西安市降尘粒度空间分布特征及环境意义

Space characteristic of grain size distribution of aerolion dust in Xi'an and its environmental significance

笔者在西安市区11个取样点进行了为期1a连续采样,采集样品14件。结果证明,降尘可以分为大小明显的两群,小于10μm的颗粒物以工业污染的产物为主,较大颗粒主要为自然源沙尘。西安市降尘粒度明显偏小,其中≤50μm的颗粒占总量的80%～98%;≤10μm的颗粒占30%～60%;≤2.5μm的颗粒占≤10μm颗粒的20%～46%。受城市风动力条件控制,沿东北—西南方向降尘平均粒径依次降低;降尘粒度分选性与小于10μm粒级颗粒的含量负相关,相关系数为-0.9212,负相关性明显。颗粒平均粒径和粒度分选性可以作为当地空气质量的综合性标志。

In order to find out the grain size distribution of aerolion dust and its contolling factors, the author collected samples of aerolion dust in 11 sampling sites from Mar. 1,2002 to Feb. 28,2003 with 14 dust samples. The analytical results testified that grain size of aerolion dust can be divided into different two group of grain size, namely, partculate from industrical pollution are most smaller than 10 μ ms and the bigger grain are mainly from nature source of sandy dust. Grain size of aerolion dust in Xi'an city is obviously partial to the smaller, dust grain ≤50 μm account for%; 80%～98%; ≤10 μm was ahout 30%～60%; ≤2.5 μm account for 20%～46% of the grain ≤10 μm.The average grain size of aerolion dust diminished in turn along the direction of prevailling wind blowing from the northeast to the southwest. The gradation of the dust grain size and the content of grain less than 10 μm are negative correlation. The correlation coefficient is -0.921 2 and correlativity is comparatively obvious.