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

量化分子成分在气相和汽相之间的分配对于理解广泛背景下的气溶胶非常重要，包括空气质量和气溶胶材料的无意，内在或有意释放。这些可能分别包括汽车的蒸气和颗粒的人为排放、北方森林中有机成分的生物源排放以及爆炸物释放的蒸气和颗粒。相分离不仅决定了气溶胶颗粒的质量浓度和尺寸分布，而且还决定了物质从源的输送，以及源物质的化学处理和降解的寿命和速率。最重要的是，这种分配取决于分子成分的温度依赖性蒸汽压、它们与其他气溶胶成分的混合以及分配对环境条件（例如相对湿度（RH））的依赖性。虽然气溶胶科学的整个努力的核心重要性，多功能和准确的模型的气体颗粒分区和组分蒸汽压力仍然在很大程度上未经验证。需要新的实验能够测量低于1帕的组分的蒸气压，代表半挥发性、低挥发性和极低挥发性组分。在该项目中，将使用电动天平测量半挥发性和低挥发性成分的蒸汽压力（1 E-6至1帕），该天平能够在相对湿度（<5%至90%）和温度（250至340 K）的大范围内测量小时时间尺度上仅几纳米的颗粒尺寸变化。将对典型的环境气溶胶成分和成分替代物进行测量，最终目的是提供一套增强的属性训练集，以完善蒸汽压的预测工具。将在不同条件（RH和温度）下进行测量，并暴露于驱动化学转化的典型氧化剂。这些改进的模型将用于气粒分离模型，包括运输和箱模型，以了解气溶胶成分一旦从源释放后的稀释、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.