Per- and Polyfluoroalkyl Substances in Field-Collected Light Non-Aqueous Phase Liquids

Abstract

Per- and polyfluoroalkyl substances (PFAS) and non-aqueous phase liquids (NAPLs) co-occur at sites where aqueous film forming foams (AFFFs) were used as part of firefighter training exercises or in response to emergencies (e.g., crashes). Till date, there are no data on PFAS in field-collected, light NAPLs (LNAPLs) recovered from groundwater wells on US military bases. Analytical methods were developed for target and suspect nonvolatile (anionic) and volatile (neutral) PFAS in field-collected LNAPLs. The validated methods were demonstrated on 17 LNAPL samples collected from the subsurface at five military installations with known AFFF impacts and where LNAPL releases date 10–70 years ago. Target and suspect anionic PFAS associated with AFFF of either electrochemical fluorination or fluorotelomerization origin were quantified and semi-quantified, respectively, in 11 LNAPLs. Perfluorooctane sulfonate (PFOS) occurred at the highest frequency, ranging from 110 to 11,100 ng/L. As a class, perfluoroalkyl sulfonamides occur at a frequency similar to that of PFOS, but at higher concentrations, with the C6 homolog ranging up to 67,500 ng/L. Only one LNAPL had quantifiable neutral PFAS (6:2 fluorotelomer alcohol), indicating potential biotransformation and/or volatilization. Residual LNAPLs at AFFF-impacted field sites may represent an undetected reservoir of PFAS that must be considered when designing remedial actions.