chapter 6 ecotoxicology environmental analytical chemistry environmental analytical chemistry...

Chapter 6 Ecotoxicology

Environmental Analytical

Chemistry

Environmental Analytical Chemistry

Chapter 6Ecotoxicology

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Chemistry

Contents

6.1 Introduction

6.2 Toxicant behaviour in living organisms

6.3 Dose-response relationships of toxicants

Contents



Chemistry

Key points and difficulties

Key points Toxicant behaviour in living organism

DifficultiesDose-response relationships of toxicants



Chemistry

‘All substances are poison; there is none that is not a poison.

The right dose differentiates a poison and a remedy’

--Paracelsus (1493-1541)

帕拉塞尔苏斯 ( 瑞士医学家 )



Chemistry6.1 Introduction The term ecotoxicology [ekətɒksɪ‘kɒlədʒɪ] 生态毒理学 is

used to define the branch of toxicology concerned with the study

of the toxic effects 毒性作用 ; 毒效 of natural and man-made

(anthropogenic) substances on the biotic (living) and abiotic

(non-living) components of the biosphere. It is often used

synonymously with 与 … 同义使用 the related term

environmental toxicology, although the latter strictly

encompasses 围绕 the effects of chemicals and other agents on

humans. Its ultimate objective is to protect natural communities

群落 of organisms from 保护… . 免受 the adverse effects 不利影响 of potential toxicants.

6.1 Introduction



Chemistry

A toxicant is an agent that has a harmful effect on a

biological system at all levels, from the subcellular, through whole

organisms to communities and entire ecosystems. The term is not

exactly synonymous with pollutant as the latter may also include

toxic agents, such as extremes 极端值 of temperature and pH,

deoxygenation 脱氧作用（反应） , noise.

While many powerful toxicants, such as heavy metals,

sulphur dioxide and aflatoxins [əfleɪ'tɒksɪnz] 黄曲霉毒素 , are

naturally produced, they usually only occur in relatively small

quantities in a very localised 局部的 area in such circumstances.

6.1 Introduction



ChemistryHowever, where human activities lead to their release into the

environment in large quantities over short periods of time they can

exert very damaging environmental effects施加影响 . Also of great

significance to the welfare 繁荣 of most natural environments today

are the toxic effects of anthropogenic substances. Not only are many

of these xenobiotic [,zenəubai‘ɔtik] 异生物质 in the strictest sense,

in that they are not produced at all by natural processes, but they too

are often found at high levels in many environments. Indeed, there

are few 极少，几乎没有 if any, natural environments where

detectable traces 检测痕迹 of some anthropogenic substance(s)

cannot be found.

6.1 Introduction



Chemistry6.2 Toxicant behavior in living organismsThe most important factors influencing the toxicity of a

substance are its physicochemical properties as these determine its

biological activity at the cellular level, which in turn dictates its impact

at higher structural levels in a biological system. The use of models

derived from the so-called quantitative structure-activity relationships

(QSARs) 定量结构活性关系 of potential toxicants is an increasingly

important aspect of ecotoxicological work. Here, the physical and

structural components of the compound (molecule descriptors) are used

as interpreters 解释器 , perhaps more importantly, as predictors 预报器 of their likely toxic impact. Some of the more important biochemical

and other effects of toxicants on organisms are summarised in Tables

6.1 and 6.2.

