Advancing our understanding of peroxy radical chemistry in the atmosphere

增进我们对大气中过氧自由基化学的理解

• 批准号: 2444858
• 金额: --
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2444858
• 关键词: Advancing; our; understanding; peroxy; radical

The focus of this project is to better understand the chemistry of peroxy radicals, RO2, which are the critical intermediates following the oxidation of primary emissions. For example, CH3O2, the simplest organic peroxy radical, is formed from the oxidation of methane, an important greenhouse gas, yet there have been no measurements of the concentration of this molecule in the atmosphere. Peroxy radicals react quickly with nitric oxide, NO, a major emission from traffic and other industry, to form NO2, which is rapidly photolysed by sunlight leading to ozone formation, which is harmful to humans and ecosystems. In addition, oxidation of more functionalised volatile organic compounds, for example aromatic and carbonyl species, leads to more complex peroxy radicals, which can undergo novel and poorly understood chemistry, for example rapid autooxidation to form highly oxidised molecules (HOMs) which have low vapour pressures and rapidly condense to form SOA. However, there are no measurements of these functionalised RO2, and their kinetics are poorly characterised, yet they form the critical link between emissions and harmful secondary particulate matter.The project is a combination of fieldwork, laboratory studies and numerical modelling, and have the following specific objectives:(1) Development of a new field instrument, based on the FAGE technique, to make the first ever measurements of CH3O2 in the atmosphere. We have already developed a laboratory prototype with the required sensitivity and selectivity. Following commissioning, the instrument will be deployed in collaborative field campaigns in both clean and polluted environments (for example as part of the Clean Air Program) to make measurements alongside OH and HO2 radicals, OH reactivity (the rate at which OH is removed from the atmosphere) and the sum of peroxy radicals (measured using the ROxLIF method)(2) Making use of our laboratory facilities, for example the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC), in which individual VOCs can be photo-oxidised under controlled conditions, a range of peroxy radicals will be generated and detected using the ROxLIF technique. The focus will be on the generation of functionalised RO2, in order to further develop their detection, to study over a wide range of NOx their chemical kinetics, which are assumed in models to be similar to those of simple RO2 species (but may not be the case), and to explore the links with HOMs via autooxidation and the formation of SOA.(3) Perform analysis and interpretation of field and laboratory data and perform numerical modelling. The model will incorporate the Master Chemical Mechanism, which contains 17,000 reactions and 7,000 species, and will be used to calculate the concentrations of peroxy radicals for comparison with measurements. In this way it is possible to quantitatively evaluate how well the chemistry of RO2 is understood.The research will lead to an improved representation of chemical oxidation mechanisms in models that are used for the prediction of future changes in climate and air quality. The student will benefit from using a wide range of instrumentation (lasers, optics, vacuum and gas handling, data acquisition, electronics) and modelling tools, and by working with expert investigators will receive advanced technical training and enhance their skills base considerably. The Leeds FAGE instrumentation is part of the National Centre for Atmospheric Science. There is scope for further collaboration with atmospheric scientists in Leeds and elsewhere.

该项目的重点是更好地了解过氧自由基，RO 2，这是一次排放氧化后的关键中间体的化学。例如，最简单的有机过氧自由基CH3O2是由甲烷氧化形成的，甲烷是一种重要的温室气体，但尚未测量这种分子在大气中的浓度。过氧自由基与交通和其他工业的主要排放物一氧化氮（NO）迅速反应形成NO2，NO2被阳光迅速光解，导致臭氧形成，这对人类和生态系统有害。此外，更多官能化的挥发性有机化合物（例如芳族和羰基物质）的氧化导致更复杂的过氧自由基，其可以经历新的和知之甚少的化学，例如快速自氧化以形成高度氧化的分子（HOM），其具有低蒸气压并快速冷凝以形成SOA。然而，没有测量这些功能化的RO2，他们的动力学是很差的特点，但他们形成的排放和有害的二次颗粒物之间的关键环节。该项目是一个结合实地考察，实验室研究和数值模拟，并有以下具体目标：（1）开发一种新的现场仪器，基于FAGE技术，使有史以来第一次测量大气中的CH3O2。我们已经开发出了具有所需灵敏度和选择性的实验室原型。在试运行之后，该仪器将在清洁和污染环境中的合作实地活动中部署（例如作为清洁空气计划的一部分）与OH和HO2自由基一起进行测量，OH反应性（OH从大气中去除的速率）和过氧自由基的总和（使用ROxLIF方法测量）（2）利用我们的实验室设施，例如用于大气化学的高仪器化反应器（HIRAC），其中单个VOC可以在受控条件下被光氧化，将产生一系列过氧自由基并使用ROxLIF技术检测。重点将是功能化的RO2的生成，以进一步开发其检测，在广泛的NOx的化学动力学研究，这是假设在模型中是类似于简单的RO2物种（但可能不是这样），并探索通过自氧化和SOA的形成与HOMs的联系。(3)对现场和实验室数据进行分析和解释，并进行数值建模。该模型将纳入主化学机制，其中包含17，000个反应和7，000个物种，并将用于计算过氧自由基的浓度，以与测量结果进行比较。通过这种方式，可以定量评估对RO2化学性质的了解程度。该研究将改善用于预测未来气候和空气质量变化的模型中化学氧化机制的代表性。学生将受益于使用广泛的仪器（激光，光学，真空和气体处理，数据采集，电子）和建模工具，并通过与专家研究人员合作，将接受先进的技术培训，大大提高他们的技能基础。利兹FAGE仪器是国家大气科学中心的一部分。与利兹和其他地方的大气科学家有进一步合作的余地。