Chemical Mechanisms of Nucleation and Growth of Secondary Organic Aerosol from the Oxidation of Biogenic Compounds

该项目的总体目标是使用一套分析技术来阐明二次有机气溶胶(SOA)的成核和随后增长所涉及的详细的化学和物理机制，这些二次有机气溶胶是由选定的挥发性有机化合物(VOC)通过气相和多相反应氧化而成的。该项目的工作将从开发一种分析有机气溶胶颗粒化学成分的新技术开始。这将包括将离子陷阱质谱仪(ITMS)与为实时粒子化学分析而开发的热解吸粒子束质谱仪(TDPBMS)相耦合。然后，这些TDPBMS技术将与其他技术一起用于研究选定的单萜类化合物和模型化合物与臭氧、羟基自由基和硝酸根在大体积环境室中反应生成SOA的化学。这些反应中的颗粒成核化学将通过层流管式反应器通过成核和生长阶段来控制颗粒尺寸分布来研究。我们还将研究一些初级生物来源的VOCs及其氧化产物与臭氧在酸催化的多相反应中生成SOA的化学。这项研究将有助于确定单萜氧化在大气SOA形成中的重要性以及发生这种氧化的化学机制(包括成核、生长和非均相反应)。在全球范围内，SOA的形成被认为是由生物源有机化合物的反应产物主导的。这些细小的SOA颗粒有可能影响全球气候、大气能见度、异质化学和人类健康。该项目还将使一些研究生和本科生能够在大气化学领域以及更一般的环境问题方面接受教育。

The overall objective of this project is to use a suite of analytical techniques to elucidate the detailed chemical and physical mechanisms involved in the nucleation and subsequent growth of secondary organic aerosol (SOA) from the oxidation of selected volatile organic compounds (VOCs) via gas phase and heterogeneous reactions. Work on this project will begin with the development of a new technique for analyzing the chemical composition of organic aerosol particles. This will involve coupling an ion trap mass spectrometer (ITMS) to a thermal desorption particle beam mass spectrometer (TDPBMS) that has been developed for real-time particle chemical analysis. These TDPBMS techniques will then be used with others to investigate the chemistry of SOA formation from reactions of selected monoterpenes and model compounds with ozone, hydroxyl radicals, and nitrate radicals in a large-volume environmental chamber. The chemistry of particle nucleation in these reactions will be studied by using a laminar flow tube reactor to control particle size distributions through the nucleation and growth stages. The chemistry of SOA formation from acid-catalyzed heterogeneous reactions of selected primary biogenic VOCs and their oxidation products with ozone will also be investigated. This research will help to determine the importance of monoterpene oxidation in atmospheric SOA formation and the chemical mechanisms by which this occurs (including nucleation, growth, and heterogeneous reactions). On a global scale, SOA formation is thought to be dominated by the products of reactions of biogenic organic compounds. These fine SOA particles have the potential to impact global climate, atmospheric visibility, heterogeneous chemistry, and human health. This project will also make it possible to educate a number of graduate and undergraduate students in the area of atmospheric chemistry as well as more general environmental issues.