单细颗粒物的捕获、悬浮、控制、老化过程及其理化性质的精确测量

In the formation of haze in China, one focus is how to understand the transfomation of volatile organic componds (VOCs) to semi-volatile organic componds (SVOCs), which allows the condensation of VOCs, leading to explosive growth of PM2.5, deacrease of invasibility, and environmental degradation. During the condesation of VOCs, how to achive the saturated vapor pressure of SVOCs, the Henry's constant of VOC gas-liquid equilibrium, the uptake coefficient of trace gas at aerosol interface, and the extinction coefficient in aerosol aging are the key problems in understanding the PM2.5 formation machanism in China. In this project, Laser suspension and electrodynamic balance suspension technology are utilized to capture and suspend single aerosol particle. To solve the key scintific problems in gas pahse condensation, gas-liquid or gas-solid equilibrium, and aerosol interface reaction processes, the ambient conditions of particle are ajusted to accurately contral the phase, composation, size and concentration of the single aerosol particle. By analysising spectral information such as spontaneous Raman scattering, stimulated Raman scattering and cavity-ring-down spectroscopy, we can measure important physical and chemical parameters (for example, the saturated vapor pressure of SVOCs, the Henry's constant of VOC gas-liquid equilibrium, the uptake coefficient of trace gas at aerosol interface, hygroscopic growth factor, and the extinction coefficient) of the single aerosol particle, in order to understand the corralations beteen these parameters and the chemical coposation, size, pahse state, temperature and environment relative humidity of the particle, provide basic data for knowing the formation machanism of haze.

我国雾霾的形成，一个瓶颈问题就是挥发性有机物（VOC）如何转换为低挥发性有机物，进而发生气粒转化，导致爆发式PM2.5增长，引起能见度急剧下降、空气质量恶化。如何获得气粒转化过程中低挥发性有机物饱和蒸汽压、VOC气液分配平衡亨利系数、气溶胶界面对痕量反应气体摄取系数、以及老化过程中消光系数，对于认清我国PM2.5形成机制，具有重要的科学意义。本项目利用光悬浮和电悬浮技术，捕获、悬浮单个气溶胶微粒，控制其周围环境的氛围，针对气粒转化、气粒分配平衡、气粒化学反应等过程中的关键科学问题，原位获得相态、组成、尺度、浓度可以精确控制的单个气溶胶颗粒物自发拉曼、受激拉曼、光腔衰荡光谱等信息，测量低挥发性有机物的饱和蒸汽压、挥发性有机物的亨利系数、与臭氧等气体反应的摄取系数、吸湿增长因子、消光系数等重要理化参数，以及这些参数与化学组成、尺度、相态、温度、相对湿度的依赖关系，为揭示雾霾的形成机制提供数据。

我国雾霾的形成过程中，细颗粒物的形成机制是一种复合的反应机制，既包含伦敦雾的反应机制，也包含洛杉矶的光化学烟雾形成机制，还有很多界面反应机制。本项目利用光镊悬浮技术，压力脉冲技术，显微共聚焦拉曼测量技术，衰减全反射红外测量技术等捕获，悬浮单个气溶胶微粒，控制其周围环境的氛围，对其老化过程及其理化性质进行测量，进行了悬浮粘性气溶胶颗粒中1，2，6-己三醇的挥发性进行了研究以及甘油在悬浮和器壁上沉积的甘油/硝酸钠/水液滴间的重新分配研究等，对玻璃态气溶胶颗粒的扩散系数和粘性的理化性质进行精确测量，对气溶胶颗粒中的传质过程挥发性界面反应过程相内反应过程酸度的测定吸湿性相变过程挥发性界面过程等进行了深入的观测以及研究。