There are a number of different potential sources of perflorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS) and other per- and polylfuoroalkyl substances (PFAS) of concern to the environment, though there is not yet an established approach that can distinguish sources. Given the widespread use of PFAS-containing materials and the growing litigation over their presence in the environment, there is a clear and immediate need for PFAS source attribution, particularly for PFOA and PFOS. There is nowhere this need is more evident than at Aqueous Film-Forming Foam (AFFF)-impacted Department of Defense (DoD) sites, where contamination from DoD firefighting activities may be blending with PFAS contamination stemming from other sources.

The overall objective of this work is to provide a framework for PFAS forensics in environmental samples. The three steps to achieving this objective include 1) establishing a PFAS forensic library of source materials; 2) validating PFAS forensic approach using environmental samples and determining the extent to which forensic information is preserved in environmental samples; and 3) characterizing changes to select PFAS forensic signatures associated with environmental fate and transport.

The technical approach for this work will employ a tiered analytical approach to characterizing PFAS source materials. The three tiers of this approach include 1) particle-induced gamma emission spectroscopy to measure the total fluorine content of a sample and full scan liquid chromatography with mass spectrometry (LC-MS) to characterize the holistic PFAS signature; 2) a standard method to sensitively and defensibly measure concentrations of target PFAS; and c) LC-MS/MS to characterize the branched and linear isomers of perfluorohexanoic acid, perfluorohexanesulfonic acid, PFOA, and PFOS.

This tiered approach will be applied to a number of source materials to establish a forensic library of PFAS source materials and identify diagnostic characteristics that distinguish sources from each other. It will then be applied to a number of soil and water samples amended with selected PFAS source materials to determine the extent to which diagnostic PFAS characteristics may be measured in environmental media. Lastly, it will be applied to a set of soil column studies and incubations with biosolids to determine how the PFAS signature, including important forensic diagnostic characteristics, changes during environment transport and microbial transformation, respectively.

This research will allow scientists and regulators to identify features of PFAS associated with AFFF formulations versus those associated with other classes of PFAS. Additionally, this work will establish a PFAS source library (including AFFF and other classes of source materials) identifying PFAS characteristics that will distinguish individual sources or classes of sources from each other and evaluate the extent to which those diagnostic features can be evaluated in environmental samples. Lastly, by evaluating the PFAS forensic signatures associated with environmental fate and transport of different source materials, this work will provide the scientific community with empirical data which might be used to validate models that predict changes to AFFF mixtures over time. (Anticipated Project Completion - 2025)