降水对武汉2次空气污染过程的湿清除特征

Wet Scavenging Characteristic of Precipitation in Two Air Pollution Processes in Wuhan

为了研究降水对空气中污染物冲刷作用,利用2014年秋季发生在武汉市2次持续性空气污染过程的地面空气质量、气象观测和雨滴谱等监测资料,对比分析了不同类型降水对雾霾天气中污染物的湿清除特征。结果表明:(1)这2次过程首要污染物均为颗粒污染物PM,在均压场天气条件下,污染物不易扩散,容易累积叠加,导致"09.26—29"和"11.13—24"2次重度雾霾天气过程,过程末期由于分别受对流云和层状云降水的冲刷,各污染物浓度迅速下降,空气质量显著好转;(2)"09.26—29"过程后期受对流云降水影响,对各污染物清除效果依次是PM10、PM2.5颗粒污染物最好,O3、SO2和NO2次之,最差的是CO,而受层状云降水影响的"11.13—24"过程,对各污染物清除效果依次是PM2.5、PM10最好,NO2、SO2和CO次之,最差的是O3;(3)通过这2个过程分析,不同类型降水对应的平均碰并系数E也不同,武汉地区对流云和层状云降水对气溶胶的平均碰并系数分别可取0.33~0.43和0.25~0.35。

To study the scavenging effect of precipitation on pollutants in the air, a comparative analysis of wetscavenging characteristics of different types of precipitation were conducted by using the air pollutionmonitoring data, surface meteorological observation data and rain spectrum monitoring data of two air pollutionprocesses in Wuhan in autumn, 2014. The results showed that：（1） the main pollutants in the two processeswere PM pollutants, and under the condition of stable atmospheric stratification and slight wind, the airpollutants were difficult to spread and easy to accumulate, leading to＂09.26-29＂and＂11.13-24＂two severeair pollution processes, until influenced by the convective clouds precipitation and stratiform cloudsprecipitation, respectively, the pollutant concentrations decreased rapidly and the air quality was significantlyimproved;（2） in the later period of＂09.26-29＂process which was influenced by the convective cloudsprecipitation, the wet scavenging effect on PM10 and PM2.5 was the best, the effect on O3, SO2 and NO2 was thesecond, and the effect on CO was the worst, while in＂11.13-24＂process, which was influenced by thestratiform clouds precipitation, the wet scavenging effect on PM2.5 and PM10 was the best, the effect on NO2, SO2 and CO was the second, and the effect on O3 was the worst;（3） through the analysis of the two processes, thetwo average scavenging coefficients E corresponding to different types of precipitation were different, the E ofconvective clouds precipitation and stratiform clouds precipitation on aerosol was 0.33-0.43 and 0.25-0.35 in Wuhan, respectively.