北京市大气细粒子质量浓度与能见度定量关系初探

THE DISCUSS ON RELATIONSHIP BETWEEN VISIBILITY AND MASSCONCENTRATION OF PM2.5 IN BEIJING

中文关键词:  细粒子(PM2.5)，能见度，定量关系

英文关键词:Fine particles (PM2.5),Visibility, Quantitative relation.

中文摘要:

      北京近年的监测结果表明，大气中通过消光作用使大气能见度下降的气溶胶细粒子的污染水平呈现上升趋势。中国气象局北京城市气象研究所与北京大学合作于2001年春季（3月）、夏季（6月）、秋季（9月）和冬季（12月）开展了大气细粒子与气象能见度的同步综合观测，旨在探求细粒子的物理化学特征及其与大气能见度的关系。监测结果表明，能见度与PM2.5质量浓度在春季呈乘幂关系；夏季除高相对湿度外，呈指数关系；秋季呈对数关系；冬季呈指数关系。为了便于比较，将两者间的关系全部用指数关系表示。北京市大气能见度与细粒子质量浓度呈现很好的负相关性，无疑细粒子污染是造成大气能见度下降的主要原因，它已成为目前中国大气污染研究的重要内容之一。

英文摘要:

      The recent years' monitor results of Beijing indicate that the pollution level of fine particles PM2.5 owing to atmospheric visibility deterioration through light extinction shows an increasing trend. Institute of Urban Meteorology, CMA, in cooperation with Peking University, performed a monitoring of PM2.5 and visibility in 2001 at four seasons which were spring (March), summer (June), autumn (September), and winter (December). Its purpose was to investigate fine particle's physical and chemical characteristic, and the relationship between fine particle and atmospheric visibility. Six Anderson RAAS 400 samplers with four PM2.5 channels were used to collect PM2.5 particles. They were installed in six different stations to perform simultaneous sampling: Atmosphere Exploration Base of China Meteorological Administration (AEBCMA), Peking University (PKU), DongSi (DS), Capital Airport (CA), Yongledian (YLD), Mingling (ML). The sampling flow rate of four sampling channels is 16.7 L/min. The sampler used three kind filters: 2 Teflon filters with 2　μm aperture, anylon filter with 1μm aperture, and a quartz filter with 1 μm aperture. One Anderson's CAMMS PM2.5 sampler was installed onthe ground of AEBCMA, which measured the real time mass concentrations of PM2.5. And for the filters, trace elements, ionic species and OC, EC of PM2.5 were analyzed by ICP, x-ray fluorescence and thermo optical method. The DPVS (Digital Photo Visibility System) is installed on the top of bungalow of AEBCMA' observation site, about 3 m above ground, monitoring the real time atmospheric visibility. Other relevant meteorological data were available from routine observation at AEBCMA, including diurnal horary wind speed; relative humidity at four times a day (02:00, 08:00, 12:00, 20:00 BST); precipitation data at 2 durations a day (20:00—08:00, 08:00—20:00). The relationship between mass concentration of PM2.5 and visibility varied with meteorological parameters like relative humidity, and also varied with size distribution and chemical compositions of PM2.5, it was power in spring, exponential in summer except at higher relative humidity, logarithmic in autumn, power or exponential in winter. As in each season the meteorological parameters such as air temperature and relative humidity change from day to day, probably the reason of above correlations between PM2.5 and visibility obtained at different seasons come from the differences in chemical compositions of PM2.5. The pollution of fine particles PM2.5 is the main factor that results in atmospheric visibility dropping, and has become one of the most important issues in the air pollution aspect in China. To avoid the complexity of mechanisms of impact of PM2.5 on visibility, it would be helpful to obtain the statistical relationship between mass concentration of PM2.5 and visibility in a city, which would provide a quick response of level of PM2.5 pollution from solely visibility measurement. This work will investigate the quantitative relationship between mass concentrations of PM2.5 and visibility under various meteorological conditions from a whole year measurement, and provide data for further detailed studies to understand the mechanisms of optical properties of PM2.5.