灰霾与颗粒物吸湿增长  

Haze and hygroscopic growth

作　　者：叶兴南[1] 陈建民[1] 

机构地区：[1]复旦大学环境科学与工程系,副教授上海200433

出　　处：《自然杂志》2013年第5期337-341,共5页Chinese Journal of Nature

基　　金：上海市科委重点基础研究项目(12DJ1400100);国家自然科学基金面上项目(41075088)

摘　　要：灰霾频发是中国当前遭遇的最严峻的环境挑战之一。以二次离子为主的细颗粒物浓度上升是灰霾频发的主要原因,这反映了中国煤烟和汽车尾气复合型大气污染特征。二次颗粒物在大气中容易潮解和吸湿增长,显著改变颗粒物的折光率和粒径分布。颗粒物的吸湿性主要取决于化学组成,也受粒经效应制约。受风化滞后影响,大气颗粒物很可能在较低湿度下仍然以湿霾形态存在。中国城市大气气溶胶包含近疏水颗粒物、弱吸湿颗粒物和强吸湿颗粒物三种类型,各类型的含量在各城市存在差异。灰霾期间吸湿增长对大气能见度降低的贡献可能达到60%,超过颗粒物本身的消光作用。颗粒物吸湿增长还可以为气态污染物提供非均相转化载体,促进硫酸和硝酸盐等细颗粒物的生成,进—步降低大气能见度。China is facing the critical situation of the high occurrence of haze. The enhancement in secondary inorganic species in PMz5 is largely responsible for the haze formation, reflecting the complex pollution with coal-burning and traffic emissions. Both particle size distribution and refractive indices are remarkably changed after deliquescence and hygroscopic growth of secondary aerosols in atmospheric environment. Aerosol hygroscopicity is largely dependent on chemical composition as well as size effect. The aerosols may exist as liquid droplet under rather lower relative humidity due to the drag hysteresis. The urban aerosols contain in China nearly-hydrophobic, less-hygroscopic and more-hygroscopic mode particles, varying content of each mode among cities. Hygroscopic growth may contribute 60% to the visibility decrease during haze episode, exceeding extinction effect of dry aerosols themselves. Hygroscopic growth can also provide a carrier for heterogeneous reaction with gas pollutants. This process favors the formation of sulfate and nitrate, which further deteriorate the visibility.

关 键 词：细颗粒物污染 吸湿性 能见度降低 

分 类 号：X513[环境科学与工程—环境工程]