Influence of black carbon and chemical planarity on bioavailability of sediment-associated contaminants.

Black carbon (BC) and chemical properties may play a significant role in defining the bioavailability of hydrophobic organic compounds (HOCs) in sediment. In the current study, bioavailability of four HOCs with differing planarity was determined in sediments amended with two types of BC (soot and charcoal) at different concentrations by matrix solid-phase microextraction (matrix-SPME) and bioaccumulation testing using the freshwater oligochaete Lumbriculus variegatus. Furthermore, the applicability of the matrix-SPME method to bioavailability estimation in BC-amended sediment was tested. The charcoal treatment significantly reduced the bioaccumulation of the planar compounds (3,3',4,4'-tetrachlorobiphenyl and benzo[a]pyrene) in L. variegatus, and the matrix-SPME method showed a similar trend as contaminant bioaccumulation in L. variegatus. Conversely, manipulation of sediment with soot had no effect or slightly increased bioavailability of the planar compounds in both bioaccumulation and matrix-SPME tests. Little if any affect was noted in bioavailability of the nonplanar compounds (2,2',4,4',5,5'-hexachlorobiphenyl and permethrin) with the soot and charcoal amendments. Results showed that the role of BC in defining bioavailability of HOCs depends not only on the type and concentrations of BC present, but also the planarity of the HOCs. Copyright 2010 SETAC.