昆明市街道灰尘粒度特征及其环境意义

GRAIN SIZE CHARACTERISTICS OF STREET DUST IN KUNMING AND ITS ENVIRONMENTAL SIGNIFICANCE

对昆明市2008年1、3、4、5、7和9月份6次采集的街道灰尘样品进行了粒度分析。结果表明:昆明市街道灰尘粒度主要呈三峰特征,第一众数为65～125μm,第二众数为3～15μm,第三众数为0.15～0.3μm,平均粒径范围在39.91～255.85μm,平均值为87.1μm,旱季(90.6μm)大于雨季(83.7μm);粒度分布以正偏度为主,峰态为中等到偏窄且不对称,分选很差;与现代粉尘源区尘暴降尘的粒度分布模式高度相似,街道灰尘沉积是大气环流对远近不同距离粗细颗粒物的混合搬运的结果,应是风积作用的继续;灰尘细粒含量较高,≤100μm的颗粒平均为63.5%,在适当的大气动力条件下,昆明市街道灰尘颗粒有60%～90%可以进入大气;灰尘主要来源于土壤风沙尘、建筑尘、工业烟尘和汽车尾气排放,灰尘中可吸入颗粒平均占25.2%,潜在危害性大。

Grain size analysis of street dust collected in January,March,April,May,July and September,2008 in Kunming City showed a three peaks distribution spectrum,where the first mode was 65～125μm,the second was 3～15μm and the third was 0.15～0.3μm.The average grain sizes were ranging from 39.91～255.85μm and the mean value was 87.1μm.The average grain size of the dry season（90.6μm）was significantly greater than that of the rainy season（83.7μm）.Distribution of grain size was skewed positively.The kurtosis was from middling to narrow and asymmetrical frequency curves,being the poor sorted.This is similar to the grain size distribution of modern dust storms of source,which indicates that street dust is a mixture of coarse grains derived from local area and fine grains transported over long distances,and is derived from aeolian processes.The content of fine-grain in the street dust was higher relatively,≤100μm particles on average 63.5%.Under proper aerodynamic conditions,60%～90% of the street dust particles were picked up and transported by suspension.The street dust mainly originates from soil wind sand dusts,cement dusts,coal combustion dust,motor vehicle exhausts.The average respirable suspended particles in street dust are of 25.2%,showing the high potential hazards.