Per- and polyfluorinated substances in reservoir water from a metropolitan city in the Guangdong-Hong Kong-Macao Greater Bay Area, China, and their ecological risks

Per - and polyfluorinated substances (PFASs) are synthetic chemicals with thermal and chemical stability, widely used in consumer products such as food packaging, fire-fighting foams, non-stick coatings, and lubricants. Their potential threats to human health and aquatic ecosystems have prompted restrictions on their usage. However, they are still widely found in freshwater systems due to their environmental persistence. Given that reservoirs are a vital source of drinking water for coastal city residents, this study collected water samples from 35 reservoirs in SZ City and its special cooperation zone to quantify 17 PFASs. Seasonal and spatial distributions of contaminant concentrations were analyzed and ecological risks were assessed. The results showed a widespread presence of PFASs in various reservoirs, although perfluoroalkane sulfonic acids (PFSAs) were infrequently detected. The concentration of ΣPFASs in the dry season (median: 20.5 ng/L) was significantly higher than that in the wet season (6.58 ng/L), likely attributable to a dilution effect after rainfall. Pentadecafluorooctanoic acid (median: 2.76 ng/L) and perfluoro-n-butanoic acid (3.90 ng/L) dominated in the wet and dry seasons, respectively. For spatial distribution, the ΣPFASs concentration in tributaries was markedly higher than that in reservoirs during the dry seasons (median: 58.1 ng/L vs. 20.5 ng/L), probably due to the diminished wet deposition of contaminants and the reduced mobility of tributary water flow. Furthermore, the concentration of short-chain PFASs was significantly greater than that of long-chain PFASs in the dry seasons (median: 16.0 ng/L vs. 3.10 ng/L), possibly related to the widespread application of short-chain compounds. Overall, the risk to the ecosystem and humans from PFASs in reservoirs is not significant. Future regulations on fluorochemical plants may be warranted to reduce the use and discharge of PFASs. Also, subsequent studies could include a wider range of samples to better estimate the potential risk posed by PFASs with varying chain lengths and functional groups to aquatic environment. • PFAS concentrations in reservoirs are significantly higher in the dry season. • PFOA and PFBA prevailed in the wet and dry seasons, respectively. • In the dry season, ΣPFAS concentrations in tributaries exceed those in reservoirs. • Short-chain PFASs are more abundant than long-chain variants in the dry season.