挥发性有机物大气氧化机理研究：自由基中间体和中间产物的同步辐射光电离质谱探测

挥发性有机物(VOCs)是导致大气对流层臭氧浓度和颗粒物浓度升高的重要前驱体，研究VOCs的大气氧化机理对于理解VOCs对空气质量的影响至关重要。VOCs的大气氧化以自由基反应和光化学过程为主，其中自由基动力学是确定VOCs氧化机理的重点但也是实验的难点。至今为止在VOCs大气氧化机理研究中的重要进展无一不与中间体自由基的检测和自由基动力学研究有关。本项目拟采用同步辐射光电离质谱技术，试图探测VOCs氧化过程中自由基和中间产物的存在，通过m/z比和光电离效率谱确定其结构，结合理论计算，确定中间体(自由基)的结构。我们拟尝试探测VOCs氧化过程中的过氧自由基、烯烃臭氧化反应中的Criegee中间体和非Criegee机理中的双自由基中间体和产物。以此为基础，提出更可靠的VOCs大气氧化机理。

Volatile organic compounds (VOCs) are the important precursors elevating the concentrations of ozone and particulate matter in the troposphere. Studies on the atmospheric oxidation mechanism of VOCs are key to the understanding of impact of VOCs on air quality. Atmospheric oxidation of VOCs consist mostly of radical reactions and photochemical processes, of which the kinetics of free radicals is the most important properties in determining the VOCs oxidation mechanism. However, detection of free radicals and study of their reaction kinetics are also the most difficult part in study of VOCs oxidation mechanism. Up to now, the achievements in VOCs oxidation mechanism studies are all related to the detection of free radicals and the study of their reaction kinetics. In this project, we propose to detect and identify the free radicals and intermediates involved in the processes of VOCs oxidation using UVU Synchrotron Radiation Photo Ionization Mass Spectrometry method. Combining the acquired Photo Ionization Efficiency Spectroscopy, appearance energies from quantum chemistry calculations, and the calculated photo ionization efficiency, we hope to identify a few important free radicals and intermediates in the course of VOCs oxidation under the atmospheric conditions. We aim to detect the peroxy radicals and the Criegee intermediates formed in ozonolysis of alkenes. We will also try to probe the possibility of non-Criegee mechanism in ozonolysis of alkenes via diradical. With the information on intermediate radicals and products, we will propose the oxidation mechanism of a few VOCs with better reliability.