The overarching goal of this project is to demonstrate and validate the applicability of no-purge, passive sampling techniques as an easy-to-implement, inexpensive, and investigation-derived waste (IDW)-free alternative to conventional low-stress, low-flow groundwater sampling methodology at sites impacted by aqueous film-forming foam (AFFF). The specific objectives of this field demonstration are as follows:

• Confirm that no-purge sampling devices do not accidentally introduce per- and polyfluoroalkyl substances (PFAS) into the collected samples (under laboratory settings).
• Compare the accuracy and reproducibility of emerging no-purge, passive sampling techniques that have been recently developed to conventional low-stress, low-flow groundwater sampling methodology with respect to analysis of target PFAS as well as suspect anionic, cationic, and zwitterionic PFAS present in AFFF-impacted groundwater. This comparison will be performed for a range of waters with varying PFAS concentrations, geochemical conditions (pH, total organic carbon, salinity), presence/absence of co-occurring chemicals, and at both source area and downgradient monitoring locations.
• Assess potential differences in PFAS concentrations between a discrete, single-point, bulk measurement (via conventional and no-purged, non-PFAS-specific sampling techniques such as the Snap Sampler^® or HYDRASleeve™ that do not account for depth-discrete variability in groundwater flow velocities) versus time and mass-flux-integrated measurements of freely dissolved (and therefore most bioavailable) PFAS.
• Assess the ease of use and potential cost savings associated with the use of no-purge, passive PFAS sampling techniques (to be deployed by field technicians rather than the developers) compared to conventional low-stress, low-flow groundwater sampling methodology.

The technical approach involves collection of groundwater at three AFFF-impacted sites using both conventional and no-purge sampling methodologies. The collected samples will be analyzed for target PFAS, as well as a suite of field and geochemical parameters. The total oxidizable precursor (TOP) assay and adsorbable organic fluorine also will be performed on collected samples to assess the behavior of unidentified polyfluorinated compounds that may be present in the groundwater, but are not individually captured by the currently available commercial analytical methods. Semi-quantitative assessment of suspect PFAS also will be conducted. Multiple sampling events will be performed at each demonstration site to ascertain temporal variability, to provide sufficient data for the robust statistical evaluation needed to compare the different sampling methodologies, and to identify factors that may contribute to sampling biases due to corresponding PFAS uptake at the air-water interface. 

Conventional low-stress, low-flow groundwater sampling methodology is arguably the most widely accepted approach for collecting formation-representative PFAS groundwater samples at or emanating from AFFF-impacted sites; however, management and disposal of IDW generated as part of this popular purging sampling technique results in significant level of effort, logistical complications, and overall monitoring costs over time. Validation of a no-purge groundwater sampling methodology will allow for accurate, reproducible, and inexpensive collection of formation-representative PFAS groundwater samples while eliminating complications often associated with IDW generation, characterization, and disposal. Significant cost savings will likely be realized if no-purge groundwater sampling techniques are employed widely at AFFF-impacted sites and will ultimately bolster operational capabilities and warfighter preparedness of by mitigating the impacts of these chemicals. (Anticipated Project Completion - 2028)