Integrated basin-scale assessment of legacy and emerging PFAS in the Xiangjiang River Basin, China: Occurrence,...

The increasing detection of per- and polyfluoroalkyl substances (PFAS), including short-chain and emerging alternatives, raises concerns about basin-scale exposure and risk potential. Target-centric monitoring with limited analyte lists constrains source attribution and risk prioritization. To address these limitations, this study presents an integrated assessment of the Xiangjiang River Basin that combines suspect and non-target screening with targeted quantification, source apportionment, mass-loading analysis, and ecological risk prioritization. Suspect and non-target screening identified 88 PFAS (61 at Confidence Levels 1-3; 27 at Levels 4-5). In parallel, a targeted panel of 57 PFAS was quantified, of which 46 were detected in surface waters. Ambient concentrations at most sites were low (total PFAS 2.61-34.4 ng/L) and dominated by legacy PFAS; however, industrial hotspots showed elevated levels of replacements, exemplified by HFPO-DA reaching 933 ng/L in effluents. Positive Matrix Factorization attributed basin-wide contamination primarily to paper and fluorochemical industries. Furthermore, spatiotemporal analysis revealed that wet-season hydrology drives contaminant mobilization from source-proximal areas, enhancing downstream export. Importantly, the prioritization framework revealed distinct drivers for emerging replacements: 8:2 FTCA was identified as high priority (RI ≥ 0.1) driven by intrinsic toxicity coupled with measured exposure, whereas short-chain acids such as PFBA ranked highly primarily due to their environmental prevalence and mobility. These findings indicate that surveillance focused only on legacy PFAS underestimates basin-wide ecological pressure and support expanding regulatory monitoring to capture these diverse priority patterns associated with replacement chemistries.