Abstract: With data from 19 meteorological observing stations and Environmental Monitoring Station of Lanzhou, it has been statistically analysed that during 1975-1997, the annual days of sand dust storms(AD) occurred over the district of Gansu Hexi had clear relation with Total Suspended Particulates (TSP)or Inhaled Particulates (IP) in the air of Lanzhou City. There was a positive correlation between AD and TSP (IP). Especially during the late 1970s and round about 1986 the frequently occurring years of sand dust storms in the district of Gansu Hexi were just corresponding to the high concentrations of TSP in Lanzhou. In spring, sand dust storms occurred frequently, the positive correlation between AD and TSP is more remarkable and their correlation coefficient reached 0.706; both tendencies of interyear variations were almost corresponding. In the district of Gansu Hexi the AD values during March to April occupy 46.2% of a year, which results in the high IP concentration during this period in Lanzhou city. Therefore the annual variation of monthly mean IP concentrations became a two peak pattern, that is, the highest peak value appeared in December and the second peak value appeared in April. The pattern differed greatly from that of other several main air pollutants such as SO₂ etc. whose annual variation characteristics presented a one peak pattern, and the highest monthly mean concentration of them appeared in December. In addition, in spring when a sand dust storm occurred over the district of Gansu Hexi, and there were a lot of dust transported to the Lanzhou City, TSP concentration in Lanzhou would rise. As the synoptic process of the sand dust storm ended, TSP concentration would drop. In a word, the above mentioned results all showed that the sand dust storms in the district of Gansu Hexi would seriously affect the air pollution of TSP or IP in Lanzhou.

Key words: sand dust storm, air pollution, total suspended particulates (TSP), inhaled particulates (IP)