Tiered ecological risk assessment of perfluoroalkyl acid mixtures based on relative potency factor and species sensitivity distribution.

The Qiantang River, Zhejiang Province's largest water system, faces significant perfluoroalkyl acids (PFAAs) pollution concerns. However, the absence of water quality standards tailored to the river's aquatic life hinders comprehensive assessment of the compounds' combined toxicity and ecological risks. This research aims to investigate the distribution, sources, and ecological risks associated with PFAAs in the waters and sediments of the Qiantang River. The concentrations of total PFAAs (∑PFAAs) in water samples were found to range from 4.05 to 3694 ng/L, while in sediment samples, they ranged from 7.68 to 54.1 ng/g dry weight. Notably, the concentration of ∑PFAAs in water is significantly elevated during the low-flow period compared to both the high-water and normal-water periods, but these seasonal and hydrological changes don't significantly affect PFAAs levels in sediment. The spatial distribution showed a decrease followed by an increase in PFAAs concentrations from upstream (Quzhou City) to downstream (Hangzhou City), with higher levels near neighboring cities and densely populated areas. PFAAs concentrations in sediments showed no clear spatial variation. The acute and chronic toxicity parameters for indigenous aquatic organisms were assessed utilizing the species sensitivity distribution method in conjunction with the relative potency factor. Using perfluorooctanoic acid (PFOA) toxic equivalent concentrations and a four-tier ecological risk assessment methodology, it was determined that PFAAs in the water pose a significant risk to aquatic organisms. Notably, the chronic risk associated with these substances warrants greater attention than the acute risk.