The overall goal of this proof-of-concept project is to develop ion exchange membrane (IEM)- and ion exchange fiber (IEF)-based strategies for passive sampling of chemically-diverse per- and polyfluoroalkyl substances (PFAS) at Department of Defense (DoD) facilities. The project goal will be accomplished through investigation of the following specific objectives:

1. Develop IEM- and IEF-based passive samplers capable of concentrating short- and long-chain PFAS with varying log D values (i.e., log Kow values that account for speciation);
2. Establish selectivity coefficients for 24 PFAS of concern in the IEM and IEF samplers to quantitatively describe PFAS uptake/partitioning;
3. Confirm that the IEM- and IEF-based passive samplers are capable of effective deployment and performance in synthetic and real groundwater, surface water, stormwater, and porewater from DoD facilities;
4. Investigate ion exchange-based passive samplers for cationic, zwitterionic, and anionic PFAS;
5. Ensure consistent IEM and IEF performance for single- and multi-sorbate scenarios;
6. Characterize effects of solution pH, ionic strength, background ions (e.g., Ca²⁺, Mg²⁺, Na⁺, SO₄^2-, HCO₃^-, Cl^-, etc.), temperature, and dissolved organic matter (DOM) on passive samplers; and,
7. Deploy passive samplers in laboratory-based mesocosms to confirm the ability of the IEM and IEF materials to resolve spatiotemporal variations in PFAS concentration.

The IEM and IEF passive samplers represent a paradigm shift in passive sampling strategies for organic contaminants and PFAS, in particular. This shift stems from the wide-ranging physicochemical properties of PFAS, which complicate traditional passive sampling strategies. The specific objectives will be achieved through the following: (i) batch sorption tests to identify selectivity coefficients, partitioning coefficients, competitive effects, and impacts of interfering substances for anionic, cationic, and zwitterionic PFAS; and, (ii) mesocosm studies using real groundwater, surface water, stormwater, and sediment (porewater) from DoD facilities.

Given the increased importance of PFAS to ongoing cleanup and remediation efforts at DoD facilities, new strategies are required to enable monitoring of PFAS. This project will develop, evaluate, and test innovative ion exchange-based materials for passive sampling of PFAS. Unlike other PFAS techniques, which will be adversely affected by the wide-ranging chemical properties of short-chain, long-chain, and substituted PFAS, the IEM and IEF materials developed here will offer robust solutions for the full range of PFAS of interest. The results of this project will contribute new scientific understanding to the use of ion exchange passive samplers, which may be useful for other DoD-relevant contaminants, and PFAS monitoring in various environmental matrices. These combined benefits will assist DoD with management of PFAS-contaminated sites. (Anticipated Phase II Completion - 2025)