Spatiotemporal Distributions and Ecological Risk Assessments of Typical Antibiotics in Surface Water of Taihu Lake

Using solid phase extraction-high performance liquid chromatography tandem mass spectrometry, antibiotics belonging to four classes (i.e. sulfonamides, quinolones, tetracycline, and macrolides) in the surface water of Taihu Lake were monitored monthly for a year. Moreover, the potential ecological risks of antibiotics in Taihu Lake were assessed. During the one-year monitoring, all the eighteen target antibiotics were detected to some extent in the surface water. The detection rates of five sulfonamides (sulfamethoxazole, sulfathiazole, sulfadiazine, sulfadimethazine, and trimethoprim) were higher than 50%. The concentrations of quinolones in the surface water were relatively higher. The average and medium concentrations of ciprofloxacin were 13.0 ng·L-1 and 13.5 ng·L-1, respectively. There were significant differences in the antibiotic pollution during the different months, with the average concentrations of the target antibiotics ranging from 7.3 to 33.5 ng·L-1. The concentration levels were lower from June to October, while higher concentrations were observed from February to May and in November. In the surface water of Taihu Lake, the spatial variations of antibiotics among the 20 sampling sites were not significant, with the average concentrations ranging from 13.0 to 14.3 ng·L-1. During the one-year monitoring, the rates of medium and high risks that the antibiotics posed to algae reached 57.5%. The ecological risks of antibiotics were more severe in April and November, and the quinolones may be the dominant risk factor. This issue should be carefully considered by management authorities.