Atmospheric chemistry and impacts of volatile and semi-volatile organic compounds: Fellowship extension application

向大气中排放微量物质会对环境产生各种影响，从排放地点的直接健康影响到对大气成分和气候的全球影响。有机化合物，如碳氢化合物，从自然和人为影响的来源大量排放，并有助于许多广为宣传的环境现象，例如，光化学烟雾和全球变暖。据估计，每年约有20亿吨有机物质排放到大气中。自然来源包括来自植被的排放（例如，森林），在考虑全球总排放量时，这些来源占主导地位。人为影响的排放有许多来源，特别是公路运输、汽油和其他燃料的分配、溶剂的使用和一些工业过程。在人口稠密的地区，如英国，来自这些来源的排放是进入大气的有机物质的主要输入。一些排放的有机化合物（例如苯、1，3-丁二烯和“多环芳烃”）已知对人类健康有害，例如作为致癌物。然而，大气中有机物质的化学处理产生了更广泛的影响，导致产生各种产品，有时被称为“二次污染物”。特别重要的是“臭氧”的产生，它是由阳光引发的挥发性有机化合物（VOC）和氮氧化物（NOx）的氧化产生的。臭氧是光化学烟雾的主要成分，已知对人类健康、植被（如农作物）和材料有不利影响。它也是导致全球变暖的“温室气体”。这些氧化过程的另一个副产品是产生不挥发的有机氧化产物，这可能会增加空气中颗粒的质量。大气中的颗粒物通过光和紫外线辐射的散射对能见度和气候产生重要影响，并且由于细颗粒物可被吸入肺部，因此也对健康产生直接影响。目前的研究金方案旨在提高我们对排放到大气中的有机材料的数量影响的认识和评估，并在这一领域取得了重大进展。这些都是通过（i）有机化合物氧化的实验室研究，（ii）高度详细的化学机理的发展，（称为“主化学机制，MCM”），该机制利用实验数据来建立有机化合物如何被氧化以及二次污染物如何被氧化的明确描述。（iii）在大气模型中使用化学机制来研究有机化合物的影响，以及可以做些什么来减少这些影响。拟议延长研究金期限的目的是在这项工作的基础上，系统地制定一系列不同细节的相容化学机制。这些将包括MCM的扩展版本（提供化学的详细描述，但在具有简单空气质量传输描述的模型中运行最有效），通过高度简化的大气化学表示，可以有效地应用于具有复杂空气质量传输描述的全球模型，如气象局的统一模型（UM）。通过这种方式，高度简化的化学过程将可追溯到MCM，并将间接基于大气化学实验研究的结果。这将使人们更有信心相信这种机制在适合低层大气的各种条件下以及在排放和气候方面的预测变化所产生的各种条件下的性能（在臭氧和微粒形成方面）。

The emission of trace materials into the atmosphere can have a variety of influences on the environment, ranging from immediate health impacts in the locality of the release to world-wide effects on atmospheric composition and climate. Organic compounds, such as hydrocarbons, are emitted in large quantities from both natural and human-influenced sources, and contribute to many of the well-publicised environmental phenomena, for example, photochemical smog and global warming. It is estimated that about 2 billion tonnes of organic material are emitted into the atmosphere each year. Natural sources include emissions from vegetation (e.g., forests), and such sources dominate when total global emissions are considered. Human-influenced emissions result from many sources, in particular road transport, distribution of petrol and other fuels, solvent usage and some industrial processes. In populated regions, such as the UK, emissions from such sources represent the major input of organic material into the atmosphere. Some emitted organic compounds (e.g. benzene, 1,3-butadiene and 'polycyclic aromatic hydrocarbons') are known to be detrimental to human health, for example as carcinogens. However, a much wider impact results from the chemical processing of organic material in the atmosphere, which leads to the generation of a variety of products, sometimes known as 'secondary pollutants'. Of particular importance is the generation of 'ozone', which is produced from the sunlight-initiated oxidation of volatile organic compounds (VOC) and nitrogen oxides (NOx). Ozone is a major component of photochemical smog, and is known to have adverse effects on human health, vegetation (e.g. crops) and materials. It is also a 'greenhouse gas' which contributes to global warming. Another by-product of these oxidation processes is the generation of involatile organic oxidation products which can contribute to the mass of airborne particles. Particulate matter in the atmosphere has an important influence on visibility and climate, through the scattering of light and UV radiation, and also has direct health implications because fine particles can be inhaled into the lung. The current fellowship programme set out to improve our knowledge and assessment of the quantitative impacts of organic material emitted into the atmosphere, and has made major advances in this area. These have been achieved by a combination of (i) laboratory studies of the oxidation of organic compounds, (ii) the development of highly detailed chemical mechanism (known as the 'Master Chemical Mechanism, MCM') which makes use of experimental data to build up an explicit description of how the organic compounds are oxidised and how the secondary pollutants (e.g. ozone, particulate) are formed, and (iii) the use of the chemical mechanism in models of the atmosphere to investigate the impacts of the organic compounds, and what can be done to reduce these impacts. The proposed fellowship extension aims to build upon this work by systematically developing a series of compatible chemical mechanisms of varying detail. These will range from an extended version of the MCM (which provides a detailed description of the chemistry, but which is most efficiently run in models with simple descriptions of air mass transport), through to highly simplified representations of atmospheric chemistry which can be applied efficiently in global models with sophisticated descriptions of air mass transport, such as the Meteorological Office's Unified Model (UM). In this way, the highly simplified chemistry will be traceable through to the MCM, and will be indirectly based on the results of experimental studies of atmospheric chemistry. This will allow improved confidence to be placed in the performance of such mechanisms (in terms of ozone and particulate formation) for the range of conditions appropriate to the lower atmosphere, and resulting from projected changes in emissions and climate.