6.2 Toxicant behavior in living organisms



ChemistryTable 6.1 Summary of some important biochemical effects of toxicants

Site of action Toxic effect

Protein synthesisDepression of protein synthesis in rough ER.Occasionally stimulation of microsomal 微粒体 protein synthesis

Lipid metabolismDisturbance of liver function, including cholesterol [kə’lestərɒl]胆固醇 synthesis, excess lipid accumulation

Carbohydrate metabolism

General impairment 损伤 of oxidation and glycolytic[,glaɪkə‘lɪtɪk]糖分解 processes

Microsomal enzymes Inhibition/stimulation of microsomal enzymes

Cell membraneInterference with membrane permeability, and disturbance of membrane carrier systems

Regulatory and growth processes

Adverse effects on structure and activity of regulatory enzymes and function of hormones, decrease in growth rates

RespirationDisrupted function 中断功能 of respiratory chain electron transport; uncoupling 解偶 and inhibition of oxidative phosphorylation 磷酸化

PhotosynthesisInhibition of electron transport, uncoupling of electron transport and photophosphorylation 光磷酸化 , inhibition of energy transfer




ChemistryTable 6.2 General effects of toxicants

Effect Specific effects

Death Cessation of vital activities 生命活动的终止

PhysiologicalChanges to metabolic functions, including respiration and photosynthesis, nutrition, osmoregulation 渗透调节 , circulation, body temperature

BehaviouralAlterations to sensory 感觉 and learning capacities, motor activities肌肉活动， mating behavior, predator-prey relationships, migration

GrowthBiomass 生物量（质） , body and organ growth, developmental stages

ReproductionChanges to viability of gametes, fertility, survival rates of offspring 配子活力、生育、后代存活率

GeneticChromosomal damage, mutagenic, teratogenic and carcinogenic effects 染色体损伤、致突变、致畸和致癌效应

Histopathological 组织病理学的 Tissue damage, abnormal growths 组织损伤，畸形生长




Chemistry The effects of toxicants may be elicited immediately on 因为exposure or may be delayed until some time after exposure has occurred

depending on the properties of the toxicant, its mode of action and its

susceptibility to metabolic breakdown 代谢分解的敏感性 (biotransformation) by the organism itself. Toxicants that are

biotransformed tend to be rapidly excreted [ik’skrit] 排泄 and

therefore not likely to have delayed effects.

Ecotoxicological effects can be broadly classified in a number of

different ways, for example, direct as opposed to indirect toxicity.

Direct toxicity arises as a result of internal biochemical changes within

organisms brought about by the toxicant. In contrast, indirect toxicity

occurs as a result of toxicant effects on factors external to the organism,

such as decreases in food organisms, habitat destruction, etc.




Chemistry Toxic effects can also be categorised as reversible or irreversible.

In the case of the former, reversibility may be brought about by the

normal repair mechanisms 正常修复机制 of living organisms,

perhaps necessarily accompanied 必然伴随着 by escape to a

toxicant-free environment to allow this to happen. No such recovery

is possible where damage is said to be irreversible and serious

damage or death is the inevitable [in’evitəbl] 必然发生的 result.

A further distinction can be made on the basis of the site 部位 of

action of a toxicant. Where an effect occurs at the primary site of

contact 原始接触部位 between an organism and a toxicant, it is

termed 被称为 a local effect.




Chemistry

For example, inflammation 炎症 of the surface of the lungs in

mammals, or erosion of the gills in fish 鱼鳃 when exposed to

corrosive substances in the respiratory medium. Conversely,

where a toxicant requires absorption and distribution to a target

site 目标部位 distant from the point of entry into the body 远离进入身体的点位 , it is regarded as 被认为是 systemic in

effect.




Chemistry

A number of toxicants, such as many industrial solvents, are non-

selective in their toxic effects as they appear to be able to act on a

range of target sites within organisms. Others are much more

selective in that they impair only one type of cell, tissue or function

without affecting others, either in the same or a different species.

Clearly, this latter mechanism must be due to the interaction of the

toxicant with specific receptor (target) sites in cells. Thus, for

example, organophosphate insecticides exert their toxic effect only

on nervous tissue by irreversibly binding to the enzyme

acetylcholine esterase乙酰胆碱酯酶 .




