[Spatial Distribution, Source Analysis, and Risk Assessment of Multiple Antibiotics in Chaohu Lake Basin]

Chaohu Lake is the fifth largest freshwater lake in China that meets the needs of surrounding industries for water, tourism, and flood storage, making it important for the socio-economic development and modernization of Anhui Province. As an important ecological wetland in the lower reaches of the Yangtze River, many rare bird habitats are present along the coast of Chaohu Lake. Therefore, it is eco-economically important to study antibiotic pollution in Chaohu Lake. To unveil antibiotic contamination in Chaohu Lake, surface water and sediment samples were collected from the main basin of Chaohu Lake by steamship in June 2022. Solid phase extraction and ultra-performance liquid chromatography-mass spectrometry （SPE-UPLC-MS） was used to determine the occurrence of 31 target antibiotics, including tetracyclines, sulfonamides, macrolides, and quinolones. The study focused on the spatial distribution, source analysis, and risk assessment of various antibiotics in the surface water and sediments of the main basin of Chaohu Lake. The occurrences of 20 different antibiotics were successively identified in the surface water and sediments of Chaohu Lake. These antibiotics included sulfonamides, quinolones, macrolides, tetracyclines, and others. Significant spatial differences in antibiotics were found between surface water and sediments. The horizontal spatial distribution results indicated differences in species and concentration of antibiotics in surface water and sediments. The vertical spatial distribution results showed that many types of antibiotics had consistent vertical distribution characteristics in surface water and sediments at the same point. The principal component analysis results indicated that the source of antibiotics in surface water was similar to that in sediment and considered with the actual distribution of existing industries around Chaohu Lake； the main sources were livestock and poultry breeding sewage, aquaculture sewage, and household sewage. The ecological risk quotient （RQ） results indicated that norfloxacin in the surface water of Chaohu Lake posed a high risk to algae （RQ > 1）, while sulfamethoxazole and doxycycline posed a medium risk to algae （0.1 ≤ RQ < 1）. The health risk quotient （HRQ） showed that the risk of exposure to antibiotics through drinking water was very low （HRQ < 0.01）. Our findings provide scientific support for decision makers to control antibiotic pollution and reduce the management costs of antibiotic watershed pollution.