which will have a biological and chemical oxygen demand, total N and NH3-N, P, and a higher concentration of heavy metals than observed in manure alone, considered a waste of “low density” [7]. In this context, the interest for the implementation of clean technologies to reduce the environmental impact of livestock waste in this region and take advantage of the potential for power generation through bio-digestion was generated.

Considering that the production of livestock manure in the Comarca Lagunera region has increased in recent years, reaching more than 8 million tons in 2015 (Figure 5), there is growing expectation for the potential of the region for the use of these wastes for the generation of biogas, but it is also necessary to evaluate the environmental impact of several management practices currently carried out by producers regarding the waste generated by the bio-digestion of manure, as the application of untreated biosolids into the soil and the use of digester effluent for the irrigation of crops. The efforts made in recent years by the Mexican government sector, through FIRCO for the implementation of biodigesters in the production units in this region, have not yielded the expected results, considering that of the approximately 64 digesters that exist in the region, only 8 are operating (12.5%) due to problems in management and operating costs. In systems that are currently operating, the economic benefit for large producers is notorious,

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however, these efforts should also focus on the possibilities for small producers commonly found in communities with lower resources.

It is clear that areas of opportunity in regions of intensive production, like the Laguna Region, exist; however, it is necessary the development of options for the installation of these biogas production systems on a small scale so that they could generate direct benefits in low-income rural communities that find a means of economic and alimentary sustenance in backyard livestock.

Figure 4. Geographic location of the Comarca Lagunera region.

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From this perspective, and as part of the labor of the National Institute of Forestry, Agriculture and Livestock Research (Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, INIFAP), efforts have been made to implement small-scale digesters for biogas production for domestic use in swine production communities of central Mexico. According to the agriculture, livestock and forestry census, the swine farming is the third most important livestock in Mexico with a population of swine that exceeds 15.2 million of heads. In such production, it is estimated that 10.8% is backyard, 32.3 % is semi-technified and 56.9% is technified. Swine production is carried out in all states, with the highest concentration in Central and Southeast regions. The state of Guanajuato along with Michoacan and Jalisco reached 30% of pork production nationally in 2008 [21]. Considering these numbers, the initiative for the implementation of biodigesters that

Figure 5. Production of manure in the Comarca Lagunera region. 2006-2015. Calculations were performed according to the values of fecal excretion in dairy cattle proposed by Nennich et al. [20].

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transform the problem of this waste into an economic benefit for swine producers was developed. In this sector, biogas generation systems have become important especially for their contribution to energy saving and mitigation of environmental impacts in rural areas. Nevertheless, one of its main limitations is that it requires a considerable amount of water and that the fluid effluent from the digester has features that do not comply with the Mexican Official Standards (Normas Oficiales Mexicanas, NOMs) that are responsible for regulating the quality of wastewater discharges.

As a result, the work done by Araujo et al. [22], semi biodigesters regime with various materials such as brick, cement and closed chambers made from geo-membrane were implemented. The semi regime is the most widely used in rural areas where there are small producers due to the simplicity of manufacture and operation. The design of these allows its load by gravity once a day, with a volume of mixture which depends on the fermentation time or retention and usually produces a constant daily amount of biogas. Nevertheless, the use of these systems should be considered in an integrated manner, seeking to generate economic and social benefits to producers of different orders, but taking into account the possible side impacts of products such as liquid sub affluent of the digester.

Deriving from these problems, different perspectives and areas of interest have arisen to generate scientific and technological knowledge about the complex process of anaerobic digestion that is performed through interaction and metabolic alternation of at least 11 microbial groups [23]. According to Batstone et al. [24], this process can be illustrated in four stages: hydrolysis, acidogenesis, acetogenesis and methanogenesis.

During hydrolysis, the insoluble organic solids such as cellulose or hemicellulose, and organic colloids such as proteins are

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hydrolyzed, which results in compounds subsequently catabolized by fermentative bacteria, producing alcohols and fatty acids, as well as hydrogen and CO2. During the subsequent acidogenesis and acetogenesis, through oxidation of short-chain fatty acids or alcohols, acetic acid is produced. In the last step, methanogenesis is carried out by archaea groups that obtain energy from the conversion of a limited number of substrates to methane. This process along with the associated bacteria groups is illustrated in Figure 6.Methanogens are strict anaerobes that grow mainly in substrates

Figure 6. Microbial interactions in the process of anaerobic digestion. Modified from Almeida et al. [23].

such as hydrogen and carbon (hydrogenotrophic) dioxide, and acetate (acetoclastic). Nonetheless, other methylated compounds, such as methylamines, are also substrates for these microorganisms (methylotrophic). These microorganisms are characterized by the requirement of environments with low reduction

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potentials; the presence of unique coenzymes, such as coenzyme M, factors F420 and F430, 7-methylpterin, methanopterin, methyltetrahydromethanopterin, methanofuran; also, their 16S rRNA is relatively distant from the other prokaryotes; their cell wall contains D-amino acids or muramic acid; and their lipids consist of phytanyl-glycerol ethers (cyclic and acyclic) and squalenes.

Methanogens and all microorganisms involved in anaerobic digestion systems work within narrow levels of hydrogen pressure, temperature, substrate concentration, sulfate content, among others. It should be taken into consideration that the acid-forming bacteria and methane-producing microorganisms differ widely in terms of physiology, nutritional needs, growth kinetics and, therefore, the sensitivity that each features to environmental conditions is highly variable. According to Demirel and Yenügin [25], failures related to the balance between these two groups of organisms are the main causes of instability in anaerobic digesters. In this regard, it is important to consider the most common causes of inhibition, the processes that are triggered and the alterations produced by various factors such as pH, temperature, nutrient availability, presence of toxic substances, retention time, C-N ratio and level of charge [22]. The chemical and metabolic activity typically enhances with increasing temperature, however, excessive elevation of temperature can limit the process whether enzymatic degradation exists, considering that the various groups involved in the process, especially the methanogens, are highly sensitive to changes in the temperature at which different groups carry out protein synthesis. In general, the process can be in a wide temperature range from 15 °C to 60 °C, however, methanogenesis is performed at temperatures between 30 °C and 60 °C. The optimum pH value for the methanogenic digestion is 6.5 to 7.5. This range is normally observed during the process, unless the charge is made in inconvenient proportions, generating an imbalance that can inhibit the process with pH values above 8 or below 5. Another

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important variable is the Carbon/Nitrogen ratio, main sources of supply for methanogens which consume 30 times more C than N, thereby needing an optimum ratio of 30:1 of these two elements in the feedstock, although a good biogas production can be obtained when working with smaller ratios, for example those exhibited in the swine waste.

