助剂与工业纳米颗粒对手性农药在土壤中吸附和降解的影响机制

The mechanism for the influence of pesticide adjuvants and engineering nano-particles on the adsorption and degradation of chiral pesticide over soils will be investigated in this work. The bingding ratio and constants between metalaxyl, quizalofop-ethyl and cyclodextrin and its derivatates, sodium ligninsulfonate and sodium cholate aggregates will be firstly studied to determine the binding difference of pesticide enantiomers. New adsorption model will be deduced and proposed to describe the influence of adjuvants and nano-particles (TiO2, active carbon and iron oxides) on the adsorption of chiral pesticide onto soils in order to assess the stability of pesticide in the presence of these co-existed materials. The mechanism for the infulence of adjuvants and nano-particles on the degradation of pesticide over soils will also be proposed and concluded. The work in this project are helpful to reveal the mechanism for enantioselective adsorption and degradation of chiral pesticide over soils, which are resulted from the change of micro-environmental by co-exist materials.The work can also enrich the knowledge of influence and generation of enantioselectivity of chiral pesticide through the chemical process. The results are helpful to regulate the enantioselectivity of chiral pesticide in soils, and are also helpful to design and choose environmental friendly adjuvants. The results could offer experimental basis for exploring engineering nano-particles' influence on the environmental behavior of chiral pollutants.

本申请拟研究农药助剂和工业纳米颗粒对手性农药在土壤中吸附和降解的影响机制。具体研究农药助剂（环糊精、木质素磺酸钠和胆酸盐聚集体）和手性农药（甲霜灵与喹禾灵的外消旋体及光学纯异构体）的包结方式和包结常数，判断对映体与助剂结合作用的强弱；推导和验证新的吸附模型，用于定量的描述农药助剂和工业纳米颗粒（TiO2，活性炭和铁氧化合物）对手性农药在土壤中吸附的影响，评价助剂和纳米颗粒对农药在土壤中迁移性的影响；探索农药助剂、纳米颗粒对手性农药在土壤中生物降解和化学降解的影响机制。研究有助于揭示由共存物质引起的反应微环境的改变对手性农药在土壤中吸附和降解的影响机制，丰富人们对通过化学过程影响和产生手性农药选择性行为的认识。研究成果将有助于实现对手性农药在土壤中选择性降解的调控，有利于筛选和研发更加环境友好型的农药助剂，为在对映体水平上探讨工业纳米颗粒对土壤中手性污染物环境行为的影响提供了实验依据。

项目研究了农药助剂（木质素磺酸钠，环糊精衍生物及实际商品所用的混合助剂）和纳米颗粒（SiO2，TiO2，ZnO，C60）对典型手性农药甲霜灵和喹禾灵在农田土壤中吸附和转化的影响，量化了影响程度和影响的主要产生途径。甲霜灵和喹禾灵的吸附均没有对映体选择性，农药助剂未影响两种手性农药的吸附。甲霜灵和喹禾灵在土壤中的转化表现出明显的对映体选择性。商品化农药中的组分代森锰锌显著抑制了R-甲霜灵的转化，对S-甲霜灵的抑制程度则较小。SiO2由于比表面积较大，进入土壤后，降低了甲霜灵和喹禾灵的迁移性。TiO2促进了手性农药在土壤中的化学转化。SiO2和TiO2未对细菌群落结构产生显著影响，因此，SiO2和TiO2没有影响两种手性农药的生物转化过程，因而转化的对映体分数没有发生明显改变。纳米颗粒进入土壤后，其性质会发生明显改变，因此，土壤介质中，不同TiO2对手性农药的降解的差异与溶液中的差异不同。在更接近实际环境下的温室试验中，纳米颗粒并未显著影响手性农药的生物化学转化。地表植被存在下，纳米颗粒的影响与其在裸土中的影响不同。C60-水稻-Cd的研究结果表明，这可能与纳米颗粒会影响植物吸收转运污染物等因素有关。在以后的研究中，需要强化对纳米颗粒在土壤环境老化过程中其结构-性质-影响动态变化的研究，以期更加准确地揭示纳米颗粒在土壤介质中的环境效应。