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Measuring Bioavailability at Contaminated Upland Soil and Sediment Sites
Developing reliable methods for measuring and reporting the bioavailability of chemicals at contaminated soil and sediment sites has been a major focus for the SERDP and ESTCP Environmental Restoration Program over the last 15 years. In the seminal treatise by the National Research Council (NRC), Bioavailability of Contaminants in Soils and Sediments: Processes, Tools, and Applications ( NRC, 2003), bioavailability was defined as those “physical, chemical and biological interactions that determine the exposure of plants and animals to chemicals associated with soils and sediments”. To cause harm to an organism, a chemical must 1) be released from the soil or sediment (either in the natural environment [desorption] or after ingestion [bioaccessibility]), 2) come in contact with a membrane (e.g., stomach, intestine, lung, or skin), and 3) be distributed to an organ or cell. Bioavailability assessment tools directly measuring these processes are critical to assessing the potential for human and ecological exposure and in developing site-specific remedial action objectives.
SERDP and ESTCP convened a workshop in 2008, Research and Development Needs for Understanding and Assessing the Bioavailability of Contaminants in Soils and Sediments, to determine future research and demonstration needs in the area of bioavailability and its use in the risk-based remedial decision-making process at DoD sites. A direct outcome from that meeting was the Sediment Bioavailability Initiative (SBI) to identify and develop tools that could be used to set defensible cleanup goals and more cleanup priorities based on contaminant bioavailability. A second workshop held in 2012 identified additional tools that could be used to establish bioavailability-based cleanup objectives. The findings of that workshop can be found in the 2012 Summary Report.
Specific passive sampling tools to measure the bioavailable fraction of contaminants in porewater and surface water are presented below. As part of the SBI, SERDP and ESTCP also participated in the Interstate Technology & Regulatory Council (ITRC) technical and regulatory guidance document on sediment bioavailability, and in the Society of Environmental Toxicology and Chemistry (SETAC) workshop on passive samplers.
National Guidance Documents on Use and Application of Passive Samplers
ESTCP is pleased to announce the release of two new documents that provide guidance on the application of passive sampling to manage contaminated sediment sites:
- Draft Laboratory, Field, and Analytical Procedures for Using Passive Sampling in the Evaluation of Contaminated Sediments: User’s Manual
- Integrating Passive Sampling Methods into Management of Contaminated Sediment Site: A Guide for Department of Defense Remedial Project Managers
The User’s Manual is a joint ESTCP and EPA document written by leaders in this rapidly expanding field. The User’s Manual provides chapters covering use of polyoxyemthylene (POM), polydimethylsiloxane (PDMS), and low-density polyethylene (LDPE) for hydrophobic organic compounds, diffusive gradients in thin-films (DGTs) for metals, field deployment and retrieval methods, selection and use of performance reference compounds, quality assurance and quality control procedures, and methods for laboratory analysis. Case studies, and examples of Standard Operating Procedures and Quality Assurance Project Plans are included.
The Remedial Project Managers Guide provides RPMs guidance on how to integrate passive sampling into management of contaminated sediment sites. Written as a companion document to the User’s Manual, the author team conducted extensive interviews with RPMs (DoD and EPA), scientists, analytical laboratories, and practitioners. From their input, the Guide focuses principally on passive sampling of hydrophobic organic compounds (e.g. PCBs, dioxin/furans, PAHs) using POM, PDMS or LDPE. Topics covered include what do passive samplers measure, how can they be used in remedial investigations feasibility studies or remediation, examples of use in the RI/FS and remediation process, a list of commercial laboratories that can do this work, and how to use the results in the decision-making process.
Guidance on Using Polyethylene Samplers to Measure HOCs in water and porewater
Detailed guidance for using LDPE samplers was developed under ESTCP project ER-200915 at MIT. Standard Operating Procedures for the preparation, deployment, and analysis of PE passive samplers have been posted and are available by selecting the hyperlink, above. A Performance Reference Compound (PRC) Calculator that allows users to readily process PRC data from PE passive sampler deployments also was a product from this project. The PRCC User’s Guide for the document may be downloaded from this link. There is a separate web site for the PRC Correction Calculator; versions of the PRC calculator written for the MAC, 32 bit and 64 bit Windows users will be found there.
Case studies for application of LDPE at contaminated sediments sites are presented in the EPA/ESTCP User’s Manual. Additional field demonstrations can be found at the following project web sites: ER-1496, ER-201431, and ER-2429.
Guidance on Using SPME Samplers to Measure HOCs in water and porewater
Standardized procedures for field deployable solid phase microextraction (SPME) samplers to measure freely dissolved porewater concentrations of hydrophobic organics and demonstrate were developed under ESTCP project ER-200624 by researchers now at Texas Tech University. In situ SPME is a passive sampling method that involves the insertion of a polymer sorbent into the sediments for a specific period of time, then measuring the contaminants sorbed to the polymer. The contaminant concentration on the polymer is directly proportional to the dissolved contaminant concentration in the porewater. The technology demonstrated in this project used PDMS as a polymer sorbent as a thin coating on a glass core.
Detailed guidance on preparation, deployment and analyses may be found on the project web site, or by clicking on the embedded report icon. A PRC Correction Calculator for PDMS, and the accompanying PDMS PRCC User’s Guide may be found at embedded hyperlinks.
Case studies of application of SPME at contaminated sediment sites are presented in the EPA/ESTCP User’s Manual. Additional field demonstrations can be found at the following project web sites: ER-200624, ER-1370, ER-1550, and ER-201131.
Bioavailability of Contaminants in Soils and Sediments: Status and Recommendations (2016)
Draft Laboratory, Field, and Analytical Procedures for Using Passive Sampling in the Evaluation of Contaminated Sediments (2016)
Bioavailability of Contaminants in Soil: Considerations for Human Health Risk Assessment
Guide for DOD Remedial Project Managers:
Integrating Passive Sampling Methods into Management of Contaminated Sediment Site (2016)