Emerging investigator series: sunlight photolysis of 2,4-D herbicides in systems simulating leaf surfaces
Emerging investigator series: sunlight photolysis of 2,4-D herbicides in systems simulating leaf surfaces
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DOI：
10.1039/c8em00186c
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发表时间：
2018-08-01
影响因子：
5.5
通讯作者：
Dai, Ning
中科院分区：
文献类型：
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作者：
Su, Lei;Sivey, John D.;Dai, Ning
农药通常施用于树叶，在叶表皮蜡上形成干燥沉积物。然而，它们在这种亲脂性环境中的光化学转化与地表水相比知之甚少。本文研究了六种氯代苯氧乙酸类除草剂（即，2，4-D和结构类似物）在四种有机溶剂、石英和石蜡上进行了评价。在低极性溶剂（即，正庚烷和2-丙醇），由于在这些溶剂中相对高的量子产率，2，4-D除草剂的直接光解得到增强。在石蜡上的光解比在石英上的光解慢3-9倍，但与在低极性溶剂中的光解相当。与环境相关的照射和表面负载，2，4-D除草剂在石蜡上的半衰期为27-159小时，这是在相同的范围内报告的生物降解，在目前的2，4-D命运模型的主要耗散途径。产物分析表明，光还原脱氯是有机溶剂中的主要途径，占母体化合物衰变的68-100%。然而，在石英和石蜡表面上，光还原脱氯产物占
Pesticides are commonly applied on foliage, forming dry deposits on the leaf cuticular wax. However, their photochemical transformation in this lipophilic environment is much less understood compared with that in surface water. In this work, sunlight photolysis of six chlorinated phenoxyacetic acid herbicides (i.e., 2,4-D and structural analogues) was evaluated in four organic solvents, on quartz, and on paraffin wax. In solvents of low polarity (i.e., n-heptane and 2-propanol), direct photolysis of 2,4-D herbicides was enhanced due to the relatively high quantum yields in these solvents. Photolysis on paraffin wax was slower than photolysis on quartz by a factor of 3-9, but was comparable with that in solvents of low polarity. With environmentally relevant irradiation and surface loading, the half-lives of 2,4-D herbicides on paraffin wax were 27-159 h, which are within the same range reported for biodegradation, the dominant dissipation pathway in the current 2,4-D fate model. Product analyses showed that photoreductive dechlorination is the dominant pathway in organic solvents, accounting for 68-100% of parent compound decay. On quartz and paraffin wax surfaces, however, photoreductive dechlorination products accounted for