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中无处不在。它们由液体和固体颗粒物质的复杂胶体混合物组成，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，但由于对气溶胶的来源、组成（因此物理性质）和形成机制缺乏基本知识，气溶胶对地球大气的真正影响仍有待阐明。最近的实验结果表明，有机气溶胶（OA）在本质上主要是次生的，可占大气环境气溶胶总量的很大一部分（10-70%）。然而，目前的模式明显低估了SOA（二次有机气溶胶）的产生及其形成速度。轻质挥发性物（如乙二醛（GLY， CHOCHO）和甲基乙二醛（MGLY, CH3COCHO））的吸积或寡聚反应已被证明是全球SOA的潜在重要来源，有人提出证明这种分歧是合理的。由α -二羰基引起的颗粒生长的大小、类型（可逆或不可逆）和机制仍然是一个实质性的问题。该项目的目的是定量地证明气溶胶中GLY和MGLY的异质吸收可以解释模型中缺失的SOA的很大一部分的假设。为了解决这个问题，该项目将进行一系列广泛的室外室内实验（在高度仪器化的欧洲光反应器，EUPHORE），以解决以前研究的主要局限性。实验工作将通过使用主化学机制（MCM15）进行详细的室内模拟来支持。GLY或MGLY要么直接引入腔室，要么通过OH +炔的原位反应生成。室内实验将在EUPHORE中存在（或不存在）天然太阳辐射的情况下进行，以研究这些二羰基化合物的异质反应性吸收和SOA生长是否光化学激活（光敏化）和相对湿度依赖。前驱体和氧化产物的气相和气溶胶相演变，以及HOx自由基（OH + HO2）将使用新型化学电离反应（飞行时间和四极杆）质谱法（cirr - ms）、气溶胶飞行时间质谱法（ATOFMS）、傅立叶变换离子回旋共振质谱法（FT-ICR-MS）、液相色谱-离子阱质谱法（LC-MSn）和激光诱导荧光（LIF）进行监测。为了研究城市环境中芳香化合物（二羰基的重要来源）的异质吸收对SOA形成的大气影响，我们将使用MCM进行模型敏感性模拟，并结合本研究结果的参数化，以研究芳香化合物（二羰基的重要来源）被认为是城市SOA的关键来源。

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.