上海春季沙尘与非沙尘天气大气颗粒物粒度组成与矿物成分

Particle Size Distribution and Mineral Components of Atmospheric Particles Collected in Spring of Shanghai

上海春季典型沙尘天气的湿降尘和非沙尘天气总悬浮颗粒物、自然降尘的粒度分析结果表明，沙尘天气湿降尘几乎全部由〈63μm的颗粒组成（99．45％），其中10～50μm、5～10μm和〈5μm的含量分别占49．02％、21．75％和27．14％，平均粒径为13．57μm，分选差。这一粒度特征与马兰黄土和下蜀黄土很相似。非沙尘天气总悬浮颗粒物的粒度分布范围和均值与湿降尘很接近，自然降尘颗粒则明显较粗。矿物X-衍射物相及半定量分析结果表明，上述三种大气颗粒物都由粘土矿物、石英、钾长石、斜长石、方解石、白云石、石膏、角闪石等组成，所不同的是湿降尘中含有较多来自西北干旱半干旱区远源输入的矿物颗粒；而非沙尘天气总悬浮颗粒物中石膏含量较高（达14．59％），推测为溶解在大气中的气态污染物SO2与方解石作用形成的二次污染颗粒。

By using Laser Particle Size Analyzer and XRD systems, this paper discusses the characteristics of particle size distribution and mineral components of three different types of atmospheric particles collected in the spring of Shanghai. They are the rain-born dust （RBD） as the dust-storm happening in northwest China, the total suspended particles （TSP） and the normal air-born dust （ABD）. The particle size data show that over 99.45% of RBD is less than 60 μm （13.57 μm in average） and the 〈30 μm part takes the majority with a bad sorting degree. The content of coarse silt, fine silt and clay are 49.02%, 21.75% and 27.14% respectively. Such a particle size distribution is much similar to that of Malan loess （in North China） and Xiashu loess （in lower Yangtze River） formed in Late Pleistocene, supporting that the Xiashu loess is of eoline origin. The particle size distribution of RBD can also be compared to TSP, but both much finer than ABD. The X-ray diffraction analysis data show that all the samples can be identified as clay minerals, quartz, potash feldspar, plagioclase, calcite, dolomite, gypsum and amphibole etc. But there are still some differences between each other. The RBD contains relatively more mineral materials, indicating that it derived from the northwest arid and semiarid areas in China. The content of gypsum in TSP reaches up to 14. 59%, which can be considered as the secondly polluted particulates formed by the SO2 gas in the air meeting together with calcite. The gypsum in TSP, therefore, can be used as an indicator of SO2 pollutant in the atmospheric environment of Shanghai.