Ecological risks assessment and multi-dimensional prioritization of emerging contaminants in surface waters of a...

The distribution and risks of emerging contaminants (ECs) in the aquatic systems of urbanized megacities have drawn widespread global attention. However, identifying priority contaminants for targeted control among hundreds or even thousands of pollutants remains a significant challenge. The study systematically evaluated the occurrence patterns and ecological risks of 145 ECs in the surface waters of Beijing. A multi-dimensional prioritization framework was constructed by using six indicators including detection frequency, concentration, bioaccumulation potential, persistence, ecological risk, and in vitro toxicity. Results revealed that neonicotinoid pesticides, organophosphate esters, and triazine herbicides were the most prominent contaminant categories with mean concentrations of 470 ng L^-1, 298 ng L^-1, and 251 ng L^-1, respectively. Spatial distribution analysis revealed differential contamination levels across different water body types, with urban rivers such as the Ba River and Qing River exhibiting the highest degree of pollution. Ecological risk assessment identified that imidacloprid, dichlorovos, hexazinone, and diazinon posed high risks. Further analysis based on the joint probability curves indicated that imidacloprid poses a moderate risk to 0.3%-30% of aquatic organisms. Based on the Environmental Health Priority Index (EHPi) scores, imidacloprid and TiBP were classified as Tier-I priority pollutants warranting immediate regulatory attention. Overall, this study provides scientific foundations for targeted monitoring and priority management of ECs in highly urbanized regions. This facilitates the targeted identification of key risk areas and critical contaminants, thereby supporting subsequent source-tracking investigations and the refinement of pollution control policies.