氟喹诺酮类抗生素在农业紫色土中的吸附研究

抗生素被广泛作为抗菌药物和添加剂使用在畜牧业中,造成大量抗生素随着动物粪便进入到土壤环境。吸附行为是抗生素在土壤中迁移转化的重要过程,对抗生素的风险评估及污染控制具有重要的意义。本文采用吸附试验研究了两种氟喹诺酮类抗生素(诺氟沙星(NOR)和氧氟沙星(OFL))在重庆广泛分布的紫色土中的吸附特性以及影响因素。结果表明:NOR和OFL在紫色土上的吸附过程较快,5 h就能达到吸附平衡,吸附常数Kd能达到3 082 L/kg。Freundlich吸附等温模型能很好拟合紫色土对NOR和OFL的等温吸附过程。由吸附过程的吉布斯自由能ΔG和吸附能E可知,紫色土吸附NOR和OFL主要是通过物理吸附。溶液pH6会降低紫色土对NOR和OFL的吸附。当溶液离子强度从0.005 mol/L增加至0.05 mol/L时,NOR和OFL在紫色土上的吸附量分别降低了10.2%和11.7%。土壤有机质对NOR和OFL的吸附过程影响很小。

Sorption of Fluoroquinolone Antibiotics in Agricultural Purple Soils

Antibiotics have been widely used as antimicrobial agents and additives in livestock products, causing a large amount of antibiotics entering into soil environment through the application of manures contaminated with these chemicals. As an important process of controlling the migration and transformation of antibiotics in soils, sorption behavior has great significance on the risk assessment and pollution controlling of antibiotics. The sorption of norfloxacin (NOR) and ofloxacin (OFL), two widely used fluoroquinolone antibiotics (FQNs) in agricultural purple soil in Chongqing were investigated with batch sorption experiments. The results showed that sorption processes of NOR and OFL in purple soil were very fast, and sorption equilibrium were achieved in 5 h with sorption coefficient K_d of 3 082 L/kg. Freundlich model was fitted well with sorption isotherms of NOR and OFL in purple soil. Gibbs free energy and sorption energy demonstrated that physical sorption was dominant in NOR and OFL sorption in purple soils. Solution pH greater than 6 may decreased NOR and OFL sorption in purple soil. When solution ion strength was up to 0.05 mol/L, sorption capacities of NOR and OFL were decreased by10.2% and 11.7%, respectively. Organic matter in soil had little effect on the sorption of NOR and OFL in purple soil.