Abstract / Summary
Abstract To explore the distribution characteristics, pollution sources, and ecological risks of typical antibiotics in surface water in the Baoji section of the Weihe River Basin, 16 sampling sites were established in the study area. Online solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry was used to quantify the concentrations of 29 representative antibiotics across six categories: sulfonamides, quinolones, tetracyclines, macrolides, chloramphenicols, and lincosamides. A self-organizing map (SOM) combined with K-means clustering was used to analyze the spatial distribution and clustering patterns of antibiotics, and the positive matrix factorization (PMF) model was adopted for quantitative source apportionment. Based on this, the risk quotient method was adopted to assess the aquatic ecological risks of the target antibiotics. The results showed that complex antibiotic pollution was prevalent in the surface water of the Baoji section of the Weihe River, with 27 antibiotics detected at an average total concentration of 206.24 ng/L. The total antibiotic loads exhibited obvious spatial heterogeneity along the river channel. Five antibiotics (enoxacin, ciprofloxacin, norfloxacin, enrofloxacin, and tetracycline) were detected at all sampling sites, with average concentrations of 35.91, 37.93, 34.40, 27.42, and 1.77 ng/L, respectively. The SOM algorithm divided the 16 sampling sites into six clusters corresponding to mixed diffuse sources, agricultural sources, effluents from urban sewage treatment plants, livestock and aquaculture breeding sources, surface runoff inputs, and mixed sources originating from pharmaceutical factories and livestock breeding. Quantitative PMF analysis indicated that livestock breeding activities were the dominant source of antibiotic pollution, contributing approximately 48.6% of the total antibiotic load. The risk quotient values for ciprofloxacin exceeded 1 at all sites, indicating high ecological risk, whereas enrofloxacin posed a medium ecological risk across the entire watershed. Quinolone antibiotics exhibited severe aquatic ecological risks in the Baoji section of the Weihe River, a finding that requires targeted monitoring and control.