阿特拉津对绿麦隆吸附-解吸作用的影响

采用批平衡实验,研究绿麦隆在单一及复合污染体系中的吸附-解吸行为。结果表明,无论是单一体系还是复合体系,吸附等温线均可用Freundlich模型进行良好的拟合。随着阿特拉津浓度的增加,土壤对绿麦隆的吸附作用降低,表明绿麦隆和阿特拉津之间存在竞争吸附,这可能与土壤的有机质类型和绿麦隆、阿特拉津的性质、结构有关。解吸实验表明,随着阿特拉津的浓度增加,绿麦隆的解吸作用增加。吸附过程的拟合指数n值大于解吸过程的对应值,即绿麦隆在不同体系中的解吸作用均存在一定的滞后性。应用Freundlich解吸等温线参数对吸附-解吸等温线的滞后作用进行量化,CT、（CT＋0.5AT）、（CT＋1AT）和（CT＋2AT）处理解吸等温线的滞后系数ω分别为165.200,146.132,94.534和85.945,即随阿特拉津浓度增加,绿麦隆解吸等温线的滞后性降低。

Effect of Atrazine on the Chlorotoluron Adsorption and Desorption in Soil

Batch experiments were carried out to investigate the adsorption-desorption behaviour of chlorotoluron in soil systems with chloro- toluron alone or in combination with atrazine. The results showed that the adsorption of chlorotoluron in different systems could be well fitted by Freundlich equation. The adsorption capacity of chlorotoluron decreased with the increasing concentration of atrazine, indicating the competitive adsorption occurred between the two chemicals. Types of soil organic matter, characteristics and structure of chlorotoluron and atrazine were likely factors influencing the adsorption process. Sorption occured possibly by a partition mechanism and a hole-filling mechanism. The desorption of chlorotoluron increased with the increasing concentration of atrazine. The fitted n values in the Freundlich equations corresponding to the sorption stage were larger than those corresponding to the subsequent desorption stage, suggesting a significant hysteretic desorption of chlorotoluron in tested system. Freundlich parameters derived from desorption isotherms could quantify the hysteresis between desorption and adsorption isotherms. Hysteresis coefficient, to, was applicable only for the traditional desorption isotherms. The to values were 165.200,146.132,94.534 and 85.945 in CT, （CT＋0.5AT）, （CT＋IAT） and （CT＋2AT） treatments, respectively. The results showed that the hysteretic desorption of chlorotoluron decreased in tested system as the concentration of atrazine increased. The study of competitive sorption between chlorotoluron and atrazine will help to understand the adsorption/desorption mechanisms of herbicides in combined systems.