Occurrence, fluxes and sources of perfluoroalkyl substances with isomer analysis in the snow of northern China

Abstract

In this study, perfluoroalkyl substances (PFASs) and the isomers of perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) were analyzed in fresh snow samples collected from 19 cities in northern China, 2013. The levels of total PFASs in the snow samples were 33.5–229ng/L, suggesting heavy atmospheric pollution of PFASs in northern China. PFOA (9.08–107ng/L), PFOS (3.52–54.3ng/L), perfluoroheptanoate (PFHpA) (3.66–44.8ng/L), and perfluorohexanoate (PFHxA) (3.21–23.6ng/L) were predominant with a summed contribution of 82% to the total PFASs. The particulate matters (PMs) associated PFASs contributed 21.5–56.2% to the total PFASs in the snow, suggesting PMs are vital for the transport and deposition of airborne PFASs. Partitioning of PFASs between PM and dissolved phases was dependent on the carbon chain length and end functional groups. Isomer profiles of PFOA and PFOS in the snow were in agreement with the signature of the historical 3M electrochemical fluorination (ECF) products, suggesting that the ECF products were still produced and used in China. Further source analysis showed that the airborne PFASs in urban area were mainly due to direct release rather than degradation of their precursors.