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Mechanistic Sediment Quality Guidelines Based on Contaminant Bioavailability: Equilibrium Partitioning Sediment Benchmarks
Citation:
BURGESS, R. M., W. J. BERRY, D. R. MOUNT, AND D. M. Di Toro. Mechanistic Sediment Quality Guidelines Based on Contaminant Bioavailability: Equilibrium Partitioning Sediment Benchmarks . ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 32(1):102-114, (2013).
Impact/Purpose:
This report summarizes mechanistic sediment quality guidelines (SQGs) based on equilibrium partitioning (EqP) which uses the dissolved concentrations of contaminants in sediment interstitial waters as a surrogate for bioavailable contaminant concentrations. The EqP mechanistic SQGs developed by the U.S. EPA and their collaborators are called equilibrium partitioning sediment benchmarks (ESBs). Sediment concentrations less than or equal to the ESB values are not expected to result in adverse effects and benthic organisms will be protected, while sediment concentrations above the ESB values may result in adverse effects to benthic organisms. The ESBs are intended to be useful as a complement to existing sediment assessment tools, to assist in determining the extent of sediment contamination, to help identify chemicals causing toxicity, and to serve as targets for pollutant loading control measures.
Description:
Globally, billions of metric tons of contaminated sediments are present in aquatic systems representing a potentially significant ecological risk. Estimated costs to manage (i.e., remediate and monitor) these sediments are in the billions of U.S. dollars. Biologically-based approaches for assessing the contaminated sediments which pose the greatest ecological risk range from toxicity testing to benthic community analysis. In addition, chemically-based sediment quality guidelines (SQGs) provide a relatively inexpensive line of evidence for supporting these assessments. Over the last two decades, SQGs have evolved into two basic forms: empirical and mechanistic. This report summarizes mechanistic SQGs based on equilibrium partitioning (EqP) which uses the dissolved concentrations of contaminants in sediment interstitial waters as a surrogate for bioavailable contaminant concentrations. The EqP-based mechanistic SQGs developed by the U.S. EPA and their collaborators are called equilibrium partitioning sediment benchmarks (ESBs). Sediment concentrations less than or equal to the ESB values are not expected to result in adverse effects and benthic organisms will be protected, while sediment concentrations above the ESB values may result in adverse effects to benthic organisms. In this report, ESB values are reported for 34 polycyclic aromatic hydrocarbon (PAHs), 32 other organic contaminants, and seven metals (cadmium, chromium, copper, nickel, lead, silver, zinc). Also included in this report is an overview of EqP theory, ESB derivation, three examples of calculating ESB values, and considerations when using ESBs. The ESBs are intended to be useful as a complement to existing sediment assessment tools, to assist in determining the extent of sediment contamination, to help identify chemicals causing toxicity, and to serve as targets for pollutant loading control measures.