有机成分对气溶胶云凝结核活性和雾滴形成的影响

The organic components can significantly affect aerosol cloud condensation nuclei (CCN) activation and activity. This project mainly uses field observation and simulation to explore the variation of aerosol CCN activity against organic components in polluted atmospheric environments. The main contents include (1) time variation of aerosol size-resolved organic components, particle properties and CCN spectra,(2) effects of particle aging and water-soluble organic component changes on aerosol CCN activity,(3) characterization of particle mixing state, relations between hygroscopic factor and mixing state, and establishing the formula of CCN spectrum,(4) using aerosol thermodynamic model to assess impacts of particle shape and surfactant bulk-to-surface partitionging on hygroscopicity,and estimating liquid water content,(5) construction of particle mixing, closure experiment, and comparison of measured and estimated CCN values,(6) using satellite remote sensing and meteorological data,analyses of organic component contribution to aerosol CCN acitivity changes in the formation and elimination of radiation fog, (7) using WRF-Chem model to simulate typical radiation fog to evaluate the impact of aerosol especially organic composition on the formation of fog droplets. The results will be helpful to deepen understanding the effect of atmospheric physio-chemical processes on aerosol CCN activity changes, and improve the accuracy of identifying and forecasting haze and fog.

有机成分显著影响气溶胶活化成为云凝结核（CCN）的过程和效率。本项目主要针对大气污染条件下有机成分影响气溶胶CCN活性及活化速率的机制进行研究。主要内容包括分粒径气溶胶有机成分的时间变化规律及影响因子，颗粒物特性和CCN谱变化的关系；颗粒老化及可溶有机成分变化，评价其对CCN活性的影响；表征颗粒化学的混合状态，建立颗粒CCN谱的经验计算方法；应用气溶胶热动力学模式，计算颗粒含水量，分析主控因子；分类有机成分并评价其可溶等特性,构建颗粒混合方案，进行闭合实验，对比CCN实测与估算值；基于卫星遥感及气象等资料，分析辐射雾过程中CCN活性变化及气溶胶有机成分的作用；利用WRF-Chem数值模拟，进行典型辐射雾的控制实验，评估气溶胶有机成分对雾滴形成的影响。研究结果将有助于加深了解大气理化过程对气溶胶CCN活性变化的作用，提高区分与预测霾与雾的精度。

有机物是气溶胶的重要组成，显著影响气溶胶活化成为云凝结核（CCN）的过程和效率。本项目围绕大气污染条件下有机成分影响气溶胶CCN活性及活化速率的机制进行研究。依照研究计划，科研团队在上海、广州及北京对近地面气溶胶和CCN进行加强观测，对比分析了气溶胶对CCN浓度及活化率的影响，发现大气污染对气溶胶吸湿性及CCN活性影响显著。含水量和酸性pH可反映气溶胶老化程度，发现CCN浓度随着颗粒含水量LWC和pH正增长，前期迅速而后期缓慢变化，特别在LWC低于20 μg/m3和PM2.5高于50 μg/m3时。基于气溶胶化学组成内混假设和κ-Köhler理论，考虑可溶有机物OM，构建颗粒吸湿增长因子k和CCN浓度估算参数化方案，闭合实验取得更好拟合效果，发现提高CCN观测与估算值相关性3-5%。基于地面和卫星遥感等资料，分析雾霾转化过程及主控因子，利用WRF-Chem数值模拟典型雾天气，从微物理角度考虑气溶胶对雾滴形成的影响，取得了较好模拟效果。研究结果有助于加深了解大气理化过程对气溶胶CCN活性变化的作用。