2008奥运和后奥运时段北京大气颗粒物质量浓度和数浓度比对研究

为探索奥运和后奥运时段北京地区大气颗粒物质量浓度和数浓度变化规律及其主要影响因素，于2008-08-08～2008-10-07期间，在中国科学院大气物理研究所325 m气象观测塔附近的办公楼楼顶使用微量振荡天平（TEOM）和空气动力学粒谱仪（APS）在线实时测量颗粒物质量浓度和数浓度，同时结合地面气象资料和HYSPLIT轨迹模式对颗粒物的来源和传输过程进行了探讨. 结果表明，奥运期间北京大气颗粒物粗细粒子质量浓度（PM_2.5～10和PM_2.5）平均值分别为（23.1±1.6） μg·m^-3和（55.5±7.3）μg·m^-3，比非奥运时期分别降低18.2%和16.0%，比非源控制时期分别降低22.3%和18.0%；而奥运期间粗细粒子数浓度（PN_2.5～10和PN_0.5～2.5）平均值分别为（15±1）个·cm^-3和（3138±567）个·cm^-3，比非奥运时期分别降低23.4%和27.5%，比非源控制时期分别降低29.5%和34.3%. 观测期间风速、相对湿度和前1 d的降水与颗粒物质量浓度和数浓度存在显著线性关系，逐步回归分析结果显示，风速和相对湿度可以解释细粒子质量浓度和数浓度变化的42%和53%，而风速和前1 d的降雨则可以解释粗粒子质量浓度和数浓度变化的21%和39%；观测期间北京大气颗粒物主要受保定、石家庄等偏南地区输送的影响，偏南弱气流使北京大气细粒子质量浓度和数浓度迅速增加，而偏北强气流使区域大气粗细粒子得到彻底清除，体现了北京地区大气粗粒子受局地排放控制而细粒子受区域污染输送的特征. 对比观测期间颗粒物累积清除的2次典型过程发现，气象因素影响颗粒物浓度值波动，而局地源排放减少和区域输送减弱则使颗粒物粗细粒子浓度显著降低，北京及周边省（市、区）协同减排是保障奥运期间优质空气质量的主要原因.

Particle Mass Concentrations and Size Distribution During and After the Beijing Olympic Games

To study the variance characteristics of particle mass and number concentration during and after the Beijing Olympic Games, on-line measurements of particle mass and number concentration were conducted on the rooftop of a two-story building near the 325 m meteorological observation tower in the courtyard of the Institute of Atmospheric Physics during 2008-08-08 - 2008- 10-07 by using TEOM and APS. Sources and transportation of atmospheric particles during the experiment were discussed with surface meteorology data and backward trajectories calculated using HYSPLIT model. It had been found that the average mass concentration of PM2.5-10 and PM2.5 were (23.1 +/- 1.6) microg x m(-3) and (55.5 +/- 7.3) microg x m(-3) during the Olympic time, which were 18.2% and 16.0% lower than non-Olympic time, and 22.3% and 18.0% lower than non-Source control time. In Olympic time, average number concentration of PN2.5-10 and PN0.5-2.5 were (15 +/- 1) cm(-3) and (3138 +/- 567) cm(-3), which were 23.4% and 27.5% lower than non-Olympic time, and 29.5% and 34.3% lower than non-Source control time. According to the correlation analysis result of particle matter and meteorological factors, there were significant linear relationships between wind speed, relative humidity and precipitation of prior day and particle mass and number concentrations, stepwise regression analysis showed that 42% and 53% of the variance in mass and number concentration of fine particle were both accounted for wind speed and relative humility, while 21% and 39% of the variance in mass and number concentration of coarse particle were both accounted for wind speed and precipitation of prior day. For the entire period, 46% of total air masses came from regions south of Beijing like Baoding and Shijiazhuang and were favor to increase both the mass and number concentration of fine particles, whereas air masses transported from the north and near north regions had a great effect on scavenging both fine and coarse particles in Beijing, indicating coarse particles mostly came from local sources and fine particles mainly influenced by regional transport in Beijing. According to the comparative analysis result of two accumulation- diffusion processes, meteorological factors were only the causes of particle mass and number fluctuations, while the significant decrease of coarse and fine particles concentrations were mainly contributed to weaker emission of particles from local sources and weaker transport from regional area around Beijing, suggesting synchronous emission abatement of six provinces and cities of North China is the main factor that ensured the excellent air quality during the Olympic Games.