兰州市街道尘埃粒度空间变化特征

Spatial Characteristics of Grain Size Distribution of Street Dust in Lanzhou and Its Environmental Significance

采用Mastersizer 2000激光粒度仪对2006年3月采集的兰州市街道尘埃进行了粒度分析。结果表明,兰州市街道尘埃中颗粒物平均粒径范围在46.83μm^266.59μm,平均值为118.73μm;其中(2μm的颗粒占总量的92%~99.5%,(2μm的颗粒占10%以下。受地形因素影响,兰州市西部和东部地区粒径较粗,中间地段粒径相对较细;进一步分析发现在风动能大的区域,尘埃主要以较粗物质为主;在风动能相对较弱区域,细颗粒和粗颗粒含量差别不大,而在风动能小的区域,街道尘埃主要以细颗粒物为主。由此可见,兰州市街道尘埃中的颗粒物的主要来源是由于风力和人为活动产生的土壤尘和人为排放的污染物所共同贡献的;粒度分布特征受到风动力条件和物源(污染源)两方面因素的控制。

Street dust samples collected on March 30th, 2006 in Lanzhou were analyzed by Laser Grainsize Analyzer. Results of the grain size distribution show that mean grain size vary from 46.83 to 266. 587 μm with mean value of 118.73μm. Particles with grain size more than 2μm occupied 92%- 99.5% , while particles less than 2μmaccounted for less than 10%. Controlled by landform, grain size in west and east part of Lanzhou are coarser than other areas. Coarse material is dominant in areas controlled by strong wind. The content of coarse particles and fine particles are similar in areas with relatively weak wind. In areas with very weak wind fine, particles are the main content of the street dust. The results indicate that major sources of street dust in Lanzhou are soil dust brought by strong wind and human activities. The characteristics of grain size distribution were controlled by wind power and material sources （pollution sources）.