Heterogeneous Reaction of Perfluorinated Carboxylic Acids (PFCAs) with Aerosol Proxies: Implications for Aerosol-Mediated Long-Range Transport

TREVOR VANDENBOER, Nasrin Dashti, Elizabeth Gaona-Colmán, Jeremy Wentzell, John Liggio, Cora Young, York University

     Abstract Number: 467
     Working Group: Chemicals of Emerging Concern in Indoor and Outdoor Aerosol: Sources, Vectors, Reactivity, and Impacts

Abstract
Perfluorinated carboxylic acids (PFCAs) are the notorious persistent environmental degradation end products of the oxidation of many poly- and perfluoroalkyl substances (PFASs). PFAS are highly used substances due to their stability and surfactant properties leading to industrial applications such as textiles manufacture, cookware, and firefighting foams.

These substances are ubiquitously distributed in the environment, even in remote locations such as the Arctic as they are detected and increasing in deposition in ice core records. In the atmosphere, short chain PFCAs can be emitted directly into the environment or be formed from reactions of precursors (e.g. fluorotelomers, hydrofluorocarbons) with atmospheric oxidants (e.g. hydroxyl radicals). Despite the well-known atmospheric formation of short chain fluorinated acids, there is still a gap of knowledge regarding their transport to remote locations, where aerosols could contribute to this transport, as suggested by ice core analysis. In this study we present the uptake of gas phase PFCAs onto aerosol proxies, including carbonate salts as proxies of crustal mineral dust. The experiments were performed in a flow tube reactor at 296 K and atmospheric pressure with zero air as carrier gas coupled to a chemical ionization mass spectrometer (CIMS) as detection system, using acetate as the reagent ion. Controlled amounts of gas phase perfluoropropionic acid (PFPrA) were obtained from the acid displacement reaction of HCl(g) over a salt bed of sodium perfluoropropionate. To our knowledge, this work is the first determination of the reactive uptake coefficients of gas phase PFCAs onto aerosol proxies. Reactive uptake coefficients will be presented and the implications for PFAS long-range transport will be discussed.