南京冬季大气气溶胶粒子谱分布及其对能见度的影响

2009年11～12月采用宽范围气溶胶粒径谱仪（WPS）、自动气象站和能见度仪等高分辨率仪器对南京北郊气溶胶粒子的谱分布特征与气象因子的关系及其对大气能见度的影响进行研究.结果表明,数浓度谱呈双峰分布,主峰集中在0.04～0.1μm;质量浓度谱的2个主峰位于0.5～0.7μm和2.7μm左右;表面积谱的2个主峰分别位于...

Size Distributions of Aerosol Particles and the Impact on Visibility in Winter of Nanjing

High resolution instruments were used to investigate the relationship between aerosol size distribution characteristics and meteorological factors, and its possible influence on visibility in urban Nanjing from November to December 2009. Results show that the size distribution of aerosol number concentration showed a bimodal shape with the main peak value concentrating at particle sizes of 0.04-0.1 microm. Mass concentration distribution presented a bimodal shape with the two peak values concentrating at particle sizes of 0.5-0.7 microm and 2.7 microm, and the surface area concentration distribution presented two peaks from 0.1 to 0.5 microm and from 0.5 to 0.9 microm. It is found that the diurnal and interdiurnal variations of particle concentrations are obvious. Human activities and variation of atmospheric stability had great effect on daily variation of particle concentrations, while meteorological conditions such as precipitation, wind, relative humidity and so on had strong influence on interdiurnal variation. The aerosol size distribution was significantly affected by relative humidity. When RH was lower than 54%, number concentration of aerosol particles less than 1 microm in diameter increased gradually as RH increased, and concentration of particles with diameter larger than 1 microm almost had no change. When RH was higher than 54%, number concentration of aerosol particles ranging from 0.01 to 0.2 microm and from 2.7 to 10 microm decreased with the increase of RH, in contrast, concentration of aerosol particles between 0.5 and 1.5 microm in diameter increased. In addition, the particle number size distributions were different in rainy, foggy, sunny and haze weather conditions. Compared to sunny day, concentration of particles with different sizes all decreased in rainy day. In foggy weather, The number concentration of aerosol particles ranging from 0.01 to 0.3 microm and from 2.7 to 10 microm decreased, and aerosol particles between 0.3 and 2.7 microm increased in comparison with sunny day. Scavenging action of rain and fog to particles of different sizes from high to low was that coarse particles > nuclei mode particles > accumulation mode particles. In haze day, the peak of number concentration distribution moved toward a higher value. Compared to sunny day, the number concentration of aerosol particles ranging from 0.03 to 0.1 microm decreased, and aerosol particles between 0.1 and 2.7 microm increased in haze day. Based on Mie theory, the correlation between visibility and surface area concentration with different particle sizes indicated that particles between 0.1 and 2 microm in diameter shows a good correlation with visibility, which was the major contributor to visibility degradation in Nanjing.