The role of food web models in the environmental management of bioaccumulative chemicals

When properly calibrated, food web models can be used to estimate the tissu e concentrations of bioaccumulative chemicals in aquatic organisms at vario us trophic levels. in general, such models are dependent on the knowledge o f the bioenergetics and feeding interactions within a food web and the sedi ment and water concentrations of chemicals. The results of a preliminary pr obabilistic model that was constructed fora food web of the tidal Passaic R iver in New Jersey are presented. The basis for constructing and calibratin g the model was to supplement available tissue-residue data for risk assess ment and to evaluate future trends of bioaccumulation and potential risk un der hypothetical scenarios regarding future conditions in the Passaic River . Following the construction and preliminary runs of the model, tissue-resi due data were collected to evaluate the performance of the model. The compa rison of the estimated and measured concentrations of select coplanar polyc hlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and diben zofurans (PCDDs/Fs) suggested that the model performed well for the site. T he mean estimated concentrations of these chemicals were generally within a n order of magnitude or less of the mean measured concentrations in mummich og (Fundulus heteroclitis), blue crab (Callinectes sapidus), and the edible portions of striped bass (Morone saxatilis). The utility of models is thei r ability to help evaluate events beyond the bounds of the available tissue -residue data, including future bioaccumulation potential within the food w eb under new or altered conditions. Under regulatory programs such as Compr ehensive Environmental Response, Compensation, and Liability Act (CERCLA) a nd the Resource Conservation and Recovery Act, once remedial objectives are established a food web model can be used to help develop ranges of clean-u p goals that may be necessary to achieve the regulatory objectives for bioa ccumulative chemicals.