Distribution of organic carbon and organic xenobiotics among different particle-size fractions in sediments

The distributions of benzo[a]pyrene, hexachlorobiphenyl, and total organic carbon in a Lake Michigan sediment and a Florissant soil sample were determined and related to the known bioavailability of the compounds. The distribution of organic compounds among small particles (<63 μm diameter) was different from the distribution of the total organic carbon. However, the organic matter remained the major sorbent for these compounds. Changing the fractionation conditions, by performing the fractionation in distilled water instead of natural lake water, altered the distributions for both organic carbon and xenobiotics among the particles. Further, the contaminant distribution relative to organic carbon content differed between particle-size fractions and between contaminants of different compound classes, e.g., PAHs and PCBs. The differential distribution of the contaminants in the particle-size fractions likely contributed to the observed differences in bioavailability of organic contaminants for benthic organisms and may be exacerbated by selective feeding.