Antibiotic Pollution in the Yining Section of the Ili River: Distribution, Sources, and Ecological Risk Assessment

The Ili River is a transboundary water body in Central Asia and a key region along the Belt and Road Initiative, yet antibiotic pollution in this river remains unexplored. This study investigated the occurrence, distribution, and ecological risks of 14 antibiotics in the Yining section of the Ili River and the effluent of the Huocheng Wastewater Treatment Plant (HWTP). We optimized and validated an analytical method using solid-phase extraction coupled with high-performance liquid chromatography-tandem–mass spectrometry (SPE-HPLC-MS/MS). The method achieved low detection limits (0.05–1.0 ng·L −1 ) and good recoveries (70.0–108.3%). Results showed that HWTP removed 9.8–98.3% of detected antibiotics, with negative removal observed for several compounds due to desorption or metabolite reconversion. In the Yining river section, tetracyclines dominated (55.9% of total antibiotics), followed by fluoroquinolones (33.8%), macrolides (9.7%), and β-lactams (0.6%). Ecological risk assessment using the risk quotient method revealed that the combined risk (RQ s ) in the Yining section ranged from 1.54 to 2.74, indicating a high-risk level. Chlortetracycline exhibited the highest individual risk (RQ 0.92–0.97) and is proposed as a priority pollutant. This study provides the first baseline data on antibiotic pollution in a Central Asian transboundary river and underscores the need for international cooperation in water quality management within the Belt and Road framework.