Distribution, driving factors and prediction of antibiotics in Asia's largest River Basin: Comprehensive insights of Yangtze River Basin, China

Antibiotics have been a global concern because of their widespread occurrence and adverse effects on aquatic environments, particularly in large-scale river basins. However, their environmental fate in the Yangtze River Basin remains underexplored. In the present study, we investigated 31 antibiotics in surface water throughout the Yangtze River Basin, the largest river system in China and Asia. The total antibiotic concentrations ranged from 142.05 to 345.57 ng/L, with fluoroquinolones (FQs) predominating and accounting for 75.68% of the total concentration. Higher antibiotic concentrations were observed in the midstream and downstream regions, particularly in the three major economic zones of the Yangtze River Basin, likely driven by rapid economic development and urbanization. Agricultural and livestock farming intensity, along with nitrogen and phosphorus levels, has significant positive effects on antibiotic concentrations. Antibiotic concentrations showed negative correlations with microbial diversity and community composition, suggesting potential links to shifts in microbial community structure. Analysis using the Positive Matrix Factorization (PMF) model identified four major sources of antibiotic pollution: livestock waste (31.30%), aquaculture runoff (24.89%), hospital discharges (21.95%), and sewage treatment effluents (21.86%). We also employed four machine learning (ML) models to relate antibiotic concentrations to explanatory variables, enabling prediction of their distribution across the Yangtze River Basin. The Random Forest model demonstrated superior performance in predicting the concentrations of FQs and tetracyclines (TCs), with R 2 values of 0.75 and 0.74, respectively. The results of this study provide new insights into the transport behavior and prediction of antibiotic concentrations in large river basins.