Chemical Pathways Leading to Organic Aerosol Formation from the Atmospheric Oxidation of Alkanes

本实验项目的主要目的是阐明烷烃大气光氧化形成二次有机气溶胶（SOA）的详细化学机制。烷烃是人为排放的挥发性有机化合物（VOC）中最大的一类，似乎是城市SOA的重要贡献者。烷烃衍生化合物是探索低挥发性可冷凝化合物形成过程中基本气相化学反应机制的理想体系。该项目的一般方法将是在大容量环境室中研究选定的烷烃及其第一代和潜在的第二代（和以后）产物的羟基（OH）自由基引发反应的气相和颗粒相产物。包括热解吸粒子束质谱法（TDPBMS）、大气压电离质谱法和衍生化气相色谱-质谱法在内的先进技术将被用于实时和离线分析气相和颗粒相产品，以识别和量化连续几代产品，并跟踪SOA形成和生长的化学演变。要研究的烷烃包括正癸烷和它的一些异构体。在不同组成的种子粒子存在下，SOA形成的研究将探讨粒子相聚合反应的潜在作用。这项研究将有助于确定烷烃光氧化在大气SOA形成中的重要性以及发生这种情况的化学机制。这些结果将提高目前对烷烃（大气的主要组成部分）命运的理解，并有助于开发更复杂的SOA形成和行为的大气模型。这些类型的模型被广泛用于评估气溶胶对全球气候变化、空气污染和能见度以及人类健康的潜在影响，这些都是社会面临的重要问题。这个项目也将有可能教育一些研究生和本科生，这些学生又将有机会在大气化学领域以及更一般的环境问题上教育其他人。

The primary objective of this experimental program is to elucidate the detailed chemical mechanisms leading to the formation of secondary organic aerosol (SOA) from atmospheric photooxidation of alkanes. Alkanes comprise the largest class of volatile organic compound (VOC) emissions from anthropogenic sources, and appear to be a significant contributor to urban SOA. Alkane-derived compounds present an ideal system for exploring the basic gas-phase chemical reaction mechanisms involved in the formation of low-volatility, condensable compounds. The general approach for this project will be to investigate the gas- and particle-phase products of the hydroxyl (OH) radical-initiated reactions of selected alkanes and of their first- and potentially second- (and later) generation products in large-volume environmental chambers. A combination of demonstrated, state-of-the-art techniques, including thermal desorption particle beam mass spectrometry (TDPBMS), atmospheric pressure ionization mass spectrometry, and gas chromatography-mass spectrometry with derivatization, will be used to analyze gas-phase and particle-phase products in real-time as well as off-line, in order to identify and quantify successive generations of products and follow the chemical evolution of SOA formation and growth. The alkanes to be investigated include n-decane and a number of its isomers. Studies of SOA formation in the presence of seed particles of different compositions will investigate the potential role of particle-phase polymerization reactions.This research will help to determine the importance of alkane photooxidation in atmospheric SOA formation and the chemical mechanisms by which this occurs. The results will improve current understanding of the fate of alkanes, which are a major component of the atmosphere, and aid in the development of more sophisticated atmospheric models of SOA formation and behavior. These types of models are widely used to evaluate the potential effects of aerosols on global climate change, air pollution and visibility, and human health, which are all important problems confronting society. This project will also make it possible to educate a number of graduate and undergraduate students, who in turn will have the opportunity to educate others, in the area of atmospheric chemistry as well as on more general environmental issues.