天然水体中可溶性有机质对有机氯农药光化学动力学行为的影响机制

Phototransformation is one of the main ways of pesticide pollutants degradation in natural water. Organochlorine pesticides are a chemical family of pesticides approved for use in various areas. In natural water, there is lots of dissolved organic matter, which influence the photochemical dynamics of pesticides significantly. In fact, the effect of dissolved organic matter on the photochemical dynamics of pesticides has been received much attention and big interest in science. In this proposal, multiple and hydrogen Raman shift of Nd：YAG nanosecond laser are used as excitation light source of photochemical reaction and resonance Raman experiments, which cover the UV-region of the sunlight. Resonance Raman spectroscopy technique is used to get the initial photochemical dynamics. Transient absorption spectroscopy is used to obtain the time, life and absorption wavelength of transient species, and on the basis of the transient absorption spectroscopy time-dependent resonance Raman experiments are used to explore the vibration spectroscopy of transient species during the photochemical reaction .Furthermore, the modern instrument analysis methods are applied to get the information about the component, branching ratio of the photochemical products. Quantum chemistry calculations are very powerful to predict molecular structure, spectrum, energy, electron distribution, reaction mechanism et al in photochemical processes. As a result, the photochemical transformation mechanism that dissolved organic matter influences the photochemical dynamics of organochlorine pesticides can be revealed systematically from experimental and theoretical perspectives. This proposal will be meaningful to reveal the photochemical transformation mechanism that dissolved organic matter coexisted with the main compounds in natural water influences the photochemical dynamics behavior of organochlorine pesticides and to apply the resonance Raman spectroscopy technique to explore the photochemical processes deeply.

农药在水体中的光化学转化是影响农药安全性的重要因素之一。有机氯农药是应用最广泛的农药家族之一，其使用安全性引发了科学界的广泛关注。在水体环境中，可溶性有机质能够极大地影响农药的光化学动力学行为。本课题拟利用Nd：YAG 纳秒激光器的倍频激光以及它们的氢拉曼位移激光(含太阳光中的紫外线成分280nm-400nm)作为实验光源，共振拉曼光谱用来探索分子光化学初始反应动力学特征，利用瞬态吸收光谱判断瞬态中间体的出现时间、寿命和最大吸收波长。以瞬态吸收光谱为指引，用时间分辨共振拉曼跟踪并研究瞬态物种的振动光谱，结合量子化学计算确定光化学反应中间体的结构和寿命。综合现代仪器分析方法获得光化学产物组成和分支比。关联光化学产物与过程的研究结果，得到反应机理和速率常数等信息。从实验和理论上系探明水体中可溶性有机质对有机氯农药光化学动力学行为的影响机制，为深入了解有机氯农药的归趋和安全性提供科学依据。

有机氯农药是应用最广泛的农药家族之一，其使用安全性引发了科学界的广泛关注。在水体环境中，可溶性有机质能够极大地影响农药的光化学动力学行为。本项目采用共振拉曼光谱技术、瞬态吸收光谱技术、量子化学计算等研究了有机氯农药灭草隆、敌稗、敌草隆等在不同环境下的光化学动力学行为。主要研究结果如下：（1）采用闪光光解瞬态光谱技术、共振拉曼光谱技术以及高精度量子化学计算，详细研究了有机物存在条件下不同水环境中有机氯农药灭草隆的光化学转化机理；（2）采用共振拉曼光谱技术、密度泛函理论以及全活化空间自洽场方法详细研究了有机氯农药敌草隆在共振拉曼光谱及其关联的短时动力学特征；（3）采用共振拉曼光谱技术和高精度量子化学计算研究了有机物存在的水环境中有机氯农药敌稗的紫外吸收光谱、共振拉曼光谱，详细分析了有机氯农药敌稗在水环境中的光解动力学特征及机理；（4）明确势能面交叉在有机氯农药光解动力学机理中的关键作用；（5）自制闪光光解吸收研究池，通过填充气体的不同获得有氧和无氧条件下水溶液中有机氯农药的光解机理；（6）水体环境中瞬态物种的精确鉴定方法和技术的研究和探索，结果表明联合使用飞行时间质谱（TOF-MS）、紫外、量子化学计算、拉曼光谱是研究水溶液中化合物分子结构、反应动力学过程强有力的手段，为进一步深入研究含氯类农药的动力学提供方法和技术基础。