Considering this series of factors, the installation of these systems is not recommended in places with temperatures below 15 ° C, unless additional heat and temperature control can be provided, which raises the cost of operation. While biodigesters represent a good alternative to mitigate CH4 emissions, it is necessary to consider its operation characteristics to prevent them becoming major emitters of other GHGs such as N2O. It is also necessary to consider that some systems require a high initial investment capital and therefore its adoption is only possible by large producers or when economic incentives that favor their profitability are offered.By raising these challenges and opportunities for the environmental and energy sector, the role that research centers of central and northern Mexico, where a solid study about the potential environmental impacts linked to the increase in the generation of waste such as manure, and the development of better practices that aim to a cleaner and more sustainable production have not been addressed, takes importance. In this regard, the CENID-RASPA and its Water-Soil-Plant-Atmosphere laboratory analytical ability (able to detect and quantify pesticides, heavy metals, trace elements, biomolecules, GEI and some microorganisms) can play a determinant role in the region and the country, generating knowledge about the water, soil and air polluting processes; and the complex microbiological processes involved in the management of polluting waste like livestock manure, aiming to contribute to the generation of mitigation strategies and remediation of their different impacts on the chemical and biological quality of water, fertility and soil microbiota, plant health, crop yields and GHG

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emissions, as well as alternative waste management in small and large-scale for the generation of biogas and other products such as solid and liquid bio-fertilizers. This effort is essential to improve the management practices in agricultural production, seeking for a friendlier relation with the environment and enhanced sustainability that could assist with the preservation of resources and progress towards food security in the country.

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[19] Servicio de Información Agroalimentaria y Pesquera (SIAP). Ganaderia. http://www.siap.gob.mx/ganaderia/. (accessed May 22, 2016).

[20] Nennich, T. D.; Harrison, J. H.; VanWieringen, L. M.; Meyer D.; Heinrichs, A. J.; Weiss, W. P.; St-Pierre, N. R.; Kincaid, R. L.; Davidson, D. L.; Block, E. Prediction of Manure and Nutrient Excretion from Dairy Cattle. J. Dairy Sci. 2005, 88, 3721–3733.

[21] Servicio de Información Agroalimentaria y Pesquera (SIAP). Resumen Nacional Pecuario. http://www.siap.gob.mx/resumen-nacional-pecuario/. (accessed Apr, 2016).

[22] Domínguez-Araujo, G.; Salazar-Gutiérrez, G.; Galindo-Barboza, A.J.; Xelhuantzi-Carmona, J.; Castañeda-Castillo, M.; Sánchez-García, F.J.; Hernández-Vega, P. Implementación de biodigestores para pequeños y medianos productores porcícolas. INIFAP: Jalisco, 2012; p 32.

[23] Batstone D.J.; Keller J.; Angelidaki I.; Kalyuzhnyi S.; Pavlostathis S.; Rozzi A.; Sanders W.; Siegrist H.; Vavilin V. The IWA Anaerobic Digestion Model No 1 (ADM 1). Water Sci Technol. 2002, 45(10), 65–73.

[24] Almeida, A.; Nafarrate-Rivera, E.; Alvarado, A.; Cervantes-Ovalle A.; Luevanos, M.P.E.; Oropeza R.; Balagurusamy, N. Expresión genética en la digestión anaerobia: un paso adelante en la comprensión de las interacciones tróficas de esta biotecnología. Rev. Cien. UAC. 2011, 3(6), 14-34.

[25] Demirel B.; Yenigün O. Two-phase anaerobic digestion processes: a review. J. Chemical Tech. and Biotech. 2002, 77, 743-755.

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CO2 from waste to resource: Conceptual evaluation of technological alternatives for its exploitationJorge I Chavarro

Centro de Investigación en Ciencias y Recursos GeoAgroAmbientales -CENIGAA,Neiva, Colombia. e-mail: [email protected]

The environmental issue generated by greenhouse gas (GHG) and associated with global warming is now a great challenge for the sustainability of the planet. The development of

technologies and new processes surrounding the search for solutions to mitigate the production of GHG produced by the fossil fuels industry is increasing. Some of them are focused on CO2 conversion processes as part of the strategy for generating renewable energy through the development of biomimetics, which has made it possible for this gas to be considered a resource. This article presents different options for converting CO2 using competitive intelligence techniques due to their potential implementation at a pilot scale.


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IntroductionThe industry is currently facing two great challenges that condition its status as the main global source of energy. These challenges involve seeking alternative solutions to supply the increasing energy demands of the planet, which requires the promotion of new technologies and innovative exploration and production processes such as non-conventional deposits. Moreover, it faces demanding and rigorous environmental policy that forces it to develop clean methodologies and processes, which makes procedure and project proposals developed in compatibility with the environment appealing.

Although CO2 is thought of as the main greenhouse gas and thus global warming is attributed to it, its warming potential is relatively limited compared to other greenhouse gases. However, the reason why it is actually considered the main cause of environmental issues is its high concentration in the atmosphere.

According to the International Energy Agency (IEA), 31.6 Gigatons of global carbon dioxide emissions are connected with energy consumption, which reached a historic peak in 2012.Additionally, it informs that 80% of global energy consumption is based on fossil fuels. This information is a strong source of environmental pressure for the energy sector.

Figure 1 and 2 show a comparative graph of global CO2 emissions with respect to fossil fuels used as the main energy resource and reflect their negative contribution in the form of emissions.

