Application of the LOADEST model in estimating PFAS fluxes in the Minjiang River Basin, China

Per- and polyfluoroalkyl substances (PFAS) are emerging persistent organic pollutants that pose significant risks to watershed ecological security. To clarify the characteristics of PFAS fluxes discharged into the sea from the Minjiang River, the load estimator (LOADEST) model was applied to estimate the monthly fluxes of eight PFAS compounds using hydrological and water quality monitoring data collected at the Zhuqi Hydrological Station from June 2024 to May 2025. The results indicate that the LOADEST model shows good applicability and reliability for estimating PFAS fluxes at the estuaries of large rivers in subtropical monsoon regions. The monthly fluxes of the eight PFAS compounds—perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorobutanesulfonic acid (PFBS), perfluorooctanesulfonic acid (PFOS), and hexafluoropropylene oxide dimer acid (HFPO-DA)—exhibited pronounced compound-specific characteristics and temporal heterogeneity. Among them, PFHxA, PFHpA, PFOA, PFBS, PFOS, and HFPO-DA accounted for the largest proportions of riverine flux to the sea in June 2024. PFAS contamination in the basin was dominated by HFPO-DA, and the relative contributions of major compounds showed systematic temporal variation. Overall, this study reveals the temporal variation patterns of PFAS fluxes from the Minjiang River to the coastal ocean and fills a knowledge gap regarding PFAS flux estimation in this basin. The results provide important support for PFAS source apportionment, environmental fate studies, and pollution risk management. In addition, a whole-chain management framework is proposed to support PFAS pollution prevention and control in the Minjiang River Basin and to safeguard the ecological security of adjacent coastal waters.