Chemistry6.3 Dose-response relationships of toxicants Although many classes of compound can exhibit environmental

toxicity, simple exposure to them will not necessarily always elicit a

harmful biological effect. Of paramount 至高的 importance is the

amount or does of the compound that actually enters an organism to

influence the biological processes taking place within it. Also, the

relationship between dose and biological response can be very

variable and sometimes exposure to low doses of a potential toxicant

may have unexpected positive biological effects. For example, the

biological productivity of oligotrophic[ɒləgəʊ‘trɒfɪk] 贫营养的(nutrient-poor) waters will increase when they are subjected to

modest doses of sewage effluents 污水 .




Chemistry In other circumstances no effects are observed until a particular

threshold dose 阈剂量 of a toxicant is exceeded.

The graph describing the response of a biological system to a

toxicant over a range of concentrations is known as 被称为（认为） the dose-response curve, as shown in Figure 6.1. In general

terms this relationship holds true for 适用于 virtually 几乎 all

toxicants, a notable exception being true allergic [ə’lɜ:dʒɪk] 过敏的reactions which are particular kinds of changes in the immune

system免疫系统 of organisms. Allergic reactions arise as a result of

a substance stimulating the body to release natural chemicals within

the body which are responsible for the response observed, rather than

it (response) being a direct effect of the substance itself.




Chemistry

Increasing dose/concentration

Range of increasing effect with increasing

dose

No-effect range

Maximum effect range

LD50/LC50

Figure 6.1 Dose/concentration-response curve of a toxicant




Chemistry For practical purposes the following assumptions are made

regarding the dose-response relationship.The response is graded 分级的 and a function 函数 of the

concentration of the toxicant at the site of action;The concentration of toxicant at the site of action is related to the

exposure dose;The response tested is causally related to 与…存因果关系 the

toxicant;That below a certain dose no response occurs or at least can be

detected;That once a maximum response is achieved any additional

increases in dose will have no effect.




Chemistry While in the broadest sense these assumptions hold true 成立 ,

there are various factors that may influence the dose-response

relationship as described above.

It is important to realize that the concentration of a toxicant at

the site of action may not necessarily be related to the dose or

environmental concentration to which an organism is exposed. A

great varied of factors may influence the rate at which the

toxicant enters an organism, including its chemical speciation or

particular characteristics of the organism such as surface

permeability, physiological state 生理状态 , sex, shape, etc.




Chemistry

For example, heavy metals are usually more toxic to organisms in

acid environments as they tend to form more biologically available

chemical species under conditions of low pH and will therefore be

more readily taken into the body. In ecotoxicological studies it is

therefore common to place more emphasis on the concentration-

response rather than the dose-response relationship, although with

the clear recognition that it introduces more uncertainty into these

studies. For this reason the term concentration will be largely used

hereafter 从此 in preference to 优先于 dose.




Chemistry In addition, reversible or irreversible reactions may lead to

different types of responses with regard to 对… the concentration

of a toxicant at the site of action. Thus a toxicant that elicits a

reversible reaction may give no measurable, or at best 顶多 a

transient [‘trænzɪənt] response 瞬时响应 , at a low-concentration

exposure and this will not be affected by repeated or continuous low-

concentration exposure. In contrast, where irreversible reactions are

involved, a single exposure may be sufficient to elicit a damaging

response and repeated or continuous exposure may lead to a

cumulative['kju:mjələtɪv] 累积的 toxic effect, depending on the

turnover rates 周转率 of toxicant-receptor complex 毒物 - 受体络合物 .




Chemistry While 然而 the causal relationship 因果关系 between toxicant

and response is usually straightforward and clearly established, in

some cases they may be only indirectly related and therefore do not

provide an appropriate basis for a concentration-response study. For

example, the inhibition of certain 某些 enzymes may provide the

basis for a toxicological study毒理学研究 but these must be related

to the overall toxic effect being measured. The validity of the causal

link between concentration and response is particularly vital where

epidemiological [,epɪ,di:mɪə‘lɒdʒɪkl] 流行病学 studies are involved

and considerable rigor 苛刻、严谨 must be applied to the data to

avoid false conclusions 错误结论 being made regarding the cause-

effect relationship 因果关系 .




