不同质地土壤中四环素类抗生素的吸附解吸特性研究

抗生素滥用导致的低浓度抗生素环境暴露诱导产生抗生素耐药基因,对人类健康构成潜在威胁。土壤是抗生素类污染物的主要容纳库,也是其迁移进入水环境的必经路径。采用批平衡吸附试验法,研究了四环素和土霉素在不同质地土壤(黏土、壤土和砂土)中的吸附和解吸行为。结果表明,黏土、壤土和砂土对四环素和土霉素的吸附过程可分为快速吸附阶段和慢速平衡阶段。吸附行为均可用Freundlich模型描述,平均拟合决定系数为0.996,其中壤土对四环素和土霉素的吸附能力最强,砂土的吸附能力最弱。四环素和土霉索在黏土和砂土中属于"S型"等温吸附,在壤土中的吸附属于"L型"等温吸附。研究表明,四环素在土壤中的吸附以物理吸附为主,且在黏土、壤土和砂土中解吸过程的滞后系数明显高于土霉素。

Adsorption and desorption features of tetracycline antibiotics in different texture soils

This paper is aimed to report the results of its research on the adsorption and desorption features of tetracycline (TC) and oxytetracycline (OTC) in different texture soils,which tend to account for the mobility and transfer features of the antibiotics in the soils.Therefore,it is believed that thorough study of the adsorption and desorption mechanism can help to provide a systematic scientific basis for preventing from the pollution spread in the water environment and the further environmental risks of the tetracycline antibiotics.It is coming from the above mentioned need that we have conducted the simulated adsorption experiments of the tetracycline antibiotics by using the so-called batch equilibrium techniques.In our experiments,we have analyzed the soil samples by the high performance of the liquid chromatography (HPLC) choosing.The results of our analysis of the actual situation of the adsorption indicate that it has been made possible to finish the total adsorption process promptly in an hour with the entire adsorption amount over 90.0％.We have also noticed that there exists a significant difference between TC adsorption and OTC adsorption for the same soil with the chemical properties of antibiotics playing an important role in the adsorption progress.The results prove that it would be better to divide the adsorption of the tetracycline antibiotics in clay,loam and sand into two stages,that is,the prompt adsorption equilibrium stage and the slow adsorption stage,in which the adsorption equilibrium data tend to be correlated with the linear distribution,Freundlich and Langmuir models.And,Freundlich model proves to be more suitable for demonstrating the experimental data (R2 =0.996).At the same time,the adsorption capability (Kf) of TC and OTC for the above-mentioned three kinds of soils can be illustrated in the following order:loam ＞ clay ＞ sand.What is more,the adsorption isotherms of the tetracycline antibiotics tend to be in linear curves in accordance with its adsorption strength (1/n).As to the isothermal adsorption of the tetracycline and oxytetracycline in the clay (1/n =1.118 and 1.068) in addition to the sand (1/n =1.218 and 1.241),it looks like in a letter "S" shape,while the adsorption in the loam (1/n =0.906 and 0.932) belongs to "L" type.In spite of this,the dominant mechanism of tetracycline antibiotics adsorption in the clay,loam and sand may all be attributed to the physical adsorption.In addition,the desorption hysteresis constant (HI) of the oxytetracycline in the clay,loam and sand has all been proved to be significantly lower than that of tetracycline,therefore tetracycline proves to stay in the soil for longer,which can be taken as a greater potential risk for the soil environment.