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

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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.