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Incorporating Contaminant Bioavailability into Sediment Quality Assessment Frameworks
Maruya, K., P. Landrum, R. Burgess, AND J. Shine. Incorporating Contaminant Bioavailability into Sediment Quality Assessment Frameworks. Integrated Environmental Assessment and Management. Allen Press, Inc., Lawrence, KS, 8(4):659-673, (2012).
This publication describes an approach for incorporating measures of contaminant bioavailability into the derivation of sediment quality guidelines. The approach is based on the use of the freely dissolved concentration of a given contaminant in a sediment as the exposure concentration. This concentration is then related to a guideline effects value to determine the expectation of adverse effects resulting from that sediment.
The recently adopted sediment quality assessment framework for evaluating bay and estuarine sediments in the State of California incorporates bulk sediment chemistry as a key line of evidence(LOE) but does not address the bioavailability of measured contaminants. Thus, the chemistry based LOE likely does not provide an accurate depiction of organism exposure in all cases, nor is it particularly well suited for assessment of causality. In recent years, several methods for evaluating the bioavailability of sediment-associated contaminants have emerged, which if optimized and validated, could be applied to improve the applicability and broaden the scope of sediment quality assessment. Such methods include equilibrium-based biomimetic extractions using either passive sampling devices (PSDs) or measures of rapidly desorbing contaminant pools, which provide information compatible with existing mechanistic approaches. Currently, these methods show promise in relating bioaccessible chemicals to effects endpoints, including bioaccumulation of hydrophobic organic compounds and/or toxicity due to metals. Using these methods, a bioavailability LOE for organics is proposed based on PSD and equilibrium partitioning theory. Current and future research should be aimed at comparing the performance of PSDs and their relationships with effects concentrations, field validation of the most promising methods, addressing contaminant mixtures, and providing a better understanding of the underlying diagenetic cycling of metal contaminants that lead to exposure, affect bioavailability, and drive adverse outcomes.