手性菊酯类农药在土壤-蚯蚓-蜥蜴食物链传递中的选择性环境行为研究

As the selective biodegradation and bioaccumulation, chiral pesticides have special fates in environment.Synthetic pyrethroid pesticides are of environmental significance because they are widespread in various matrices in enviroment, can easyly be accumulated and have high biotoxicity. Synthetic pyrethroid pesticides usually contain 2 or 3 stereogenic centers,thus each synthetic pyrethroid compound contains 2 or 4 enantiomer pairs, or 2 or 4 diastereomers. Pairs of enantiomers, usually differ significantly in both enviromental behaviors and biological activities. In this study, two chiral synthetic pyrethroid pesticides, lambda-cyhalothrin and bifenthrin are selected and the stereoselective behaviors of transfer in food chain of soil-earthworm-lizard will be studied. The methods for extraction, cleaning and detection of two chiral pesticides will be established. The concentrations of each enantiomer, the ratio of the enantiomer and its variation with changing of time in all the matrices will be analysed. The stereoselective degration of selected chiral pesticides in soil and the stereoselective bioaccumulation in earthworm and lizard tissues will also be studied. In addition, the main metabolites of two chiral pesticides will be detected by GC/HPLC-MS. After that metabolites can be synthesised and enantioselective behavior of the metabolites will also be studied. The soil is consided as an reservoirs of pesticide pollutions. The pollutants in soil can be accumulated by soil invertebrates,and then enter terrestrial ecosystem by predators, such as lizards, eating soil invertebrates. Both earthworms and lizards are important components of terrestrial ecosystems as well as integral components of food chains.This project aims to provide more stereoselective bioaccumulation data in food chain, and to provide more acurate information for risk assessment of chiral pesticides.

手性农药的环境归趋问题已得到普遍的重视和发展，然而其在食物链中的选择性传递情况研究甚少,本项目以手性农药高效氯氟氰菊酯和联苯菊酯为研究目标，针对其在环境中检出率高、生物富集强和生物毒性高等特点，建立对映异构体的分离分析方法及在土壤-蚯蚓-蜥蜴食物链各营养级中的提取、净化和检测方法，测定其中手性农药对映体的含量、相对比值及随时间的变化情况，确定对映体在土壤中的选择性降解、蚯蚓体内的选择性生物富集以及在蜥蜴各组织器官中的选择性分布和代谢规律，最后评价其在食物链中的生物放大行为。同时，基于GC/HPLC-MS技术，结合体外代谢实验,确定并合成代谢产物，进一步研究相关代谢产物在食物链中的传递情况。土壤被称为农药在环境中的"贮藏库"与"集散地"，而手性农药可通过不同营养级食物的摄取选择性的进入食物链，并在生物选择性富集放大作用下影响人类的健康。本项目的开展更能真实的反映相关农药的污染情况。

选择联苯菊酯和高效氯氟氰菊酯作为一类菊酯和二类菊酯的代表来研究菊酯类农药在土壤-蚯蚓体系以及蜥蜴体内的富集代谢规律，进一步揭示了高效氯氟氰菊酯单一异构体对蜥蜴甲状腺系统的干扰机制。以上研究完善了菊酯类农药对陆生生物的毒性数据，为毒性风险评价奠定了基础。. 利用GC-MS/MS、HPLC-MS/MS建立了联苯菊酯和高效氯氟氰菊酯及其代谢物3-苯氧基苯甲酸的分析方法。在蚯蚓的富集和代谢实验中，联苯菊酯和高效氯氟氰菊酯分别以经土的方式暴露于蚯蚓，结果显示联苯菊酯在蚯蚓体内的富集系数是高效氯氟氰菊酯的4 倍。土壤对化合物的吸附是影响生物可利用率的一个重要因素。高效氯氟氰菊酯暴露组中，土壤中检测到了代谢物3-苯氧基苯甲酸，高浓度暴露可以加快蚯蚓的代谢速率。联苯菊酯和高效氯氟氰菊酯在蚯蚓体内均出现了手性选择性富集。. 选择高效氯氟氰菊酯对蜥蜴进行暴露实验，结果表明除了在脂肪中容易富集，高效氯氟氰菊酯在其他组织中的代谢速率很快。肝脏作为主要的排毒器官，高效氯氟氰菊酯暴露造成了严重的肝组织损伤。与高效氯氟氰菊酯相比，代谢物3-苯氧基苯甲酸更容易在蜥蜴的脑组织中富集，可能会干扰蜥蜴的内分泌系统。高效氯氟氰菊酯的EF值在0.7-0.2之间波动。将高效氯氟氰菊酯的两个对映体分别暴露于蜥蜴，在粪便中发现了右旋单体向左旋单体转换的现象。同时两个对映体对蜥蜴甲状腺系统的干扰机制不同，右旋单体主要通过与甲状腺受体的竞争结合干扰甲状腺激素和相关基因的表达，而左旋单体主要通过干扰T4向T3转换的通路，造成甲状腺系统失去稳态。. 经食物链暴露顺式氯氰菊酯后，雌蜥的死亡率明显高于雄蜥。给药后的面包虫会明显影响到蜥蜴的食物摄入量。就产卵分布时间而言，菊酯影响了卵的发育及产卵数量。同时，对抗氧化酶系和解毒酶系的酶活，血清中的激素水平，肝脏的代谢组学数据及器官的组织病理学分析均发现，经食物链暴露后顺式氯氰菊酯对丽斑麻蜥造成了严重的毒害影响。