【作者】 谢国红；

【导师】 刘国光；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2009， 博士

【摘要】 啶虫脒属于一种新型的氯化烟碱类杀虫剂,被认为是替代有机磷农药的重要品种之一,在世界范围内已经得到了广泛的应用。但是,关于其在环境中的迁移、转化行为还没有得到系统的研究,因此,为了安全合理的使用该农药,就必须对其在环境中的迁移转化行为进行研究。本文系统地研究了啶虫脒的水解和光解行为,目的在于为全面评价其对环境的影响提供理论依据。本文首先研究了啶虫脒的水解行为。结果表明,啶虫脒的水解属于碱性水解,啶虫脒的水解符合准一级反应动力学方程。根据HPLC-MS结果推测,啶虫脒的水解产物分别为N-[（6-氯-3-吡啶）甲基-N-甲基乙酰胺和N-甲基（6-氯-3-吡啶）甲基胺。啶虫脒的水解速率随溶液pH值和温度的升高而加快。Cu²⁺、Pb²⁺和Fe（OH）₃对啶虫脒的水解具有明显的促进作用,腐殖酸对啶虫脒的水解具有抑制作用。Cu²⁺和Pb²⁺离子促进啶虫脒水解的机理是:（1）由于啶虫脒分子中的C=N基上的N原子具有一对孤对电子,能够和溶液中的Cu²⁺和Pb²⁺离子螯合形成螯合物,从而使得与之相连的C原子上的电子云密度降低,更有利于亲核试剂的进攻。（2） Cu²⁺和Pb₂在水中形成金属羟基络合物,金属羟基化合物是一种活性更强的亲核试剂,更有利于啶虫脒的水解。Fe（OH）₃促进啶虫脒水解可能是因为:Fe（OH）₃分子中的Fe可以与啶虫脒的C=N基团上的N原子所拥有的一对孤对电子配合,使得C=N键上的C原子上的电子云密度降低,更容易受到的OH-进攻。另外,溶液中悬浮的Fe（OH）₃带正电荷,并且Fe（OH）₃本身对有机物具有一定的吸附能力,可以吸引大量带负电荷的OH-和啶虫脒,从而使得局部反应物浓度增加,加快啶虫脒水解反应的速率。腐殖酸对啶虫脒水解的抑制作用是因为腐殖酸中含有许多具有酸性的官能团,抑制了溶液中氢氧根离子的活性,使得溶液碱性减弱,从而抑制了啶虫脒的碱性水解。此外腐殖酸还可以吸附啶虫脒分子,从而降低了啶虫脒分子的活性,抑制了其水解反应。本文研究了啶虫脒的光解行为。啶虫脒在氙灯照射下光解较慢,而在汞灯照射下可以迅速的发生光解,且光解速率随着光照强度的增加而加快,原因在于啶虫脒几乎不吸收氙灯的辐射,而可以吸收中压和低压汞灯的辐射。啶虫脒的光解符合准一级反应动力学方程。啶虫脒的光解产物为N-氰基-N-甲基-N（（3-氧代-2-氮杂双环[2,2,0]已-5-烯-6）甲基）乙脒。溶液的温度和pH值对啶虫脒的光解有一定的影响,啶虫脒的光解随着温度的升高而增加,其在酸性介质中的光解速率大于在碱性介质中的光解速率。溶液中溶解氧含量的增加可以加快啶虫脒的光解。溶液中的Fe³⁺、硝酸根、腐殖酸以及表面活性剂可以抑制啶虫脒的光解,而H₂O₂和TiO₂可以促进啶虫脒的光解。Fe³⁺、硝酸根和腐殖酸的抑制作用都是因为对光的竞争性吸收所引起的,而表面活性剂对啶虫脒光解的抑制作用可能是以下三种因素作用的结果:（1）对光的竞争性吸收;（2）表面活性剂形成的胶束对啶虫脒有一定的富集作用;（3）表面活性剂分子中的活性集团和啶虫脒分子结合从而改变其吸光特性。H₂O₂和TiO₂对啶虫脒光解的促进则是因为两者在光照下均可以产生活性很强的羟基自由基·OH,从而加速了啶虫脒的光解。啶虫脒在几种实验的有机溶剂和水溶液中的光解速率由快到慢依次为:丙酮、水、甲醇、乙腈和异丙醇。更多还原

