HRMS-Based Suspect and Nontarget Screening for Comprehensive PFAS Analysis of Soils near a Fluorochemical Site in Flanders

Targeted analysis of per- and polyfluoroalkyl substances (PFAS) relies on a limited number of reference standards, and consequently, many PFAS remain unidentified, which restricts comprehensive monitoring and risk assessment. Here, we apply high-resolution mass spectrometry (HRMS)-based suspect and nontarget screening (SS/NTS), alongside targeted analysis, to detect and (semi)quantify legacy, emerging, and novel PFAS in soils near a PFAS hotspot in Flanders, Belgium. Targeted analysis quantified 36 PFAS, with perfluorooctanesulfonic acid (PFOS) as the most predominant, alongside precursors such as ethyl perfluorooctane sulfonamido acetic acid (Et-FOSAA) and perfluorooctane sulfonamide (FOSA). On the other hand, SS/NTS identified over 100 PFAS homologues and isomers, including pentafluorosulfide sulfonic acids (SF₅-PFSAs), perfluorophosphinic acids (PFPiAs), and perfluorophosphoric diesters (PFPDEs). Total PFAS concentrations at the 3M site varied widely, reaching 118.5 μg/g, among the highest reported globally. These findings highlight the complexity of PFAS contamination in the study area and the need for site-specific analyses to support monitoring, source tracking, regulation, and risk assessment.