For the IEA the fight against climate change has become one of the main and more relevant characteristics of political decision-making in connection with the energy sector. This situation has significant social and economic implications in the aim to solve global warming. Even so, in its website it states that:

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CO2 from waste to resource

Figure 1. CO2 emissions, global context.

Figure 2. Global CO2 emissions by sector. Adapted from [1].

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“In compliance with the emission goals agreed by the countries by virtue of the United Nations Framework Convention on Climate Change (UNFCCC), the planet will continue emitting 13.7 thousand million tons of CO2 to the environment, which are equal to 60 % above the necessary level to maintain a change of only 2°C in global warming for year 2035” [2].

These results cause concern and expose the need to implement immediate actions aiming to reduce emissions.

The need to make a change towards alternative energy or the so-called renewable energy is made evident. This change would alarm the fossil fuels industry, but it would not be an immediate solution due to the high investment and development costs of this type of energy compared to fossil fuels, and to the high costs associated with the required restructuring process to substantially reduce the use of current non-renewable energy. Moreover, projects have been proposed and developed around making the CO2 found in those activities useful with the purpose of reducing emissions. These projects are the current focus of the petroleum industry. Carbon capture and storage, CO2

injection as an EOR technique, industrial transformation, and in situ conversion solutions (deposit) (Residual Oil Degrading Consortium, RODC) or surface conversions such as biomimetics are encompassed in the projects.

In conclusion, short-term solutions imply reducing CO2 by using less energy via improved efficiency and the use of energy resources with low or nonexistent emissions. However, global warming experts view an immediate solution in the capture and storage of the CO2 produced in the processes that generate the largest and most concentrated CO2 currents. The development of these man-made CO2 sewers would allow the world to continue spending its most economic and abundant energy resources while substantially reducing CO2 emissions at the same time.

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Figure 3. Outline of land and geologic capture of carbon dioxide emissions.

In situ CO2 conversionIn order to assess the role of CO2 in the activation of hydrocarbon degradation, the culture of hydrocarbon degradation (RCOB1) was used as a model system. RCOB is a methanogenic consortium that uses crude oil to produce methane in the presence or absence of sulfate. It was originally enriched from gas-condensate-contaminated subsurface sediments (method from Gieg et al., [3]). It has been enriched and kept anaerobically packed in a

1Residual Crude Oil Biodegradation.

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sandstone nucleus with residual crude oil and a sulfate-free medium with no freshwater or mineral salts. It also has a broad variety of hydrocarbons in its substrate: BTEX, naphthalenes (mono and disubstituted), natural gas-condensate (n-alkanes C2-C12), n-alkanes C13-C34 [3-7]. Weight loss in the steel gravimetric coupons indicate that RCOB is corrosive [8].

BiomimeticBiomimetics is the technique or science that uses natural processes as a source of inspiration, with the purpose of recreating such models to solve problems. In this case, our goal is to reduce CO2 emissions by using photosynthetic processes aiming to produce biomass and transform it into biofuel. In other words, it is based on the ability of photosynthetic organisms (microalgae) to convert carbon dioxide into lipids with high carbon content (one or two phases before exploitation in the form of biodiesel). This is an appealing alternative, as its capacity to produce biomass is far superior to that of oil crops, and it does not require land that would otherwise be occupied by food crops.

Specifically, as shown in Figure 4, this is the most promising solution for biofuel production and industrial CO2 capture.

CO2 conversion via photosynthetic microalgae“The possibility of using microalgae crops as a potential solution for reducing GHG (greenhouse gas) emissions has been increasing for a few years. Firstly, by using the biomass produced in its cultivation for obtaining biofuels that can substitute fossil fuels, and secondly, by locating these crops near power plants and refineries, among other places, to capture these GHG and thus reduce their emission into the atmosphere. To that end, multiple culture systems have been developed, mainly organized in two groups: open systems and closed systems. At present, closed culture systems have been gaining importance due to their various advantages with respect to open

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Figure 4. CO2 Conversion Technologies Maturity Analysis.

Comparison of some sources of biodiesel

Crop Oil yield(L/ha)

Land areaneed (M ha)a

Percent of existing US

cropping areaa

Corn 172 1540 846Soybean 446 594 326Canola 1190 223 122

Jatropha 1892 140 77

Coconut 2689 99 54Oil palm 5950 45 24Microalgaeb 136,900 2 1.1Microalgaec 58,700 4.5 2.5

aFor meeting 50% of all transport fuel needs of the United Statesb70% oil (by wt) in biomassc30% oil (by wt) in biomass

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culture systems.

Algae constitute a highly diverse group of photosynthetic organisms that have colonized a wide variety of aquatic and land ecosystems owing to their high plasticity and metabolic diversity. Algae can be categorized by size in: • Microalgae: all kinds of photosynthetic microorganisms,

prokaryote or eukaryote, single-celled or filamentous, smaller than 0.02 cm.

• Mesoalgae: photosynthetic microorganisms; prokaryote or eukaryote; single-celled, filamentous or colonial; unialgal or plurialgal; ranging from 0.02 to 3 cm. It is convenient to introduce this new term due to significant differences in technologies and crop costs.

• Macroalgae: multicellular algae of diverse shapes and sizes that range from a few centimeters to several meters in length. It is estimated that there are 30,000-100,000 species of microalgae that include eukaryotic as well as prokaryotic representatives (cyanobacteria or blue-green algae).

Moreover, 15,800 species of microalgae are considered among red macroalgae (6,000 species), brown macroalgae (1,800 species) and green macroalgae (8,000 species, of which 1,000 are marine species and the rest are found in freshwater)” [9].

Products derived from algaeIt must be mentioned that the products obtained from algae vary depending on algae type and species. However, the research was focused in the products described below.

Biomass: It represents the quantity of matter accumulated by each organism and transformed into a renewable energy source since their processing generates energy, either through direct burning, which converts it into heat and electricity, or through high pressure and temperature processes such as pyrolysis, gasification or hydrothermal upgrading (HTU) for the production of gas or liquid fuels. These processes require dry biomass. The drying

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process requires a large amount of energy, which has a negative effect on the energetic balance of the process and on the costs of the necessary equipment [10].

