Dual-source fingerprints and ecological risks of quinolone antibiotics in the Yellow Sea: Implications for resistance and management

Quinolone antibiotics (QNs), owing to their persistence and capacity to promote antimicrobial resistance, have become emerging contaminants of global concern. This study systematically investigated 19 QNs in the North Yellow Sea (NYS) and South Yellow Sea (SYS) to characterize their spatial patterns, sources, and ecological risks. QNs were ubiquitously detected, with significantly higher concentrations in the NYS (60.3–206.8 ng L −1 ; mean: 136.5 ng L −1 ) than in the SYS (30.7–128.7 ng L −1 ; mean: 82.6 ng L −1 ), showing a distinct pattern of higher in the north, enriched nearshore, and decreasing offshore. Compositional differences revealed that ofloxacin, ciprofloxacin, and norfloxacin dominated in the NYS, reflecting inputs from municipal and hospital wastewater, whereas enrofloxacin, flumequine, and orbifloxacin were more prevalent in the SYS, indicating contributions from aquaculture and veterinary sources. Vertically, the NYS exhibited a profile of strong input and rapid attenuation, while the SYS displayed a pattern of diffuse input and middle layer buffering. Correlation identified salinity, nutrients, and carbonate buffering capacity as key regulators of QNs distribution. Principal Component Analysis (PCA) analyses collectively verified a dual-source fingerprint characterized by concurrent human and aquaculture inputs. Ecological risk assessment suggested algae as the most sensitive group, with ofloxacin identified as a priority pollutant for management. Antimicrobial resistance risk analysis further indicated that ciprofloxacin, ofloxacin, and enrofloxacin exerted major selective pressures, particularly pronounced in the NYS. Overall, this study reveals the dual-source fingerprints and coupled environmental controls of QNs in the Yellow Sea (YS), and proposes to enhance municipal and hospital wastewater treatment in the NYS and to regulate use of antibiotics in aquaculture within the SYS. These results may provide a reference basis and practical guidance for implementing risk-based monitoring and source-oriented management and control in the YS region. • Four QNs were detected for the first time, expanding the known spectrum of pollutants. • Identified dual-source fingerprints: wastewater inputs in the north, aquaculture inputs in the south. • Highlighted higher ecological and resistance risks in the north, with ofloxacin and as a priority pollutant.