颗粒物的吸湿性是联系颗粒物微物理、化学参数的重要纽带之一，在雾霾的形成过程中起着关键性作用。柴油机排气颗粒物作为大气细颗粒物的主要来源之一，有其独特的吸湿性。本项目对柴油机排气颗粒物的吸湿性质和机理进行研究，以探明颗粒物引起大气环境问题的内在驱动力。研究大气温湿度与老化对颗粒物吸湿增长因子和质量变化的影响，建立柴油机颗粒物吸湿性与燃油类型、硫含量及工况之间的关联性；研究水蒸汽在颗粒物表面的吸附动力学和热力学特征，确定合适的动力学模型及饱和吸附量、吸附速率常数等动力学参数，计算焓变、熵变和吉布斯自由能等热力学参数。测量颗粒物的形貌、粒度分布、孔隙结构、比表面积、化学基团、官能团等表面活性吸附结构参数；通过测量气/液/固三相界面体系的接触角，计算颗粒物的表面自由能，对颗粒物的吸附性能进行评价。研究结果对于阐明颗粒物与水蒸汽之间的吸湿行为在雾霾形成中的作用机理具有重要的理论意义。

Hygroscopic properties of atmospheric particles are the bridge of micro-particle physics and chemical parameters, and play a key role in the formation of fog haze. Diesel exhaust particulates, one of main sources of atmospheric fine particles, have their unique hygroscopicity. The hygroscopic properties and mechanisms of diesel exhaust particulate matters are investigated to verify the inner impulse causing the atmospheric environment problem. The effects of the atmospheric temperature and humidity and aging on the hygroscopic growth factor and mass change of the particles are researched. The relevance between the hygroscopicity of diesel exhaust particles and fuel type, sulfur content of fuel, and engine operation are established. The adsorption kinetics and thermodynamics of water vapor onto the particle surface are studied. A suitable kinetics model is determined including saturated absorption capacity and absorption rate. The enthalpy, entropy and Gibbs free energy are calculated. The surface activity absorption parameters of the particles are measured including morphology, size distribution, pore structure, specific surface area, radical group and functional group. By measuring the contact angle among three-phase boundaries, the particle surface free energy is calculated, and the absorption performance of the particles is evaluated. The results have important theoretical significance value to clarify the hygroscopic behavior between the particles and water vapor and its effect on fog haze formation.