Chemistry of Secondary Aerosol Formation from Biogenic Hydrocarbons Investigated Using Thermal Desorption Particle Beam Mass Spectrometry

这项为期三年的研究计划的目标是研究选定的生物烃（单萜b-蒎烯、柠檬烯、月桂烯、芳樟醇、倍半萜b-石竹烯和二甲基硫化物）与重要的大气氧化剂OH、O3和NO3反应的产物、动力学和二次气溶胶形成机制。反应将在环境室中进行，测量将包括使用热解吸粒子束质谱仪（TDPBMS）、气相色谱-质谱法和扫描迁移率光谱仪进行实时粒子分析。在TDPBMS中，大约0.01-0.5 mm大小的颗粒被取样到差分抽运的真空室中，使用气动透镜聚焦成狭窄的低发散粒子束，在加热表面上撞击/汽化，然后使用四极杆质谱仪对蒸汽进行质量分析。除了室内研究外，还将从加州的森林和农业地区收集大气颗粒，并进行分析，以确定在实验室反应中发现的有机化合物是否也存在于环境颗粒中。这些研究的结果将有助于阐明生物烃在大气中形成次生气溶胶的基本化学过程。这些数据将有助于改善目前对大气有机粒子的命运及其对地球辐射平衡、大气化学和能见度以及人类健康的潜在影响的了解，并将有助于确定生物源有机化合物的大气寿命和命运。

The objectives of the proposed three-year research program are to investigate the products, kinetics, and mechanisms of secondary aerosol formation from the reactions of selected biogenic hydrocarbons (the monoterpenes b-pinene, limonene, myrcene, and linalool, the sesquiterpene b-caryophyllene, and dimethyl sulfide) with the important atmospheric oxidants OH, O3, and NO3. Reactions will be carried out in an environmental chamber and measurements will include real-time particle analysis using a thermal desorption particle beam mass spectrometer (TDPBMS), gas chromatography-mass spectrometry, and scanning mobility spectrometer. In the TDPBMS, particles in the size range of approximately 0.01-0.5 mm are sampled into a differentially-pumped vacuum chamber, focused into a narrow, low-divergence particle beam using aerodynamic lenses, impacted/vaporized on a heated surface, and the vapor is mass analyzed using a quadrupole mass spectrometer. In addition to the chamber studies, atmospheric particles will be collected from forested and agricultural areas in California and analyzed to determine if organic compounds identified in laboratory reactions are also present in ambient particles. The results of these studies will help to elucidate the fundamental chemical processes involved in atmospheric secondary aerosol formation from biogenic hydrocarbons. The data will help to improve current understanding of the fate of atmospheric organic particles and their potential effects on Earth's radiation balance, atmospheric chemistry and visibility, and human health, and will be useful in determining the atmospheric lifetimes and fates of biogenic organic compounds.