CAS: Autoxidation of Oxygenated Volatile Chemical Products in the Atmosphere

在化学系环境化学科学项目的支持下，加州理工学院的Paul Wennberg、Brian Stoltz和John Crounse博士将研究挥发性化学产品（VCPs）的大气反应。VCP是含氧碳氢化合物（如乙二醇醚和酯），是一系列产品中使用的常见溶剂，包括油漆，清洁剂和液体肥皂，除草剂，水力压裂液和织物染料。当它们被使用时，大量的这些化合物蒸发并成为光化学产生臭氧和小颗粒（气溶胶）的主要（如果不是主导的话）贡献者，这些光化学产生臭氧和小颗粒（气溶胶）导致许多城市空气质量差。由于车辆排放量的减少，车辆控制点的重要性也在增加。准确了解臭氧和气溶胶的产生量对于了解空气质量非常重要。臭氧对植物和动物有广泛的毒性，包括人类，因为它会导致肺部和支气管发炎。气溶胶使空气变得浑浊，降低能见度，并与呼吸系统和其他疾病有关。通过与哥本哈根大学和美国环境保护署（EPA）的合作，将对VCP的氧化化学进行建模研究，以了解它们如何促进空气中臭氧和颗粒的形成。除了对学生进行培训外，该团队还将在校园和当地学校开展外联活动，将空气质量作为社区高度关注的话题。在理解VCP对空气质量的影响方面的一个主要不确定性是它们的氧化是否会导致形成低挥发性化合物。特别是，自由基自氧化可能在其降解中起作用。通过有机过氧自由基的H-位移反应的自氧化可以从更易挥发的前体快速产生高度氧化的有机化合物。这些高度氧化的化合物具有低得多的蒸气压并冷凝形成气溶胶。这个实验室和计算调查将检查的假设，醚部分，常见于许多含氧VCP，提高这些H-位移的速率，使自氧化的一个重要组成部分，准确地描述其大气降解，从而对空气污染的影响。在这个项目中，研究人员将研究这些氧化反应的速率为一组不同的有机底物，包括那些占主导地位的含氧VCPs排放到大气中。 这项工作对于理解大气中氧化有机物的成因具有潜在的重要的长期科学意义，同时绘制出相关挥发性有机化合物的广泛范围的机制和产物分布。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

With support from the Environmental Chemical Sciences Program in the Division of Chemistry, Drs. Paul Wennberg, Brian Stoltz, and John Crounse at the California Institute of Technology will study atmospheric reactions of volatile chemical products (VCPs). VCPs are oxygen-containing hydrocarbons (such as glycol ethers and esters) that are common solvents used in a array of products, including paints, cleaning agents and liquid soaps, herbicides, hydraulic fracturing fluids, and dyes for fabrics. When they are used, large quantities of these compounds vaporize and become a major, if not the dominant, contributor to the photochemistry producing ozone and small particles (aerosols) that contribute to poor air quality in many cities. The importance of VCPs is also growing because of decreasing vehicle emissions. Accurate knowledge of how much ozone and aerosols are produced is important to understand air quality. Ozone is broadly toxic to plants and animals, including humans because it causes inflammation of the lungs and bronchia. Aerosols make the air hazy, reduce visibility and are associated with respiratory and other illnesses. Through a collaboration with the University of Copenhagen and the U.S. Environmental Protection Agency (EPA), modeling studies will be carried on the oxidative chemistry of VCPs to learn how they contribute to the formation of ozone and particles in air. In addition to training of students, the team will engage in outreach both at their campus and at local schools, addressing air quality as a topic of high interest to the community. A major uncertainty in understanding the impacts of VCPs on air quality is whether their oxidation results in formation of low volatility compounds. In particular, radical autoxidation may be active in their degradation. Autoxidation via H-shift reactions of organic peroxy radicals can rapidly produce highly oxygenated organic compounds from much more volatile precursors. These highly oxygenated compounds have a much lower vapor pressure and condense to form aerosol. This laboratory and computational investigation will examine the hypothesis that the ether moiety, common in many oxygenated VCPs, enhances the rate of these H-shifts making autoxidation an essential part of accurately describing their atmospheric degradation and thus their impact on air pollution. In this project, the investigators will study the rates of these oxidative reactions for a diverse set of organic substrates that include those that dominate the emissions of oxygenated VCPs to the atmosphere. There are potentially important long range scientific implications of this work for the understanding of the genesis of oxidized organics in the atmosphere, while at the same time mapping out mechanism and product distribution for a wide spectrum of relevant volatile organic compounds.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.