顺硝烯新烟碱杀虫剂环氧虫啶在水中的光降解

为了正确评估新型杀虫剂环氧虫啶(CYC)的环境风险,了解环氧虫啶在水环境中的光降解规律,探讨了CYC初始浓度、温度、初始pH值、过氧化氢浓度及硝酸根对CYC光降解的影响.结果表明,CYC的光降解符合一级动力学反应.直接光降解中,随浓度降低、温度升高,光解速率加快,环氧虫啶的反应活化能为21.27kJ/mol.通过测定CYC的pKa值为3.42以及模拟计算CYC不同粒子形式的光反应活性,可知pH值对CYC光解的影响较为复杂:酸性条件下,CYC的降解速率取决于其形态(阳离子和中性粒子)与单线态能量;碱性条件下,降解速率主要受羟基自由基数量的影响.间接光降解中,硝酸根和过氧化氢对CYC光解均表现为促进作用.在评估环氧虫啶的环境风险时,应综合考虑环境因素对其降解的影响.

Photodegradation of cis-configuration neonicotinoid cycloxaprid in water

In order to correctly evaluate the environmental risk of the new insecticide CYC, the influence of the CYC initial concentration, temperature, initial pH, concentration of hydrogen peroxide and nitrate on the CYC photodegradation in water were studied. The results show that the photodegradation of cycloxaprid was fitted to pseudo-first-order kinetics reaction. For direct photodegradation, cycloxaprid photolysis rate was accelerated with the decreasing of CYC concentration and the increase of temperature. The activation energy of photochemical reaction was 21.27kJ/mol. By measuring the CYC pKa value of 3.42 and simulation CYC reactivity of different forms of light particles, known the complicated influence of pH value on CYC photolysis:In the acidic conditions, the degradation rate of cycloxaprid depended on the different cycloxaprid forms(cations and neutral particles) and their singlet energy values. While, in the alkaline condition, the photodegradation rate was mainly affected by the number of hydroxyl radicals in the solution. For CYC indirect photodegradation, nitrate and hydrogen peroxide were confirmed to promote the role. When evaluating the environmental risk of CYC should comprehensively consider the effect of environmental factors on its degradation.