Chemistry

There is controversy [‘kɑntrə,və:si] 争议 over 对是否 the

existence of a so-called ‘no effect or threshold’ concentration for any

toxicant. Indeed, detection of any response is dependent on the

sensitivity of the methods used to measure it. The more sensitive the

methods used the easier it is to detect some kind of response,

however minimal it might be 无论它可能有多么低 . In the case of

carcinogenic toxicants, exposure to only a few molecules may be

sufficient to trigger 引发 the development of a tumour [‘tju:mə(r)]

肿瘤 in the longer term and therefore no true ‘threshold’ exposure

level can be determined for such substances.




ChemistryDespite these and other reservations 保留意见 , the concentration-

response curve is nevertheless a useful way of quantifying

ecotoxicological effects and parameters derived from it are valuable for

comparative purposes and the establishment of safe, or at least

acceptable, environmental limits 环境限制 .

In practical terms 实际上 it is the linear portion of the sigmoid

curve S型曲线 shown in Figure 6.1 that is most usefully employed to

quantify effects and establish useful parameters. To this end 为此 the

conversion of the whole curve into a linear form (Figure 6.2) using

probit analysis 概率分析法 is a standard practice. Probit analysis

depends on dividing the sigmoid concentration-response curve into

multiples 倍数 of the standard deviation from the median

concentration,




Chemistry

i.e. when 50% of test organism(s) elicit the response in question 讨论中的 . When the logarithm [‘lɒgərɪðəm] 对数 of the

concentration is used the curve becomes linear and 68% and 95.4%

of the test population is included within one and two standard

deviations either side of the median respectively.

The median concentration has a special significance in

ecotoxicological studies as it is associated with the inherent

variability of biological organisms that dictates that not all test

organisms, even those very closely related genetically, will respond

in an identical manner to the effects of any toxicant.




Chemistry The resistance to the toxicant will vary among the members of a

test population 在某个测试群体的成员之间 with the most

sensitive individuals succumbing [sə'kʌm] 屈服 ; 死亡 first, the

most resistant last and others at various points between. The median

concentration is a mathematical measure 数学指标 and therefore

its accuracy is improved with 采用 repetition of the experiments

from which it is derived.

The slope of the concentration-response curve can be an important

measure 指标 of the type of toxic response being studied. As shown in

Figure 6.3(see p458), the steep slope of curve A indicates a narrow toxic

concentration range and a site of action at 处于 a basic, fundamental

level in the metabolism of the test organism. Conversely, the shallower




Chemistry

slope of curve B is indicative of a less specific toxic reaction

associated with more inherent variables 更多的内生变量 .

A number of measures 量，指标 of the toxicity of a substance

can be derived from the concentration-response curve, one of the

simplest of which is its lethality [lɪ‘θælɪtɪ] 致命性 that, despite its

acknowledged crudity as a measure, is still widely used. It is also an

example of an ‘all or nothing’ as opposed to 而不是 a ‘graded’

response. The principal measure of lethal toxicity used is the so-

called LC50, which represents the concentration at which 50% of the

test population is killed.




ChemistryIts usefulness resides [rɪ‘zaɪd] in the ease with which it can be used

to compare the lethality of different toxicants 难易程度 , provided

假设 the same species of test organism(s) was employed under the

same conditions of exposure. The related term LD50 is more

commonly used in mammalian [mæ'meɪlɪən]哺乳动物 , including

human, toxicological studies (see Table 6.3).

Two toxicants may have a reversed toxicity relationship as 随着

their LC values vary. Thus, toxicant A in Figure 6.3 has a lower

LC50 (higher toxicity) but higher LC20 (lower toxicity) than toxicant

B. Therefore, predictions made on the basis of the ecotoxicity 生态毒性 of these substances based on the standard LC50 may be

erroneous [I’rəʊniəs] 错误的 .




