Antibiotic contamination in a typical developing city in south China: Occurrence and ecological risks in the Yongjiang River impacted by tributary discharge and anthropogenic activities

The occurrence and distribution of ten selected antibiotics from three groups (sulfonamides, macrolides, and trimethoprim) were investigated in the Yongjiang River, which flows through Nanning City, a typical developing city in China. The study also assessed the ecological risks and the potential effects caused by discharge from tributaries and anthropogenic activities. Concentrations of most of the antibiotics were elevated along the section of the river in the urban area, highlighting the significant impact of high population density and human activities on the presence of antibiotics in the environment. The concentrations in the tributaries (ranged from not detected to 1336 ng L−1) were generally higher than those in the main stream (ranged from not detected to 78.8 ng L−1), but both areas contained the same predominant antibiotics, revealing the importance of tributary discharge as a source of antibiotic pollution. A risk assessment for the surface water contamination revealed that sulfamethoxazole and erythromycin posed high ecological risks to the most sensitive aquatic organisms (Synechococcus leopoliensis and Pseudokirchneriella subcapitata, respectively) in the midstream and some tributaries. Most of the selected antibiotics presented high ecological risks (risk quotients up to 95) in the sediments.

► The selected antibiotics were ubiquitous in the water body of Nanning City, a typical developing city.
► High levels of residual antibiotics were occurred in the midstream adjacent the urban area.
► There were other sources contributing to the antibiotic contamination except tributary discharge.
► Sulfamethoxazole and erythromycin posed high ecological risks in the water from the midstream and some tributaries.
► Most of the selected antibiotics presented high risks in the sediments.