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Developing Models to Understand Atmospheric Reactions of Per- and Polyfluoroalkyl Substances (PFAS)
Citation:
D'Ambro, E., H. Pye, J. Bash, J. Boyer, C. Allen, C. Efstathiou, R. Gilliam, L. Reynolds, K. Talgo, AND B. Murphy. Developing Models to Understand Atmospheric Reactions of Per- and Polyfluoroalkyl Substances (PFAS). Atmospheric Chemical Mechanisms Conference, Davis, California, November 05 - 20, 2020.
Impact/Purpose:
PFAS is of growing concern to EPA program offices and regions due to the ubiquitous exposures across the population, and the growing evidence for adverse effects in humans. The potential for PFAS air emissions to transport and deposit on soils and waters exists but has not been sufficiently studied. EPA has determined that mitigating PFAS exposures is an Agency priority. Improved understanding of atmospheric fate and transport of PFAS is needed to identify potential sources of PFAS exposures and appropriate mitigation options. This product aims to address gaps in knowledge about atmospheric fate and transport of PFAS by characterizing PFAS air emissions from important large point sources (e.g., Chemours Processing Facility outside Fayetteville, NC) and the exploration of the effects of likely atmospheric oxidation pathways on the form and abundance of atmospherically relevant PFAS compounds.
Description:
Per- and polyfluoroalkyl substances (PFAS) are a class of man-made compounds whose research has traditionally focused on exposure via water. More recently, air emissions have been identified as a likely pathway contributing to water concentrations via transport and deposition, although few studies examine the air concentration and deposition of PFAS. Thus, our understanding of basic information like the phase state of atmospheric PFAS is evolving rapidly. Most modeling studies have focused on individual compounds and very few have investigated atmospheric chemical transformations. We present results from the Community Multiscale Air Quality model (CMAQ) applied to a case study focused on a fluoropolymer manufacturer in North Carolina. This framework includes a suite of 53 compounds and their emission rates from this point source. One significant class of compounds emitted from this facility, acyl fluorides, are well-known to hydrolyze to carboxylic acids rapidly in the condensed phase, but the feasibility in the atmosphere is unknown. We find that the assumptions made about condensed-phase reaction time significantly impacts the partitioning and deposition of these compounds. Determining the time scale of simple reactions such as hydrolysis will be vital for understanding the environmental behavior of PFAS. Finally, we implement known PFAS chemistry into a box model framework and investigate the utility of a box model approach to understanding PFAS chemistry and partitioning.
