Per- and polyfluoroalkyl substances (PFAS) are released to the environment from a variety of activities, including firefighting, plating, chemical manufacturing, municipal wastewater treatment, and waste disposal. In locations with multiple sources of PFAS, remedial efforts and PFAS source attribution can be facilitated by forensic tools capable of quantifying the relative contributions of different PFAS sources. In a limited number of situations, exploratory data analysis (EDA) has been used to differentiate among suspected PFAS sources. These initial approaches employed principal component analysis with measured concentrations of perfluoroalkyl acids (PFAAs) and a small number of polyfluorinated compounds to assess the contributions from sources known to be present at the site. To apply these methods to more complex sites where multiple PFAS sources exist and the PFAS signature has been altered by biotransformation and preferential partitioning to soil and sediments, more sophisticated and thorough data analysis methods are needed. Such methods can integrate data from a broader suite of analytes, providing a more accurate and meaningful source assessment.

To advance PFAS source attribution under complex conditions, this project will collect a detailed fingerprint of different PFAS sources prior to applying EDA methods. To provide a breadth of PFAS analysis, the project team will extend the Total Oxidizable Precursor (TOP) assay through separation and selective oxidation of polyfluorinated compounds. The project team will also investigate maximizing the accuracy of the EDA assessment by including data that are relatively inexpensive to collect (e.g., divalent cations, hydrocarbon surfactants, fluoride).

The TOP assay is a simple, robust approach that the project team developed in a prior SERDP project (ER-2128)  to characterize PFAS that are not amenable to routine analytical methods by converting polyfluorinated compounds into PFAAs by oxidation with hydroxyl radicals. The project team hypothesize that using data from the TOP assay plus a modified version of the assay during which samples are subject to separation by solid-phase extraction followed by hydroxyl radical oxidation will provide data that will be better suited for fingerprinting PFAS sources. It is further hypothesized that other easy-to-collect data can further improve PFAS fingerprinting. To test these hypotheses, the project team will first expand and standardize the TOP assay to capture PFAS fingerprints associated with various sources. Other chemical markers from common PFAS sources will then be identified using existing analytical methods. The project team also will examine how biotransformation and transport in soil and aquifers will affect the ability of the EDA methods to estimate the relative contributions of different sources. As part of the research, the project team will develop robust quality assurance and quality control methods for the existing TOP assay and its modified version and translate the findings into practice by collaborating with commercial laboratories that offer the TOP assay to their clients.

The approach developed in this research will provide a robust and accessible method to quantify the relative contributions of different PFAS sources. These methods will also inform the extent of contamination and improve the interpretation and prediction of PFAS environmental fate. (Anticipated Project Completion - 2023)