典型二噁英在气相与气-固界面微观降解机理的理论研究

Combining the experimental results of photolysis, chemical oxidation degradation, high level ab initio quantum chemistry method and molecular simulation have been used to study the heterogeneous degradation process of typical dioxin-like compounds in the gas phase and gas-solid surface, and to expound the reaction mechanism at the molecular level. Based on the quantum chemistry, the kinetic calculations have been carried out to obtain the kinetic information including the rate constants and activation energy. On the one hand, the information can provide basic data for model simulation. On the other hand, they can be used to calculate the lifetimes of the compounds in the environment. According to the quantum chemical calculation, we can also get the molecular structure parameters of the dioxin-like compounds, such as, the energies of the frontier orbitals (HOMO and LUMO orbital), energy level difference, atomic charge distribution and configuration parameters. Combined with the kinetic information of the rate constants, the numerical simulation of the genetic algorithm and partial least square method are used to research activity relationship between degradation performance and structure. Consequently, the prediction model for degradation performance of the dioxin-like compounds is built and the practical application is analysed. The microscopic degradation mechanism of the dioxin-like compounds in gas-phase and gas-solid interface reactions help to further understand the reaction activity and degradation model of the persistent organic pollutants in the environment.

本项目拟采用高精度的ab initio 量子化学方法和分子模拟技术，研究典型的二噁英物质在气相与气-固表面的降解过程，并与实验（如气相反应、气固界面催化反应等）结果相验证，从分子水平上阐明反应的微观机理。在量子化学的基础上进行动力学计算，获得反应速率常数、反应活化能等动力学信息，一方面可以为模式研究提供基本数据，另一方面可以计算各物质在环境中的寿命。通过量子化学计算还可以得到二噁英物质的分子结构参数，如：前沿分子轨道HOMO和LUMO轨道能量、能级差、原子电荷分布、构型参数等，结合动力学计算得到的反应速率常数等动力学信息，采用遗传算法和偏最小二乘法数值模拟，进行降解性能与结构之间的构效关系研究，构建二噁英类物质的降解性能预测模型。明确典型二噁英物质在气相与气-固表面中的微观降解机理，有助于更好地理解持久性有机污染物在大气环境中的反应活性和降解规律。

在本项目实施期间,我们采用了高精度的量子化学方法，对典型的二噁英物质在气相与气-固表面的降解过程进行了研究，并且与已有的实验结果进行了相互验证。主要研究了大气中典型的二噁英类物质(2, 3, 7, 8-四氯代二苯-并-对二噁英(2, 3, 7, 8-TCDD)，2, 3, 7, 8-四氯代二苯并呋喃(2, 3, 7, 8-TCDF))的氧化降解机理, 以及对2, 3, 7, 8-TCDD在HOx、O3、NO3、Cl引发下的大气降解机理及动力学行为进行了研究。应用定量构效关系(QSAR)方法研究了PCDDs氯原子取代数目和位置对反应速率常数的影响。我们也对介质阻挡放电技术中O(3P)对八氯代二苯-并-对二噁英(OCDD)原子降解的机理进行了研究。另外，我们也关注并研究了其它物质在大气中的降解机理以及动力学行为，比如研究了典型生物质燃烧标识物（左旋葡聚糖、脱氢揪酸)及生物质排放的VOCs(单萜烯等）在大气中的降解机理及动力学行为；典型有机杀菌药物（三氯生、林丹、左氧氟沙星）在环境中由OH引发的降解机理及动力学行为；典型农药（三氯杀虫酯和野麦畏）在大气中的氧化降解机理及动力学行为。总的来讲，我们通过量子化学计算明确了典型二噁英物质在气相与气-固表面中的微观降解机理，结合动力学计算得到了反应速率常数等动力学信息。这些结果有助于更好地理解持久性有机污染物在大气环境中的反应活性和降解规律，具有很强的理论指导意义和应用价值。