Identification of Novel PFAS Transformation Products in AFFF-Impacted Surface and Groundwater

The widespread use of Aqueous Film-Forming Foams (AFFF) has left thousands of contaminated "hotspots" across North America. In Canada, only 25 per-/polyfluoroalkyl substances (PFAS) are regulated in drinking water at 30 ng/L. In the present study, cyclic ion mobility-tandem mass spectrometry (cIMS-MS2) was used to identify 17 regulated and 52 unregulated PFAS in surface waters near a former firefighting training facility in Atlantic Canada, including 6 new PFAS that have not been previously reported in environmental waters: hydrido-ketone-5:2-fluorotelomer sulfonate (FTS), ketone-8:2-FTS, unsaturated 8:2-FTS, N-methyl-perfluorohexane sulfonamido sulfinate, N-methyl-perfluorooctane sulfonamido sulfinate, and perfluorohexane sulfonamido propionate. Semi-quantitation of unregulated PFAS was enabled by a machine-learning model validated using a set of 21 targeted PFAS (R2 > 0.95). The total concentration of PFAS declined from 2500 ng/L to 364 ng/L as the surface water entered the North Atlantic approximately 5 km away from the hotspot. Seven of forty-two drinking water wells located along a 5 km transect from the source were characterized by exceedances between 30 and 191 ng/L. Twenty-seven PFAS were identified in the wells, including 13 that are unregulated and 5 that result from (bio)transformation of AFFF. While the fraction of unregulated PFAS was low (<18%), these transformation products may inform forensic studies aimed at establishing links between the source of pollution and its receptors.