Evaluation of the environmental fate and risks of antibiotics in the Yangtze River Basin using a dynamic gridded multimedia fugacity model

The widespread use of antibiotics has raised growing concern about their environmental risks, yet quantifying their basin-scale fate, transport, and associated risks remains challenging due to complex emission sources, multi-media processes, and strong hydrological connectivity. Here, a Spatially Explicit Dynamic Gridded Fugacity Model (SE-DGFM) integrated with a detailed emission inventory was developed to quantify the emissions, transport, and risks of 66 antibiotics across the Yangtze River Basin (YRB). The framework is grounded in mass-balance theory and represents intermedia exchange and degradation processes across multiple media, while hydrological transport is explicitly resolved to capture riverine connectivity. Annual antibiotic emissions ranged from 3757 to 5513 tonnes between 2010 and 2022, primarily from swine (58%) and poultry (27%) farming. Model simulations revealed pronounced spatial and seasonal heterogeneity, with elevated concentrations in the upper basin and during winter, reflecting the combined effects of emission intensity and hydrological transport. More than 200 tonnes of antibiotics were transported downstream annually toward estuarine and coastal ecosystems, underscoring strong hydrological connectivity and long-range pollutant transfer. Ecological and resistance risks were widespread: over 20% of antibiotics posed high ecological risks, and resistance risk hotspots emerged in the upper basin and peri-urban regions, driven mainly by ciprofloxacin, enrofloxacin, and penicillin. Human health risks were generally low, though children aged 2–7 years exhibited elevated exposure potential. These findings provide a basin-wide quantitative assessment of antibiotic pollution in the YRB and establish a transferable modeling framework for large-scale contaminant fate analysis, offering critical insights for targeted mitigation and antibiotic pollution governance. • A 0.1°×0.1° dynamic fugacity model simulates 66 antibiotics in the YRB. • Advective transport and emission are the dominant parameters in antibiotic fate. • Mainstream river discharges over 200 tonnes of antibiotic into marine environments. • Over 20% of antibiotics pose high ecological or resistance risks in the YRB. • The model framework facilitates the identification of pollution and risk hotspots.