Heterogeneous Chemistry of Gas-Phase Intermediates in the OH-oxidation of Dimethyl Sulfide

在化学系环境化学科学项目的支持下，麦迪逊的威斯康星州大学的蒂莫西·伯特伦教授和他的学生正在研究与大气有关的硫化学。从海洋表面排放的挥发性有机化合物在地球大气中被氧化，导致形成低挥发性分子，这些分子可以使新的气溶胶颗粒成核或凝结到现有的气溶胶颗粒上。二甲基硫（DMS）是海洋大气中最丰富的还原硫源，在海洋环境中气溶胶颗粒的形成和增长中起着核心作用。尽管二甲硫醚在地球气候中的重要性，但对二甲硫醚氧化过程中的中间产物的全面了解有限，导致对硫酸和甲磺酸产量（二甲硫醚氧化的关键终点）的估计存在很大差异。本项目将研究DMS氧化过程中关键中间体的非均相动力学，以及它们如何调节硫酸和MSA的产生。这个项目将支持一个化学研究生的博士论文和多个本科论文项目。该研究小组将继续参与UW麦迪逊化学招聘计划（CHOPS，CHembertopportunitieS）和旨在支持化学代表性不足的学生的化学博士学位计划的桥梁。此外，研究团队将与当地K-12学校合作，测量和评估公立学校的室内空气质量。该项目将使用实验室测量结果：1）量化DMS OH-氧化中关键中间体的非均相和多相反应速率; 2）确定过氧化氢硫代甲酸甲酯（HPMTF）凝聚相反应的产物产率和化学机理在气溶胶和云水中。具体而言，使用与化学电离质谱仪耦合的夹带气溶胶流反应器，该团队将确定二甲基亚砜（DMSO），甲烷亚磺酸（MSIA），MSA和HPMTF对代表性海洋气溶胶模拟物（例如，海雾、硫酸铵）作为相对湿度和颗粒酸度的函数。使用在线和离线采样技术相结合，产品产量的HPMTF在云水和海洋气溶胶模拟物的凝聚相反应将被确定。预计这将允许更准确地评估DMS排放的形成硫酸盐气溶胶的部分。该奖项反映了NSF的法定使命，并已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的支持。

With support from the Environmental Chemical Sciences Program of the Division of Chemistry, Professor Timothy Bertram and his students at the University of Wisconsin, Madison are studying sulfur chemistry related to the atmosphere. Volatile organic compounds, emitted from the surface ocean, are oxidized in the earth atmosphere resulting in the formation of low volatility molecules that can nucleate new aerosol particles or condense onto existing aerosol particles. Dimethyl sulfide (DMS) is the most abundant source of reduced sulfur to the marine atmosphere and plays a central role in the formation and growth of aerosol particles in marine environments. Despite the importance of DMS in climate on earth, a comprehensive understanding of the intermediate products in the oxidation of DMS is limited, leading to large variability in estimates of sulfuric acid and methanesulfonic acid (MSA) yields; the key endpoints of DMS oxidation. This project will investigate the heterogeneous kinetics of key intermediates in the oxidation of DMS and how they regulate the production of sulfuric acid and MSA. This project will support the PhD thesis for one chemistry graduate student and multiple undergraduate thesis projects. The research team will continue to be involved the UW Madison chemistry recruitment program (CHOPS, CHemistry OPportunitieS) and the Bridge to the Chemistry Doctorate program designed to support underrepresented students in chemistry. Additionally, the research team will partner with local K-12 schools on the measurement and assessment of indoor air quality in public schools.This project will use laboratory measurements to: 1) quantify the rate of heterogeneous and multiphase reactions of key intermediates in the OH-oxidation of DMS and 2) determine the product yields and chemical mechanism for the condensed phase reaction of hydroperoxymethyl thioformate (HPMTF) in aerosol and cloud water. Specifically, using an entrained aerosol flow reactor coupled to a chemical ionization mass spectrometer, the team will determine the reactive uptake coefficient of dimethyl sulfoxide (DMSO), methanesulfinic acid (MSIA), MSA and HPMTF to representative marine aerosol mimics (e.g., sea spray, ammonium sulfate) as a function of relative humidity and particle acidity. Using a combination of online and offline sampling techniques, the product yields for the condensed phase reactions of HPMTF in cloud water and marine aerosol mimics will be determined. This is expected to permit a more accurate assessment of the fraction of DMS emitted that forms sulfate aerosol.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.