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Current environmental models use organism lipid concentrations to estimate maximum pollutant bioaccumulation potentials. This collaborative study has shown that significantly different lipid concentrations (3.5X) are found when using common, but different, extraction solvents and methods. Based on these variable lipid values, models that estimate tissue pollutant concentrations normalized to lipid will give significantly different bioaccumulation estimates. To reduce that variability, a standard lipid method needs to be developed or adopted.

The utility and limits of applicability of a simple equilibrium partitioning model for predicting the maximum concentration of neutral organic compounds which can be accumulated by infaunal organisms exposed to a contaminated sediment were examined. Accumulation factors (AFs) for PCBs, the lipid normalized PCB concentration in organisms divided by the organic carbon normalized PCB concentration in sediments, were measured for PCBs in infaunal mollusks and polychaetes at field sites with a range of sediment Aroclor (A-1254) and total organic carbon (TOC) concentrations. The average AFs for A-1254 were found to be higher (X = 4.94; range 3.76-7.27) at sites with lower contaminant concentrations (15.0-48.3 ng A-12541g dry sediment) than at more contaminated sites (328-9,200 ng/g), where AFs were lower (2 = 2.62; range 1.14-5.04). AF data grouped on the basis of sediment A-1254 and TOC concentration differed statistically between, but not within each group. Significant differences in mean AFs were found between some species and between some PCB congeners. When all data were considered, the variability associated with AFs was lower than that found for bioaccumulation factors on a wet weight basis, indicating the utility of lipid and organic carbon normalization.

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