Sediment Bioavailability Initiative: Development of Standard Methods and Approaches for the Use of Passive Samplers in Assessing and Managing Contaminated Sediments
SERDP and ESTCP have supported a considerable body of work on the development of methods for measuring bioavailability and on the application of measures of sediment bioavailability to various projects involving innovative sampling devices, engineered caps, in situ stabilization, treatment additives, and sediment measurement and monitoring tools. The Sediment Bioavailability Initiative is a product-oriented initiative that seeks to provide scientific support for the use of innovative tools and practices and to standardize the use of passive samplers as measures of contaminant bioavailability. The objectives of this project are to: (1) prepare a Practices Manual that summarizes the current state-of-the-practice for passive sampler methods and standard operating procedures for field and laboratory applications; (2) develop standard methods with accompanying quality control measures; (3) develop an Integrated Assessment/Management Framework that will provide potential users with a clear picture of how to use information on bioavailability for assessing and managing exposure; and (4) provide outreach and scientific support for incorporation of reliable measures of bioavailability into remedial management decisions.
The passive sampler approach assumes that the chemical activity of a hydrophobic organic contaminant (HOC) in sediment is directly proportional to its freely dissolved concentration in pore water (i.e., not associated with particulates or dissolved organic carbon) and that the freely dissolved concentration is proportional to the bioavailable concentration. It is generally accepted that the freely dissolved concentration in pore water is a better measure of potential exposure than is the total concentration of contaminant in bulk sediment. This approach does not imply that exposure is limited to uptake from pore water, only that the pore water concentration is a better reflection of the fraction of total contaminant in bulk sediment that is available to freely partition among all environmental compartments, including tissue of sediment-associated organisms. Various methods for applying passive samplers have been developed, including deployment in the field or laboratory, with or without mixing, for sufficient times to allow sediment-sampler equilibrium. Alternatively, samplers can be inserted in unmixed sediment in the laboratory or in the field, and corrections can be made if exposure times are too short to reach equilibrium. Performance reference compounds (PRCs) incorporated into passive samplers before deployment can be used to estimate equilibrium concentrations. Sampler-water partition coefficients are used to estimate freely dissolved concentrations from concentrations associated with the sampler. Although several types of passive sampler methods have been developed for measuring concentrations of freely dissolved contaminants, this project focuses on those methods that have been the focus of considerable research by SERDP and ESTCP, including solid phase microextraction (SPME) with polydimethylsiloxane (PDMS), low density polyethylene (LDPE), polyoxymethylene (POM) for hydrophobic organic contaminants, and diffusion gradient in thin films (DGT) for metals.
Explicit consideration and acceptance of bioavailability for exposure assessment and management will make it possible for the Department of Defense (DoD) to use more cost-effective remedial methods that are based on reducing exposure by reducing bioavailability (treatment and reactive caps). Actual measures of exposure that incorporate bioavailability also generally lead to more focused remedial approaches (i.e., smaller areas or volumes requiring remediation). Preliminary estimates show that remedial costs for contaminated sediments can be reduced by orders of magnitude when these two aspects are combined. In addition, because explicit consideration of bioavailability can reduce the footprint of remediation and the potential harm of remediation (by using more passive treatment methods), DoD-impacted waterways may benefit from reduced disruption to natural resources. (Anticipated Project Completion - 2014)
Points of Contact
Dr. Charles Menzie
SERDP and ESTCP
- Project Overview - Brief project summary with links to related documents and points of contact.
- Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
- Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
- Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
- Guidance - Instructional information on technical topics such as protocols and user’s guides.
- Workshop Report - Summary of workshop discussion and findings.
- Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
- Model/Software - Computer programs and applications available for download.
- Database - Digitally organized collection of data available to search and access.