Occurrence, spatiotemporal distribution and potential ecological risks of antibiotics in Dongting Lake, China.

We investigated the occurrence and distribution of 18 antibiotics in surface water from Dongting Lake, as well as in influents and effluents from a municipal wastewater treatment plant (WWTP) and a swine farm. The total concentrations of target antibiotics in surface water ranged from limit of quantification to 3107 and 5.32-107 ng L-1 in the dry season and wet season, respectively. Among these studied antibiotics, ciprofloxacin (CIP) and lomefloxacin were as the main components in the dry season, while CIP, oxytetracycline, and chlortetracycline were the main components in the wet season. The concentrations of target compounds exhibited obvious temporal-spatial variation characteristic in the studied region, suggesting their different emission sources related to pig breeding, aquaculture, and human activities, as well as possible degradation in the aquatic system. We estimated that the daily total input and output masses of antibiotics in the influent and effluent from the swine farm were 12.1 mg d-1 pig-1 and 7.49 μg d-1 pig-1, while they were 103 μg d-1 inhabitant-1 and 22.9 μg d-1 inhabitant-1 in the WWTP. The risk assessment results indicated that CIP posed a moderate or high risk to algae in most locations in Dongting Lake.