Chemistry

Further, a toxicant with 具有 a large LC50 can be regarded as

practically nontoxic, but this does not mean that it will not produce

harmful effects, even at small concentrations. In this context 在这种背景下 , another measure, the TC50 is used. This represents the

concentration that will produce signs of toxicity 中毒症状 , as

opposed to death, in 50% of the test organisms. These and other

common measures used in toxicity studies are defined in Table 6.3.




ChemistryTable 6.3 Some commonly used terms in

toxicologyTerm Definition

LC50 Lethal concentration of a substance that causes the death of 50% of test organisms

LD50 Lethal dose of a substance that causes the death of 50% of test organisms

EC50 Effective concentration of a substance that produces a change in sublethal 亚致死behavior or physiological response in 50% of test organisms

ED50 Effective dose of a substance that produces a change in sublethal behavior or physiological response in 50% of test organisms

IC50 Inhibitory concentration 抑制浓度 that reduces response of an organism by 50%

TC50 Concentration at which a substance produces a toxic response in 50% of test organisms

TD50 Dose at which a substance produces a toxic response in 50% of test organisms

SC Maximum concentration of a potential toxicant that is harmless to organisms after long-term exposure of at least one generation

MATC Minimum allowable toxicant concentration




Chemistry

All these measures have drawbacks since toxicity assessment is a

complex process with many factors such as temperature, light, food,

stress 压力 , age, sex, health and others influencing the results of

any tests undertaken. A true assessment of the ecotoxicity of a

particular substance involves a comparison of many concentration-

response curves covering a range of toxic effects. For example, a

toxicant may be extremely toxic if swallowed 吞咽 (oral exposure

口腔接触 / 暴露 ) but have low toxicity if inhaled (respiratory

exposure) or applied to the skin (topical exposure). 吸入（呼吸暴露）或应用到皮肤（局部暴露）




Chemistry As well as 除了 the concentration-response relationship of

toxicants, their so-called time-effect 时间 - 效应 relationships are

also important to understanding their effects. Figure 6.4 shows the

relationship between LC50 and time for a typical aquatic toxicant.

The principal feature of this curve is the point at which the

concentration becomes asymptotic [æsɪmp‘tɒtɪk] to 渐渐接近 the

time axis and thereby defines the ‘threshold’ or ‘incipient’

[ɪn’sɪpiənt] 初始的 LC50. This is important as concentrations

below this level will not cause lethality in the short term and may be

used in establishing risk criteria for organisms exposed to potential

chronic pollution (see below).建立暴露于潜在的慢性污染的生物风险标准




Chemistry

Assignment and preview



Chemistry References

1. Fifield F.W. and Haines P.J. Environmental Analytical

Chemistry (Second Edition). Blackwell Science Ltd, 2000.

2. 但德忠主编 . 环境分析化学 . 高等教育出版社 , 2009.

3. Radojevic Miroslav. Practical Environmental Analysis.

The Royal Society of Chemistry, MPG Books Ltd,

Bodmin, Cornwall, UK, 1999

4.胡国成 ,许木启 , 等 .硫丹对水生生物毒理效应研究进展 .

中国水产科学 ,2007,14(6): 1042-1047

References



ChemistryContents

6.4 Toxicants and the environment

6.5 Toxicity testing

6.6 Ecological risk assessment

Contents



Chemistry

Teaching requirements

Mastery of the basic methods of ecological

toxicology analysis;

Comprehension of the basic methods of

ecological risk assessment.

Teaching requirements



Chemistry

Key points and difficulties

Key points Some bioassays methods of ecotoxicology

DifficultiesEcological risk assessment of toxicant in living organism



Chemistry


When a toxicant enters the natural environment it will be subject

to a variety of interactions with both naturally occurring

constituents and any other toxicants present and therefore its effects

on the living organisms it encounters may be modified. Mechanisms

of such interactions, as suggested by Anderson and D’Apollonia

(1978), include:Environment phase 环境相 . Chemical interactions to produce

new compounds, complexes or changes to the physicochemical

properties of toxicants.




