CWR6252Environmental Biogeochemistry of

Trace Metals

Dr. Lena Q. MaProfessor

Soil and Water SciencesTel: 352-392-9063 ext. 208

Dr. Jean-Claude J. Bonzongo Associate Professor Environmental Engineering Tel: 352-392-7604

1.1. Course description and objectivesThis course focuses on fate and impacts of trace metals/metalloids as they cycle through geological and biological environmental compartments.

The course provides students with a scientific basis to biogeochemical approaches and a foundation upon which they can develop the ability to analyze, predict, and solve environmental problems related to metal pollution.

1.2. Pre-requisites:

Include at least one of the following: general chemistry, inorganic/organic chemistry, biochemistry, environmental chemistry, soil and water chemistry or permission of the instructors

1.3. Textbook: None

1. SYLLABUS

1.4. Course Format

The course consists of lectures, student presentations, and chats using Mbreeze. Location: McCarty Hall D G-001 M, W & F 4th period (10:40 to 11:30 am) for on-campus (OC) students Delivery via internet for distant education (DE) students. For DE students, presentations will be delivered via Mbreeze.

1.5. Course Web SiteChat web site via Mbreeze: http://mbreeze.ifas.ufl.edu/cwr6252: enter as a guest and type your first name. Everyone is required to attend chat sessions, starting the second week.

1.6. Class web site: http://lqma.ifas.ufl.edu/cwr6252/cwr6252.html.

1.7. Assessment Methods:

Grades will be determined based on performance on homework, term papers, and oral presentations. The weight of the above assignments towards the final grade will be calculated as follows: 60% for homework, 30% for term papers, and 10% for oral presentations

1.8. Grade ScaleA 95 – 100A- 90 – 94B+ 85 – 89B 80 – 84B- 75 – 79

______________________________C+ 70 - 74 C 65 – 69C- 60 - 64

1.9. Course Structure

INTRODUCTIONGEOCHEMICAL BACKGROUND

METALS IN THE HYDROPSHERE

METALS IN SOILS AND PLANTS

CASE STUDIESBIOGEOCHEMISTRY OF SELECTED TRACE

METALS

LECTURE 1

Concepts in Environmental Science

1. Understanding of natural orders

2. Identification of anomalous deviations from natural orders

3. Solving environmental problems

4. Accumulate knowledge that support proactive approaches to avoid or limit future environmental and health problems

Example of Natural Order: The Periodic Table

IMPORTANCE OF TRACE ELEMENTS AND ENVIRONMENTAL

IMPLICATIONS

EARTH ATMOSPHERE

• Nitrogen 78.0842%• Oxygen 20.9463%• Argon 0.9342%• Carbon dioxide 0.0381%• Water vapor ~1.0000%• Other 0.0020%

WHY FOCUS ONLY ON TRACE METALS?

• Occurrence at very low ( trace) levels

• Sensitivity to anthropogenic activities

• Toxic at relatively low levels and impacts on living organisms and human health

• THE BEGINNING

• BIG BANG: widely accepted model based on a giant explosion some 10 to 15 BYA

ORIGIN OF THE EARTH SYSTEM AND

ELEMENTAL ABUNDANCE

THE ORIGIN OF THE ELEMENTS

Log [abundance]Si = 6

Atomic Number

NUCLEAR CHEMISTRY CONTROLS THE NATURAL ABUNDANCE OF

CHEMICAL ELEMENTS

Cosmic Abundances of the Elements (cont’d)

321

4

Cosmic Abundances and Origin of the Elements

H-Fusion

1

Synthesis by H-fusion stopped at Li b/c formation of next elements such as carbon required higher density particles and different T-range.

Big bang produced H and He served as “feed stock” from which all heavier elements were later created

Cosmic Abundances and Origin of the Elements

Alpha addition

)He(additionparticle 42

2

Triple sequence: 4He+4He8Be+4He12CSubsequent additions produce elements up to Fe

Reactions are highly exothermic = energy source

These nuclear bombardments are reactions that produce free neutrons (n) as illustrated below

13C(,n)16O and 22Ne(,n)25Mg

nMgNe

nOC

10

2512

42

2210

10

168

42

136

Cosmic Abundances and Origin of the Elements

Low flow of neutron S-process

Neutrons produced during -addition reactions interact with nuclei of any mass at existing

temperature to produce chemical elements up to Bi, which is the heaviest stable element in the

periodic table. (Mechanism on next slide)

-decay stops the buildup of neutron and limits the formation of

new elements to bismuth (Bi). At this point, the r-process is necessary for formation of much heavier elements

CsXand

55zandz154

128AandA0128

XXe Az

01

12854

Cosmic Abundances of the ElementsOccurs in explosive environments such as supernovae, and where the neutron flux is very high and the interaction time between neutrons and nuclei is very shortSimilar to the s-process, but is more rapidNo time for isotopes to undergo -decayProduces highly unstable (radioactive) elements

r-process

ENVIRONMENTAL IMPLICATIONS OF ELEMENT NATURAL ABUNDANCES

• Trace metals are rare and usually extracted from crude ores

• Mining and processing release trace metals to different environmental compartments

• Exposure to high levels of trace metals

• Toxicity on human health and impacts on ecological functions