PM2.5-Bound PFAS in the Qiantang River Basin: Sources, Spatial Patterns, and Transport.

Per- and polyfluoroalkyl substances (PFAS) have attracted widespread concern because of their environmental persistence, long-range transport potential, and potential toxicity. However, the occurrence patterns and governing mechanisms of atmospheric PFAS at the watershed scale remain poorly understood. Here, atmospheric PM2.5 samples collected from eight cities spanning the upper to lower reaches of the Qiantang River Basin were analyzed to characterize PFAS contamination, identify dominant sources, and assess inhalation exposure risks. PFAS were ubiquitously detected in atmospheric PM2.5 at relatively elevated levels, exhibiting pronounced spatial heterogeneity across the basin. Kecheng emerged as a major pollution hotspot, with ∑PFAS concentrations reaching 592.31 pg/m3, significantly exceeding those observed in other cities. Compositionally, ultra-short-chain and long-chain PFAS predominated, indicating substantial structural diversity in atmospheric PFAS profiles. Integrated receptor modeling and regional transport analyses revealed that atmospheric PFAS pollution was jointly driven by local industrial emissions, particularly fluorochemical-related activities, and regional-scale atmospheric transport, which promoted basin-wide accumulation and redistribution. Meteorological conditions further influenced PFAS environmental partitioning and transport behavior. Although inhalation exposure risks were generally low under current conditions (HI < 1), children exhibited relatively higher exposure, and pollution hotspots showed elevated potential health concern. Overall, this study demonstrates that atmospheric PFAS contamination in industrialized watersheds is shaped by the coupling of emission sources and regional transport processes, highlighting the need for source-oriented control and cross-regional collaborative management of PFAS pollution.