The project will demonstrate and validate a commercially-available passive sampler for measuring per- and polyfluoroalkyl substances (PFAS) in sediment and surface water via: 1) demonstrating an in situ field deployment in sediments and water, and 2) validating the ability of in situ passive sampler freely dissolved concentration (C_free) measurements to relate to bioavailability (concentrations in aquatic biota). These demonstration and validation results will be disseminated to potential end users within the Department of Defense (DoD), analytical laboratories, regulators, and consultants to inform the use of passive sampling technology in site-specific PFAS investigations of fate and risk.

Dialysis samplers (“peepers”) are a type of passive sampler that function by allowing a small water compartment to chemically equilibrate with sediment porewater via passive diffusion through a semi-permeable membrane. After an equilibration period in which the passive sampler is exposed to sediment or water, the passive sampler is retrieved, and the passive sampler water is analyzed for target analytes via standard (i.e., Environmental Protection Agency (EPA) SW-846) methods. Dialysis samplers are available commercially, have been applied at sites under regulatory oversight, and are simple and familiar tools for regulatory decision-makers and end users.

Recently, the successful application of a simple dialysis passive sampler to measure dissolved PFAS in groundwater was demonstrated under ESTCP project ER21-5104. In a separate, internally-funded (Geosyntec/SiREM) research effort, the project team conducted a series of experiments using a similar commercially-available sampler design (currently being applied by this research team for inorganics via a three-year ESTCP project ER20- 5261) to measure PFAS in surface water and sediment. The internally-funded research focused on bench-scale experiments and sediment field experiments, confirming the viability of this simple and robust sampler design for PFAS passive sampling in both sediment and water.

This passive sampler design is ready to apply and has several advantages. For example, the design is simple and rugged, based on a tried-and-tested “peeper” design that has been used for over 40 years, is available commercially, and produces a simple liquid water sample that can be analyzed by any commercial analytical laboratory via standard methods (e.g., EPA Draft Method 1633).

Traditional chemical analysis methods in sediment are widely recognized to overestimate bioavailability and risk. In contrast, passive sampling has been shown to be a powerful tool in providing measurements of C_free that can be used to improve site-specific investigations of fate and risk. The project team expects that this project will have a high return on investment to the DoD by demonstrating and validating a PFAS passive sampler that is robust, simple, familiar to the end user and regulatory communities, and currently commercially available. (Anticipated Project Completion - 2026)