Bioconcentration, described

Bioconcentration describes the nondietary uptake of chemicals and is defined as an equilibrium partition of a compound between an organism and a contaminated medium [9-11], The bioconcentration factor (BCF) is often expressed as the ratio of the concentration of a compound in an aquatic or semiaquatic organism (e.g., a fish, amphibian, or a submerged plant) to the concentration of the compound in the surrounding water. 

Connell, D.W., Hawker, D.W. (1988) Use of polynomial expressions to describe the bioconcentration of hydrophobic chemicals by fish. Ecotoxicol. Environ. Safety 16, 242-257. 

Matsuo, J. (1981) i/o - Characters to describe bioconcentration factors of chlorobenzenes and naphthalenes - meaning of the sign of the coefficients of 2i/2o in the correlating equations. Chemosphere 10, 1073-1078. 

The risk posed by the potential to concentrate into sediments was approached similarly to the aquatic compartment, i.e. using a PEC/PNEC ratio (Table 3.2). When no actual effect data on sediment organisms were available, PNECs in sediments were estimated on the basis of physico-chemical parameters and PNECs in water [1]. The risk posed by the potential to bioconcentrate in fish was assessed by the methodology described by Nendza et al. [2] with the determination of the critical body burden (CBB). This parameter predicts the level of the chemical in the organism which could... 

The BCF describes the degree of bioconcentration as the ratio between the chemical concentration in the organism or a specific tissue and the chemical concentration in the medium, in the steady state [1,18,52,55,56] or over a discrete exposure time period [44,45,57]. The steady state is reached when the ratio of concentrations in the organism and in the water no larger vary with time. 

The first type of model is based on models describing bioconcentration, which in turn are based on an analogy with chemical reaction kinetics. For this reason we will refer to this type of model as the chemical-reaction kinetics (CRK) model. The exchange process is thought of as the net result of a forward (uptake) and a backward (release) reaction that is first order with respect to reactant concentration. Hence, the rate of change of the solute concentration in the SPMD (Cs) is given by... 

Figure 10.5 Terms and parameters frequently used to describe accumulation of chemicals in aquatic organisms. Note that the term bioaccumulation (BAF,) is used to describe the total accumulation by all possible routes (e.g., passive uptake, intake by food and digestion, etc.). The term bioconcentration is sometimes...

Describe in words, the parameters (1) bioconcentration factor, (2) biomagnification factor, (3) biota-sediment- and biota-soil- accumulation factor, and (4) bioaccumulation factor. 

Because PAHs are hydrophobic, they tend to accumulate in lipids of organisms that are unable to metabolize them. There are several partition coefficients that can describe the accumulation of PAHs in organisms. Direct partitioning of aqueous phase PAHs to an organism is described by the bioconcentration factor ... 

Bioconcentration can be described by a bioconcentration factor (BCF), which is the ratio of the chemical concentration in an organism (CB) to the concentration in water (Cw) ... 

The bioconcentration process can be modeled by an organism-water two-compartment toxicokinetic model where the organism is described as a single compartment in which the chemical is homogeneously distributed. 

Bioaccumulation is the result of simultaneous bioconcentration and biomagnification. It usually is observed under field conditions but can be measured in laboratory experiments, as well. In terms of a toxicokinetic model, where the organism is presented as a single compartment, addition of equations (13) and (25) can describe the bioaccumulation of a chemical in an organism ... 

Uptake and elimination. Illustrative example of the uptake and elimination of a chemical substance in a bioconcentration test consisting of an uptake period, where the organism is exposed to a constant concentration of a chemical substance in the water phase, and an elimination period, where the organism is exposed to clean water. In this example, bioconcentration is described by a first order organism-water two compartment model. The concentration in the organism is CB, the freely dissolved concentration in the water is CWD. 

Bioconcentration in aquatic macrophytes also has been described by equilibrium partitioning of chemical between the macrophytes lipid or organic carbon fraction and water (e.g., Gobas et al., 1991). If the lipid-water partition coefficient is used to describe the partitioning of chemical between macrophytes and water, then the chemical concentration in macrophytes (CM, g chemical/kg organism) is approximately equal to the product of the freely dissolved chemical concentration in water (CWT), g chemical/L water), the lipid content of the macrophytes (LM, kg lipid/kg organism), and the lipid-water partition coefficient (K L water/kg lipid), which Kow can approximate ... 

A number of authors (e.g., Bruggeman et al., 1981 and 1984 Opperhuizen et al., 1985 Gobas et al., 1989) have applied simple kinetic models (i.e., equations (13)-(15), (25)-(27), (29, (30))to fish. In most cases, the models are used in a descriptive sense to describe empirical data derived from bioconcentration or bioaccumulation tests. These models can play an important role in the analysis of the results of bioconcentration tests, but they are generally inapplicable to bioaccumulation under field conditions. 

Spade, A., and J.L Hamelink. 1982. Alternative models for describing the bioconcentration of organics in fish. Environ. Toxicol. Chem. 1 309-320. 

Relatively little attention has been given to aquatic organisms other than fish, and predictive equations for fish do not necessarily hold for other organisms. For example, Kenaga and Goring (5) compared bioconcentration by Daphnia with bioconcentration by several species of fish and found that although values were not the same there was at least a statistically significant relationship between them. This was described by the equation ... 

There is virtually no literature describing bioconcentration of organic compounds by wild aquatic macrophytes in spite of the facts that these plants are often the major primary producers in shallow inland waters, and are essential habitat components for both aquatic and terrestrial animals. Lockhart et al. (14) provided a regression equation describing uptake curves for a variety of organic compounds by duckweed (Lemna minor) cultures in laboratory exposures. Predictions from the regression equation agreed quite well with field observations on bioconcentration of permethrin in outdoor ponds (15). 

Estimates of the persistence of compounds in the environment are made from a variety of programs. These include those from the EPISUITE software described in Table 19.2, such as BIOWIN for biodegradation, BCFWIN for bioconcentration, and PCKOCWIN for soil sorption. 

Several terms have been used to describe this phenomenon, namely, biomagnification, bioconcentration, and bioaccumulation. However, the pesticide is not always concentrated or magnified as it moves up to the food chain, so the latter term is preferable (Nakatsugawa and Nelson, 1972). For example, dieldrin residue in cod at 0.009 ppm (whole fish bases) was less than in the sand eel, the major diet of the cod, at 0.016 ppm. Dieldrin residue in a macrozooplankton (crustacea) at 0.16 ppm was higher than in any of the fish examined... 

Section A9.5. This section will describe the relationship between the partition coefficient criteria and the bioconcentration factor (BCF), provide guidance on the interpretation of existing data, how to estimate the partition coefficient by the use of QSARs when no experimental data are available and in particular deal with the specific problems identified above for difficult substances. The problems encountered when dealing with substances of high molecular mass will also be covered. 

A9.5.1.3 Data on bioconcentration properties of a substance may be available from standardized tests or may be estimated from the structure of the molecule. The interpretation of such bioconcentration data for classification purposes often requires detailed evaluation of test data. In order to facilitate this evaluation two additional appendixes are enclosed. These appendixes describe available methods (Appendix III of Annex 9) and factors influencing the bioconcentration potential (Appendix IV of Annex 9). Finally, a list of standardized experimental methods for determination of bioconcentration and Kow are attached (Appendix V of Annex 9) together with a list of references (Appendix VI of Annex 9). 

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