Spatiotemporal trends and source contributions of legacy and emerging PFAS in PM_2.5 from eastern China

Per- and polyfluoroalkyl substances (PFAS) in atmospheric particulate matter remain poorly characterised at large spatial and temporal scales. This study investigated the spatiotemporal distribution, long-range transport and source contributions of both legacy and emerging PFAS in PM_2.5 across eastern China. A total of 540 PM_2.5 samples from ten cities in Zhejiang Province (2020-2023) were analysed. Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) trajectory modelling and positive matrix factorization (PMF) identified potential source regions and contributions. Total PFAS concentrations (∑PFAS) ranged from 9.1 to 12,264.6 pg/m³, with a median of 64.9 pg/m³. Perfluorooctanoic acid (PFOA) was the predominant PFAS (median 21.7 pg/m³), whereas hexafluoropropylene oxide dimer acid (GenX) exhibited the highest median concentration (3.2 pg/m³) among emerging PFAS. ∑PFAS levels in northeastern inland cities were higher in summer than in winter, likely due to southwesterly transport from a nearby fluorochemical industrial park. Seasonal variability in PFAS was also influenced by precursor oxidation, as evidenced by positive correlations between secondary organic carbon and selected perfluoroalkyl carboxylic acids. PMF analysis identified fluorochemical production as the dominant source in inland areas, while sea spray aerosol contributed substantially to coastal regions. Interannual trends showed declining legacy PFAS but increasing detection frequencies and concentrations of alternatives (e.g., GenX, 6:2 fluorotelomer sulphonate). Additional emerging PFAS were detected through suspect screening near the industrial area, indicating growing compositional complexity. Overall, these results emphasise the continued impact of fluorochemical industrial emissions on atmospheric PFAS and the ongoing transition in PFAS profiles from legacy to emerging compounds in particulate matter.