Assessing PFAS fingerprints and precursor burden in AFFF-impacted waters and sediments: An operational screening
Jeonghoon Park1, Soobin Choi2, Taeyeon Kim2
1Department of Environmental Health Sciences, School of Public Health, Seoul National University, Seoul, South Korea; Institute of Health & Environment, Seoul National University, Seoul, South Korea.
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An integrated fingerprinting framework was developed to characterize AFFF-derived PFAS contamination in surface waters and sediments at three AFFF-impacted sites in South Korea (one firefighting training facility and two air force bases). Fifty target PFAS were quantified by LC-tandem mass spectrometry, suspects were screened by ion mobility-high-resolution mass spectrometry with collision cross section support to strengthen class-level assignment, and surface waters were subjected to the total oxidizable precursor (TOP) assay to estimate oxidizable perfluoroalkyl carboxylate (PFCA) precursors. Surface waters contained up to 7940 ng/L ΣPFAS, with PFOS and PFHxS up to 2133 and 1580 ng/L, respectively, whereas sediments were dominated by long-chain perfluoroalkyl sulfonates, including PFOS up to 3570 ng/kg⋅dw. Suspect screening identified 8 PFAS classes, including sulfonamide-based species typical of electrochemical fluorination (ECF) formulations and a fluorotelomer (FT) betaine observed exclusively near the Republic of Korea Air Force Base. To the best of current knowledge, Class 1 bis-perfluoroalkyl sulfonimides were tentatively identified for the first time in AFFF-impacted environmental media. TOP assay results indicated large pools of unknown precursors (182-4972 pM; 14-51 mol% of total PFAS). Ratio-based fingerprint indicators, TOP-derived precursor indices, and flow-corrected contrast metrics, interpreted together with suspect-class profiles, supported screening-level evaluation of ECF- and FT-related signatures, hotspot prioritization at outfalls and screening-level prioritization of downstream confluences across the three study areas, and quantification of oxidizable precursor burdens. These operational indicators provide a practical screening tool to support prioritization of investigation, treatment, and sediment management at PFAS-impacted sites, and are intended as screening-level decision support rather than definitive source apportionment.
