Emerging contaminants in the lower Yangtze River basin: spatiotemporal distribution, ecological risks in surface water, and fate in wastewater treatment plants.

Emerging contaminants (ECs) have drawn significant attention due to their adverse effects on aquatic ecosystems. This study investigated the spatiotemporal distribution and ecological risks of 43 ECs in surface water and examined their fate in wastewater treatment plants (WWTPs) in the lower Yangtze River basin. In surface water, 34 ECs were detected, including 13 antibiotics, 4 endocrine-disrupting compounds, 9 pharmaceutical and personal care products, 4 perfluoroalkyl and polyfluoroalkyl substances and 4 organophosphate esters. Specifically, doxycycline, ethinyl estradiol, salicylic acid, perfluorooctanoic acid and triisobutyl phosphate showed dramatic spatiotemporal variations. Temporally, doxycycline, salicylic acid, ibuprofen, diclofenac and perfluorooctanoic acid peaked in winter, whereas ethinyl estradiol and triisobutyl phosphate showed higher concentrations in summer and autumn. Spatially, bisphenol A and octyl phenol were more concentrated in the downstream section, while triisobutyl phosphate levels were higher in the upstream section. Risk assessment indicated 82 out of 87 water samples posed medium or high ecological risk, and sulfamethoxazole, roxithromycin, ethinyl estradiol and octyl phenol were identified as primary contributors. Although the removal efficiencies of ECs in industrial and municipal WWTPs were 87.1 ± 1.5 % and 83.6 ± 1.5 %, respectively, EC concentrations in effluents were 2.70 and 6.15 times higher than those in surface water. Correlation analysis further confirmed that the discharges from WWTPs were highly related to the existence of these ECs in the lower Yangtze River. The effluent concentrations of perfluorooctanoic acid, doxycycline, Triethyl phosphate, roxithromycin and Tris-(2-chloroisopropyl) phosphate usually exceeded 20 ng/L due to their low removal efficiencies, where moreover, ECs with high influent concentrations but removal efficiencies above 80 % still posed significant effluent risks. These results suggest that, besides adopting advanced treatment technologies (e.g., adsorption, ion exchange), source control is also crucial. This study offers key insights into Yangtze River EC pollution, supporting better monitoring and management.