Spatial heterogeneity and drivers of PFASs distribution in an arid-semiarid city waters system

Investigating the occurrence of emerging per- and polyfluoroalkyl substances (PFASs) in diverse urban surface water bodies of Hohhot, a representative arid and semi-arid city, is essential for understanding their environmental behavior and potential ecological risks under water-scarce conditions. This study systematically characterized the occurrence, spatial distribution, compositional profiles, and environmental factors associated with the spatial heterogeneity of PFASs. The concentrations of ΣPFASs exhibited pronounced spatial heterogeneity (6.3–81.4 ng/L), with elevated levels observed in water bodies more strongly influenced by anthropogenic activities. PFASs compositional profiles differed among water body types, with short-chain PFASs constituting a substantial proportion of the overall PFASs composition. Long-chain PFASs nevertheless remained widely detectable across the studied waters. PFASs covaried with multiple hydrochemical characteristics, but these associations weakened after accounting for functional water-body type, highlighting water-body differentiation as an important context for PFASs spatial heterogeneity. Despite the higher concentrations of short-chain PFASs in several water bodies, ecological risk was primarily associated with residual long-chain PFASs, particularly perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Collectively, these findings highlight the need for source-oriented monitoring and region-specific PFASs management in arid–semi-arid urban watersheds, while the potential influence of hydroclimatic conditions requires quantitative hydrological validation.