Are glyoxal and methylglyoxal critical to the formation of a missing fraction of SOA (Secondary Organic Aerosol)?: (Pho-SOA).

大气气溶胶在地球大气层中无处不在。它们是由液体和固体颗粒物质的复杂胶体混合物组成的，了解它们的化学和物理性质对于阐明它们对环境和健康的影响至关重要。然而，尽管在过去十年中进行了大量的科学努力，但由于存在很大的不确定性，而且缺乏关于其来源、组成(因此物理性质)和形成机制的基础知识，气溶胶对地球大气的真正影响尚未阐明。最近的实验结果表明，有机气溶胶在自然界中主要是次要的，可以占环境大气气溶胶总量的很大一部分(10%-70%)。然而，目前的模型严重低估了二次有机气溶胶的产量及其形成速度。乙二醛(GLY，CHCHO)和甲基乙二醛(MGLY，CH3COCHO)等轻质挥发物的吸附或齐聚反应已被证明是全球SOA的潜在重要来源，以证明这种分歧是合理的。由于α-二羰基引起的颗粒生长的大小、类型(可逆或不可逆)和机理仍然是实质性的问题。这个项目的目的是定量地证明气溶胶中GLY和MGLY的不同吸收可以解释模型中缺失的SOA的很大一部分的假设。为了解决这一问题，该项目将进行一系列广泛的室外室内实验(在高度仪表化的欧洲光反应堆EUPHORE中)，以解决以前研究的主要限制。实验工作将通过使用主化学机制(MCM15)的详细室内模拟来支持。Gly或MGLY将被直接引入到反应室中，或通过OH+炔烃的反应原位生成。室内实验将在EUPHORE中有(或没有)自然太阳辐射的情况下进行，以调查这些二羰基化合物的异相反应吸收和SOA生长是否被光化学激活(光敏化)和相对湿度相关。利用新型化学电离反应(飞行时间和四极杆)质谱仪(CIR-MS)、气溶胶飞行时间质谱仪(ATOFMS)、傅立叶变换离子回旋共振质谱仪(FT-ICR-MS)、液相-离子陷阱质谱仪(LC-MSN)和激光诱导荧光(LIF)，将监测前体和氧化产物以及HOx自由基(OH+HO2)的气体和气溶胶相演变。模型敏感性模拟将使用MCM与吸收气-气溶胶分配的表示法相结合，并结合本研究结果中的参数，以调查通过异质吸收二羰基化合物而形成的SOA对城市环境的大气影响，其中芳香族化合物(二羰基的重要来源)已被认为是城市SOA的主要来源。

Atmospheric aerosols are ubiquitous in the Earth's atmosphere. They are made up of complex colloidal mixtures of liquid and solid particulate matter and understanding their chemical and physical properties is crucial in elucidating their environmental and health impacts. However, despite much scientific effort over the last decade, the true impact of aerosols on the Earth's atmosphere is yet to be elucidated owing to large uncertainties and lack of fundamental knowledge on their sources, composition (hence physical properties) and formation mechanisms. Recent experimental findings indicate organic aerosols (OA) are predominantly secondary in nature and can account for a significant fraction (10-70%) of total ambient atmospheric aerosol. However, current models significantly underestimate SOA (Secondary Organic Aerosol) production and their rate of formation. Accretion or oligomerization reactions of light weight volatiles such as glyoxal (GLY, CHOCHO) and methylglyoxal (MGLY, CH3COCHO), which have been shown to be a potentially important source of global SOA, have been proposed to justify such disagreement. The magnitude, type (reversible or irreversible) and mechanism of particle growth owing to alfa-dicarbonyls are still substantial questions. The aim of this project is to quantitatively demonstrate the hypothesis that heterogeneous uptake of GLY and MGLY in aerosols can explain a significant fraction of the missing SOA in models. To address this, the project will carry out an extensive series of outdoor chamber experiments (in the highly instrumented European Photoreactor, EUPHORE) that will address the main limitations of previous studies. The experimental work will be supported by detailed chamber simulations using the Master Chemical Mechanism (MCM15). GLY or MGLY will either be introduced directly into the chamber or generated in-situ by the reaction of OH + alkynes. The chamber experiments will be carried out in the presence (and absence) of natural solar radiation in EUPHORE in order to investigate whether heterogeneous reactive uptake of these dicarbonyl compounds and SOA growth is photochemically activated (photosensitized) and relative humidity dependent. The gas and aerosol phase evolution of the precursor and oxidation products, together with HOx radicals (OH + HO2) will be monitored using novel chemical ionisation reaction (time-of-flight and quadrupole) mass spectrometry (CIR-MS), Aerosol Time of Flight Mass Spectrometry (ATOFMS), Fourier Transform Ion Cyclotron resonance Mass Spectrometry (FT-ICR-MS), liquid chromatography-ion trap mass spectrometry (LC-MSn) and laser induced fluorescence (LIF). Model sensitivity simulations using the MCM coupled to a representation of absorptive gas-to-aerosol partitioning incorporating parameterisations from the findings of this study, will be carried out in order to investigate the atmospheric implications of SOA formation via heterogeneous uptake of dicarbonyl compounds for urban environment where aromatics compounds (significant sources of dicarbonyls) have been proposed as key urban SOA sources.