红壤对土霉素的吸附特征及影响因素研究

Adsorption Characteristics and Influencing Factors of Oxytetracycline in Red Soil

为了解红壤吸附抗生素的能力以及作用机制,本文采用批量平衡法和超高效液相色谱-三重四极杆串联质谱(UPLC-MS/MS)测试技术,以典型兽用抗生素土霉素(oxytetracycline,OTC)为目标污染物,江西宜春养猪场区所采集的粉砂质红壤为试验对象,研究OTC在红壤中的吸附-解吸特征及影响因素。结果表明,OTC在红壤中的吸附非常快,6 h即可基本达到平衡,准一级动力模型仅能较好地拟合吸附初期1 h的吸附过程,准二级动力模型能非常好地拟合整个吸附过程,解吸过程存在明显的滞后性;Freundlich模型能够更好地拟合试验土壤对OTC的等温吸附过程;OTC在试验土壤上的吸附量与pH呈负相关;共存阳离子中,随着离子强度增加,吸附量均呈逐渐减少的趋势,且阳离子价态越高,离子半径越大,吸附抑制性越强;共存阴离子中,仅HCO-3对吸附存在影响,影响程度与pH相关。该研究证明了土霉素在红壤中残留的可能性非常大,污染持久性强,对土壤环境污染程度高。

In this study,the adsorption ability and mechanism of oxytetracycline in red soil were investigated using the batch equilibrium method and ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry(UPLC-MS/MS).Oxytetracycline(OTC),a commonly used veterinary antibiotic,was chosen as the target pollutant.The silty red soil collected from Yichun pig farm in Jiangxi Province was used to study the adsorption-desorption characteristics and influencing factors of OTC in red soil.The results revealed that the adsorption of OTC in the red soil occurred rapidly reaching equilibrium in approximately 6 hours.The pseudo-first-order kinetic model only adequately described the adsorption process within the first hour,while the pseudo-second-order kinetic model provided a much better fit for the entire adsorption process.The desorption process exhibited significant h ysteresis.The Freundlich model proved more effective in representing the isothermal adsorption process of OTC in the tested soil.Additionally,the adsorption amount of OTC on the tested soil exhibited a negative correlation with pH.Among coexisting cations,the adsorption capacity decreased gradually with increasing ionic strength,and cations with higher valence state with larger ionic radius showed stronger adsorption inhibition.Among the c oexisting anions,only HCO-3 was found to affect the adsorption and this effect was pH dependent.This study demonstrates that oxytetracycline residues in red soil can lead to persistent and significant environmental pollution,posing a high degree of soil contamination.