Discovery and Implications of C2 and C3 Perfluoroalkyl Sulfonates in Aqueous Film-Forming Foams and Groundwater

Historically, 3M aqueous film-forming foams (AFFFs) were released at U.S. military and civilian sites to extinguish hydrocarbon-based fuel fires. To date, only C-4-C-10 homologues of the perfluoroalkyl sulfonic acids (PFSAs) are documented in 3M AFFFs. Perfluoroethanesulfonate (PFEtS) and perfluoropropanesulfonate (PFPrS), two ultra-short-chain PFSAs, were discovered by liquid chromatography (LC) quadrupole time-of-flight mass spectrometry. Once they were identified, PFEtS and PFPrS were then quantified in five 3M AFFFs and in one groundwater sample from each of 11 U.S. military bases by LC tandem mass spectrometry. Concentrations of PFEtS and PFPrS in the five AFFFs ranged from 7 to 13 mg/L and from 120 to 270 mg/L, respectively. For the groundwater, PFEtS was quantified in 8 of the 11 samples (11-7500 ng/L) and PFPrS in all samples (19-63000 ng/L). The high water solubility, mobility, and detection frequency of these ultra-short-chain PFSAs indicate that groundwater contaminant plumes may be larger than previously believed, and their removal by conventional activated carbon will be challenging.