Occurrence, Pollution Characteristics, Mass Load and Ecological Risk Assessment of Per- and Polyfluoroalkyl Substances in the Dianchi Basin, China.

Per- and polyfluoroalkyl substances (PFASs) have attracted attention as emerging contaminants due to their persistence, bioaccumulation, and toxicity risks. This study investigated the characteristics, sources, mass loads, and ecological risks of 17 PFASs in surface waters and sediments from Dianchi Lake and its tributaries. During the wet season, the PFAS concentrations in the lake and river waters ranged from below the MDL (N.D.) to 11.21 ng/L and N.D. to 20.79 ng/L, respectively, while in the sediments, they were N.D. to 10.21 ng/g dry weight (dw) and N.D. to 9.63 ng/g dw. In the dry season, the lake and river water concentrations were N.D - 9.49 ng/L and N.D. - 15.67 ng/L, with those in sediments ranging from N.D. to 11.47 ng/g dw and from N.D. to 9.93 ng/g dw. Distribution coefficient analysis indicated that long-chain PFASs and sulfonic acid groups were preferentially enriched in sediments. In rivers, major sources included industrial discharges, domestic inputs, metal electroplating activities, and atmospheric deposition. In the lake, PFASs were mainly derived from mixed sources, atmospheric deposition, and riverine inflow, the latter being dominant. The PFAS loads from tributaries were estimated at 24.75 kg in the wet season and 8.79 kg in the dry season. The risk quotient values were low in waters (0.01) but ranged from 0.01 to 1 in sediments, indicating low to moderate risk, primarily from long-chain PFASs. Although ecological risk is limited, persistent inputs and contributions from tributaries highlight the necessity for continued monitoring and management. The results of this study deepen the understanding of PFAS contamination in this and other similar plateau lake basins, providing references for environmental management.