To learn about the status of antibiotic contamination and their ecological risks in Chinese surface-water environments, the risk quotient (RQ) and joint risk quotient (RQSUM) methods were applied to assess the ecological risks of five typical surface-water environments in China during the flood season. The results showed that the main types of antibiotic contamination in the five regions were sulfamethoxazole (SMX), sulfamethazine (SM), erythromycin (ETM), roxithromycin (RTM), tetracycline (TC), oxytetracycline (OTC), norfloxacin (NOR), and ofloxacin (OFL). Among eight types of antibiotic contamination, sulfamethoxazole (SMX) and erythromycin (ETM) occupied a dominant position. The contribution rate of SMX in the Yangtze River Delta and Chaohu Basin was 91.1% and 98.5%, respectively. Meanwhile, the contribution rates of ETM in Jianghan Plain, Pearl River Delta, and Yellow River Delta were 94.4%, 81.8%, and 60%, respectively. Based on the joint risk quotients (RQSUM), the order of ecological risks in the research areas was:Jianghan Plain (20.204) > Yangtze River Delta (8.769) > Chaohu Basin (2.692) > Yellow River Delta (1.943) > Pearl River Delta (1.222).
Keywords: antibiotics; contribution rate; ecological risks; pollution status; surface-water; the risk quotient.