Abstract:

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.