Characterization of the number and chemical size distribution as well as hygroscopicity of fine and ultrafine particles in Beijing, China

本文介绍的项目是北京大学大气环境模拟国家重点实验室和德国莱比锡对流层研究所的联合研究。本项目的主要目标是确定北京市高污染城市气溶胶的粒子数谱分布、吸湿特性和化学谱分布。北京是一个拥有1500多万人口的城市，正处于向现代化城市转型的时期。北京的气溶胶主要由三种类型的颗粒物组成，即家庭燃煤产生的含碳气溶胶，急剧增加的汽车、公共汽车和卡车交通排放的气溶胶，以及来自中国沙漠地区的细尘。这些气溶胶与由于高光化学作用而形成的二次气溶胶的组合产生了可见的颗粒空气污染。由于北京的气溶胶颗粒物的粒径特性，特别是粒径小于100 nm的气溶胶颗粒物的粒径特性尚不清楚，因此尚不能估计颗粒物污染对人体呼吸道疾病的可能的强烈影响。为了更好地了解未来北京城市气溶胶对人类健康的影响，必须研究气溶胶的物理和化学性质。具体地，将确定低至3 nm的粒径分布数、20-250 nm的尺寸范围内的吸湿性和低至10 nm直径的化学组成。数量大小分布将在一个连续的基础上运行，并将在两年的时间内提供昼夜，每周和季节性变化，而其他属性将在两个密集的活动中进行测量，一个在夏季，一个在冬季。

The project described here is a joint investigation between the State Key Laboratory for Atmospheric Environmental Simulation at the Peking University, Beijing, China, and the Institute for Tropospheric Research, Leipzig, Germany. The major goal of this three-year project is to determine number size distributions, hygroscopic properties, and chemical size distributions of the highly polluted urban aerosol in Beijing. Beijing is a town with more than 15 million inhabitants and it is in the period of transition to a modern city. The aerosol in Beijing consists mainly of three types of particles, the carbonaceous aerosol from domestic coal burning, the emission from the drastically increasing car, bus, and truck traffic, and the fine dust from desert regions in China. The combination of these aerosols in combination with secondary aerosol formation due to the high photochemistry creates a visible particulate air pollution. Since sizedependent aerosol properties especially in the size range smaller than 100 nm are unknown for Beijing, an estimate of the possible strong influence of the particulate pollution on human airway diseases cannot be made yet. To understand better the impact of the Beijing urban aerosol on human health in future, sizedependent physical and chemical aerosol properties down to the ultrafine size range has to be investigated. Specifically, numer size distributions down to 3 nm, hygroscopic properties in the size range 20-250 nm, and chemical composition down to 10 nm in diameter will be determined. The number size distribution will be operated on a continuous base and will provide diurnal, weekly, and seasonal variations over a two year period, while the other properties are measured during two intensive campaigns, one in summer and one in winter time.