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.

在这项提案中，我们的目标是实现更好的机制理解过氧自由基的行为，一个关键的家庭的大气中间体，中央了解对流层氧化化学的挥发性有机化合物（VOCs）。暴露于空气污染中每年导致全球700万人死亡。过氧自由基化学控制二次污染物臭氧、二氧化氮和二次有机气溶胶（SOA）的形成，SOA是颗粒物（PM）的关键成分。2015年，暴露于直径小于2.5微米的PM导致全球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（辐射强迫约为二氧化碳的25%），是羟基自由基（天然洗涤剂）的主要来源，对作物和生态系统有害，并且仅通过过氧自由基反应产生。很大一部分PM是二次性的（即通过化学氧化产生），其中大部分是SOA。然而，尽管其重要性，过氧自由基化学仍然知之甚少，在模型中没有很好地表示，需要提高机械的理解，以改善空气污染的预测，并提供更好的评估建议的干预措施和排放量的长期变化的影响。为了解决这个问题，在本提案中，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实地研究，并进行有针对性的实验室实验。实地工作将包括参与UKRI/Met Office战略优先基金清洁空气计划。我们将提供现场测量的RO 2作为模型计算的目标，和新的动力学数据RO 2过程作为输入models.The最小和最丰富的有机过氧自由基在大气中的甲基过氧（CH 3 O2），这是直接形成的羟基自由基与甲烷的反应。CH 3 O2与一氧化氮的反应是对流层臭氧最重要的原位来源之一。尽管它的重要性，CH 3 O2从来没有被直接测量在大气中，在这个建议中，我们将开发一个现场仪器，这样做的第一次，并部署在偏远，清洁的环境和污染的城市中心。较大的过氧自由基，统称为RO 2，也是臭氧和二次有机气溶胶的重要前体，我们还将测量RO 2浓度的总和在外地。高度氧化的分子（HOM）来自一系列自然或人为VOCs的氧化是理解SOA如何形成的核心。过氧自由基是HOM的重要组成部分，但HOM类RO 2的去除机制还很不确定。现场工作将通过有针对性的实验室室室研究来增强，其中单独的VOC或VOC的混合物用于在一系列NOx下产生HOM-like RO 2，以确定HOM-RO 2物种清除的动力学速率和产量。使用这种现场和室内研究的组合，我们将进一步验证RO 2转化的当前机制的代表性，提高模型在氮氧化物浓度范围内计算臭氧和二次有机气溶胶形成率的能力。该提案汇集了来自利兹和曼彻斯特的领先互补专业知识，他们在现场测量、气体和气溶胶过程的实验室测量以及使用气体和耦合气体-气溶胶机制的数值模拟。