Chemistry

Dynamic phase 动态相位 . Many toxicants acting at the same target site(s) 靶位点 or at different sites but contributing to the same adverse effect. Multiple toxicants mutually [‘mjutʃuəli] 相互，彼此 producing a toxic response that differs from that produced by each individually or where one changes the response of an organism to others.

Kinetic phase 动力学相 . Multiple toxicants alter the availability of toxicants to the target site(s) or induce excess metabolites [mɪ‘tæbəlaɪt] 代谢物 compared to individual toxicants.




ChemistryIn general terms, the reaction of two substances is said to be 被称为是 synergistic [‘sɪnɚdʒɪstɪk] 协同的 when, in combination, their

toxic effects are greater than those manifested when they are

administered separately. If one of them is previously nontoxic but is

rendered toxic by the interaction, this is more correctly termed

potentiation [pətenʃi’eiʃən] 增强作用 . Thus, exposure of plants to

ozone and sulphur dioxide simultaneously is more damaging than

exposure to either gas alone. Conversely and more rarely, there are

occasions when the simultaneous exposure of an organism to two

toxicants results in less damaging effects than when they are

administered separately. This is called antagonism 拮抗作用




Chemistryand is known to occur, for example, between certain heavy metals,

such as copper and zinc, where they compete for the same sites of

uptake in several species of mammals.

Toxicants entering the environment can have a variety of

adverse ecological effects that may involve short- or long-term

changes to the normal functioning 正常的功能 of ecosystems and

result in social, economic or aesthetic [ɛs‘θɛtɪk] 美学上的 losses.

Short-term or acute 急性的 toxic effects of a substance are

generally more readily measured than its long-term or chronic 慢性的 impacts. They may also be of lesser significance in terms of

就…而言 the ultimate survival 最终的生存 of an ecosystem.




Chemistry A good example of acute toxicity is the sudden and massive巨大

impact of a large crude oil spill 原油泄漏 , such as those resulting

from the Torrey Canyon and Amoco Cadiz oil tanker disasters 油轮灾难 . These brought about 造成 the virtual 事实上的

wholesale destruction of shoreline and benthic biological

communities 底栖生物群落 in the affected areas as a result of the

adverse effects of the physicochemical properties of the crude oil.

However, once the oil had been naturally or artificially removed

from the environment, rapid recovery of these communities took

place to such an extent that their effects became barely noticeable

几乎不易看到 within 5-10 years.




Chemistry

Chronic toxicity, which involves the sustained input 持续输入

of low levels of toxicants into an environment, may have greater and

certainly more insidious [ɪn‘sɪdɪəs] 隐伏的 effects than acute

events. Typical examples of these are low level but continuous

seepages 渗漏 of toxic substances into the environment from

industrial plants, such as oil refineries 炼油厂 or metal smelters

金属冶炼厂 . Here, the ecosystem is adversely affected by 由于 the

low-level contamination itself and by the lack of opportunity to

recover because of the constant input of contaminants over a

prolonged period 长时间 .




Chemistry


A great variety of toxicity tests have been developed to examine

the effects of toxicants in a broad range of ecosystems using a wide

variety of species 物种 . The majority, termed bioassays 生物检测 , have strictly defined formats 格式 relating to such factors as

methodology, apparatus, details of test organisms, test materials,

safety precautions, references, data analysis methodologies and

reliability criteria. These have been developed to allow for the

uniformity 一致性 and comparability 可比性 of experimental

procedures that can be readily replicated 复制 by different

laboratories, whose results can then be combined if necessary. They

also provide a useful baseline 基线 from which other studies can

be launched 得以展开 and to set criteria 制定标准 regarding关于




Chemistrythe suitability 适宜性 of the test data for decision-making by

regulatory and other authorities 监管和其他当局决策 . However,

it should be noted that while 虽然 standardized and other tests have

certain advantages they are usually only designed to provide answers

to very specific, narrow questions of ecotoxicological concern.

