The Role of Perfluorinated Acyl Fluoride Hydrolysis in Regional-Scale Model Predictions of Per- and Polyfluoralkyl Substance (PFAS) Chemistry, Transport, and Fate

Per- and polyfluoroalkyl substances (PFAS) have been released into the environment for decades and are a concern for human and environmental health. PFAS are considered largely inert, but studies show that some PFAS can undergo chemical reactions that can impact their environmental behavior. In this work, the hydrolysis in particle and cloud water of three perfluorinated acyl fluorides, an important class of emissions from a global manufacturer, to perfluorinated carboxylic acids is added into a PFAS atmospheric model built upon the Community Multiscale Air Quality model (CMAQ-PFAS). Nearly all of the hydrolysis is predicted to proceed in the clouds, with minimal occurrence in particles. Henry's law constants increase by three or more orders of magnitude when acyl fluorides hydrolyze into carboxylic acids, increasing the predicted domain-wide annual deposition for these compounds. A larger relative increase in deposition is observed further from the facility, although predicted deposition 110 km away from the facility is lower than measurements by a factor of ∼20 or more. The reasons for this underprediction are discussed, and future research needs to better simulate and understand PFAS in the atmosphere are proposed.