Characterizing Seasonal Patterns, Gas-Particle Partitioning, and Potential Sources of Airborne Per- and Polyfluoroalkyl Substances in Japan

The global ubiquity of perfluoroalkyl and polyfluoroalkyl substances (PFAS) highlights the important role of atmospheric transport. This study monitored 47 PFAS, including perfluoroalkyl acids (PFAAs), emerging PFAS, and precursors of PFAAs (pre-PFAAs), in seasonal ambient air in Japan between 2022 and 2023, quantifying 38 of them in collected samples. The profiles were dominated by 6:2 fluorotelomer alcohol, perfluorobutanesulfonic acid, and perfluorobutanoic acid, with median levels of 245, 117, and 78.0 pg m^-3, respectively. Pre-PFAS and perfluoroalkyl carboxylic acids (PFCAs) exhibited relatively higher concentrations in the warm seasons, whereas perfluoroalkyl sulfonic acids (PFSAs) were more abundant in the cold seasons. Particle-bound fractions of PFCAs with carbon number (C_n) ≤ 13 and PFSAs with C_n ≤ 8 were found at lower levels than in previous reports. Additionally, an odd-even pattern in the gas-particle distribution ratio was observed for PFCAs, with relatively higher values for odd-numbered compounds than for their even-numbered counterparts. Using positive matrix factorization analysis, aqueous film-forming foam-related activities, waste stream emissions, and fluoropolymer manufacturing were proposed as potential major sources in the studied areas, with their relative contribution quantified. These findings enhance our understanding of the atmospheric behavior of PFAS and facilitate the development of tailored PFAS mitigation strategies.