The tests may be 可以是 of both short- and long-term duration

and involve single or multiple species. Tests of limited duration are

termed 称为 acute tests and cover only a small period of the test

organism’s life span 寿命 . Since many acute tests typically range

from 24h to a maximum of only a few days, the longer lived the test

species the smaller the proportion of their life span the test occupies.




Chemistry

Where unicellular 单细胞 test organisms with generation times

其传代时间 that are measured in hours are used, the term acute

may not be applicable 合适的 in any circumstances. Mortality 死亡率 is the most common parameter measured during acute tests but

others include immobilization 固定（化） and other behavioural

and reproductive effects (see Table 6.4).




ChemistryTable 6.4 Summary of principal methods used for bioassays

Type of organism Method of assay

Bacteria,fungi [‘fʌndʒaɪ]真菌 , Protozoa [prəʊtə'zəʊə]原生动物

Mutagenicity [,mju:tədʒə‘nɪsətɪ]致突变性BODNitrification [,naɪtrəfɪ‘keɪʃən] 硝化作用 studiesDecomposition studies

Algae[‘ældʒi]藻类 and other plants

Biostimulation 生物刺激 and growth ratesReproductive rates繁殖率Photosynthetic rate光合速率Respiratory rate 呼吸速率Chlorophyll [‘klɔrəfɪl] 叶绿素 contentMutagenicity [,mju:tədʒə‘nɪsətɪ]致突变性Morphological and histological effects形态学和组织学影响（效应）

Invertebrates [ɪn’və:təbrɪt]无脊椎动物and vertebrates脊椎动物

Lethal effects 致死效应Reproductive ratesDevelopment abnormalities发育异常Growth rates; Feeding rates 摄食率Respiratory rates; Biochemical changesMorphological and histological effectsBehavioural changes 行为改变




Chemistry In contrast, chronic tests are designed to last 维持 for a

significant proportion of a test organism’s life span but are not

usually designed to be multigenerational 多代同堂的 . The

parameters tested are very variable, but commonly involve the

measurement of respiratory, feeding 摄食的 , growth and

reproductive rates and of biochemical, carcinogenic or teratogenic [,terətəu‘dʒenik] effects 致癌致畸作用 .

Full field studies on the effects of a toxicant are the most difficult

and expensive part of ecotoxicological monitoring and are greatly

influenced by the vast heterogeneity [,hetərə‘dʒə’ni:ətɪ]异质性，不均匀性 of natural environments, even in a localized area局部 .




Chemistry


This often renders it difficult to translate laboratory-derived data to

把… 转化为 the situation in the field 现场 and often even from one

field situation to another. Continuing research in this area is therefore

of vital importance 至关重要的 to the future of ecotoxicological

monitoring.

Toxicants are only one of a number of stressors 压力源 that may

adversely affect an ecological system. Others include fires, ionizing

radiation, genetically engineered 基因工程的 or introduced

organisms. The process by which the probability that one or more

stressors will cause such adverse effects is called ecological risk

assessment and may very well be the objective of an

ecotoxicological study but not necessarily 未必 the only one.



Chemistry Risk assessment is a management tool for making decisions 作出决策 and, unlike those based on scientific results, its endpoint(s)终点 has greater uncertainty as it may be significantly influenced by

societal perceptions and values.社会观念和价值 Therefore, a chemical 在种化学品 may be shown by a scientific

hazard assessment to be highly toxic to wildlife 野生生物 but its

use may be permitted if it is considered of economic importance or

that the risk of it entering the environment in large quantities is

minimal. Thus, the internal combustion engine is indisputably 无可争辩地 responsible for the introduction of large amounts of a

variety of toxicants, such as tetraethyl lead 四乙基铅 and

polyaromatic




Chemistryhydrocarbons多环芳烃 , into the atmosphere. However, because of

the enormous value that society attaches to 依附（恋）于 the use

of this device this is generally regarded as 被认为是 an acceptable

risk to the environment and humans, despite the obvious damage

caused.

