Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Institute of Atmospheric Sciences, Fudan University, Shanghai 200433, China.
Institute of Mass Spectrometer and Atmospheric Environment, Jinan University, Guangzhou 510632, China.
Sci Total Environ. 2018 Nov 15;642:1008-1019. doi: 10.1016/j.scitotenv.2018.06.053. Epub 2018 Jun 19.
Atmospheric pollutions have an important impact on aerosol, condensation nuclei (CN) and cloud condensation nuclei (CCN) loadings near the ground through disturbing particle size, number, chemical composition and reactions, mixing state, hygroscopicity, and so on. Aerosols and CCN were measured in urban Guangzhou during pollution and post-rain periods to examine effects of particulate pollutants on aerosol CCN activity and compare their mechanisms between summer and winter. In contrast with different levels of pollutions, particle matter (PM) and number (CN) and CCN almost showed an opposite trend to aerosol activity (CCN/CN). In summer, new particle formation (NPF) events triggered by photochemical reactions (e.g. O) always occurred in no-pollution daytime, and increased significantly CN and CCN as a dominant contributor to secondary aerosols. Under pollution conditions, the gas-to-particle transition driven by photochemical reactions guided the formation and aging processes of particles in daytime, especially in changing soluble species, whereas atmospheric oxidation and heterogeneous reactions dominated at night. In winter, stagnant weather conditions, high pollutant levels and relatively high RH were in favor of particle growing and aging through enhancing secondary particle formation and heterogeneous reactions. The wet scavenging of precipitation reduced greatly CCN amount by scouring pre-existing particles in winter, and during post-rain period the photochemical reactions did not promote the burst of secondary particle formation in the absence of ozone, compared with summer. The results may provide insights into the relationship between aerosol moisture absorption and pollution that may be useful for improving air quality.
大气污染通过干扰颗粒物粒径、数量、化学成分和反应、混合状态、吸湿性等因素，对地面附近的气溶胶、凝结核（CN）和云凝结核（CCN）负荷有重要影响。在污染和雨后时期，在城市广州测量了气溶胶和 CCN，以考察颗粒物污染物对气溶胶 CCN 活性的影响，并比较夏季和冬季的机制。与不同水平的污染相比，颗粒物（PM）和数量（CN）和 CCN 几乎与气溶胶活性（CCN/CN）呈相反趋势。在夏季，光化学反应（例如 O）引发的新粒子形成（NPF）事件总是在无污染的白天发生，并显著增加了 CN 和 CCN，这是二次气溶胶的主要贡献者。在污染条件下，光化学反应驱动的气粒转化指导了白天颗粒的形成和老化过程，尤其是在可溶性物质的变化方面，而夜间则以大气氧化和非均相反应为主。在冬季，停滞的天气条件、高污染水平和相对较高的 RH 有利于通过增强二次粒子形成和非均相反应使粒子生长和老化。降水的湿清除通过冲刷冬季已有粒子，大大减少了 CCN 的数量，与夏季相比，在雨后时期，缺乏臭氧时，光化学反应并没有促进二次粒子形成的爆发。这些结果可能为气溶胶水分吸收与污染之间的关系提供了一些启示，这可能对改善空气质量有用。
