Does Ozonolysis Chemistry affect Atmospheric Marine Boundary Layer Sulphur Cycling ?

该泵启动项目将启动与中国领先研究小组（中国科学院广州地球化学研究所王新明教授）的新合作。我们的目标是评估一个新的大气反应的重要性，最近由英国团队通过当前的NERC研究资助，使用广州独特的模拟室设施发现。更广泛的项目背景是硫物质的大气处理。众所周知的大气化学过程会分解硫物质--二甲基硫（DMS）或二氧化硫等分子--这些反应由气相中的OH自由基驱动，并形成硫酸盐气溶胶颗粒，这些颗粒会散射阳光并催化云滴的形成--因此硫物质的处理对气候产生重大影响。硫磺加工产生硫酸也会导致雨水酸度增加。我们目前的NERC项目旨在研究一组新的化学反应物对硫磺加工的影响-稳定的Criegee中间体（SCIs）。SCIs是由烯烃-臭氧反应（在整个边界层中发现）和烷基碘光解（在海洋边界层中）形成的，可以作为大气氧化剂，如OH，引发SO2等物质的处理。我们目前的项目的动机是最近发现SCI + SO2反应比以前认为的快三个数量级-但SCI行为尚未在现实的大气条件下进行测试。我们的方法是使用EUPHORE大气模拟室（西班牙的一个200立方米的反应器，其中可以引入人工大气-包含例如烯烃，臭氧和SO2 -并配备仪器以监测不断变化的化学成分）。在EUPHORE中，我们研究了SCIs与SO2、H2O的反应及其热分解--到目前为止已经有五篇论文--还发现由异戊二烯-臭氧反应形成的SCIs与DMS反应。DMS是主要的天然硫排放物（与火山SO2），因此DMS氧化的任何增强（例如SCIs和OH）将增加硫酸盐气溶胶形成的速率并改变其空间分布，这对大气成分和气候具有潜在的重大意义。然而，EUPHORE的仪器无法确定SCI + DMS反应的产物;我们也无法评估它们对用于形成SCI的烯烃的依赖性。在这个项目中，我们建议使用新开发的室在广州，以解决这些不确定性-GIG室仪器可以检测气相和凝相DMS氧化产物，最近已被用于研究SCI化学在汽车尾气。该项目将包括PI /研究人员交流，以详细计划和模拟室实验，然后通过模拟室测量来探测广州的SCI-DMS系统。这些实验将最终确定这种新反应在真实大气边界层条件下的重要性。这一提议是在Bloss和Wang在北京的会议上进行讨论以及Bloss于2015年3月访问GIG设施后提出的。除了具体的科学目标外，它还将促进英国团体（在进行模拟室实验方面具有丰富的专业知识）与GIG的中国领先研究人员（拥有独特的室设施）在大气化学方面的合作，未来有可能建立联系，例如在即将到来的NERC-Newton-NSFC“中国特大城市的城市空气污染”项目中。中国正在迅速成为一个研究领先的国家，这种参与与顶级科学家（即，中国科学院大气科学研究所（中科院大气科学研究所），从而支持英国在大气科学领域的国际声誉。

This Pump-Priming project will initiate a new collaboration with a leading Chinese research group (Prof Xinming Wang, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences). Our aim is to assess the importance of a new atmospheric reaction, recently discovered by the UK team through a current NERC research grant, using the unique simulation chamber facility available in Guangzhou.The wider project context is the atmospheric processing of sulphur species. Well understood atmospheric chemical processes break down the sulphur species - molecules such as dimethylsulphide (DMS) or SO2 - these reactions are driven by OH radicals in the gas phase, and form sulphate aerosol particles, which scatter sunlight and can catalyse the formation of cloud droplets - so the processing of sulphur species exerts a major influence upon climate. Sulphur processing leading to sulphuric acid also contributes to rainwater acidity.Our current NERC project aimed to investigate the impact of a new set of chemical reactants upon sulphur processing - the Stabilised Criegee Intermediates (SCIs). SCIs are formed from alkene-ozone reactions (found throughout the boundary layer) and alkyl iodide photolysis (in the marine boundary layer), and can act as atmospheric oxidants, like OH, initiating the processing of species such as SO2. Our current project was motivated by the recent discovery that the SCI + SO2 reaction was three orders of magnitude faster than previously thought - but SCI behaviour had not been tested under realistic atmospheric conditions. Our approach was to use the EUPHORE atmospheric simulation chamber (a 200 m3 reactor in Spain, in which an artificial atmosphere may be introduced - containing, for example, alkenes, ozone and SO2 - and fitted with instruments to monitor the evolving chemical composition). In EUPHORE, we have studied reactions of SCIs with SO2, H2O and their thermal decomposition - leading to five papers so far - and also discovered that SCIs, formed from isoprene-ozone reactions, react with DMS.DMS is the dominant natural sulphur emission (with volcanic SO2), so any enhancement in DMS oxidation (e.g. by SCIs, alongside OH) will increase the rate and change the spatial distribution of sulphate aerosol formation, of potentially substantial importance for atmospheric composition and climate. However, the instruments in EUPHORE could not determine the products of the SCI + DMS reaction; nor were we able to assess their dependence upon the alkene used to form the SCI. In this project, we propose to use the newly developed chamber in Guangzhou to resolve these uncertainties - the GIG chamber instrumentation can detect the gas- and condensed-phase DMS oxidation products, and has recently been used for a study of SCI chemistry in vehicle exhausts. The project will consist of PI / research staff exchanges to plan and model the chamber experiments in detail, followed by simulation chamber measurements to probe the SCI - DMS system in Guangzhou. These experiments will definitively determine the importance of this new reaction, under realistic atmospheric boundary layer conditions.This proposal has developed following discussions between Bloss and Wang at meetings in Beijing, and a visit by Bloss to the GIG facility in March 2015. In addition to the specific science goals, it will nurture a developing collaboration between UK groups (with substantial expertise in the conduct of simulation chamber experiments) and leading Chinese researchers at GIG (with unique chamber facilities) in atmospheric chemistry, with potential for future links, for example in the context of forthcoming NERC-Newton-NSFC "Urban Air Pollution in a Chinese Megacity" projects. China is rapidly emerging as a research-leading nation, and this engagement links to top scientists (i.e., within the Chinese Academy of Sciences) thereby supporting the UK's international reputation in atmospheric science.