Improving our understanding of aerosol formation, transformation and lifetime in the atmosphere

对气相和气相之间的分子组成的分配进行量化，对于在包括空气质量和气雾化材料的无意、固有或有意释放在内的广泛环境中理解气雾剂非常重要。这些排放可能包括汽车排放的蒸气和颗粒物，北方森林有机成分的生物排放，以及爆炸性材料排放的蒸气和颗粒物。相分配不仅控制气溶胶粒子的质量浓度和粒度分布，而且还控制物质从源头向外的输送，以及源物质的化学处理和降解的寿命和速率。最重要的是，这种分配依赖于分子组分随温度变化的蒸汽压，它们与其他气溶胶组分的混合，以及分配对环境条件的依赖，如相对湿度(RH)。尽管对气溶胶科学的整个努力具有核心重要性，但关于气体-颗粒分配和成分蒸气压力的通用和准确模型在很大程度上仍未得到证实。需要新的实验来测量低于1pa的组分的蒸气压力，这些组分代表半挥发性、低挥发性和极低挥发性组分。在本项目中，将使用电动天平测量半挥发性和低挥发性组分(1E-6到1Pa.)的蒸气压，该天平能够在RH(&lt；5%到90%)和温度(250到340K)的大范围内测量几个小时的时间刻度上的颗粒尺寸变化。将对典型的环境气溶胶成分和成分替代品进行测量，最终目的是提供一套增强的性能培训，以完善蒸气压力的预测工具。测量将在不同的条件(相对湿度和温度)下进行，并在典型氧化剂驱动化学转化的情况下进行。这些改进的模型将用于气体-颗粒分配模型，包括运输模型和盒子模型，以了解一旦从源头释放的气溶胶成分的稀释、扩散和寿命。

Quantifying the partitioning of molecular constituents between the gas and vapour phases is important for understanding aerosols in a broad range of contexts including air quality and the unintentional, intrinsic, or intentional release of aerosolised material. These might include anthropogenic emissions of vapours and particles from cars, the biogenic emissions of organic components in a boreal forest, and the release of vapours and particles from explosive materials, respectively. Not only does phase partitioning govern aerosol particle mass concentrations and size distributions, but it governs the transport of material away from source, and the lifetime and rates of chemical processing and degradation of the source material. Most importantly, this partitioning is dependent on the temperature-dependent vapour pressures of the molecular constituents, their mixing with other aerosol constituents, and the dependence of the partitioning on environmental conditions such as relative humidity (RH). Although of central importance to the whole endeavour of aerosol science, versatile and accurate models of the gas-particle partitioning and component vapour pressures remain largely un-validated. New experiments are required capable of measuring the vapour pressures of components below 1 Pa, representing semi-volatile, low-volatility and extremely low-volatility components. In this project, measurements of the vapour pressures of semi-volatile and low volatility components (1E-6 to 1 Pa) will be made using an electrodynamic balance capable of measuring particle size changes of only a few nanometres on a timescale of hours over wide ranges in RH (<5% to 90%) and temperature (250 to 340 K). Measurements will be made for typical environmental aerosol constituents and surrogates of components, with the ultimate aim of providing an enhanced training set of properties to refine predictive tools for vapour pressures. Measurements will be made with varying conditions (RH and temperature) and with exposure to typical oxidants driving chemical transformation. These improved models will be used in models of gas-particle partitioning, including in transport and box models, to understand the dilution, dispersal and lifetime of aerosol constituents once released from source.