Molecular characteristics of emerging perfluoroalkyl and polyfluoroalkyl substances (PFAS) and dissolved organic matter (DOM) in surface waters around fluorine-related industries in a Chinese Megacity

Fluorine-related industrial discharges are the main source of per- and polyfluoroalkyl substances (PFAS) contamination in surrounding surface waters, but the long-term environmental impacts of their residual PFAS and the interactions between PFAS and dissolved organic matter (DOM) in field waters have rarely been discussed. In this study, the concentrations of 32 target PFAS were quantified, 50 PFAS were identified and semi-quantified by suspect and nontarget screening, and the molecular characteristics of DOM were analyzed in the surface water of Shanghai. Concentrations of ∑PFAS were 284 ∼ 3018 ng/L. Perfluorobutane sulfonate acid (PFBS) and perfluorooctanoic acid (PFOA) remained the predominant compounds at most sampling sites, but hexafluoropropylene oxide trimer acid (HFPO-TA) exhibited extremely high values at a few specific sites. Near a historical fluorotelomer manufacturer which was closed in 2017, ∑PFAS concentration was still at a high-level of 1800 ng/L. Thirteen nontarget and suspect PFAS including 7 iodinated perfluoroalkyl acids (IPFAAs) were identified in 100 % samples. A total of 8134 DOM molecular formulas were identified. For elemental composition, CHOS (24 %) has the highest percentage, while for molecular species, lignin (36 %) has the highest proportion of molecules. When the assignment of fluorine was included in the elemental analysis, the percentage of fluorine-containing substances reached to 55 %, suggesting the anthropogenic influences. Emerging PFAS, i.e., perfluoropentanoic acid (PFPeA) and hexafluoropropylene oxide dimer acid (HFPO-DA) were negatively related to DOM concentration (p < 0.05) due to microorganism activities. This study revealed the persistent impact of fluorine-related industries and the environmental behavior of PFAS and DOM in aquatic environments, providing support for the systematic and comprehensive evaluation of surface water health.