2008年北京奥运会期间大气气溶胶物理特征分析

应用MODIS卫星的气溶胶产品资料和地面的光学粒子计数器的资料,对比分析了北京地区2006、2007、2008年7～9月的气溶胶光学厚度、细粒子光学厚度、Angstrom指数、气溶胶粒子数浓度谱及体积谱,发现2008年北京奥运会期间(7月20日～9月20日)的气溶胶光学厚度比2006、2007年同期明显降低,气溶胶细模态光学厚度占总光学厚度的比上升,Angstrom指数上升,气溶胶细粒子数浓度没有明显相对变化,而粗粒子数浓度则减少约50%.利用大气标高,将MODIS反演的气溶胶柱的质量浓度转化为地面气溶胶质量浓度.用粒子计数器得到的体积谱,在假定气溶胶粒子密度的情况下,计算出其质量浓度.将这两种方法得到的气溶胶质量浓度与国家环境保护部公布的空气质量指数换算得到的可吸入颗粒物(PM10)质量浓度进行比较.结果表明:北京奥运期间空气质量总体达到了国家二级空气质量标准;与2006、2007年同期相比,2008年气溶胶PM10质量浓度明显下降,而这主要是由气溶胶粗粒子的减少引起的.

Analysis of Physical Properties of Aerosols during the 2008 Beijing Olympic Games

The aerosols optical depth (AOD), optical depth due to fine aerosol particles, Angstrom index, and number concentration and volume size distribution of aerosol particles during the Beijing Olympic Games (20 July to 20 September 2008) were compared with data in the same periods of 2006 and 2007 using the MODIS retrieved aero-sols product and the data measured by the optical particle counter on the ground.Decrease in AOD during the Bei-jing Olympic Games was primarily attributed to the reduction in coarse mode aerosol particles.The Angstrom index and particle counter data also approved this.The MODIS retrieved aerosols mass was converted to the surface aero-sol mass concentration by dividing by the atmospheric scale height in Beijing, while another aerosol mass concentra-tion was gained by the particle volume size distribution assumed the density of aerosol particles. Comparison of these two concentrations with the particulate matter with aerodynamic diameter less than 1o μm (PM10) concentration translated by air pollution index (APD showed that Beijing air quality in the 2008 Olympic Games was improved and achieved class Ⅱ national standard, which primarily owes to the reduction in coarse mode aerosol particles.