北京上甸子典型天气个例的大气气溶胶数谱分布特征
The Characteristics of Particle Number Size Distribution under Typical Meteorological Conditions at Shangdianzi Regional Station in Beijing
中文摘要：
使用差分淌度粒径分析仪（TDMPS）和空气动力学粒径分析仪（APS）对上甸子区域本底站气溶胶（直径3nm～10μm）数谱分布特征进行观测。利用2008年的观测结果，分析了不同天气（包括沙尘天气、干洁天气和雾霾天气）条件下大气气溶胶数谱分布及其与气象要素和气团来源的关系。结果表明，沙尘天气条件下，上甸子站受西北方向的气团控制，风速较大，粗粒子数浓度明显增加，PM10的质量浓度可以迅速增加到毫克每立方米（mg·m－3）的量级。典型的“香蕉型”新粒子生成事件通常发生在比较干洁晴朗的天气条件下，西北气团主导，大气中背景气溶胶数浓度较低，核模态气溶胶数浓度迅速增长，气溶胶的粒径呈现明显的增长过程，核模态可以平稳地增长到约80nm，达到成为云凝结核的尺度。雾霾天气通常是在西南气团影响下，细颗粒物（1μm以下）不断累积、相对湿度不断升高的条件下发生的。雾霾天气条件下数谱分布的几何中值粒径出现在积聚模态，积聚模态数浓度也高于非雾霾天。个例研究表明，雾霾天气条件下，PM2.5质量浓度可以达到非雾霾天的10倍左右，其中以细颗粒物的贡献为主。在雾霾天气条件下，上甸子站数浓度较高的积聚模态颗粒物主要来自城区的传输，因此对背景地区气溶胶数谱的研究可以为解析城区气溶胶复杂来源提供依据。
中文关键词：
沙尘天气，干洁天气，雾，霾，气溶胶数谱分布，新粒子生成事件
KeyWords：
dust storm, dry and clean day, fog, haze, particle number size distribution, new particle formation event
Abstract：
By using the instruments of Twin Differential Mobility Particle Sizer (TDMPS) system and an Aerodynamic Particle Sizer, measurements of particle number size distribution (PNSD) in the range of 3 nm~10 μm were taken at Shangdianzi Regional Station. Based on the dataset in 2008, the characteristics of particle number size distribution under different meteorological conditions such as dust storms, new particle formation events and haze days were investigated. On a dust storm day, the air mass originated from the northwest, with high wind speed. The coarse mode particle number concentration increased sharply and PM10 mass concentration could reach up to milligrams per cubic meter. A new particle formation event of a typical “banana shape” occurred when the atmosphere background was quite dry, clean and clear, with the air mass coming from the northeast. The nucleation mode particle could grow to a larger size, around 80 nm, having the potential to be activated as cloud condensation nuclei. A haze day usually occurred when southwest air mass arrived, along with the meteorological conditions of high humidity. The conditions favored fine particles (<1μm) accumulating. The case study showed that the PNSD on a haze day was dominated by the accumulation mode and higher number concentration than a non-haze day. The mass concentration of PM2.5 could increase by 10 times on a haze day, which was mainly attributed to fine particles. On haze days, the accumulation mode particles, with a high number of concentration were mainly transported from the urban area. Thus the study of PNSD at rural sites could also provide information for analyzing the complex emission sources in the urban area.