July 20, 2020
Making enhanced risk-based decisions for contaminated sediment sites
The U.S. Environmental Protection Agency's (EPA's) Technology Innovation and Field Services Division recently highlighted a publication that presented a state-of-the-art protocol for the use of passive sampling in sediments and soils. Passive sampling is a technique that measures concentrations of bioavailable contaminants in sediment, soil, surface water, and storm water. This technique presents many advantages over traditional analytical methods in terms of cost and data quality. Passive samplers are increasingly used at contaminated sediment sites to estimate bioavailability of organic contaminants and associated risk to aquatic life, and their use in site characterization and assessment is gaining considerable regulatory support. For example, California's Sediment Quality Objectives program endorses the use of passive samplers as a tool to understand chemical bioavailability and risk.
Passive samplers (such as a thin sheet of polyethylene) are exposed to contaminated sediment or water in the field or in the lab for an average of 4 — 6 weeks. After analysis in the laboratory, the measured concentrations of contaminants in the samplers are used to estimate the concentration of freely dissolved contaminants in the sediment porewater or surface water, which can be used to estimate potential exposure and risk to aquatic organisms.
How Exponent Can Help
Exponent scientists co-authored two guidance documents on passive samplers with EPA and the U.S. Department of Defense. Exponent's multidisciplinary team of environmental scientists and toxicologists can partner with expert laboratories to design and implement pilot- and bench-scale passive sampler studies for site characterization and to demonstrate the effectiveness of sediment remediation treatments (e.g., activated carbon) in reducing the bioavailability of contaminants, including mercury, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons. Exponent can help clients obtain and use passive sampler data in risk assessments and to advocate for cost-effective remedial practices.