Atmospheric Impacts of Criegee Biradical Chemistry

空气质量差每年给英国造成的损失超过200亿英镑。这种糟糕的空气质量是由大气的化学成分以及大气中多种不同化学物质之间的相互作用控制的。这些相互作用通常由高活性痕量气体种类介导，导致化学转化，不仅控制空气质量，而且控制臭氧消耗和气候变化。我们对大量化合物及其在大气中的转化的理解决定了我们理解、预测和解决这些环境问题的能力。多年来，一类被称为Criegee双自由基的痕量物种被理论化为参与大气中的化学转化，在自然过程主导的区域和受人类影响的区域中。由于它们的高反应性和瞬态性质，Criegee双自由基已被证明难以直接测量，导致其化学性质及其对大气成分的影响存在很大的不确定性。最近的突破性实验导致了对Criegee双自由基的首次直接观察，并表明它们比以前基于间接测量和理论计算的预期更具反应性。最简单的Criegee双自由基（CH2OO）与二氧化硫（SO2）的反应速度比之前预期的快1000倍，可能揭示了大气中三氧化硫（SO3）产生的未知途径，并影响了我们对硫酸，酸雨和硫酸盐气溶胶的大气生产的理解，对空气质量和气候变化都有影响。然而，这些实验是在低压（小于大气压力的1%）下进行的，并且在与大气相关的较高压力下的反应速率和产物可能不同于在低压实验中观察到的那些。评估反应对大气的影响需要了解反应速率和产物产率，这项工作将利用新的机会探索Criegee双自由基在大气中的化学和影响，使用的技术将能够在与大气相关的温度和压力下调查反应速率和产物产率。最初的实验将在利兹大学化学学院使用现有的实验仪器进行。随后的实验，与项目合作伙伴在加州的桑迪亚国家实验室合作，将开发新的仪器，以监测Criegee双自由基及其反应产物在大气温度和压力下在实验室的理想条件。研究期间开发的仪器将用于测量利兹大气反应室中更复杂系统中的Criegee双自由基，并有可能在未来发展到大气中Criegee双自由基的实地测量。与约克大学和马萨诸塞州理工学院（MIT）的世界领先研究小组合作。

Poor air quality costs the UK in excess of £20billion per year. This poor air quality is controlled by the chemical composition of the atmosphere, and the interactions between the multitude of different chemical species in the atmosphere. These interactions are typically mediated by highly reactive trace gas species, leading to chemical transformations which control not only air quality but also ozone depletion and climate change. Our understanding of the vast array of chemical compounds and their transformations in the atmosphere dictates our ability to understand, predict, and address these environmental problems.For many years, one class of trace species known as Criegee biradicals have been theorised to participate in chemical transformations in the atmosphere, both in regions dominated by natural processes and in those influenced by man. Owing to their high reactivity and transient nature, Criegee biradicals have proven difficult to measure directly, leading to large uncertainties in their chemistry and their impacts on atmospheric composition. Recent ground-breaking experiments led to the first direct observations of Criegee biradicals, and showed them to be much more reactive than previously anticipated on the basis of indirect measurements and theoretical calculations. The simplest Criegee biradical (CH2OO) was shown to react with sulfur dioxide (SO2) 1000 times faster than previously expected, potentially revealing a previously unknown route for production of sulfur trioxide (SO3) in the atmosphere and impacting our understanding of atmospheric production of sulfuric acid, acid rain and sulfate aerosol, with implications for both air quality and climate change. However, these experiments were performed at low pressures (less than 1 % of atmospheric pressure), and the reaction rate and products at higher pressures relevant to the atmosphere may be different to those observed in the low pressure experiments. Assessment of the atmospheric impacts of a reaction requires knowledge of both the rate of the reaction and the product yields.This work will take advantage of the new opportunities to explore the chemistry and impacts of Criegee biradicals in the atmosphere, using techniques which will enable investigation of both reaction rates and product yields at temperatures and pressures relevant to the atmosphere. Initial experiments will be performed with existing experimental apparatus in the School of Chemistry at the University of Leeds. Subsequent experiments, in collaboration with project partners at the Sandia National Laboratory in California, will develop novel instrumentation to monitor Criegee biradicals and their reaction products at atmospheric temperatures and pressures under idealised conditions in the laboratory. The instrumentation developed during the fellowship will be applied to measurements of Criegee biradicals in more complex systems in an atmospheric reaction chamber in Leeds, and has the potential for future development to field measurements of Criegee biradicals in the atmosphere.Atmospheric impacts of experimental results obtained in this work will be assessed through the use of detailed numerical models of the atmosphere, in collaboration with world-leading research groups at the University of York and the Massachusetts Institute of Technology (MIT).