Effect of Sedimentary Organic Matter Composition on the Partitioning and Bioavailability of Dieldrin to the Oligochaete Lumbriculus variegatus

Current hypotheses link the bioavailability of contaminants in sediments to their partitioning behavior to organic matter in sediments. Because contaminant partitioning varies with sediment composition, it follows that composition should also affect contaminant bioavailability. In this study, variations in dieldrin partitioning and bioavailability, as measured by organic carbon/lipid-normalized bioac cumulation factors for Lumbriculus variegatus, were related to sediment composition. Study sediments covered a wide range of composition and organic matter content. Normalizing the bioaccumulation factors to the organic carbon content of sediments and lipid content of organisms reduced ranges of measured dieldrin accumulation factors from 38-fold to 8-fold. Factors describing sediment composition were tested to determine whether they explained the remaining variability between sediments. Variations in partitioning were best explained by the proportion of sedimentary organic matter that was solvent extractable. However, bioavailability correlated most strongly to pH. There was little correspondence between factors that explained variability in partitioning and those covarying with bioaccumulation.