A comparison of the transport and fate of polychlorinated biphenyl congeners in three Great Lakes food webs.

A food web bioaccumulation model was used to compare transport and fate of polychorinated biphenyls (PCB) congeners in three food webs in the Laurentian Great Lakes of North America. The model was used to quantify the contribution of sediment-derived and freely dissolved PCBs to the body burden of aquatic biota. In eastern Lake Erie (OH, USA), almost 100% of the chemical body burden of biota originates from sediment. In western Lake Erie, benthic invertebrates accumulated slightly more than half of their PCB body burden from sediment while fish accumulated less than half of their chemical body burden from sediment. Fish from Lake Ontario, Canada, accumulated less than 30% of their body burden of PCB congeners with log Kow < 6.4 from sediment and approximately half of their body burden of PCB congeners with log Kow > or = 6.4 from sediment. Field data and the model were also used to determine the effects of declining concentrations of PCBs in water and sediment on concentrations of PCBs in aquatic biota. Results indicate that, as concentrations of PCB congeners in the ecosystem decline, the role of sediment as the source of contaminant to aquatic biota increases. Furthermore, as sediment becomes the predominant source of contaminant to aquatic biota. the concentration of PCB congeners in biota tends to equilibrium with bottom sediment.