Distribution and dry deposition of alternative and legacy perfluoroalkyl and polyfluoroalkyl substances in the air above the Bohai and Yellow Seas, China

A total of 26 alternative and legacy perfluoroalkyl and polyfluoroalkyl substances (PFASs) were investigated in air collected above the Bohai and Yellow Seas during a research cruise between June 28 and July 15, 2016. ∑PFAS concentrations ranged from 70 pg m−3 to 430 pg m−3 (mean 230 ± 100 pg m−3). Trifluoroacetic acid (TFA, mean 120 ± 80 pg m−3) and 8:2 fluorotelomer alcohol (8:2 FTOH, mean 34 ± 46 pg m−3) were the predominating compounds of ionizable PFASs (i-PFASs) and neutral PFASs (n-PFASs), respectively. The contributions of C4 and C6 i-PFASs were higher than those of C8 i-PFASs. Alternative substances, such as chlorinated 6:2 polyfluoroalkyl ether sulfonic acids (Cl-6:2 PFESA, mean 1.6 ± 1.2 pg m−3) and diPAPs (mean 1.6 ± 1.3 pg m−3), were only detected on the filter. The distribution coefficient of 10:2 FTOH was higher than 8:2 FTOH, which could be explained by the length of the carbon chain. The gas phase dry deposition velocities were simulated, and the values ranged from 0.08 ± 0.12 cm s−1 to 0.85 ± 0.28 cm s−1. For i-PFASs and diPAPs, the estimated fluxes of the particle phase were higher than those of the gas phase. For n-PFASs and TFA, the gas phase deposition played a key role. The ∑PFASs dry deposition fluxes were 11–290 ng (m2 d)−1 (mean 72 ± 67 ng (m2 d)−1). The measurement of the concentrations in the gas and particle phases simultaneously provided a more comprehensive understanding of PFAS behaviours in air.