“Lipids and biodiesel: Lipids are one of the main components of microalgae. Depending on species and growth conditions, lipids can constitute from 2 to 60 % of total dry matter as membrane components, storage products, metabolites and energy conservation. Lipids can be used as liquid fuel adapted for engines as Straight Vegetable Oil (SVO). Triglycerides and free fatty acids (a portion of the total lipid content) can be transformed into biodiesel. Compared to SVO engines, algae oil is mostly unsaturated and is therefore less appropriate for direct combustion in sensitive engines. With the purpose of efficiently producing biodiesel from algae, the choice of strains with high growth levels and high oil content is recommended (FAO, 2009)” [9].

Table 1 shows a list of the main microalgae species by dry matter content percentage.

Algaculture

Algaculture for algae products must be performed in a controlled environment for optimal development, which requires the presence of the following elements that will ensure the photosynthetic production of these microorganisms (microalgae):

1. A source of light such as solar power supplied with precision, in the recommended and required quality and quantity depending on the species.

2. CO2 injection. This is the main objective of the research as it makes surface CO2 conversion possible and therefore reduces emissions to the environment and provides added value to the industry. In order to achieve the CO2 required by the cultured microalgae

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it is necessary to follow a series of stages including capture, transportation and, finally, carbon dioxide injection, a process that has an approximate total cost of $27 to $82 US dollars per ton of CO2, of which the largest portion is spent in the capture stage, as shown in Figure 5.

3. The stress that algae must be subjected to: This parameter is necessary to enhance and stimulate microalgae development and

Species Oil (% MP)Botrycoccus Braunii 25-75

Chlorella sp. 28-32

Crypthecodinium cohnii 20

Cylindrotheca sp. 16-37

Dunaliella primolecta 23

Isochrysis sp. 25-33

Monallanthus salina >20

Nannochloris sp. 20-35

Nannochloropsis sp. 31-68

Neochloris oleoabundans 35-54

Nitzschua sp. 45-47

Phaeodactylum tricornutum 20-30

Schizochytrium sp. 50-77

Table 1. Oil contents of some microalgae species referred to as dry matter percentage. Adapted from [9].

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Figure 5. Proportions of the costs in the capture, transportation and CO2 injection stages.

ConclusionThe CO2 conversion alternatives show different possibilities of using this residue from the industrial activity. The selection of conversion technology will depend on the state of development or technological maturity and the cost-benefit ratio in the context of fuel prices in the different markets; this is a key point for the promotion of any technological implementation in the framework

growth. 4. Feeding with nutrients.The latter are very important for deciding the different types of algae to cultivate. The same nutrients are not appropriate, for instance, for nannochloropsis and for chlorella in terms of microalgae, or undaria, when referring to macroalgae [11].

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of contributing to the mitigation of emission of greenhouse gases.

References

[1] Bennaceur, K.; Gupta, N.; Monea, M. et al. CO2 Capture and Storage- A solution within. Oilfield Review, 2004, 16, 44-61.

[2] International Energy Agency (IEA). Topics Climate Change. http://www.iea.org/topics/climatechange. Consulted: October 10, 2014.

[3] Gieg, L.M.; Kolhatkar, R.V.; McInerney, M.J. et al. Intrinsic bioremediation of petroleum hydrocarbons in a gas condensate-contaminated aquifer. Environ. Sci. Technol. 1999, 33, 2550–2560.

[4] Elshahed, M.S.; Gieg, L.M.; Mcinerney, M.J.; and Suflita, J.M. Signature Metabolites Attesting to the In Situ Attenuation of Alkylbenznenes in Anaerobic Environments. Environ. Sci. Technol. 2001, 25(4), 682-689.

[5] Callaghan, A.V.; Gieg, L.M.; Kropp, K.G.; Sulfita, K.G. and Young, L.Y. Comparison of mechanisms of alkane metabolism under sulfate-reducing conditions among two bacterial isolates and a bacterial consortium. Appl. Environ. Microbiol. 2006, 72, 4274-4282.

[6] Gieg L. M.; Duncan K. E.; Suflita J. M. Bioenergy production via microbial conversion of residual oil to natural gas. Appl. Environ. Microbiol. 2008, 74, 3022–3029.

[7] Suflita, J.M.; McInerney, M.J. Microbial approaches for the enhanced recovery of methane and oil from mature reservoirs. In: Bioenergy: Microbial Contributions to Alternative Fuels. Wall J. D., Harwood C. S. and Demain A., Eds. ASM Press, Washington, DC. pp. 389-403, 2008.

[8] Suflita, J.M. and M.J. McInerney. 2008. Microbial approaches for the enhanced recovery of methane and oil from mature reservoirs. In: Bioenergy: Microbial Contributions to Alternative Fuels. Wall J. D., Harwood C. S. and Demain A., Eds. ASM Press, Washington, DC. pp. 389-403.

[9] García, M.J. Captura de CO2 mediante algas unicelulares. Madrid, 2010.

[10] Wijffels, R.. Presentation, Microalgae for production of energy. 2007. http://

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www.worldbiofuelsmarkets.com/downloads/presentations/Algae_15th/rene_wi jjfels.pdf. Date and time: 08/04/10. 17:10.

[11] Oilfox SA http://www.oilfox.com.ar/. Accessed on Tuesday, Colsulted: October 14, 2014.

Community action

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Community criteria for integral management of domestic solid wasteAlejandro Martinez1, Luz E. Muñoz2, Erika Nadachowski3

The following chapter presents the results of the community process of residential solid waste characterization and subsequent settlement proposal by the Association of

sustainable project managers of the village of Santa Cecilia (AGPS), Municipality of Pueblo Rico, Department of Risaralda (Colombia). Activity characterization was developed by members of the AGPS of the village of Santa Cecilia with support from the Autonomous Corporation of Risaralda CARDER and participation of the University of Santa Rosa de Cabal (UNISARC). The results show a production of solid waste of 0.40 kg/person/day for the village of Santa Cecilia.

