Surface Mediated Transformation of Pesticides

矿物-水界面强烈影响土壤环境的整体生物地球化学。矿物为有机和无机溶质、胶体或微生物的吸附提供了活性表面，但也促进了吸附物的水解或电子转移反应。与过去的非极性、疏水性农药相比，现代有机农药通常是高度官能化的。对于这类农药，与矿物表面的特定相互作用有助于甚至可能主导它们在土壤中的命运。拟议研究的总体目标是从机理上阐明天然土壤A和B层中矿物表面(氧化物、粘土)对表面介导的农药热化学反应的影响。为此，我们选择了一系列含有现代农用化学品典型活性结构特征的杀虫剂(灭草胺、苯达松、甲霜灵)。更具体地说，我们建议在实验室批处理模型系统中评估对矿物表面的吸附和/或与矿物表面的相互作用在多大程度上影响农药水解的速度、反应机理和产物光谱。Ii)可能是立体选择性的，因此可能影响手性农药的转化率和产物光谱(异构体比)，除了水解外，我们还将考虑iii)农药中氨基的表面介导的氧化转化反应和iv)农药中硫部分的表面介导的还原转化反应。我们期望这项研究的结果将有助于预测非生物转化反应对土壤中农药的整体降解率和机理的重要性。

The mineral-water interface strongly influences the overall biogeochemistry of soil environments. Minerals provide reactive surfaces for the adsorption of organic and inorganic solutes, colloids or microorganisms, but also facilitate hydrolysis or electron transfer reactions of the sorbates. In contrast to non-polar, hydrophobic pesticides of the past modern organic agrochemicals typically are highly functionalized. For such pesticides, specific interactions with mineral surfaces contribute to or even may dominate their fate in soils. The overall goal of the proposed research is to elucidate on a mechanistic basis the effects of mineral surfaces (oxides, clays) representative of those present in A and B horizons of natural soils on surface mediated thermochemical reactions of pesticides. To this end, we have chosen a set of pesticides (Fenhexamid, Bentazone, Metalaxyl) that contain reactive structural features typical for modern agrochemicals. More specifically, we propose to evaluate in laboratory batch model systems to what extent sorption to and/or interactions with mineral surfaces i) affects the rates, reaction mechanisms and product spectrum of pesticide hydrolysis. ii) may be stereoselective and thus may affect the transformation rates and the product spectrum (isomer ratios) of chiral pesticides Besides hydrolysis , we will also consider iii) surface mediated oxidative transformation reactions of amino moieties present in pesticides and iv) surface mediated reductive transformation reactions of sulfur moieties present in pesticides. We expect that the results of this research will help to predict the significance of abiotic transformation reactions to the overall degradation rates and mechanisms of pesticides in soil.