National-scale, field-based evaluation of the biota-sediment accumulation factor model

The biota-sediment accumulation factor (BSAF) model has been suggested as a simple tool to predict bioaccumulation of hydrophobic organic compounds (H OCs) in fish and other aquatic biota from measured concentrations in sedime nt based on equilibrium partitioning between the sediment organic carbon an d biotic lipid pools. Currently, evaluation of this model as a predictive t ool has been limited to laboratory studies and small-scale field studies, u sing a limited number of biotic species. This study evaluates the model, fr om field data, for a suite of organochlorine HOCs from paired fluvial sedim ent and biota (fish and bivalves) samples throughout the United States and over a large range of biotic species. These data represent a real-world, wo rst-case scenario of the model because environmental variables are not cont rolled. Median BSAF values for fish (3.3) and bivalves (2.8) were not stati stically different but are higher than theoretically predicted values (1-2) . BSAF values varied significantly in a few species. Differences in chemica l-specific BSAF values were not observed in bivalves but were statistically significant in fish. The HOCs with differing BSAF values were those known to be biotransformed. Sediment organic carbon content and biota lipid conte nt had no effect on BSAF values in fish and only a weak effect in bivalves. This study suggests that the BSAF model could be useful under in situ rive rine conditions as a first-level screening tool for predicting bioaccumulat ion; however, variability in BSAF values may impose limits on its utility.