Spatial distribution, potential sources, and dry deposition fluxes of per- and polyfluoroalkyl substances (PFAS) in atmospheric particles (PM2.5) in the offshore eastern China sea (OECS)

A total of 26 alternative and per- and polyfluoroalkyl substances (PFAS) were investigated in atmospheric particles collected above the offshore Eastern China Sea (OECS) during a research cruise from April 20 to May 18, 2018. The total concentrations of these 26 PFAS ranged from 35.59 to 1646.53 pg/m³, with an average of 316.79 pg/m³. The concentrations of short-chain perfluorocarboxylic acids (PFCAs) were significantly higher than those of long-chain PFCAs, with perfluorobutanoic acid (PFBA) being the dominant PFCA congener. PFBA was detected in all particle samples, accounting for 77.9 % of the total PFCAs, with an average concentration of 222.05 pg/m³. Moreover, perfluorosulfonic acid (PFSA) analogues showed lower concentrations and detection frequencies than PFCAs, possibly due to the ban on PFOS-related substances. Other PFAS congeners, such as fluorotelomer sulfonic acids (FTSAs) and perfluorooctane sulfonamide (FOSA), were detected at lower concentrations, possibly because they predominately exist in the gaseous phase. The levels of PFAS in atmospheric particles over the OECS were comparable or higher than those in other areas of China and abroad. The coast of Fujian Province and the Yangtze River estuary were two hot-spots for PFAS, mainly influenced by emission sources (various industrial and port transportation activities). In contrast, regions with low PFAS concentrations likely benefited from their geographical locations and meteorological factors, as inferred from backward trajectory analysis. Positive matrix factorization (PMF) modeling identified four primary sources of PFAS; electronic product manufacturing, PFOS-based products, aqueous film-forming foam extinguishing (AFFF) agent usage, and paper packing production. Among these, electronic product manufacturing and PFOS-based products contributed more of the PFAS in the PM_2.5 particle samples. The estimated dry deposition of ΣPFAS ranged from 0.77 to 35.56 ng/m²/d, with an average value of 6.55 ng/m²/d. PFBA, perfluorooctanoic acid (PFOA), and perfluoropentanoic acid (PFPeA) were the dominant contributors. The total PFAS input into the East China Sea and the Yellow Sea via dry deposition in Spring was estimated to be about 518 kg and 328 kg, several times lower than the riverine input reported in previous studies. These findings clearly demonstrate that dry deposition is a significant pathway by which PFAS enter seawater and needs more attention.