A generally agreed summary framework 共同议定的总结性框架 for ecological risk assessment is shown in Figure 6.5.(see

p469)

Problem formulation 公式化 involves an evaluation of stressor

characteristics, identification of the ecosystem(s) at risk, ecological

impacts, endpoint selection, e.g. mortality 死亡率 of selected

organisms, type and quality of input data and potential modeling

systems.




Chemistry Analysis involves the characterization of the ecosystem of concern,

which is sometimes difficult to delineate [dɪ‘lɪnɪeɪt] 勾画，描绘given the size and complexity of many ecosystems and the fact that

they are dynamic entities undergoing constant change 不断变化的动态实体 . Also included under this heading 标题 is an

assessment of exposure, i.e. the environmental concentration of the

stressor, or better still the dose received, by the biota. This is

particularly problematic because of the interaction of stressors with

the biotic and abiotic 生物和非生物 components of an ecosystem,

biotransformations 生物转化 and possible uncertainties regarding

routes of entry and levels of toxicants present.




ChemistryAnalytical chemistry plays an important role in determining these

parameters and is used in conjunction with certain assumptions

about contact and uptake of toxicants by components of the

environment and mathematical models to assess exposure. However,

considerable uncertainty will inevitably remain.

An absolutely critical aspect 绝对关键的方面 of analysis

associated with ecological risk assessment includes an evaluation of

the ecological effects of the stressor. Data on the toxicity of the

stressor is compiled汇编 ; 编辑 from various sources, including

both laboratory and field studies and a so-called stressor-response

profile can be built up to match ecosystem impacts to 与…匹配




Chemistrystressor concentrations. However, this is not as straightforward as it

appears. For example, complications 复杂化 are introduced by the

almost inevitable need to draw upon 利用 qualitative data when

quantifying this relationship and the requirement usually to

extrapolate [ɪk‘stræpəleɪt] 推算，推断 data from single species to

multiple species, from laboratory studies to natural environments and

from one species to another so-called phylogenetic [faɪləʊdʒə’netɪk]

系统发育的 extrapolation推断 . Thus, uncertainties can arise from

using a single algal [‘ælɡəl] 海藻的 species in a test to represent all

photosynthetic organisms, which in reality it clearly cannot.




Chemistry

The final stage 最后阶段 of the risk assessment process is risk

characterization, which requires the analysis and integration 分析与整合 of risk estimation 估计 and risk description elements to

以 determine the probability of the effects of a stressor given its 给定其 particular distribution in the environment under study.

Throughout the entire process of risk assessment the acquisition

采集 , verification and monitoring of data is essential, as are

discussions between the risk assessor and risk manager. It is the

latter that will pave the way to 为… 铺平道路 the final decision-

making 决策 process by the risk manager.




ChemistryEcotoxicology




Chemistry



Chemistry

References

1. Fifield F.W. and Haines P.J. Environmental Analytical

Chemistry (Second Edition). Blackwell Science Ltd, 2000.

2. 但德忠主编 . 环境分析化学 . 高等教育出版社 , 2009.

3. Radojevic Miroslav. Practical Environmental Analysis.

The Royal Society of Chemistry, MPG Books Ltd,

Bodmin, Cornwall, UK, 1999

4. 庄一延 .水生生物毒理实验在水环境监测中的应用 [J].福建环境， 1996 ， 13 （ 6）： 12-13

References

Thank you!www.cne.cdut.edu.cn/eac/

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