铜离子络合对咪唑啉酮类除草剂土壤吸附的影响

Effects of copper complexation on soil adsorption of imidazolinone herbicides

采用吸收光谱技术研究了铜离子与3种咪唑啉酮类除草剂的络合作用,采用序批式实验技术考察了铜络合作用对除草剂土壤吸附的影响.结果表明,除草剂通过咪唑环上内酰胺的氮及吡啶环上的氮结合一个铜离子,生成稳定的五元环络合物,络合能力依次为：咪唑乙烟酸＆gt;咪唑烟酸＆gt;甲基咪唑烟酸.铜离子增强了3种咪唑啉酮类除草剂的土壤吸附,吸附量增加到1-3倍.除草剂的吸附平衡常数K_f和非线性常数1/a随铜离子浓度增加而线性增加,其中络合能力最强的咪唑乙烟酸的吸附平衡常数变化最为显著.基于除草剂、铜的形态识别和吸附分配系数的同时测试,发现除草剂与铜离子络合物的吸附分配系数为14.17±5.49 L/kg（咪唑乙烟酸）,7.38±3.18 L/kg（咪唑烟酸）和11.35±3.84 L/kg（甲基咪唑烟酸）,分别是除草剂自身的5.25,4.64,4.42倍,显示络合物的吸附能力强于除草剂自身.因此,铜离子通过络合作用生成了高吸附性能的络合物从而增强了该类除草剂的土壤吸附性能,可能增加其土壤残留.

Complexation of three imidazolinone herbicides with copper was investigated spectroscopy titration method. It appeared that imidazolinone herbicides bound cupric ion through using the the lactam nitrogen of imidazole and the pyridine nitrogen and formed a 1 ： 1 pentacyclic complex. Stability constants of the complex of three herbicides decreased in the order of imazethapyr 〉 imazapyr 〉 imazameth. Batch experiments about effects of copper on adsorption of these herbicides were conducted. It was found that the presence of copper increase adsorption capacities of imidazolinone herbicides by 1- 3 folds. For these herbicides, two Freundlich model parameters, Kf and 1/a, are linearly correlated with copper concentration and imazethapyr have the largest slopes. Adsorption distribution coefficients of the complex are attempted to quantify based on discriminating aqueous concentrations and adsorption amounts of the free and complexed species of both herbicides and copper. The complexes of three herbicides had adsorption distribution coefficients of 14.17±5.49 L/kg （ Imazethapyr）, 7.38±3.18 L/kg （Imazapyr） and 11.35±3.84 L/kg （Imazameth） and are 4-6 fold higher than those of herbicides in the free form. All results demonstrate that the complexes of imidazolinone herbicides with copper have greater adsorption potential in soil, suggesting that these herbicides persist in soil to a greater extent when copper coexists.