Target analysis of per- and polyfluoroalkyl substances in surface water: Occurrence, seasonal trends, and risk-based...

Although thousands of per- and polyfluoroalkyl substances (PFAS) are used globally, most research has focused on a limited subset, potentially underestimating their environmental risks. In particular, PFAS pollution in long river systems originating in high mountains and flowing into densely populated plains remains poorly understood. Here, we developed a target analysis method to identify and (semi-)quantify 74 PFAS compounds in surface water samples from the Minjiang River, the largest tributary of the Yangtze River. Fifty-seven PFAS were detected with total concentrations up to 87.5 ng/L. The ∑₅₇PFAS concentrations increased from the upstream to midstream and were relatively higher in summer and fall than in winter and spring. Short-chain PFAS were present at lower concentrations than long-chain PFAS, while legacy and emerging PFAS exhibited concentrations of 9.69 ± 9.24 ng/L and 14.0 ± 16.0 ng/L, respectively. Among the 57 identified PFAS, 32 (56.1 %) were classified as persistent, bioaccumulative and toxic (PBT) substances, with 6:2 diPAP exhibiting the highest hazards, followed by C6/C6 PFPiA. ToxPi scores ranged from 0.11 to 0.62, with 6:2 diPAP showing the highest score, followed by C6/C6 PFPiA, and PFBA showing the lowest score. Among the 18 attributes contributing to the ToxPi score, bioconcentration factor (BCF) was the primary contributor, followed by log K_ow, Biowin1, Biowin3, and Biowin5, suggesting persistence and bioaccumulation as key drivers. Our study identified 8:2 FTCA, 8:3 FTCA, PFOA, PFOS, and PFNA as high-priority contaminants for remediation in the surface water of the Minjiang River.