Model bioaccumulation

FIGURE 4.2 (a) A bioaccumulation model for terrestrial organisms. A kinetic model for... 

Schnoor, J.L. Rao, N. Cartwright, K.J. Noll, R.M. Ruiz-Calzada, C.E. Verification of a Toxic Organic Substance Transport and Bioaccumulation Model" EPA-600/3-83-007, U.S. Environ. Prot. Agency, Environ. Research Lab. Athens, Georgia, 1983 p. 164. 

Thomann, R.V. (1989) Bioaccumulation model of organic chemical distribution in aquatic food chains. Environ. Sci. Technol. 23, 699-707. 

As seen above (equation (5)), the basis of the simple bioaccumulation models is that the metal forms a complex with a carrier or channel protein at the surface of the biological membrane prior to internalisation. In the case of trace metals, it is extremely difficult to determine thermodynamic stability or kinetic rate constants for the adsorption, since for living cells it is nearly impossible to experimentally isolate adsorption to the membrane internalisation sites (equation (3)) from the other processes occurring simultaneously (e.g. mass transport complexation adsorption to other nonspecific sites, Seen, (equation (31)) internalisation). 

Kelly B.C. and Gobas, F.A.P.C. (2003) An Arctic terrestrial food chain bioaccumulation model for persistent organic pollutants. Environ Sci Technol, 37, 2966-2974. 

Model Equation, Parameters, and their Units of the Zooplankton Bioaccumulation Model of Thomann et al. (1992)... 

Landrum et al. (1992) developed a kinetic bioaccumulation model for PAHs in the amphipod Diporeia, employing first-order kinetic rate constants for uptake of dissolved chemical from the overlying water, uptake by ingestion of sediment, and elimination of chemical via the gills and feces. In this model, diet is restricted to sediment, and chemical metabolism is considered negligable. The model and its parameters, as Table 9.3 summarizes, treat steady-state and time-variable conditions. Empirically derived regression equations (Landrum and Poore, 1988 and Landrum, 1989) are used to estimate the uptake and elimination rate constants. A field study in Lake Michigan revealed substantial differences between predicted and observed concentrations of PAHs in the amphipod Diporeia. Until more robust kinetic rate constant data are available for a variety of benthic invertebrates and chemicals, this model is unlikely to provide accurate estimates of chemical concentrations in benthic invertebrates under field conditions. 

Definitions and Units of Model Parameters Used in the Benthic Bioaccumulation Model of Thomann (1991, 1992). 

Model Equations, Parameters and their Units of the Benthic Invertebrate Bioaccumulation Model for Filter Feeders and Benthic Detritovores of Morrison et al. (1996.)... 

Bioaccumulation Models for Fish 9.5.6.1 Equilibrium Partitioning Models... 

Thomann et al. (1992) developed a steady-state food web bioaccumulation model that combines kinetic and bioenergetic parameters to quantify chemical uptake and elimination by zooplankton, benthic invertebrates and fish. First-order kinetic rate constants quantify uptake of freely-dissolved chemical from interstitial water and overlying water and total chemical elimination from gills and feces. Various physiological and bioenergetic parameters quantify chemical uptake from diet and growth dilution. 

Gobas (1993) published a foodweb bioaccumulation model to predict chemical concentrations in phytoplankton, macrophytes, zooplankton, benthic invertebrates, and fish, based... 

Morrison, H.A., F.A.P.C. Gobas, R. Lazar, and G.D. Haffner. 1996. Development and verification of a bioaccumulation model for organic contaminants in benthic invertebrates. Environ. Sci. Technol. 30 3377-3384. 

The biomagnification LOE involves determining concentrations of contaminants such as DDT, PCBs, dioxins, TBT, and methyl mercury in benthic invertebrates or fish. This LOE only applies to those few organic contaminants that actually biomagnify. Concentrations are compared to reference areas or literature-based toxicity reference values (TRVs) and assessed via food chain bioaccumulation models (Grapentine et ah, 2002). 

D. Endicott and D. J. Kandt, MICHTOX A Mass Balance and Bioaccumulation Model for Lake... 

J. P. Connolly, Bioaccumulation Model for Green Bay Mass Balance Study, Final Report to USEPA Large Lakes Research Station, Grosse lie, MI, 1995. 

MacLeod M, Fraser AJ, Mackay D. 2002. Evaluating and expressing the propagation of uncertainty in chemical fate and bioaccumulation models. Environ Toxicol Chem 21 700-709. 

In the present study, bioconcentration, biomagnification and bioaccumulation models are presented using models which describe the concentrations of chemicals in the organisms and environment and food. Other models use fugacities to describe the bioaccumulation processes [e.g. 19,20]. For the sake of simplicity, however, we continue with describing the models based on concentrations. 

Fig. 4. Time and exposure concentration dependent concentrations in fish in addition to the lethal body burden (horizontal solid line) for 1,2,3-trichlorobenzene. The dotted lines are theoretical curves calculated with a bioaccumulation model. Exposure concentrations are 55.9 pmol 1 (I), 3.78 pmol (II), and 1.92 pmol (III). The symbols represent the mean of the internal effect concentrations of ten fish [9], reproduced with permission...

Uptake of contaminants is very likely to precede effects, since first the contaminant has to reach the receptor, which can be very specific or non-specific, to exert its adverse biological effect. Since uptake is an important part of the bioaccumulation process, the relationship between bioaccumulation and ecotoxi-city is shown. However, there are a number of gaps in knowledge which prevent a broad use of bioaccumulation models to be incorporated in predicting ecoto-xicological effects. 

A well-known subacute effect is the growth reduction in algae. Hitherto, only external effect concentrations have been reported for this type of subacute effect, since experimental problems make it difficult to determine those internal effect concentrations, and existing bioaccumulation models for, e. g., fish, do not apply to algae, e.g. [78]. It must be noted that algae and other small organisms are prone to diffusive uptake for contaminants from the ambient environment for which the link between bioconcentration and the internal effect concentration concept would be very promising. 

Amot JA and Gobas FAPC, A food web bioaccumulation model for organic chemicals in aquatic ecosystems, Environ. Toxicol. Chem., 23, 2343, 2004. 

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