现代尘暴降尘与非尘暴降尘的粒度特征

Particle Size Analysis of Aeolian Dust Derived from Duststorm and Non-duststorm

据搬运风力大小和源区差别将大气降尘分为尘暴降尘和非尘暴降尘。选择典型尘暴和非尘暴天气搜集两类降尘,并对其进行粒度测定。结果表明:两类降尘物除外观色泽不同外,粒度特征差别明显。总体上看粒径为5-6准和> 8准的颗粒物是大气降尘的较稳定组分。尘暴降尘粒度比非尘暴降尘偏粗,分选更差。典型非尘暴降尘粒度频率曲线呈近似正态分布。尘暴降尘呈现双峰态粒度分布特征,其原因是远近距离共同搬运和强烈气流对粗细颗粒的混合搬运共同作用。现代尘暴和非尘暴降尘粒度分布曲线与黄土—古土壤的十分相似,说明现代降尘是地质时代风尘活动的继续,现代风积作用仍在进行。但现代尘暴和非尘暴降尘与黄土—古土壤的粒度参数存在差异,表明降尘堆积物受到环境改造作用的影响,黄土化过程使降尘堆积物丧失一部分风成特征。

The collected samples under typical duststorm and non-duststorm weather were used to make a particle size analysis, the results showed that there are many differences between the two samples. First, aeolian dust derived from duststorm has a light yellow colour while dark brown-yellow from non-duststorm, on which the two samples can be distinguished by eye. As a whole, both samples of duststorm and non-duststorm are essentially composed of two relatively common groups of grain with sizes of 5-6φand >8φ. With poor sorting, dust derived from storm is courser than that from non-storm. The particle size distribution of sample derived from duststorm is approximatively normal while that from non-duststorm is bimode, which can be explained by the coaction of far and near existent sources and violent wind power sweeping course and fine grains. Compared with the particle size distribution of loess-paleosol with eolian cause of formation, modern eolian dust presents largely similarity to the ancient dust accumulation. Hint thus is given that modern aeolian sedimentary process in vogue continues from geological history and modern dust accumulation has ingenerated relationship with the ancient sediment.