1Centro de Educación para el Desarrollo Corporación Universitaria Minuto de Dios, Carrera 9a No 20-54 Pereira Risaralda Colombia. e-mail: [email protected]ón Universitaria de Santa Rosa de Cabal, UNISARC Kilómetro 4 vía santa Rosa de Cabal – Chinchiná. Santa Rosa de cabal, Risaralda Colombia.. e-mail: [email protected] general de Areas protegidas, Coorporación Autónoma Regional del Risaralda CARDER, Avenida de las Américas Calle 46 No 46-40, Colombia e-mail: [email protected]


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IntroductionThe Chocó biogeographic region is located in the north-western corner of South America, extending from the province of Darien in Panama to the province of Manabi, in north-western Ecuador, and covering the entire Pacific coastal region of Colombia. The Chocó is characterized by the presence of ecosystems and habitants with high levels of biodiversity[1]. Compared with the national average of 32 inhabitants per square kilometer, the Chocó region of Colombia has a population density of about nine people per square kilometer, one of the lowest population densities in the country.

Waste management at Santa Cecilia village is not too different from that reported for other municipalities in the Chocó. A typical case of such management is reported for the municipality of San Jose de Tadó, a place where solid wastes are thrown into water sources and open areas, creating a high degree of soil and water pollution. Similar situations are reported by other authors [2-3].

According to the Institute for Environmental Research of the Pacific Region of Colombia (IIAP) [4], dumping of solid waste into water sources is one of the main problems associated with contamination of water resources. The Institute reports that this situation is common in different sub-basins belonging to the great basin of the San Juan River [4]. The IIAP mentions the need for a strategy to solve the problems associated with inadequate management of solid waste. Table No 1 shows different management alternatives used in some municipalities in Chocó.

The municipality of Pueblo Rico presents the largest territory of all the municipalities belonging to the Department of Risaralda (See Figure 1). The figure 2 shows the position of the village of Santa Cecilia in the municipality of Pueblo Rico Department of

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LOCAL MANAGMENTE ALTERNATIVES

TYPE OF MANAGMENTE

CONDOTO (Chocó)

Production per capita in the urban area is 1.22 kg/day, where 60% is organic waste. The goal is to reduce by 15% annually through: separation, composting and disposal to landfill to open sky controlled type. [8-9].

x

MEDIO SAN JUAN

(Chocó)

Production per-capita is 0.45 kg / day. With 18% of the population performing partial recycling of organic waste. The San Juan river is reported as a disposal site. The management model proposed includes increased awareness and community participation in the implementation of a community collection company. The 2006 report mentions no process or management program for waste collection [8].

x

GUARATO (Chocó)

The development plan of San José de Tado municipality 2012 - 2015 mentions the lack of collection in rural districts and a partial collection (60%) in urban areas. The proposed management program is based on training of a group of women to start a process associated with solid waste management. The consulted documents do not show production per-capita data [2].

x

Com

mun

ityIn

s ti tu

t iona

l

withco

mmunity

In

stitu

tiona

l

Table 1. Types of solid waste management for three municipalities at the Chocó region in Colombia.

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Figure 1. Location of the municipality of Pueblo Rico (Dark Grey) in the Department of Risaralda and reference location of Risaralda in the context of Colombia and South America.

Figure 2. Reference location of Santa Cecilia in the context of the municipality of Pueblo Rico (Dark Grey) and position of Pueblo Rico in the Department of Risaralda.

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Community criteria for management of solid waste

Risaralda.

This territory is influenced by cultural practices from the region of Chocó [5]. Cultural influences have produced landscape modification processes with human settlements located on the banks of major rivers (Figure 3).The river is used by the inhabitants of the township as a final waste disposal site and, paradoxically, it is also identified by villagers

Figure 3. Location of Santa Cecilia Village on the right bank of the San Juan River.

as an element of enjoyment and recognized as vital heritage (See Figure 4).

The village of Santa Cecilia has previously developed an initiative

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Figure 4. Activities of enjoyment and waste disposal (Yellow arrow) in the San Juan River in the village of Santa Cecilia.

of solid waste management focused on a model of waste separation during the collection process and the use of an organic composting plant that, at the time of this study, was operating below its capacity and showing deterioration (See Figure 5).

According to Sanchez et al. [2], another initiative developed

Figure 5. Current status of the composting plant for organic waste located in Santa Cecilia.

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previously for solid waste management in the area of the village of Santa Cecilia was the construction of sheds where cardboard accumulates until collection. During the development of the characterization activities, it was observed that these sheds had either been demolished or were in poor condition (See Figure 6).

Figure 6. Cardboard collection shed located in the town of Santa Cecilia.

Because soil conditions in the village of Santa Cecilia are not suitable for the installation of a landfill [2], all previous initiatives of solid waste management have focused on local processing and transfer of waste to the town of Pueblo Rico. This activity is carried out once a week using a truck conditioned like a dump-truck, with an expanded load capacity of 17 m3 (see Figure 7); the truck was not conditioned with separate compartments for recycling organic waste and, therefore, cannot make proper waste handling in accordance to the management criteria of recyclables.

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Figure 7. Truck type reference “International Durastar” used for solid waste collection at the village of Santa Cecilia.

Methods

The characterization of household solid waste was conducted by members of the “Asociación de Gestores de proyectos sostenibles de Santa Cecilia” (AGPS) with the support of professionals from the environmental authority of the department (CARDER) and the University of Santa Rosa de Cabal (UNISARC). The activity was carried out in seven sectors of the urban area of Santa Cecilia: La Union, Piedras, Plaza, Remolinos, Cinto bajo, Cinto medio and Cinto Alto (Figure 5). The solid waste characterization was done

Figure 8. Reference location of the sectors characterized at the village of Santa Cecilia.

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in November of 2015. The period for waste collection in all sectors was seven days (one week).

Under conditions of proportional stratified sampling the staff distributed different color bags; the process of waste separation according to color code was explained in each house. The codes are described in Table 2.

