【作者】 郭敏；

【导师】 单正军； 宗良纲；

【作者基本信息】 南京农业大学 ， 环境科学， 2008， 硕士

【摘要】 氟虫腈是一种新型苯基吡唑类杀虫剂,是我国农业部推荐的高毒有机磷农药的重要替代品种之一,其对人畜安全性较高,对许多水生生物具有高毒。目前有关氟虫腈环境行为特性及其降解机制研究较少,全面了解氟虫腈在环境中的滞留、转化以及其对生态环境可能存在的潜在影响,为科学评价氟虫腈使用的环境安全性以及该农药能否在我国大规模推广应用提供理论基础,有着十分重要的现实意义。为此,本文对氟虫腈及其代谢产物在土壤与水溶液中的降解特性与降解机制以及土壤中氟虫腈的提取测定方法等方面进行了研究。根据研究内容,全文分为下述四个部分:首先进行了文献综述,详细介绍了氟虫腈的性质、用途和毒理学特性等,并对农药的水解、光解、土壤降解及环境中农药的提取方法等方面的相关概念、理论和国内外研究现状进行了介绍和评述。第二,研究了土壤中氟虫腈及其代谢产物的残留检测方法。详细研究了ASE-GC快速提取分析技术对土壤中氟虫腈及其代谢产物的提取效率及影响因素,确定了ASE的最佳提取条件,并与传统的提取方法进行了比较分析。结果表明:(1)采用加速溶剂萃取法提取不同类型土壤中的氟虫腈及其代谢产物,在温度80℃,压力1500 Pa的条件下,用二氯甲烷/丙酮(1:1,v/v)的混合溶液静态提取2次,氟甲腈(MB46513)、硫醚(MB45950)、氟虫腈、砜(MB46136)的回收率在79%～111%之间,相对标准偏差在1.2%～9.5%之间。(2)与微波助萃取法和振荡提取法相比,加速溶剂提取的效果均高于微波助萃取与振荡提取;而且加速溶剂提取操作简单、耗时短、有机溶剂用量少,并且能实现自动化处理。第三,研究了氟虫腈在3种不同类型土壤中的降解动力学特征以及不同环境条件对其降解速率的影响,同时较为详细地研究了氟虫腈在土壤环境中的代谢行为,对其在土壤降解过程中的代谢产物的消长机制做了初步的研究。结果表明:(1)微生物是氟虫腈在土壤中降解的主导因子。氟虫腈在中性太湖水稻土中降解速率最快;在酸性江西红壤中降解最慢,且在好气、渍水与灭菌3种不同条件下,其在红壤中降解速率变化不大,说明土壤微生物选择性降解氟虫腈,氟虫腈在酸性环境中较为稳定。氟虫腈在渍水土壤中降解速率加快,说明渍水土壤中的厌氧菌属有利于氟虫腈的降解。同时,连续施药对氟虫腈的降解速率影响也很大。(2)氟虫腈在土壤中的降解代谢途径主要是氧化-还原作用,好气条件下不同土壤中的代谢机制不同,在东北黑土中以氧化代谢为主,太湖水稻土中以还原代谢为主,而在江西红壤中是氧化-还原共同作用的结果。(3)评价氟虫腈在环境中的残留性及其对生态环境的安全性时,不能只局限于氟虫腈母体,应该结合氟虫腈的代谢产物作综合性的评价。第四,研究了氟虫腈在不同pH值和温度条件下的水解特性,对其在水溶液中的降解途径做了初步探讨。结果表明:氟虫腈在不同条件下的水解速率差异较大。弱酸性(pH5.0)时,氟虫腈农药在25℃和50℃条件下水解半衰期分别144.4d和119.5d,具有较强的化学稳定性,为较难水解农药;中性(pH7.0)时,在25℃和50℃温度条件下,水解半衰期分别为123.8d、39.8d,常温下较为稳定,水解性较弱;弱碱性(pH9.0)时,水解速率明显加快,25℃和50℃温度条件下的水解半衰期分别为10.0d和8.1h。高温、碱性有利于氟虫腈的水解。本文采用快速溶剂萃取-气相色谱技术,建立了土壤中氟虫腈及其代谢产物快速提取测定方法;系统地研究了氟虫腈土壤降解与水解等环境行为特性及其影响因素;系统研究了氟虫腈土壤降解与水解过程中不同代谢产物的消长规律,探讨并揭示了氟虫腈在环境中的降解机理,为科学评价氟虫腈使用的环境安全性提供了相应的科学依据与理论基础。更多还原

