Unraveling Nitrate Photochemistry in the Environment

解开环境中硝酸盐光化学的谜团

• 批准号: 2305164
• 负责人: Cort Anastasio
• 金额: $ 62.84万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-06-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2305164&HistoricalAwards=false
• 关键词: Unraveling; Nitrate; Photochemistry; Environment

With support from the Environmental Chemical Sciences Program in the Division of Chemistry, Drs. Cort Anastasio, Ted Hullar, and Davide Donadio from the University of California at Davis and their teams will study the influence of surfaces and organic molecules on nitrate photochemistry. Nitrogen oxides (NOx), which are emitted during combustion of fossil fuels, play major roles in the production of smog. During smog formation, NOx is converted to nitrate, which traditionally was thought to be an unreactive final product. However, research over the past 20 years suggests that some nitrate in the environment – such as on surfaces or in the presence of certain carbon-containing molecules – can absorb sunlight to very quickly reform NOx. If true, this would lead to more smog than expected from the initial NOx emissions. The collaborative UC-Davis team will address this discrepancy in the projected studies. This project also includes the training of undergraduate and graduate students as well as contributions to podcasts and fact sheets about environmental chemistry for middle and high school students.This project will study nitrate photochemistry on surfaces and in the presence of organic molecules by combining computational chemical modeling with experimental measurements in the laboratory. The modeling will leverage ab initio molecular dynamics of the (photo)excited triplet state to unravel the molecular pathways and free energy surface of nitrate photochemistry in solution. This will allow predictions of nitrate quantum yields, which will be benchmarked against published measurements. This approach will then be applied to predict quantum yields on a variety of environmentally relevant surfaces, which will be integrated with computed nitrate absorption spectra to estimate nitrate photolysis rates. Simultaneously, rates of nitrate photolysis on the same surfaces will be measured in the laboratory using newly developed techniques to study solid-state photochemistry with monochromatic illumination. Unlike most past studies, the measurements will also employ chemical actinometry on the surface to better quantify photon fluxes. Then by combining the modeling and experimental results, the team aims to establish the extent to which faster nitrate photolysis on surfaces is due to an increase in light absorption and/or an increase in photochemical efficiency. Using computational and experimental approaches, this project will also assess how organic molecules impact nitrate photolysis in solution and explore the underlying mechanisms.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.

在化学系环境化学科学项目的支持下，加州大学戴维斯分校的 Cort Anastasio、Ted Hullar 和 Davide Donadio 博士及其团队将研究表面和有机分子对硝酸盐光化学的影响。化石燃料燃烧过程中排放的氮氧化物 (NOx) 在烟雾形成过程中发挥着重要作用，氮氧化物会转化为硝酸盐。传统上被认为是一种不反应的最终产品，然而，过去 20 年的研究表明，环境中的某些硝酸盐（例如表面上或存在某些含碳分子的情况下）可以吸收阳光并很快重新形成。如果属实，这将导致最初的氮氧化物排放量超出预期，加州大学戴维斯分校的合作团队将在计划研究中解决这一差异。该项目还包括对本科生和研究生的培训以及对氮氧化物的贡献。播客和有关中学生和高中生环境化学的情况说明书。该项目将通过将计算化学建模与实验室实验测量相结合，研究表面和有机分子存在下的硝酸盐光化学。该建模将利用（从头算）分子动力学。光）激发三重态，以揭示溶液中硝酸盐光化学的分子途径和自由能表面，这将允许预测硝酸盐量子产率，然后将其与已发布的测量结果进行比较。各种环境相关表面上的量子产率，将与计算的硝酸盐吸收光谱相结合，以估计硝酸盐光解速率，同时，将使用新开发的技术在实验室中测量硝酸盐光解速率，以研究固态。与大多数过去的研究不同，测量还将在表面上使用化学光化学来更好地量化光子通量，然后通过结合建模和实验结果，该团队旨在确定程度。表面上更快的硝酸盐光解是由于光吸收的增加和/或光化学效率的提高，该项目还将使用计算和实验方法评估有机分子如何影响溶液中的硝酸盐光解并探索潜在的机制。授予 NSF 的法定使命，并通过评估反映使用基金会的智力优点和更广泛的影响审查标准，被认为值得支持。