Waste type

Toilet paper Organic

Paper and

card-board

Plastic GlassMetal

and alu-minum

Bag Color Red Green Blue Yellow Grey White

Table 2. Color used for the classification of residential solid waste in the township of Santa Cecilia.

Bags were delivered to residents after passage of the garbage truck and were collected one week later, just before the arrival of the truck. Data on population settled in urban area as well as information on population density were compared with the data recorded by Manco, S. et al [6].

For each sector it was made a random separation of one quarter of the waste. To determine humidity was used a 20 liters sample, the sample was subjected to drying conditions according to procedures described by Sakuray [7]. The characterization parameters were processed according to proportional stratified sampling conditions and based on a sample established by the following relationship:

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Where:Z2 = 1.96N= 219α= 0.04E = 10%A minimum sample of 61 homes was obtaided. Table No 3 shows the sample distribution for each sector. Due to the

SECTOR TOTAL NUMBER OF HOUSEHOLDS SAMPLE

Piedras 51 14

Cinto Bajo 47 13

Remolinos 9 4

La Unión 12 4

Cinto Alto y Medio 88 25

Plaza 12 4(Residential) 4 (Commercial)

TOTAL 219 64 (Residential)

Table 3. Total number of households for each urban sector and sample obtained.

existence of food kiosks located in Santa Cecilia’s main plaza and in order to estimate the waste generation of that sector, a characterization of 50% of those establishments was made. All characterized samples were weighed and then classified. To determine compliance with classification by individuals and to estimate the level of acceptance of the separation exercise, an instrument consisting of a simple survey, was designed. Table No 4 shows the instrument used.

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CLASSIFICATION DESCRIPTOR

1. No separation no explanation

There was no separation, the bags are used interchangeably to deposit in them all kinds of waste and there was no answer on the reason for the situation

2. No separation with explanation)There was no separation. Lack of information was manifested as a cause of the situation

3. (Separation codeless) proper classification was made without following the code proposed

4. (proper separation) proper classification was carried out in line with the proposed code

Table 4. Categories acceptance separation method

The staff consisted of ten people divided into two groups of five people each. Both groups used the same procedure and equipment to enhance the characterization procedure. The elements used are listed below and are shown in Figure 9:

Figure 9. Equipment used by staff during characterization.

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- PVC yellow apron 88Cm * 62Cm- Rubber boots- 32 Cm Nitrile Rubber gloves - Disposable mouth and nose protection- Disposable hats- 200 Kg weighing scale - Electronic Digital scale

The characterization data were socialized and discussed in community workshops; based on these results, an assessment of solution scenarios was performed. Scenarios were assessed through participatory evaluation. Three scenarios were constructed for the activity; their characteristics and conditions are presented in Table 5.

SCENARIO NAME CHARACTERISTICS

Isolation

AGPS members do not have help from any institution. The only facility for waste collection is the existing compost plant.

Shared capacityAGPS has support from CARDER for material and equipment to manage the waste

Three stakeholders

AGPS has support from CARDER to develop a management program in partnership with the municipality of Pueblo Rico and under municipal guidelines

Table 5. Evaluation scenarios discussed during the workshop characterization results

The participants (12 people) were divided into four groups of three people each. Each group had the task of evaluating advantages and disadvantages of each scenario. Each group presented its proposals on each scenario and then assigned to each scenario a number of

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points. The maximum score for each scenario was ten points. Solution conditions for each scenario were organized under three categories (equipment, commitment and indispensable stakeholders).

Results

Wastes generated from 64 homes in seven different residential areas were characterized, as well as four commercial kiosks located at the main plaza. All samples obtained according to data reported in Table 3. Estimated numbers of inhabitants per sector are shown in table 6.

Sector

Total Number of Hou-seholds

% of totalMean

(people/ household)

Number of households

inhabitants registered

in each house

Characte-rized

Sector%

Estimated Population

Sector

La Unión 12 5,48 5 4 20 33,33 111

Piedras 51 23,29 4 14 56 27,45 472

Cinto bajo 47 21,46 4 13 52 27,66 435

Cinto Médio y

Alto88 40,18 4 25 100 28,41 815

Remolinos 9 4,11 4 3 12 33,33 83

Plaza Viviendas 12 5,48 4 4 16 1,83 111

Plaza Quiscos 12

50% Comercio

PlazaN/A 4 N/A 50,00 N/A

Total Hous-eholds

219 100% Mean

67 256

Total population 2027 4,17

Table 6. Ratio of household and population estimated in all urban sectors characterized at Santa Cecilia.


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A total of 495.69 kg of solid waste was characterized with an estimated production of 0.4 kg per capita per day. The overall results are discriminated in table 7.

Organic

Paper and

card-board

Plastic

Metal, glass and

alu-minum

Toilet paper Others Total

% 68,78 5,46 8,89 4,74 6,59 5,54 100,00

Kg 340,96 27,04 44,08 23,47 32,68 27,45 495,69

Table 7. Total kilograms of waste characterized Corregimiento Santa Cecilia (Risaralda).

The results of the survey (instrument shown in Table 4) are useful to determine compliance with classification by individuals and to estimate the level of acceptance of separation.Table 8 shows the frequency distribution found for 61 of the 64 elements (households) characterized.

DESCRIPTOR OUTCOME % FREQUENCY1. No separation no explanation 6,56 4

2. No separation with explanation) 24,59 15

3. (Separation codeless) 44,26 274. (proper separation) 24,59 15

Table 8. Estimate of the level of acceptance of separation under the color classification scheme.

Table 9 shows the estimated generation of solid waste for a period of one week. The data were projected from the information of number of homes and population presented in Table 6.

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Table 10 shows the generated waste mean density for the village of Santa Cecilia. The data are presented in association with the total volume generated and compared with the installed capacity of the transport used by the municipality of Pueblo Rico (Durastar truck with 17m3 capacity).