【Abstract】 Acetamiprid belongs to a new-style insecticide known as chloro-neontictinoids. It was regarded as an important substitute of organophosphorus pesticides, and has beed extensively used worldwide.To our knowledge, no reports have been found to investigate the environmental behavior of acetamiprid up to now.Thus,information of the transformation of acetamiprid in environment is indispensable for an ecotoxicological evaluation of it.The hydrolysis and photolysis of acetamiprid were investigated thoroughly in this dissertation.The hydrolysis of acetamiprid was studied firstly in this dissertation.The results indicated that the hydrolysis of acetamiprid belongs to alkaline hydrolysis and the hydrolysis of acetamiprid fits the pseudo-first-order kinetics well.Two hydrolytic product, N-[（6-chloro-3-pyridyl）methyl]-N-methylacetamide and N-methyl（6-chloro -3-pyridyl） methylamine were identified by HPLC-MS. The hydrolytic rate of acetamiprid was increased with the increases of the values of pH and temperatures of the reaction medium.The presence of Cu²⁺、Pb²⁺ and Fe（OH）₃ could promote the hydrolysis of acetamiprid and humic acid could inhibit the hydrolysis of acetamiprid.The mechanism of the promoting effect of Cu²⁺and Pb²⁺ was suggested as followed:（1） Cu²⁺ and Pb²⁺ were coordinated with the atom of N of the group of C=N in the acetamiprid molecule and leads to withdrawing electron density away from the C and generating a more reactive electrophile, which made the bond of C-N more easily broken when attacked by OH-.（2） Cu²⁺and Pb²⁺ could induce the deprotonation of coordinated water molecules, therby generating metal hydroxo species, which is more stronger than OH-.The promoting mechanism of Fe（OH）₃ was suggested as followed:（1） Fe（OH）₃ was coordinated with the atom of N of the group of C=N in the acetamiprid molecule,and leads to withdrawing electron density away from the C atom and generating a more easily broken when attacked by OH-.（2） Fe（OH）₃ takes positron and has strong absorption ability,which made it can absorb acetamiprid molecule and OH- to form a environment with high concentration of reactants around the Fe（OH）₃,more quick hydrolysis of acetamiprid.The mechanisms of inhibting effect of humic acid on acetamiprid hydrolysis were proposed as followed:（1）Humic acid owns some acidic groups which could lower the pH values of the reaction medium and then inhibit the alkaline catalyzed hydrolysis of acetamiprid;（2）Humic acid could absorb acetamiprid and decrease the activity of acetamiprid,which inhibit the hydrolysis of acetamiprid.The photolysis of acetamiprid was also studied in this dissertation. Acetamiprid kept stable when xenon lamp was served as light source,but degraded quickly when exposed to the irradiation of medium-pressure or low-pressure mercury lamp,and the rate constant increased significantly with the increase of light intensity,which was due to acetamiprid could’t absorb the irradiation of xenon lamp,but could absorb the irradiation of low-pressure and medium-pressure mercury lamp effectively.The photolysis of acetamiprid fits the pseudo-first-order kinetics well. N₂ -cyano-N1-methyl-N1（（3-oxo-2-azabicyclo[2,2,0]hex-5-en-6）methyl）acetamidine was identified as photolytic product of acetamiprid by use of HPLC-MS.Effects of temperature and the values of pH were faint, the photolytic rate of acetamiprid increased slightly with the increases of temperature. Acetamiprid degraded rapidly in acidic medium. Dissolved oxygen could increase slightly the photolytic rate constant of acetamiprid. Fe³⁺, NO₃^-, humic acid and surfactant could inhibit the photolysis of acetamiprid. H2O₂ and TiO₂ could stimulate the photolysis of acetamiprid. The mechanisms of the inhibiting effect of Fe³⁺, NO₃^- and humic acid on photolysis of acetamiprid were all due to the competitive absorption of light between Fe³⁺, NO₃^- and humic acid with acetamiprid.The balance between the competitive absorption of light,the combination of the surfactant’s active groups with the acetamiprid molecule,and the relatively high concentration of acetamiprid in the hydrophobic environment formed by micelles of surfactant resulted in the inhibiting effect of surfactant on photolysis of acetamiprid. The OH·generated by the irradiation on H₂O₂ and TiO₂ could promote the photolysis of acetamiprid.The photolytic rate constant of acetamiprid followed the sequence: acetone>water>methanol> acetonitrile>isopropyl.更多还原