Developing sediment remediation goals at superfund sites based on pore water for the protection of benthic organisms from direct toxicity to non-ionic organic contaminants (presentation)
Citation:
Burkhard, L., R. Burgess, Dave Mount, S. Ells, AND M. Greenberg. Developing sediment remediation goals at superfund sites based on pore water for the protection of benthic organisms from direct toxicity to non-ionic organic contaminants (presentation). SETAC North America, Minneapolis, MN, November 12 - 16, 2017.
Impact/Purpose:
Superfund has requested a methodology for developing remedial goals for the protection of benthic organisms using passive sampling measurements of chemical concentrations in sediment pore waters. The developed methodology will be presented and discussed. After publication later this year (EPA 600/R-15/289), the guidance methodology will be used at Superfund sites with contaminated sediments.
Description:
Passive sampling is becoming a frequently used measurement technique at Superfund sites with contaminated sediments. Passive sampling measures the concentrations of freely dissolved chemicals (Cfrees) in the sediment pore water. Cfree has been found to be a very practical means for estimating the concentrations of bioavailable chemical in the sediments. Building from this approach, a methodology has been developed to derive sediment Pore Water Remediation Goals (PWRGs) for the protection of benthic organisms from direct toxicity using Cfrees measured with passive sampling. The methodology builds upon EPA’s Equilibrium Partitioning Sediment Benchmarks (ESBs) approach where ESBs are derived using the product of the organic carbon normalized sediment-water partition coefficient (KOC) and the Final Chronic Value (FCV) from EPA’s ambient water quality criteria for the protection of aquatic life. In the developed methodology, ESBs are used as a screening level to determine where passive sampling measurements should be performed at the site. With passive sampling measurements, site-specific KOC values are determined and subsequently, used with EPA’s FCVs to estimate risk to benthic organisms. If unacceptable risks to benthic organisms exist, PWRGs are developed for the site. The PWRGs may be expressed on Cfree:PWRG (µg/L), CSOC:PWRG (µg/kg-OC), or CS:PWRG (µg/kg-dw) bases. The PWRG approach should also facilitate comparison of sediment toxicity data to sediment chemistry, by indexing chemistry to bioavailability (Cfree). The methodology will be presented along with illustrative examples and published as EPA guidance (EPA 600/R-15/289). This abstract does not necessarily reflect U.S. EPA policy.