Perfluoroalkyl acids (PFAAs) such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are in the spotlight due to their environmental persistence and adverse health effects. Aqueous film forming foams (AFFFs) are among the largest sources of per and polyfluorinated alky substances (PFAS) to the environment. Some AFFFs contain a wide variety of fluorinated precursor compounds capable of transforming to PFAAs. The lack of commercially available analytical standards for most of the precursor compounds makes them challenging to study. As a result, their reactivity and fate in natural and engineered environments are still poorly understood. This study sought to investigate UV and hydroxyl radical mediated transformations of PFAA precursors contained in AFFF. Solutions containing dilute AFFF and bicarbonate were subjected to a UV/H<sub>2</sub>O<sub>2</sub> system to mimic the oxidative treatment of an AFFF impacted groundwater. Direct and indirect photochemical transformations in simulated sunlight were also investigated. Using solutions of AFFF, instead of focusing on the few PFAA precursors for which analytical standards are available, is a novel approach to investigating abiotic PFAA precursor transformation. Liquid chromatography quadrupole time-of-flight mass spectrometry was used to identify reactive compounds and assess transformation rates and product formation. The implications of our results will be discussed in the context of hydroxyl-radical based water treatment processes and natural waters, where hydroxyl radicals are produced by indirect photolysis or during the oxidation of reduced natural organic matter and minerals.

UV and hydroxyl radical mediated transformations of perfluoroalkyl acid precursors in aqueous film forming foams

ACS Spring Meeting 2021

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