MODELING THE PARTITIONING AND BIOACCUMULATION OF TCDD AND OTHER HYDROPHOBIC ORGANIC-CHEMICALS IN LAKE-ONTARIO

Lake trout and sediment data were used to define the biota-to-sediment ratio (BSR) for hydrophobic organic chemicals (HOCs) in Lake Ontario, including 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDD s) and dibenzofurans (PCDFs). The BSRs for bioaccumulative PCDD/PCDFs were found to be approximately two orders of magnitude (i.e., 100x) lo wer than for other HOCs of similar hydrophobicity. To evaluate this di fference, a modeling framework is applied which accounts for the signi ficant processes affecting BSR: bioaccumulation, partitioning, and sed iment-water chemical distribution. If these processes are indexed by c hemical hydrophobicity alone, the approach taken in this model, the ob served discrepancy in BSRs between PCDD/PCDFs and other HOCs is inadeq uately explained. The possible influence of chemical metabolism on the BSR of PCDD/PCDFs is suggested.