Comparison of chemical approaches for assessing bioavailability of sediment-associated contaminants

Two chemical approaches, Tenax extraction and matrix solid-phase microextraction (matrix-SPME), were compared to assess the bioavailability of hydrophobic contaminants from sediment. Hexachlorobiphenyl, DDE, permethrin, chlorpyrifos, and phenanthrene were individually spiked into two sediments differing in physical characteristics. Bioaccumulation was determined by exposing the oligochaete, Lumbriculus variegatus, to the spiked sediments. The rapidly desorbing fraction from Tenax extraction at 6 h and fiber concentration at 14 d from the matrix-SPME were compared for predicting bioaccumulation. Further, a comparison between laboratory-spiked and field-contaminated sediments was conducted. A regression between the rapidly desorbed sediment concentration at 6 h and the amount bioaccumulated across compounds and sediments described 94% of the variation in the data when phenanthrene was excluded. Phenanthrene was excluded because of complications due to a combination of biotransformation and rapid elimination during the sampling process. Contaminant accumulation by L. variegatus also correlated well with matrix-SPME fiber concentrations, accounting for 92% of the variation in the data, again excluding phenanthrene. Both chemical methods provided matrix- and chemical-independent estimations of bio-accumulation for hydrophobic contaminants without extensive biotransformation.