Suspect screening and total oxidizable precursor (TOP) assay as tools for characterization of per- and polyfluoroalkyl substance (PFAS)-contaminated groundwater and treated landfill leachate

Landfill facilities are a major source of release of per- and polyfluoroalkyl substances (PFAS) to the surrounding environment. In this study, landfill leachate treated in a conventional wastewater treatment plant and PFAS-contaminated groundwater were subjected to suspect screening analysis and semi-quantification using total oxidizable precursor (TOP) assay and liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS). TOP assays yielded expected results for legacy PFAS and their precursors, but showed no discernible evidence of degradation of perfluoroethylcyclohexane sulfonic acid. TOP assays also produced significant evidence of presence of precursors in both treated landfill leachate and groundwater, but the majority of precursors had probably degraded into legacy PFAS after many years in the landfill. Suspect screening identified a total of 28 PF AS, of which six were not included in the targeted method and were identified with confidence level (CL) ≥3. Semi-quantification of these six compounds showed very low concentrations, indicating that they are not as great a concern as the target PFAS.