A Novel Controlled Thermal Desorption Technique for Evaluation of Organic Aerosol Component Volatility and Absorptive Partitioning

大气中的颗粒物质对气候和人类健康都有重大影响;特别是较细的颗粒物质（直径小于1微米）是造成大部分辐射和空气质量影响的原因。虽然无机组分易于定量，但有机组分占颗粒材料的大部分，通常大于总质量的50%。这一部分的量化或描述非常差。已知一些有机材料直接排放到大气中，因此被称为主要材料。这通常是总有机气溶胶质量的一小部分，其余部分包括“次要”组分（气溶胶是颗粒和气体组分的总和）。次要组分可以以多种方式定义，但有用的工作定义是它们是从气相进入颗粒的组分，或由从气相进入颗粒的组分在颗粒中形成的组分。二次有机气溶胶（SOA）组分形成的吸收分配模型已被广泛应用，并发现提供了一个有用的框架来解释气体到粒子的转换过程。最近有一个假设的重要途径的凝聚相反应和潜在的形成这些次要成分的反应性吸收，这将影响SOA形成的可逆性和解释SOA形成的吸收分区单独的能力。在曼彻斯特气溶胶室，我们最近注意到一些有趣的结果稀释SOA样品。由于吸收分配的预测，预计SOA质量的减少将超过由于挥发性更强的组分的蒸发而稀释的量。这在我们的实验中还没有观察到在几个生物前体系统，具有非常重要的大气影响。如果吸收分区是证明无法解释室的结果，那么许多模型的大气有机气溶胶行为的基础上室产量数据将有问题。以前的实验已经使用热扩散器来探测SOA的波动性，并粗略地推断SOA形成的可逆性。建议设计和建造一种新型的热扩散器系统，结合控制稀释，探测在生物和人为有机前体的室光氧化中形成的二次有机气溶胶组分的挥发性。扩散管系统的特点是使用已知的组成和性能的颗粒在实验室中产生的耦合之前，它的曼彻斯特气溶胶室建立广泛接受的气溶胶形成的吸收分区模型的有效性。扩散管系统预期的上级性能将适合于量化组分挥发性，并通过将其耦合到稀释实验中的腔室，用于评估吸收分配理论预测的可逆性。

Particulate material in the atmosphere has a major effect on both climate and human health; specifically the finer particulate material (below around one micron in diameter) being responsible for the majority of the radiative and air quality impacts. Whilst inorganic components are readily quantified, organic components comprise a large fraction of the particulate material, normally greater than 50% of the total mass. This fraction is very poorly quantified or described. Some of the organic material is known to be emitted directly into the atmosphere and is therefore known as primary material. This is normally a minority of the total organic aerosol mass, the rest comprising 'secondary' components (aerosol being the sum of the particulate and gaseous components). Secondary components may be defined in a number of ways, but a useful working definition is that they are the components that have entered the particles from the gas phase or have been formed in the particle from components that have entered the particles from the gas phase. The absorptive partitioning model of secondary organic aerosol (SOA) component formation has been widely applied and found to provide a useful framework for explanation of the process of gas to particle conversion. More recently there has been a postulation of significant pathways for condensed phase reaction and potential formation of these secondary components by reactive uptake which would impact on the reversibility of SOA formation and the ability to explain SOA formation by the absorptive partitioning alone. In the Manchester aerosol chamber, we have recently noticed some interesting results on dilution of SOA samples. Because of the predictions of absorptive partitioning, it would be expected that SOA mass would reduce more than the amount by which it has been diluted owing to evaporation of more volatile components. This has not been observed in our experiments in several biogenic precursor systems and has very significant atmospheric implications. If absorptive partitioning is demonstrably incapable of explaining the chamber results, then many models of atmospheric organic aerosol behaviour based on chamber yield data will have problems. Previous experiments have used thermal denuders to probe the SOA volatility and loosely infer reversibility of SOA formation. It is proposed to design and construct a novel thermal denuder system to probe, in combination with controlled dilution, the volatility of secondary organic aerosol components formed in the chamber photo-oxidation of biogenic and anthropogenic organic precursors. The denuder system will be characterised using particles of known composition and properties generated in the laboratory prior to coupling it to the Manchester aerosol chamber to establish the validity of the widely accepted absorptive partitioning model of aerosol formation. The anticipated superior performance of the denuder system will be suitable for quantifying component volatility and, by coupling it to the chamber in dilution experiments, for assessing the reversibility predicted by absorptive partitioning theory.