Elucidating Nitrogen and Chlorine Recycling Mechanisms from Multiphase Photochemistry of Oxidized Nitrogen

在化学学部环境化学科学项目的支持下，印第安纳大学的乔纳森·拉夫将研究在环境表面发现的污染物硝酸盐和其他氧化形式的氮（例如，大气颗粒、土壤矿物质和海盐）如何影响空气污染，空气污染是全球过早死亡的主要原因。有重要的证据表明，硝酸盐与阳光的相互作用可以改变大气的组成，从而导致空气质量差或影响云的形成。所涉及的化学机制仍然没有得到很好的理解。实验室实验将在土壤、海盐和气溶胶的良好特征模型上进行，使用灵敏的仪器，在真实的环境条件下实时跟踪化学反应。这项研究将有助于澄清大气中污染物是如何形成和破坏的，对空气污染的原因具有潜在的长期科学意义，特别是对大气中可能从硝酸盐化学中获得的氧化氮物种的性质。研究生和本科生将参与这项研究。后者将包括来自代表性不足群体的一年级新生，他们将开展暑期研究项目，旨在提高他们对科学、技术、工程和数学（STEM）专业的兴趣。此外，该项目的成果将用于加强当地一所高中的科学教育的外展活动。根据该奖项，由印第安纳大学Jonathan Ruff领导的研究小组将研究硝酸、硝酸盐和有机硝酸盐在环境表面的光化学反应性，重点是阐明导致氮氧化物和氯原子前体释放和再循环的化学机制，这些化学机制有助于大气的氧化能力。实验方法将涉及紫外-可见和红外漫反射光谱，以及光化学流动反应器，通过化学电离质谱和化学发光分析进行气相产物检测。除了揭示氮氧化物和氯循环的机制外，该项目还将提供动力学和光化学数据，以提高建模和预测氧化氮多相光化学的能力。这项研究的长期更广泛的科学影响包括提供一个更完整的反应树，由大气硝酸盐发出，特别关注氧化氮物种星座，在与来自太阳的紫外线/可见光相互作用时产生光化学反应。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

With support from the Environmental Chemical Sciences Program in the Division of Chemistry, Jonathan Raff at Indiana University will study how the pollutant nitrate and other oxidized forms of nitrogen found on environmental surfaces (e.g., atmospheric particles, soil minerals, and sea salt) influence air pollution, which is a leading cause of premature death globally. There is significant evidence that interactions of nitrate with sunlight can change the composition of the atmosphere in ways that can lead to poor air quality or influence cloud formation. The chemical mechanisms involved are still not well understood. Laboratory experiments will be carried out on well-characterized models of soil, sea salt and aerosols using sensitive instrumentation that follows chemical reactions in real time and under real environmental conditions. This research will help clarify how pollutants in the atmosphere are formed and destroyed, with potential long terms scientific relevance to the causes of air pollution, particularly, to the nature of oxidized nitrogen species that might obtain in the atmosphere from nitrate chemistry. Graduate and undergraduate students will be involved in this research. The latter will include entering first-year students from underrepresented groups who will carry out summer research projects designed to increase their interest in pursuing science, technology, engineering and mathematics (STEM) majors. In addition, the outcomes of this project will be used in outreach activities to enhance science education at a local high school.Under this award, the research team led by Jonathan Ruff at Indiana University will study the photochemical reactivity of nitric acid, nitrate, and organic nitrates on environmental surfaces with a focus on elucidating chemical mechanisms leading to the release and recycling of nitrogen oxides and chlorine atom precursors that contribute to the oxidizing capacity of the atmosphere. Experimental approaches will involve UV-visible and infrared diffuse reflection spectroscopy, and photochemical flow reactors with gas phase product detection by chemical ionization mass spectrometry and chemiluminescence analysis. In addition to revealing mechanisms of nitrogen oxide and chlorine recycling, the project will provide the kinetics and photochemical data needed to advance the ability to model and predict multiphase photochemistry of oxidized nitrogen. The long term broader scientific impacts of this research include providing a more complete reaction tree emanating from atmospheric nitrates with a particular focus on the constellation of oxidized nitrogen species that is produced photochemically upon interaction with UV/vis light from the sun.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.