Occurrence of typical antibiotics in Nansi Lake’s inflowing rivers and antibiotic source contribution to Nansi Lake based on principal component analysis-multiple linear regression model

The occurrence and distribution of 14 antibiotics in the surface water and sediment of Nansi Lake’s inflowing rivers were studied. The concentrations of the antibiotics in the sediment and water were not detected (ND)-193,440 ng kg−1 and ND-694 ng L−1, respectively, and ofloxacin was identified as the main antibiotic. The target antibiotics were identified at decreased levels in the study area compared with the inflowing rivers of other lakes. The decreased antibiotic concentrations resulted from the dilution effect, strong biodegradation, and rapid photolysis during the wet season. The spatial variations were due to the differences in regional contributions; the concentrations of antibiotics from Jining and Peixian were the highest. Antibiotic pollution in different seasons originated from different sources; pollution levels were determined by water levels and rainfall as well as complicated runoff generation and confluence mechanisms. Based on the risk quotients, ofloxacin, sulfamethoxazole and sulfadiazine were identified as the main antibiotics that contributed to high ecological risks. Algae and aquatic plants were the main model organisms exposed to these risks. This study has great significance for environmental prevention and the control of antibiotic contamination in Nansi Lake, which is an important water transport channel and the main impounded lake for the eastern route of the south-to-north water diversion project.