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

这项建议的总体目标是在广泛的条件下开发涉及从选定类别的烷烃和烯烃及其反应产物的羟基(OH)引发的反应形成二次有机气溶胶(SOA)的气相和多相/多相反应的定量化学机理，并利用这些机理和关于气-颗粒-壁分配的信息来开发二次有机气溶胶的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对OH自由基引发的反应的实验研究。这些化合物包含大气挥发性有机化合物(VOC)和SOA中存在的大多数基本结构特征。反应将在代表污染和清洁空气的大型特氟龙环境室中进行，并将探索相对湿度和颗粒化学成分、酸度和质量负荷对反应的影响。气相和颗粒相中存在的反应产物将使用实时和离线方法进行鉴定和定量，这些方法包括热解吸粒子束质谱仪、与各种检测器耦合的液体和气相色谱以及在没有官能团衍生化的情况下和在官能团衍生化的帮助下的分光光度法。还将在环境室和具有真实或替代反应产物的较小反应器中进行实验，以研究气壁分配、蒸汽压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。这些结果将被用来建立这些过程的综合动力学模型，这些过程包括气相和多相/多相反应以及气相-颗粒壁分配。由于基本反应路径、产物和官能团的相似性，所获得的关于气相反应路径的反应产物和支化比、多相/多相反应动力学和平衡以及气相-颗粒壁分配的数据的主要影响将应用于许多其他VOC-氧化剂体系。由于特氟龙室的广泛使用，结果将有助于评估和改进环境室研究的方法和解释，这些研究提供了被大气化学和气溶胶模型界广泛使用的有价值的数据，并改进了化学反应机理和作为三维空气质量模型模块的SOA模型。这些模型用于评估气体和颗粒物对区域能见度、人类健康、生态系统和气候的潜在影响。该项目还将培养两名或两名以上的研究生，作为其博士论文的基础，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领域的培训，根据他们的学位计划，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，并在地方、地区和国家会议上发表研究成果。因此，学生们将为未来在工业、学术界或致力于环境问题的政府机构的职业生涯做好充分准备。数据和成果将通过出版物、会议报告和一个网站传播，这将扩大数据的价值和用途。

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.