Legacy and emerging per- and poly-fluoroalkyl substances in surface seawater from northwestern Pacific to Southern Ocean: Evidences of current and historical release.

Knowledge on distribution of per- and poly-fluoroalkyl substances (PFASs) in open oceans is limited. By taking part in the 32nd Chinese Antarctic Research Expedition, 41 surface seawater samples were collected in the northwestern Pacific Ocean (NW-PO), eastern Indian Ocean (E-IO) and Southern Ocean (SO), and 23 PFASs comprised of legacy perfluoroalkyl carboxylic acids, perfluoroalkyl sulfonate acids and some new emerging homologs such as 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) were measured. The concentrations of the total PFASs decreased in the order of NW-PO>E-IO>SO. Perfluorooctanoic acid (PFOA) was the most dominant, followed by perfluorooctane sulfonate (PFOS). The PFOA concentration declined exponentially with the offshore distance, while such trend was not obvious for PFOS and other legacy PFASs, suggesting that PFOA was mainly derived from the ongoing land-based emissions, while PFOS was mainly from historical residues. 6:2 Cl-PFESA was identified (<11.1-170 pg/L) in the oceanic waters with relatively high level at the sites near Australia. Multiple receptor models indicated that PFASs in the SO were mainly contributed by atmosphere input, while those in the NW-PO and E-IO were originated from land sources. Isomeric profiles of PFOA showed that telomere-based source became more outstanding than electrochemical fluorinated production in recent years.