基于云雾过程外场观测的有机物液相反应机制研究

Formation of secondary organic aerosol in the aqueous phase (aqSOA) by cloud and fog processes imposes an important influence on climate and air quality. The previous studies focused on the laboratory experiment and model simulation. Simultaneous in-situ observations of cloud/fog and aerosol particles are still rare. In this project, the observation platform of aqueous reaction of organic compounds during cloud/fog processes will be developed. We focus on the hill cap cloud characterized by high O3 level, and fog by high NOx pollution. The molecular formulas and chemical compositions of aqSOA and their precursors during cloud/fog onset, evolution and dissipation stages will be investigated. Cloud/fog droplets are sampled by a ground-based counterflow virtual impactor and the submicron-sized residues are analyzed by on-line single particle aerosol mass spectrometer (SPAMS) and off-line ICP-MS, FT-ICR-MS, GC-MS and so on. During cloud-free periods, the submicron out-of-cloud aerosol is analyzed using these instruments. The molecular markers, which could trace aqSOA under different pollution characterization, will be determined. The influence of cloud droplet acidity, size, mixing state, dissolved precursors, and atmospheric oxidation capacity on the formation and evolution of aqSOA during different cloud/fog stages will be discussed. The key species and environmental factors will be revealed in this project. These results will provide scientific base for the study on the formation of complex air pollution and formulation of effective control strategies.

通过云雾液相反应形成的二次有机气溶胶（aqSOA）对气候和空气质量有重要影响。但目前对aqSOA形成机制方面的研究还非常薄弱，特别是缺乏基于云雾过程的外场观测数据。本项目拟建立先进的云雾过程有机物液相反应研究综合观测平台，以广东为研究靶区，重点研究以O3污染为特色的山帽云和以NOx污染为特色的城市雾从发生、发展到消散整个过程aqSOA的形成和演化机制。利用FT-ICR-MS、ICP-MS和GC-MS等离线及地用逆流虚拟撞击器-单颗粒气溶胶质谱仪在线分析等多种手段，分析云雾水、活性云雾滴残余物和间隙颗粒的粒径和化学组成，筛选出能够用于指示高O3和高NOx污染特征的aqSOA示踪物质，探讨云雾滴酸度、大小、混合状态、前体物、大气氧化性等对云雾过程aqSOA形成和演化的影响，揭示影响云雾过程aqSOA形成的关键反应物种和环境因子，为大气复合污染成因机制的研究及相应控制策略的制定提供科学依据。

通过云雾液相反应形成的二次有机气溶胶（aqSOA）对气候和空气质量有重要影响。但目前对aqSOA形成机制方面的研究还非常薄弱，特别是缺乏基于云雾过程的外场观测数据。本项目首先是建立了研究云雾过程有机物液相反应的外场观测平台，通过对广东南岭高山站点、青岛郊区和广州市区大气颗粒物和云雾液滴及间隙颗粒的在线和离线分析，获得了云/雾滴和间隙颗粒的化学组成和分子组成特征，从分子层面，揭示了云雾过程aqSOA的形成机制；利用机器学习、多元线性回归等方法评估了云雾滴酸度、混合状态、前体物、大气氧化性、温度、湿度等对云雾过程aqSOA变化的影响，明确了影响云雾过程典型aqSOA形成的关键前体物和环境因子；筛选出可以指示云雾过程aqSOA和棕色碳形成的分子标志物。本项目的研究结果为大气复合污染成因机制的研究及相应控制策略的制定提供科学依据。