Improvement of composition and property prediction techniques for for Secondary Organic Aerosol (SOA)

气溶胶粒子仍然是气候变化的高度不确定因素，它们通过太阳辐射的散射和吸收直接影响气候，并通过它们作为云凝结核的作用间接影响气候。大气颗粒物负荷对城市空气质量也有严重影响。历史上，人们认为气溶胶颗粒只由无机物质组成。然而，已经发现有机成分可能构成气溶胶成分的很大一部分，根据地点的不同，占细颗粒物的比例从20-60%不等。冷凝有机物质要么直接排放（初级），要么通过冷凝和转化由人为和生物源挥发性有机化合物（二级有机气溶胶：SOA）的光氧化产生的低挥发性和半挥发性产物在现场形成。气体到气溶胶的划分，或SOA的创建，是确定气溶胶颗粒的化学成分和负载的关键。因此，要评估SOA对大气过程、气候和人类健康的影响，就需要详细了解SOA的形成、属性和转换。然而，有机材料可以包含成千上万的化合物，这些化合物大部分尚未被识别，具有广泛的特性。因此，与二次有机气溶胶（SOA）形成相关的化学和物理过程是复杂和多样的，对SOA形成的定量和预测性理解尚不存在，因此代表了大气科学的主要研究挑战！已经确定了与我们对SOA形成的理解相关的关键不确定性。如果化合物的平衡蒸气压足够低，它就会分解成颗粒相。这取决于纯组分的蒸气压，如果化合物在气溶胶相中发生凝聚相反应，则蒸气压会进一步降低，从而增强气体/颗粒的分配。不幸的是，与纯组分蒸气压和混合物的有效挥发性有关的不确定性足以引起气溶胶质量的不确定性，其范围可达4个数量级。蒸汽压力预测技术在很大程度上基于工业工程中使用的与大气无关的化合物，并且在假定的相关凝聚相反应的速率和重要性方面存在很大差距，我们甚至无法使用当前的分析实验室技术来阐明这一点。在本提案中，我们的目标是通过1)使用我们完善和验证的Knudsen液质谱法测量纯组分蒸汽压力来解决这些基本的不确定性。结果数据将被吸收到多特蒙德数据库（DDB）和新的模型修订将由我们的工业合作伙伴进行。2)首次将化学成分与混合物中的挥发性直接联系起来3)评估在大气模式中真正捕获SOA形成所需的复杂性。

Aerosol particles remain highly uncertain contributors to climate change, influencing climate directly by the scattering and absorption of solar radiation and indirectly through their role as cloud condensation nuclei. Atmospheric loading of particulate matter also has serious implications for urban air quality. Historically, it was assumed that aerosol particles were composed only of inorganic material. However, it has been found that organic components may constitute a substantial fraction of the aerosol composition, ranging from 20-60% of the fine particulate matter depending on the location. Condensed organic material is either directly emitted (primary) or formed in-situ by condensation and transformation of low-volatility and semi-volatile products derived from photo-oxidation of anthropogenic and biogenic volatile organic compounds (secondary organic aerosol:SOA). Gas-to-aerosol partitioning, or creation of SOA, is key to determining the chemical composition and loading of aerosol particles. A detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. However, organic material can comprise many thousands, as yet largely unidentified, compounds with a vast range of properties. As a consequence, the chemical and physical processes associated with secondary organic aerosol (SOA) formation are complex and varied, and a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science!Key uncertainties associated with our understanding of SOA formation have been identified. A compound will partition to the particulate phase if its equilibrium vapour pressure is low enough. This is dependent on the pure component vapour pressure, which can further decrease if the compound undergoes condensed phase reactions in the aerosol phase, enhancing gas/particle partitioning. Unfortunately, uncertainties associated with pure component vapour pressures and effective volatility of mixtures are enough to cause uncertainties in aerosol mass spanning up to 4 orders of magnitude. Vapour pressure predictive techniques are largely based on atmospherically irrelevant compounds used within industrial engineering and there is a large gap concerning the rates and importance of postulated relevant condensed phase reactions which we cannot even elucidate on using current analytical laboratory techniques.In this proposal we aim to address these fundamental uncertainties via 1) Measurement of pure component vapour pressures using our well-established and validated method of Knudsen Effusion Mass Spectrometry. The resulting data will be assimilated into the Dortmund Databank (DDB) and new model revisions will be carried out by our industrial partner.2) Directly link chemical composition to volatility within mixtures for the first time3) Assess the complexity required to truly capture the SOA formation in atmospheric models.