Integrated Experimental and Modeling Studies of the Chemistry of Organic Aerosol Formation from the Atmospheric Oxidation of Hydrocarbons

本提案的总体目标是发展气相和非均相/多相反应的定量化学机制，这些反应涉及在广泛的条件下由选定类别的烷烃和烯烃及其反应产物的羟基（OH）自由基引发的反应形成二次有机气溶胶（SOA）。并将这些机制与气体-颗粒-壁分配信息结合起来，开发SOA形成和氧化老化的综合模型。该方法将涉及在广泛的碳数范围内OH自由基引发反应的实验研究。这些化合物含有大气挥发性有机化合物（VOC）和SOA中存在的大部分基本结构特征。反应将在一个大型的聚四氟乙烯环境室中进行，在污染和清洁空气的条件下进行，并探讨相对湿度和颗粒化学成分、酸度和质量负荷对反应的影响。存在于气相和颗粒相中的反应产物将使用实时和离线方法进行鉴定和定量，包括热解吸颗粒束质谱法，耦合各种检测器的液相和气相色谱法，以及没有或借助官能团衍生化的分光光度法。实验也将在环境室和较小的反应器中进行，用真实的或替代的反应产物来研究气壁分配、蒸汽压力和反应产物的活度系数，以及它们潜在的多相/多相反应的动力学和平衡。这些结果将用于开发这些过程的综合动力学模型，包括气相和非均相/多相反应以及气体-颗粒壁分配。由于基本反应途径、产物和官能团的相似性，所获得的数据对气相反应途径的反应产物和分支比、多相/多相反应动力学和平衡以及气-颗粒壁分配的广泛影响将被应用于许多其他voc氧化系统。由于聚四氟乙烯室的广泛使用，研究结果将有助于评估和改进环境室研究的方法和解释，这些研究提供了有价值的数据，被大气化学和气溶胶模拟界广泛使用，以及改进作为三维空气质量模型模块的化学反应机制和SOA模型。这些模式用于评估气体和颗粒对区域能见度、人类健康、生态系统和气候的潜在影响。本项目还将培养2名或2名以上的研究生并作为其博士学位论文的基础，并为本科生提供研究机会。学生将接受有机分析、动力学、大气气相和气溶胶化学等领域的培训，并且根据他们的学位课程，还将接受更广泛的化学、环境毒理学或环境科学方面的教育。学生将在科学期刊上发表研究成果，并参加地方、区域和国家会议并展示研究成果。因此，学生将为未来在工业界、学术界或政府机构从事环境问题工作做好充分准备。数据和结果将通过出版物、会议发言和网站传播，这将扩大数据的价值和使用。

The overall objective of this proposal is to develop quantitative chemical mechanisms for the gas phase and heterogeneous/multiphase reactions involved in the formation of secondary organic aerosol (SOA) from the hydroxyl (OH) radical-initiated reactions of selected classes of alkanes and alkenes and their reaction products over a wide range of conditions, and to use these mechanisms with information on gas-particle-wall partitioning to develop comprehensive models of SOA formation and oxidative aging. The approach will involve experimental studies of OH radical-initiated reactions over a wide range of carbon numbers. These compounds contain most of the basic structural features present in atmospheric volatile organic compounds (VOC) and SOA. Reactions will be conducted in a large, Teflon environmental chamber under conditions representative of polluted and clean air, and the effects of relative humidity and particle chemical composition, acidity, and mass loading on the reactions will be explored. Reaction products present in the gas and particle phases will be identified and quantified using real-time and offline methods including thermal desorption particle beam mass spectrometry, liquid and gas chromatography coupled to a variety of detectors, and spectrophotometry without and with the aid of functional group derivatization. Experiments will also be conducted in the environmental chamber and in smaller reactors with authentic or surrogate reaction products to investigate gas-wall partitioning, vapor pressures, and activity coefficients of reaction products, as well as the kinetics and equilibria of their potential heterogeneous/multiphase reactions. The results will be used to develop comprehensive kinetic models of these processes that incorporate gas phase and heterogeneous/multiphase reactions and gas-particle-wall partitioning.Broader impacts of the data obtained on reaction products and branching ratios for gas phase reaction pathways, heterogeneous/multiphase reaction kinetics and equilibria, and gas-particle-wall partitioning will be their application to many other VOC-oxidant systems because of the similarity in fundamental reaction pathways, products, and functional groups. Because of the widespread use of Teflon chambers, the results will be useful for evaluating and improving methodology and interpretation of environmental chamber studies, which provide valuable data that is widely used by the atmospheric chemistry and aerosol modeling community, as well as improving chemical reaction mechanisms and SOA models that serve as modules in 3-dimensional air quality models. These models are used to evaluate potential effects of gases and particles on regional visibility, human health, ecosystems, and climate. This project will also educate two or more graduate students and serve as the basis for their Ph.D. dissertations, and provide research opportunities for undergraduate students. Students will be trained in the areas of organic analysis, kinetics, and atmospheric gas phase and aerosol chemistry, and, depending on their degree program, will also be educated more broadly in chemistry, environmental toxicology, or environmental science. Students will publish research results in scientific journals and attend and present results at local, regional, and national conferences. As a result, students will be well prepared for future careers in industry, academia, or a government agency working on environmental problems. Data and results will be disseminated through publications, conference presentations, and a website, which will expand the value and use of the data.