北京地区春末─秋初气溶胶理化特性的观测研究

An Observational Study of Physical and Chemical Characteristics ofAtmospheric Aerosol Particles from Late Spring toEarly Autumn over the Beijing Area

摘 要 分析了1997年5～9月和1998年4～9月北京整层大气气溶胶光学厚度、近地面气溶胶粒子数浓度的日变化，季节变化及其与气象要素的关系，还分析了1997年5月16日、7月21日和 8月2日收集的北京单个气溶胶粒子样品的形态、大小和化学元素组成。结果显示，北京地区春末一秋初整层大气气溶胶光学厚度在0.1～1.6之间变化；气溶胶数浓度（D＞0.3μm）为几～几百个／cm3；整层大气气溶胶光学厚度的日变化型式下与近地面气溶胶数浓度呈现相反的走向；气溶胶光学厚度和数浓度的日、季节变化显示了整层大气和近地血大气气溶胶与该地区气象、气候条件的关系。气溶胶数浓度与大气相对湿度呈正相关，与风向的关系是偏东风数浓度大，西、西南风数浓度小。电子显微镜分析的结果表明：颗粒物的形态以不规则形、丸形，液态滴形和方形为主；颗粒物化学元素组成有Si、K、S、Al、Mg、Ca、Fe等元素；人类活动排放的Zn、P、Ti、Pb，Ba等元素也探测到；北京近地面粒子的一个显著特点是富含Ca和 K元素。它们可能分别来自建筑粉尘和有机物的燃烧；给出了一个典型的碳黑粒子和一个粒子经过凝结过程的“卫星”滴环绕的矿物粒子的照片和元素谱图。

Abstract Physical and chemical characteristics of the atmospheric aerosols over the Beijing area arc studied in this paper. Observed items include their optical depth and the number density, and the morphology, size and chemical element composition of individual particles near the ground. The observation period covered May-September, 1997 and April~ September, 1998. The results show that: (1) the total optical depth ot' the atmospheric aerosols ranges from 0,1 up to 1.6; (2) the number densityof atmospheric aerosols with D>0.3 um covers from several to several hundred particles per cubic centimeter; (3) (he diurnal and seasonal variations ol the column optical depth and number density are influenced by the local meteorological and climatic conditions; (4) (he number density is closely related to the atmospheric humidity; (5) the relationship between the number density and the wind direction shows that density is larger when the wind direction is between 0°and 180°, while it is smaller as the wind direction is in 180°-270°; (6) the elements of Si. K, S. Al, Mg. Ca and 1 e have been detected in the particles. The elements of Zn. P. Ti. Pb and Ba, which come from the lossil fuel burning, are also de tected. A remarkable characteristic ol aerosol particles is that many particles are Ca-rich and K-rich, which may come from the construction sites and the hiomass burning. Photographs ol three typical par tides are presented. One of them is a black carbon particle, another one is a C'a-rich particle with a 'square' shape, and the third one is a dust particle surrounding some 'satellite' droplets. The element spectra ofcach particle are also presented.