【Abstract】 Fipronil,a recently developed phenylpyrazole insecticide,is a highly effective and broad-spectrum insecticide.Since organophosphorus pesticides were gradually limited in application due to their high toxicity,fipronil was recommended by Agricultural Ministry as a principal replayer of organophosphorus pesticides.Fipronil is safe to human beings and animals but poses a significant risk to many hydrobios.There was little research about behaviors and degradation mechanism of fipronil nowdays,so it was very emergent and important to investigate the persistence,transformation and potential hazards of fipronil in ecological environment in order to assess correctly the environmental safety and enact utilize policy of fipronil.The results are briefly summarized as below:Firstly,the paper introduced properties,utilization and toxicology of fipronil,and reviewed briefly the basic concepts,theories and current research advance about hydrolysis, photodecomposition,soil biodegradation and extraction methods for pesticides.Secondly,a method for determining the residue of fipronil and its metabolites in soils was developed by ASE-GC.The results showed:(1) The recoveries of MB46513, MB45950,fipronil and MB46136 were in range of 79%～111%and precision(RSD) was generally less than 10%adopted ASE condition at 80℃,1500 Pa for two cycles with a mixed solution of dichloromethane and acetone(1:1,v/v).(2)Primarily ASE was a rapid extraction technique taking not only less solvent,shorter time but also automatic processing compared with microware assisted extraction(MAE) and extraction by shaking(SH).Third,degradation mechanisms of fipronil and its metabolites in three kinds of soils and the influence factors were investigated separately.The results showed:(1) The half-lives were much longer in sterilized soils,which may contribute to low microorganism quantity in soils.Anaerobic condition was advantageous to the degradation of fipronil which indicated fipronil was mainly degraded utilizing anaerobic bacterium.The results showed that fipronil degraded the fastest in Rice soil and the slowest in Red Soil,and fipronil seemed stable in acid because the half-lives of fipronil changed a few under different conditions.History and amount of fipronil application affected its degradation process greatly.(2) In soil,degradation of fipronil was governed mainly by oxidization and reduction accompanying with the production of the metabolites,MB46513 and MB46136. Oxidization and reduction played different roles in different aerobic soils.In Black Soil, oxidization producted the major effect in degradation of fipronil,while reduction played the major role in Rice Soil.The results showed that degradation of fipronil in Red Soil was happened by oxidization and reduction.(3) The results of this research indicated comprehensive that the metabolites of fipronil may adversely affect ecosystem,and these motabolites should be properly considered incorporated into a risk assessment strategy to ecosystem.Fourth,the hydrolysis kinetics and mechanism of fipronil were studied in aqueous solution with different pH values and temperature.Results were observed as follow: hydrolysis of fipronil in the buffer solutions of pH5,pH7 and pH9 could be described by the first-order kinetics equation.Hydrolysis of fipronil increased with the increasing pH value of the solution,and its hydrolysis half-life in the buffer solutions of pH5 at 25℃and 50℃were 144.4d and 119.5d,respectively,suggesting that fipronil should be very stable in acidic solution.The half-lives in the buffer solution of pH7 at 25℃and 50℃were 123.8d and 39.8d.It could be concluded that fipronil was stable at room temperature in neutral solution.Furthermore,the half-lives of fipronil in alkaline solution were 10.0d and 8.1d respectively at the temperature of 25℃and 50℃.The highest of hydrolysis rate was observed in alkaline solution.Annex 1,additionally,solid phase extraction of Oasis~R HLB and photolysis of DA-6(hexanoic acid 2-(diethyl amino) ethyl ester) in water were further systematically studied and probed at length.This paper was conducted to evaluate the fate of fipronil in environment and provide the basis of using this insecticide.Extraction methods of fipronil and its metabolites in soils using the combination of accelerated solvent extraction(ASE) and gas chromatography was studied, meanwhile the degradation dynamics of fipronil and its metabolites in environment and the influence factors were studied in detail.更多还原