SectorPércapitaPer area

Estimated Popula-

tion # Hab

Estimated produc-

tion

Estimated organic produc-

tion

Paper and

card-board

Plastic

Metal and

Alumi-num

Others

La Unión 0,36 111 283,0 177,06 17,55 31,70 17,72 38,86

Piedras 0,48 472 1594,1 1160,83 157,82 111,75 93,26 69,66

Cinto bajo 0,41 435 1257,2 711,09 69,02 169,22 19,86 288,03

Cinto Medio y Cinto Alto 0,36 815 2070,0 1462,85 38,92 172,64 100,39 295,18

Remolinos 0,33 83 191,7 134,13 0,00 18,04 8,88 30,65

Plaza 0,42 111 326,5 217,51 38,50 16,85 11,56 42,16

Plaza Comercial Quioscos Familiares

2,34 15 245,4 183,94 4,05 22,89 19,26 15,21

Mean 0,40 2027 5967,93 4047,41 325,85 543,08 270,93 779,75

Table 9. Projection of domestic waste generation for Santa Cecilia based on the characterization process estimated on kg/week.

Waste density total volume of waste generated

Installed capacity transport volume volume deficit Deficit in kilograms

0,32 Kg/Lt* 18,084 m3 17 m3 1,083 m3 351 Kg

Table 10. Density and volume of solid waste generated compared to current installed capacity.

The compost plant is able to process 15 m3 of organic waste every two months. Under these conditions the plant can process approximately 611 kg of organic waste per week equivalent to 15% of the total waste generated in Santa Cecilia.

Santa Cecilia is generating an estimated 351 kg of clean cardboard per week and 270.93 kg of aluminum and metal; both are suitable materials for commercial activities. However, there is not an

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appropriate location for storing such material in the village. Every week 543.08 kg are produced; 13.82% of that amount is suitable for commercialization, this percentage is equal to approximately 75Kg weekly. The village does not have a warehouse and required equipment for crushing and storing this material.Table 11 presents the results and scores from the four groups of participants during the workshop of socialization of the characterization results and also sets out the proposed solutions.

SCENARIO ADVANTAGE DISADVANTAGESTOTAL SCORE OBTAINED

G1 G2 G3 G4

Isolation

- Would provide greater cohesion to the community by the fact of having to find a joint solution.- Anyone could market the recycled material generating business alternatives. - Incrases community confidence in themselves- Promotion of ideas of use and processing of many materials that actually are throwing away.

- Not having adequate space for storing material. - Many people are not aware of their role as part of the solution- The solution will takes a long time

5 3 4 5

TOTAL SCORE17

Shared capacity

- Best warehouses, and equipment to make a more appropriate waste management. - There are possibilities of more training opportunities to involve more people.- The solution will be concentrated in AGPS and community.- The experience can be replicated in other districts.- The solution could be faster.

- The legal procedures with the environmental authority (CARDER) It takes too much time and too much bureaucracy

5 5 4 4

TOTAL SCORE18

Three stakeholders

- AGPS could manage municipal resources for solid waste management.

- The dependence of local authorities is a risk due to little commitment they have with Solution- When local administration changes, conditions may also change.- People do not have much confidence in the municipality

0 2 2 1

TOTAL SCORE5

Table 11. Outcome assessment of scenarios.

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Table 12 sets out the conditions for the discussed scenarios.

Scenario Required equipment Conditionings Responsibilities and key stake holders

1. Shared capacity

Total Score18

A- The composting equipment capacity should be doubled. B-Three wheeled vehicle adapted like waste transport C- Warehouse to store plastics, cardboard and other commercial materialsD- Plastic crusher

A- The Community and AGPS will operate the composting plant. B- The organic waste micro-routing is performed twice a week and reusable material micro-routing once a week.C- Plastics are crushed to reduce volume and stored in the warehouse for further transportation to Pereira and / or Pueblo Rico.

Responsables:- CARDER: Investment in composting beds, three wheeled vehicle and plastic crusher machine- Operation and maintenance of composting beds and installed equipment will be the responsibility of AGPS and the communityKey StakeholdersPassenger transport companies (social responsibility funds could be used to adapt buses to transporting recover plastic to La Virginia. Promotion of awareness with passengers should be done.)Business owners (To support awareness campaigns, To installing signs in their business, promoting responsible consumption and purchases)Schools and Church (awareness campaigns) involve students from grade 10 and 11 to promote recycling, and responsible consumption and purchases campaigns

2. Isolation

Total Score17

A. Existing composting bedsB. Adaptation of cargo bikes for micro - routing (One cargo bike per urban sector)

A. Improve the operation of the composting plant establishing full capacity.B. AGPS and Community (Students) will operate the cargo bikes for organic and recycling material micro-routing daily.- Manual volume reduction of plastic and cans should be made in order to transport them to other municipality to be commercialized

Responsables:AGPS, teachers and students of educational institutions (in charge of micro routings every day) Business owners: To promote the commercialization of recyclablesKey StakeholdersBusiness owners will sponsor the transport of commercial waste to biggest towns (La Virginia and Pereira) profits will be distributed with themConstant awareness campaigns will be made and participation of students will be required to promote the right management of hazardous waste

3. Three stakeholdersTotal Score

5

Same requirements as expressed in Scenario 1(Shared Capacity

Same as Scenario 1 with the following addendum: Reducing waste by composting allows the municipality to reduce transportation costs. Some of that resource will support awareness of proper waste classification and disposal

Responsables - CARDER: Investment in composting beds three wheeled vehicle. Mayor Office (plastic crusher machine)- Operation and maintenance of composting beds and installed equipment will be AGPS and community responsibility.Key Stakeholders: Same as manifested in Scenario 1(. Shared capacity)

Table 12. Conditions and responsibilities of proposed scenarios.

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Discussion of Results

Data analysis of physical and chemical parameters of waste indicated a pH of 6.72, arsenic in values of 4.32 ppm, and lower figures for mercury 0,01ppm. These results do not demand specific control interventions, but they do emphasize the need to avoid the disposal of waste in water sources. The calorific potential recorded for the type of waste generated is 3358 Kcal/Kg, enough to produce electricity from the use of an incineration plant combined cycle gas and steam, however the amount of waste currently generated (5.96 Ton/week) do feasible the installation of a plant of this type which require a weekly estimate generation 20 Ton/week.

