Nationwide occurrence and site-scale dynamics of antibiotics in landfill-associated waters in China.

Municipal solid waste (MSW) landfills are increasingly recognized as important reservoirs and secondary sources of antibiotics; however, their cross-media occurrence, seasonal variability, and nationwide distribution patterns in China remain insufficiently understood. In this study, two MSW landfills located in southwestern China (Landfill 1) and eastern China (Landfill 2) were investigated to characterize the occurrence and transport of antibiotics in leachate, groundwater, and surface water, complemented by a nationwide dataset compiled from published studies covering >50 landfills across China. At Landfill 1, sulfamethazine (SMZ), sulfadiazine (SDZ), and ofloxacin (OFL) were detected. Total antibiotic concentrations (ΣABs) showed a clear gradient: leachate (5156-24,130 ng/L) ≫ groundwater (7.6-88.2 ng/L) > surface water (ND-49.1 ng/L), indicating strong attenuation during off-site migration. Multivariate analysis showed that ΣABs covaried with several hydrochemical indicators, while PCA separated leachate from groundwater and surface water along a leachate-strength axis, highlighting medium-dependent differentiation during transport. Leachate concentrations peaked in autumn, whereas surface water showed discontinuous detection and greater sensitivity to short-term hydrological fluctuations. At Landfill 2, 11 antibiotics were detected in leachate, dominated by fluoroquinolones (62.9%) and sulfonamides (33.0%), while no target antibiotics were detected in groundwater. Nationwide, ΣABs ranged from 839.2 to 1.71 × 105 ng/L in leachate, 18.8-2655.8 ng/L in groundwater, and 137.69-35,607.47 ng/L in surface water, with fluoroquinolones and sulfonamides dominating most regions. These results provide a more comprehensive understanding of antibiotic fate in landfill environments and support risk management strategies for emerging contaminants in MSW landfill systems.