A systematic survey was conducted on twenty-six per- and polyfluoroalkyl substances (PFASs) in fifty-one paired samples of surface water, sediment, and soil from Dagang Oilfield, Tianjin, China. Perfluorooctanoic acid, perfluorooctane sulfonic acid, p-perfluorous nonenoxybenzenesulfonate (OBS), and 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) were ubiquitous in the oilfield with field log Kd of 1.3-2.2, indicating a high partition potential from surface water to sediment. Total petroleum hydrocarbons (TPH) are a predictor for PFAS contamination at oilfield. The concentrations of OBS and 6:2 FTAB were higher in surface water and sediment with elevated TPH level. With total oxidizable precursor assay, unknown precursors for C2-C3 perfluoroalkyl carboxylic acids (PFCAs) (57-99 mol%) contributed more than those for C4-C12 PFCAs in the three mediums. The unknown C4-, C6-, and C8-based precursors tended to be precursors for perfluoroalkyl sulfonates at the oilfield, and C8 fluorotelomer-based precursors particularly occurred in the surface water. The concentrations of C4- and C8-based precursors were found positively correlated with TPH levels (r = 0.67-0.72, p < 0.05), while C6 precursors may also come from other sources. Further studies are necessary to clarify the mass balance and risk assessment for unknown PFASs.
Keywords: Oilfield; Perfluoroalkyl substances; TOP assay; Total petroleum hydrocarbons; Unknown precursors.
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