The U.S. Environmental Protection Agency (EPA) has recently published guidelines for developing sediment remediation goals at Superfund sites from pore water concentrations that are protective of benthic organisms. The guidelines are based on a comparison of concentrations of freely dissolved non-ionic organic contaminants measured in pore water with chemical-specific final chronic values (FCV) derived during the process of establishing ambient water quality criteria. The document lays out the evolution in thinking over the last few decades, moving away from empirical bulk sediment benchmarks to equilibrium partitioning approaches, which better reflect actual exposure concentrations to benthic organisms.
EPA procedures for passive sampling at contaminated sediment sites were also published earlier this year, and it is the maturation of these sampling methods that has allowed for development of the new guidelines. Passive sampling measurements account for the bioavailability of the contaminant, enabling site-specific sediment remediation goals to be developed using established toxicity thresholds (e.g., EPA’s FCV). Despite passive samplers offering numerous advantages over traditional field sampling methods, the methodology presented in the guidelines continues to require that bulk sediment concentrations be determined.
As clearly explained by the authors, the guidelines apply only to non-ionic organic contaminants and the protection of benthic organisms and therefore are limited mostly to polycyclic aromatic hydrocarbons, certain pesticides, chlorobenzenes, several low molecular weight organic compounds, and phthalates. Although passive samplers can provide accurate measures of more bioaccumulative organic chemicals (e.g., polychlorinated biphenyls), this specific guidance is not designed to be protective of higher trophic level benthic organisms, or human health, which are often the main risk drivers at large Superfund sediment sites.
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For more information on these guidelines or passive sampling, contact Dr. Gomez-Eyles at firstname.lastname@example.org