The objective of this Statement of Need (SON) was to develop passive sampling methods to provide repeatable and environmentally relevant measures of per- and polyfluoroalkyl substances (PFAS). The focus of this work should have been for at least the USEPA 24 PFAS shown in Table 1 and total PFAS in groundwater, surface water, stormwater run-off, and porewater in soils and/or sediments (collectively referred to here as “water”). Specific objectives of this SON included:

• Develop passive sampling media competent to quantitatively “concentrate” the wide range of PFAS (nonionic, anionic, and zwitterionic) of interest from water.
• Establish physical-chemical properties, including sorbent/water partition coefficients, molecular diffusivities of PFAS in water and sorbent media.
• Establish the range of PFAS that can be quantifiably sampled using the sorbent(s) (e.g., long chain vs short chain, precursors versus perfluoaroalkyl acids).
• Characterize the impacts of co-contaminants and various water quality and conditions (e.g., freshwater versus salt water, surface waters with biofouling versus groundwater).
• Develop a fundamental understanding of the natural solid-water sorption coefficients of PFAS as a function of sorbate properties, natural solids, and solution properties (pH, major ions, dissolved organic carbon).
• Develop passive samplers that yield representative spatial and temporal interrogation of site contaminants when deployed.
• Develop passive sampling methods/procedures that are capable of being efficiently deployed and retrieved in widely varying field applications (e.g. groundwater, stormwater, surface waters, porewaters).

Proposers should have considered means of establishing equilibria in sampling media, including suitable performance reference compounds across the wide range of PFAS expected, or methods for determining time weighted averages of PFAS loading into aquatic systems. Proposers should have been aware of the requirements of the Department of Defense Quality Systems Manual for Environmental Laboratories (QSM 5.1) in terms of ultimate targets for quality assurance and quality control. Proposals should have addressed one or more of the objectives listed above.

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