Standardization of Polymeric Sampling for Measuring Freely Dissolved Organic Contaminant Concentrations in Sediment Porewater

Dr. Mandy Michalsen | U.S. Army Corps of Engineers

ER-201735

Objective

Passive samplers are an alternative to actively sampling sediment porewater using Henry samplers and pumping or centrifugation. Passive samplers consist of hydrophobic polymers (e.g. polyethylene, polydimethylsiloxane), which sorb freely-dissolved organic compounds present in sediment porewater. Henceforth, passive samplers are referred to as polymeric samplers for clarity. Polymeric samplers can be directly inserted into saturated sediment in the laboratory or in the field to yield depth-discreet measures of freely dissolved (Cfree) organic contaminant concentrations present in sediment porewater. Cfree measured by polymeric samplers represents the fraction of contaminants not sorbed to settling solids or associated with suspended colloidal matter and has been linked directly to exposure and risk to sediment-dwelling organisms. This has been demonstrated in research supported by a number of organizations including SERDP and ESTCP. However, lack of standardized methods and commercial availability to support polymeric samplers for environmental monitoring purposes has been a barrier to effective technology transfer and polymeric sampler use. This project will demonstrate use of standardized polymeric sampler procedures developed under ESTCP project ER-201216 for quantifying Cfree in contaminated sediment porewater by multiple participating public- and private-sector analytical laboratories.

ER-201735 Photo

University of Maryland Ph.D. student Mandar Bokare holding up a polyethylene (PE) sheet and a solid-phase microextraction (SPME) fiber (in bottle, see also inset) in front of a gas chromatograph/mass spectrometer (GC/MS) used to measure organic contaminants adsorbed to the PE and SPME samplers.

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Technology Description

Passive samplers may be used to measure Cfree in the laboratory using static or continuously mixed methods. This project will demonstrate both methods using a single, homogenized sediment sample containing both PAHs and PCBs. The demonstration will be conducted by multiple laboratories under carefully controlled conditions to demonstrate method accuracy and reliability. However, the start-to-finish method details utilized will be applicable to those who wish to employ this technology directly in the field. This demonstration includes the following key tasks.

  • Leverage existing guidance to develop a standardized methodology for polymeric sampler preparation and analysis in collaboration with multiple public- and private-sector laboratories. This methodology will describe how to:
    • Prepare polymeric samplers, including loading performance reference compounds;
    • Expose polymeric samplers to sediment;
    • Retrieve polymeric samplers from sediment and extract the organic contaminants and performance reference compounds;
    • Perform chemical analysis of polymeric sampler extracts; and
    • Interpret results and use them to determine the freely-dissolved organic contaminant concentrations present in sediment porewater.
  • Public- and private-sector laboratories will work collaboratively to finalize the standardized polymeric sampler methodology, then validate the methodology through a phased interlaboratory comparison.
  • Document the standardized methods and interlaboratory method comparison results in a guidance document prepared following EPA SW846 guidelines, in addition to posting freely available webinars and instructional videos via YouTube and other online platforms.

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Benefits

Standardization of polymeric sampling methods – coupled with documented method accuracy and reliability through the phased interlaboratory study – is expected to dramatically improve regulatory acceptance. Further, at the conclusion of this demonstration, at least six commercial laboratories will have new polymeric sampling capabilities, which they will market widely. This demonstration will support ongoing DoD efforts to employ polymeric sampling, and encourage remedial project managers (RPMs) to begin using this technology. (Anticipated Project Completion - 2020)

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Points of Contact

Principal Investigator

Dr. Mandy Michalsen

U.S. Army Corps of Engineers

Phone: 206-764-3324

Fax: 206-764-3706

Program Manager

Environmental Restoration

SERDP and ESTCP

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