New field measurements and mechanistic understanding of peroxy radicals (PEROXY)

过氧自由基 (PEROXY) 的新现场测量和机理理解

• 批准号: NE/V000861/1
• 负责人: Dwayne Heard
• 金额: $ 86.46万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV000861%2F1
• 关键词: New; field; measurements; mechanistic; understanding

In this proposal we aim to achieve a better mechanistic understanding of the behaviour of peroxy radicals, a key family of atmospheric intermediates, central to understanding the tropospheric oxidation chemistry of volatile organic compounds (VOCs). Exposure to air pollution kills 7 million people worldwide per year. Peroxy radical chemistry controls the formation of the secondary pollutants ozone, nitrogen dioxide and secondary organic aerosol (SOA), a key component of particulate matter (PM). Exposure to PM less than 2.5 micrometres in diameter led to 4.2 million deaths globally in 2015 and 29,000 in the UK. Tropospheric ozone is also an important greenhouse gas (radiative forcing ~25% that of carbon dioxide), is the main source of the hydroxyl radical (nature's detergent), is harmful to crops and ecosystems, and is only generated via reactions of peroxy radicals. A large proportion of PM is secondary in nature (i.e. generated via chemical oxidation), with much of this being SOA.However, despite its importance, peroxy radical chemistry remains poorly understood and not well represented in models, and improved mechanistic understanding is required to improve prediction of air pollution and to provide better assessment of the impact of proposed interventions and long term changes in emissions. To address this problem, in this proposal we will develop novel instrumentation to measure peroxy radicals, conduct field studies in clean and polluted environments and carry out targeted laboratory chamber experiments. The fieldwork will include participation in the UKRI/Met Office Strategic Priority Fund Clean Air Programme. We will provide field measurements of RO2 as a target for model calculations, and new kinetic data for RO2 processes as input for models.The smallest and most abundant organic peroxy radical in the atmosphere is methyl peroxy (CH3O2), which is formed directly by the reaction of the hydroxyl radical with methane. Reaction of CH3O2 with nitric oxide constitutes one of the most important tropospheric in situ sources of ozone. Despite its importance, CH3O2 has never been measured directly in the atmosphere, and in this proposal we will develop a field instrument to do so for the first time, and deploy it in both remote, clean environments and polluted urban centres. Larger peroxy radicals, together known as RO2, are also important precursors to ozone and secondary organic aerosol, and we will also measure the sum of RO2 concentrations in the field.Highly oxidised molecules (HOMs) deriving from the oxidation of a range of natural or anthropogenic VOCs are central to understanding how SOA forms. Peroxy radicals form an important component of HOM, however the removal mechanisms of HOM-like RO2 are highly uncertain. The fieldwork will be augmented by targeted laboratory chamber studies where individual VOCs or mixes of VOCs are used to generate HOM-like RO2 under a range of NOx, in order to determine kinetic rates and yields for the scavenging of HOM-RO2 species.Using this combination of field and chamber studies, we will further validate the representation of current mechanisms for RO2 transformations, to improve the ability of models to calculate formation rates of ozone and secondary organic aerosol over a range of NOx concentrations.This proposal brings together leading complementary expertise from groups in Leeds and Manchester who both have considerable experience in field measurements, laboratory chamber measurements of gas and aerosol processes, and numerical modelling using gas and coupled gas-aerosol mechanisms.

在此提案中，我们旨在更好地理解过氧自由基的行为，这是大气中间体的关键家族，是了解挥发性有机化合物（VOC）的对流层氧化化学的核心。暴露于空气污染每年在全球700万人丧生。过氧自由基化学控制二氧化碳，二氧化氮和二级有机气溶胶（SOA）的形成，这是颗粒物质的关键组成部分（PM）。直径不到2.5微米的PM暴露导致2015年全球420万人死亡，英国有29,000人死亡。对流层臭氧也是一种重要的温室气体（辐射强迫约25％的二氧化碳），是羟基自由基的主要来源（自然的洗涤剂），对农作物和生态系统有害，仅通过过氧自由基的反应而产生。很大一部分PM在本质上是次要的（即通过化学氧化产生的），其中大部分是SOA。尽管如此，尽管其重要性，但在模型中，过氧自由基化学反应仍然很糟糕，并且在模型中没有很好地代表，并且需要改善的机械理解以改善空气污染的预测并更好地评估拟议干预措施和长期变化的影响。为了解决这个问题，在此提案中，我们将开发新的仪器来测量过氧自由基，在清洁和污染的环境中进行现场研究，并进行有针对性的实验室室实验。该野外工作将包括参加乌克里/大都会办公室战略优先基金清洁空气计划。我们将提供RO2的现场测量作为模型计算的靶标，而RO2过程的新动力学数据作为模型的输入。大气中最小，最丰富的有机过氧自由基是甲基过氧（CH3O2），它是由羟基自由基与甲烷的反应直接形成的。 CH3O2与一氧化氮的反应构成了最重要的对流层原位臭氧来源之一。尽管它的重要性，但CH3O2从未在大气中直接测量过，在此提案中，我们将开发一种现场工具，以便第一次这样做，并将其部署在远程，干净的环境和污染的城市中心中。较大的过氧自由基，称为RO2，也是臭氧和次要有机气溶胶的重要前体，我们还将测量该田间RO2浓度的总和。高氧化的分子（HOMS）源自一系列天然或人为over的氧化，源自自然或人为over的氧化，这是了解如何形成SOA的核心。过氧自由基构成了HOM的重要组成部分，但是HOM样RO2的去除机制高度不确定。有针对性的实验室研究将增强现场工作，其中使用单个VOC或VOC组合来在一系列NOX下生成类似HOM的RO2，以确定动力学速率和单个HOM-RO2物种的能力和产量。使用这种野外和室内研究的组合，我们将进一步验证RO2转换的机制的第二个组合，以进一步验证o2的机制的代表。该提案汇集了利兹和曼彻斯特群体的领先互补专业知识，他们在现场测量中都有丰富的经验，对气体和气雾剂过程的实验室室测量以及使用气体和使用气体的数值建模。