OCCURRENCES AND SORPTION OF FLUOROQUINOLONE ANTIBIOTICS IN VEGETABLE FARM SOIL FROM SICHUAN BASIN, CHINA

The occurrence of four fluoroquinolone antibiotics (ciprofloxacin, enrofloxacin, norfloxacin, and ofloxacin) and sorption process of enrofloxacin in soils from the vegetable farms in Sichuan Basin, southwestern China, were investigated in this study. Concentrations of target antibiotics in the soil samples ranged from not detectable to 29.8 mu g/kg dry weight. Enrofloxacin was the dominate fluoroquinolone antibiotics in soil samples from vegetable farms with the highest average concentration (1.73 mu g/kg) and detection frequency (81.7%). Enrofloxacin was rapidly adsorbed by purple soil with high sorption coefficients. Sorption isotherms were well fitted by Freundlich model. Solution pH strongly affected the sorption process. When solution pH was increased from 5 to 10, the sorption capacity and coefficients of enrofloxacin in the purple soil declined by 19.6% and 95.8%, respectively. The cation-exchange was the dominant sorption mechanism of enrofloxacin sorption in purple soil according to the sorption energy and ionic strength effects. The sorption process showed the high sorption affinity of fluoroquinolone antibiotics in purple soil, which may cause the accumulation of fluoroquinolone antibiotics in soil.