Nontargeted Analysis of Surface and Groundwaters Impacted by Historic PFAS Waste Sites

Per- and polyfluoroalkyl substances (PFAS) make up a diverse class of anthropogenic chemicals with widespread industrial and commercial uses. Historical manufacturing and disposal of PFAS have led to their introduction to the environment, although only a fraction of existing PFAS are routinely monitored using targeted analysis methods. Here, nontargeted analysis was used to investigate the identity and fate of PFAS present in eight groundwater and nine surface water samples collected near St. Paul, MN, surrounding two sites that historically received wastes from a PFAS manufacturer in the 1940-1970s. A total of 210 PFAS, split across 33 different homologous series, were identified in surface and groundwater samples both at and downstream of the two waste sites. Identified compounds included perfluorinated, polyfluorinated, and unsaturated sulfonic and carboxylic acid species as well as a variety of sulfonamide and sulfonamido chemistries. PFAS measured downgradient included legacy perfluorinated sulfonic and carboxylic acids, as well as their polyfluorinated, unsaturated, keto, and ether-containing analogs. Two-thirds of the identified PFAS were unique to the groundwater at one site. The lack of these PFAS at downstream sites likely reflects dilution below the limit of detection during downgradient transport. The identified species reveal previously unknown and substantial ongoing contamination of the watershed due to historic PFAS manufacturing and waste disposal.