乙虫腈和丁虫腈在稻田生态系统中选择性环境行为及毒性差异研究

As is well known, the enantiomers of chiral pesticides always have different biological activities to target biological objects and possess the enantioselective toxicities. But in most cases, the enantiomers are always treated as one compound in traditional analysis. Consequently, the risk evaluations of chiral pesticides residue in food and environment matrix based on the data obtained by traditional achiral methods are incomplete and nonspecific. Phenylpyrazole chiral insecticides were extensively used to control the pest insects on paddy production, however, they were nearly high toxic to aquatic organism and persistent in environment. Therefore, two typical extensively used phenylpyrazole chiral insecticides ethiprole and flufiprole were selected for the investigation, and their single enantiomers were separated and prepared to make sure the bioactivity on target organisms and ecotoxicity. The racemate and optical pure enantiomers fungicides were simulated to be applied in paddy ecosystem and the stereospecific environmental fate of chiral pesticide in paddy sludge, water and paddy plant was studied, to find out the main metabolites and degradation products, and to explore the major mechanisms of chiral pesticide stereoselectivity. The fate of high toxicity body and high bioactivity body of ethiprole and flufiprole in paddy sludge, water and paddy plant were revealed, to ensure the critical control points of the paddy production and environmental safety. It is helpful to provide a theoretical basis for food and environmental risk assessment of phenylpyrazole chiral insecticides used in paddy production in China.

目前考察手性农药对人类健康和环境安全的影响通常不区分对映体差别，而往往对映体生物活性和毒性差异悬殊，因而，常导致手性农药的风险评估不够准确。尤其在我国水稻生产中大量使用的苯基吡唑类手性农药，其残留和生态安全问题更为突出，开展对映体水平的农药残留行为和毒性差异研究是解决该问题的有效途径。本课题拟选择典型苯基吡唑类手性杀虫剂乙虫腈和丁虫腈为研究对象，进行手性对映体分离及光学纯单体制备，研究其对靶标生物的活性和对非靶标生物的毒性差异，明确其高效体和高毒体。在水稻生态环境下分别将供试手性农药的外消旋体和手性单体模拟施药，研究其在稻田底泥、稻田水和水稻中的选择性环境行为和降解规律，明确其主要降解产物和代谢途径，并探讨其立体选择性机制。揭示供试手性农药高毒体和高效体的主要行为归趋，明确水稻生产和环境安全的关键控制点，为水稻生态系统中吡唑类手性农药的环境风险评估提供数据支持。

手性农药对映体在生物过程中存在较大的差异性，使其生物活性、生态毒理及环境行为往往存在很大不同，因而手性农药的使用及环境安全已成为一个新的关注中心。本课题利用超高效液相色谱-串联质谱手性固定相方法研究了苯基吡唑类手性杀虫剂乙虫腈和丁虫腈在稻田生态系统中的立体选择性环境行为，同时开展了上述两种农药光学纯对映体的毒性和活性差异研究。. 考察比较了纤维素-三[3,5-二甲基苯基氨基甲酸酯](Lux-C1)；纤维素-三[3-氯-4-甲基苯基氨基甲酸酯] (Lux-C2)；纤维素-三(4-苯甲酸甲酯)( Lux-C3)；纤维素-三(4-氯-3-甲基苯基氨基甲酸酯) (Lux-C4)；直链淀粉-三(5-氯-2-甲基苯基氨基甲酸酯)( Lux-A2)等五种手性固定相对乙虫腈、丁虫腈及其手性代谢物的化学分离与手性分离结果，发现Lux-C4固定相具有最高手性分离能力。通过进一步对改性剂种类及含量、分离温度等手性分离因素的优化，成功实现了乙虫腈、丁虫腈及其代谢物对映体的同时基线分离。. 通过模拟实际生产，开展了乙虫腈和丁虫腈对映体在稻田生态系统中的选择性行为研究。数据表明乙虫腈和丁虫腈对映体在稻田系统中降解符合一级动力学规律。R-(+)-乙虫腈在谷壳和糙米中相对富集，而在水稻植株和稻田水、底泥中乙虫腈两个对映体降解速率没有显著性差异；S-(-)-丁虫腈在谷壳、糙米及水稻植株基质中优先降解；而R-(+)-丁虫腈在稻田水和底泥中优先降解。. 开展了乙虫腈和丁虫腈外消旋体及光学纯对映体对斜生栅藻和大型溞等水生生物的急性毒性差异研究。乙虫腈和丁虫腈对映体对上述两种水生生物急性毒性存在不同，毒性顺序分别为：(R)-(+)-乙虫腈>(S)-(-)-乙虫腈，(R)-(+)-丁虫腈>(S)-(-)-丁虫腈，乙虫腈和丁虫腈外消旋的毒性均处于其对映体之间。. 开展了乙虫腈和丁虫腈外消旋体及光学纯对映体对水稻二化螟和褐飞虱等靶标害虫的活性差异研究。对于试验选定的靶标而言，乙虫腈和丁虫腈对映体的杀虫活性存在明显差异，乙虫腈和丁虫腈活性大小顺序为：(R)-(+)-乙虫腈> (S)-(-)-乙虫腈；(S)-(-)-丁虫腈>(R)-(-)-丁虫腈；乙虫腈和丁虫腈外消旋体活性均处于其对映体之间。.