环丙沙星在亚高山草甸不同深度土壤上的吸附及其影响因素

兽用抗菌药物环丙沙星(CIP,ciprofloxacin)的大量使用引发了人们的广泛关注.文章研究了CIP在亚高山草甸土剖面土壤上的吸附动力学、吸附热力学和pH、有机质含量、阳离子交换量等因素对吸附的影响,以揭示CIP在亚高山草甸土上的吸附机制,为CIP的生态风险评价提供一定的依据.结果表明,CIP在亚高山草甸土上的吸附过程符合准二级动力学模型,并分为快吸附和慢吸附阶段,快吸附为0—6 h,慢吸附为6—48 h.CIP在供试土壤中的吸附等温线均能被Freundlich方程及线性方程很好的拟合,且|ΔH^θ|小于40 kJ·mol^-1,说明其吸附过程以物理吸附为主.其吸附等温线符合L-型,表明在CIP浓度较低时,草甸土与CIP分子间作用力较强,而浓度增大至一定程度时,溶剂分子与CIP分子间作用力占主导地位,吸附减弱.剖面土壤上CIP的吸附量随温度升高和土壤深度增加下降,这与有机质含量、阳离子交换量、黏粒含量以及pH有关.实验表明,在pH=5时,其吸附量最高.pH值在3—5时,吸附量随pH升高而升高,而在pH>5时,吸附量随pH升高而降低.表明阳离子交换为其吸附机制之一.

Adsorption characteristics and effect factors of ciprofloxacin in the different layers of subalpine meadow soil

The environmental problem derived from the application of veterinary antibiotics such as ciprofloxacin(CIP), has caused wide public concern. In order to clarify adsorption mechanism and ecological risk of CIP in the soil environment, the adsorption kinetics, adsorption thermodynamics and influencing factors, such as pH, organic matter content and cationic exchange capacity were studied. Results showed that the adsorption processes of CIP on subalpine meadow soil fitted well with the quasi-second-order kinetic model and the adsorption process could be divided into two stages: fast adsorption stage(0—6 h) and slow adsorption stage(6—48 h). The adsorption isotherm data of CIP was fitted well by the Freundlich and linear model,and the changes of Enthalpy(ΔH^θ) less than 40 kJ·mol^-1, which revealed that the adsorption process was mainly physical adsorption. The adsorption isotherm was in line with L-type, indicating that the intermolecular force between the meadow soil and CIP was strong at a low CIP concentration, and weakened at a high CIP concentration because the intermolecular force between the solvent and CIP was dominant. With the increase of temperature and soil depth, the adsorption of CIP on meadow soil decreased, which was influenced by organic matter content, cation exchange capacity, clay content and pH value. Experiments showed that the adsorption capacity is the highest at 5 of pH value. When pH was from 3 to 5, the adsorption capacity increased with the increase of pH value, and the adsorption capacity decreased beyond 5. The results show that cation exchange is one of the adsorption mechanisms.