National Water-Quality Assessment (NAWQA) Project
Biota sediment accumulation factors (BSAF) have been proposed as a means to predict bioaccumulation of chlorinated organic compounds in aquatic biota from concentrations in bed sediment. However, evaluation of BSAFs as a predictive tool has been limited to laboratory studies or local-scale field studies, and to a small number of species. The validity of BSAFs was assessed for a suite of chlorinated organic compounds (e.g., DDT, chlordanes, and PCBs) from paired samples of bed sediment and fish or Corbicula (freshwater clam) collected from about 500 stream sites throughout the United States as part of the U.S. Geological Survey's National Water Quality Assessment (NAWQA). Sites were located within agricultural and urban watersheds and in associated major rivers draining large basins with mixed land uses. The national distribution of sites, wide variety of land use environments, and number of species sampled provided an opportunity to test the usefulness of the BSAF approach over a broad range of environmental conditions. BSAFs were calculated from contaminant concentrations in bed sediment (organic-carbon normalized) and whole fish or Corbicula (lipid normalized), and then compared to possible controlling factors. Preliminary analysis indicates that there is substantial variability in BSAFs among sites nationwide.