Silicon-containing secondary organic aerosols in ambient air (Si-SOA)

这个泵启动项目将与中国大气物理研究所傅平清教授领导的中国领先研究小组开展新的合作。我们的目标是通过在IAP-CAS和UoB使用新技术，首次提供关于通过光化学大气处理形成含硅二次有机气溶胶（si - soa）的明确证据。更广泛的项目背景是氧化含硅挥发性有机化合物（Si-VOCs），它广泛用于个人护理产品和工业应用。Si-VOCs是室内空气中含量最多的VOCs，在中国的特大城市，Si-VOCs的浓度可超过10微克/立方米（这是非常高的）。Si-VOCs可被羟基自由基氧化形成二次有机气溶胶（SOAs），是造成区域性雾霾污染的主要原因之一。我们目前的NERC项目中国大城市空气污染物的来源和排放- airpollo -Beijing (NE/N007190/1)（2016 - 2020）整合了最新的建模，通量测量，卫星检索，塔垂直剖面测量和化学输送建模，以前所未有的细节和准确性全面了解北京空气污染物的来源和排放。作为伯明翰大学项目的一部分，我们分析了冬季运动（2016年11月至12月）收集的单个颗粒的化学成分，发现50%的细颗粒含有硅，质量分数为> 0.01。这表明硅可能在细颗粒的形成中起重要作用，而细颗粒会造成广泛的雾霾，对人体健康造成不利影响。我们还发现，在中国大城市下风处收集的个别富硫颗粒中，硅以涂层的形式存在，而不是以固体颗粒的形式存在，这表明硅不是直接从主要来源排放的（即在大气中形成）。这些新发现促使我们假设环境空气中二次颗粒中的硅是由气相含硅voc的化学处理形成的。Si-SOA项目将严格检验这一假设。为了做到这一点，我们将首次应用一系列新技术来研究硅的细颗粒。我们将使用STEM（扫描透射电子显微镜）和NanoSIMS（纳米二级离子质谱仪）来确定大气细颗粒中的硅，并确认单个二级颗粒中的硅是否以有机硅的形式存在。如果得到证实，这将为通过大气处理形成硅有机气溶胶提供“确凿的证据”。我们还将应用ESI-HRMS（电喷雾电离-高分辨率质谱仪）来鉴定细颗粒中含硅的有机分子，然后气相色谱-质谱仪来量化在APHH-China活动期间收集的选定细颗粒样品中ESI-HRMS鉴定的si - soa的浓度。Si-SOA项目将通过确认细颗粒中硅氧烷氧化产物的存在并量化其浓度，为AIRPOLL-Beijing增加价值。它将更好地了解二次有机气溶胶的来源，这是airpoll -北京的一个关键目标。该项目将包括PI /研究人员的交流，以详细计划和执行实验，然后讨论发表。该提案是在SHI和FU于2017年5月在北京举行的会议上讨论后制定的，该会议是由发现硅作为单个次级富硫酸盐颗粒的涂层以及在超过50%的单个细颗粒中检测到硅而发起的（见上文）。除了具体的科学目标之外，Si-SOA还将培养英国研究小组和IAP的主要中国研究人员之间不断发展的合作，并有可能在未来建立联系。

This Pump-Priming project will initiate a new collaboration with a leading Chinese research group led by Prof Pingqing Fu at Institute of Atmospheric Physics (IAP-CAS). Our aim is to provide definitive evidence, for the first time, on the formation of silicon-containing secondary organic aerosols (Si-SOAs) via photochemical atmospheric processing by using the novel techniques at the IAP-CAS and the UoB. The wider project context is the oxidation of Si-containing volatile organic compounds (Si-VOCs), which are widely used in personal care products and industrial applications. Si-VOCs are the most abundant VOCs in indoor air and its concentration in Chinese megacities can be over 10 microgram per cubic meter (which is extremely high). Si-VOCs can be oxidised by hydroxyl radicals and form secondary organic aerosols (SOAs), which contributes to the regional haze pollution. Our current NERC project Sources and Emissions of Air Pollutants in a Chinese Megacity - AIRPOLL-Beijing (NE/N007190/1) (2016 - 2020) integrates recent modelling, flux measurements, satellite retrievals, tower vertical profile measurements, and chemical transport modelling to provide thorough understanding of the sources and emissions of air pollutants in Beijing, at unprecedented detail and accuracy. As part of this project awarded to the University of Birmingham, we analyzed the chemical composition of individual particles collected during the winter campaign (Nov-Dec 2016) and found that >50% the fine particles contain silicon with mass fraction > 0.01. This suggests that silicon may play an important role in the formation of fine particles, which cause widespread smog / haze and lead to adverse human health effects. We also discovered that silicon is present as a coating, rather than as a solid grain, in individual sulphur-rich particles collected downwind of Chinese megacities, suggesting that the silicon is not directly emitted from primary sources (i.e., formed in the atmosphere). These new findings promoted us to hypothesize that silicon in the secondary particles in ambient air is formed from chemical processing of gas phase Si-containing VOCs. Si-SOA project will rigorously test this hypothesis. To do this, we will apply a series of novel techniques to study silicon in fine particles for the first time. We will use STEM (Scanning Transmission Electron Microscopy) and NanoSIMS (Nanoscale Secondary Ion Mass Spectrometer) to speciate silicon in atmospheric fine particles and confirm whether silicon in individual secondary particles is present as organosilicon. If confirmed, thiswill provide "smoking gun" on the formation of silicon organic aerosol by atmospheric processing. We will also apply the ESI-HRMS (Electrospray ionisation - high resolution mass spectrometer) to identify Si-containing organic molecules in fine particles and then gas chromatography - mass spectrometer to quantify the concentration of Si-SOAs identified by ESI-HRMS in selected fine particle samples collected during the APHH-China campaigns. Si-SOA project will add value to the AIRPOLL-Beijing by confirming the presence and quantify the concentration of siloxane oxidation products in fine particles. It will provide a better understanding on the sources of secondary organic aerosols, a key objective of AIRPOLL-Beijing. The project will consist of PI / research staff exchanges to plan and carry out the experiments in detail, followed by discussions on publication(s). This proposal has been developed following discussions between SHI and FU at meetings in Beijing in May 2017, which was initiated by discovery of silicon as coating in individual secondary sulphate-rich particles and the detection of silicon in over 50% of individual fine particles (see above). In addition to the specific science goals, Si-SOA will nurture a developing collaboration between UK groups and leading Chinese researchers at IAP, with potential for future links.