The assessment of scenarios shows a similarity in weight between two scenarios: Shared and isolation. This similarity suggests several important aspects:• High confidence of the community (members of AGPS) in

their management capacity;• Evidence of the existence of a sense of trust of the community

to in the processes developed with support from the environmental authority CARDER

The urgent need to create spaces to raise awareness in the community regarding its responsibility for in the management of solid waste was expressed during the workshop of socialization. Other factors that, in the opinion of the community, must be linked to any solution are:1 Independent collection (Reduce dependence on collection scheme from the municipality of Pueblo Rico)2. Marketing of material generated in the village.3. Re - activation and promotion of the plant and composting activity.

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4. Provide incentives to the population for appropriate separation. Production data, per-capita percentages of composition of organic matter and production of material with potential for commercial use, are consistent with similar studies in other locations of Chocó.

The percentage of population that was willing to carry out the exercise of separation (24.59%) plus the percentage that did it without adhering to the color code (44.26 %) show that the awareness campaign was successful and that it must continue with some sort of stimulus added to it. The data make it possible to measure the receptivity of the population in relation to the environmental awareness activities conducted by AGPS and supported by CARDER.

The percentages and amounts of recoverable material (clean cardboard, paper, aluminum, metal) are not enough to initiate a marketing activity on a weekly basis with a focus in the municipality of Pueblo Rico and/or in the city of Pereira. However, a gathering station based in the village of Santa Cecilia with the support of the municipality by facilitating the transportation management process, might give viability to a proposal to include such a component.

While the caloric potential of generated waste in the village is suitable for the generation of electricity through a combined cycle plant, this option it is not appropriate because the actual production of organic waste is not enough to cope with a plant of this type. However, local, and type of waste are suitable for installing a child generation plant and biogas (anaerobic fermentation).

The proposed management phases reduce the amount of organic waste being transferred to the municipality of Pueblo Rico, promote the generation of business ventures in the community and provide social empowerment of solutions to problems of

References

[1] Merlano, D. J. M.; Harders G. F. “El Chocó Biogeográfico de Colombia”. Libros de la Colección Ecológica del Banco de Occidente. available in http://www.imeditores.com/banocc/choco/creditos.htm. 2009. Consulted in September 22th of 2015.

[2] Plan de desarrollo del Departamento del Chocó. 2012 available in http://www.choco.gov.co/apc-aa-files/39636366663438353663646466323738/Plan_

context .

The alternative solutions presented in this report need to be enriched by adding the experience of other professionals, with the expectation of developing a pilot model that can be replicated in several municipalities of Chocó.

Acknowledgments

The project was drawn up by agreement between the Regional Autonomous Corporation of Risaralda – CARDER (Risaralda´s environmental authority) and the University of Santa Rosa de Cabal - UNISARC. The project was supported by the Santa Cecilia association of sustainable projects managers (AGPS), whose members participated actively in field work and workshops; the results of their efforts are the basis of this report.

The collaboration of the electrical engineer Juan José Gallo Mejia, who proposed alternatives for generating electrical energy from organic solid waste, and the assistance of ecologist David Martinez, who supported the initial training workshops on plastic classification, are sincerely appreciated. The generosity of the CARDER staff, always attentive to provide logistical support for the efficient execution of the activities is also acknowledged and appreciated.

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de_Desarrollo.pdf Consulted in September 17th of 2015.

[3] Sanchez, B.; Nasachowski, C. E.; Bedoya, M.; Valencia, Y. Plan de Manejo de Los Recursos Naturales del Territorio Colectivo de Las Comunidades Afro de Santa Cecilia, Pueblo Rico Risaralda, Colombia. 2012 . Available in file:///C:/Documents%20and%20Settings/John%20Harold%20Casta%C3%B1o/Mis%20documentos/Downloads/PLAN.DE.MANEJO.pdf Consulted in September 21th of 2015.

[4] IIAP, Instituto de Investigaciones Ambientales del Pacífico. Plan estratégico de la Macrocuenca del Pacífico. 2013. Pág. 152, 278. available in http://siatpc.iiap.org.co/docs/avances/pemp.pdf pdf Recovered in December of 2015.

[5] Pineda, C. C. Evaluación de los impactos socio-económicos del proyecto alianza productiva: banano bocadillo en el Municipio de Pueblo Rico, Risaralda. 2012. Available in http://hdl.handle.net/11182/580. Consulted in September 19th of 2015.

[6] Manco, S.; Deibys, G. Estrategias de Gestión para el mejoramiento del sistema de abastecimiento de agua y saneamiento básico, Corregimiento de Santa Cecilia, Pueblo Rico. 2010, 45-48. Available in http://repositorio.utp.edu.co/dspace/bitstream/11059/1300/1/36361M269.pdf Consulted in September 23th of 2015.

[7] Sakuray, K. Método Sencillo Del Análisis De Residuos Sólidos Manuales CEPIS/OPS. 2010. available in http://www.bvsde.paho.org/eswww/proyecto/repidisc/publica/hdt/hdt017.html Consulted in September 10Th of 2015.

[8] PROGRAMA NACIONAL MEJORAMIENTO INTEGRAL DE LA GESTIÓN DE RESIDUOS SÓLIDOS EN COLOMBIA, 2006. Plan de Gestión Integral de residuos sólidos del Municipio de Medio San Juan departamento del Chocó. available in http://www.mediosanjuan-choco.gov.co/apc-aa-files/64356135333163663435336663636162/PGIRS_Medio_San_Juan.pdf Consulted in September 20th of 2015.

[9] Castro, R. W. 2011 Plan De Negocios Para El Aprovechamiento De Materiales Presentes En Los Residuos Sólidos Urbanos, En El Municipio De Condoto (Choco). available in http://repositorio.utp.edu.co/dspace/bitstream/11059/2235/3/3637282R374. pdf Recovered in September 19th of 2015.

FEALAC-Cbionano International workshop Environment and Energy: Challenges and Opportunities from Bio and Nanotechnology. Bogotá, Colombia, March 2016.