Spatial–Temporal Distribution and Ecological Risks of Quinolone Antibiotics in Coastal Wetlands

Quinolone antibiotic (QA) residues in various natural environments have recently received massive scientific attention. Nevertheless, there is limited information on the distribution characteristics and potential hazards of antibiotics in coastal wetlands. Here, the occurrence, spatial and seasonal distribution, and ecological risk assessment of eight QAs including pipemidic acid (PPA), ofloxacin (OFL), enrofloxacin (ENR), ciprofloxacin (CIP), sarafloxacin (SAL), lomefloxacin (LOM), flumequine (FLU), and oxolinic acid (OA) in coastal wetland were investigated through collected water, sediment, benthos, and plant samples along the Jiangsu coastline in four seasons. The results demonstrated that all selected QAs were detected with varying frequencies and degrees, and their mean concentrations in water, sediment, plants, and benthos ranged from n.d. to 6.11 ng L−1, 3.10 μg kg−1, 6.14 μg kg−1, and 17.13 μg kg−1, respectively. The seasonal differences in antibiotic concentration indicated higher values in winter and significantly lower values in summer, while no significant variations were observed between spring and autumn. Based on the risk quotient (RQ) method, the ecological risk assessment revealed medium risks for OFL, ENR, CIP, and LOM, and low or no risks of other QAs. It is suggested that the differences in PNEC values between seasons and toxicity of antibiotic mixtures should be considered in future studies for better illustration of actual risk levels. This research provides fundamental data and an assessment pattern that governments and other scientific groups all over the world could use as reference to evaluate QA residues in coastal wetlands.