2006年4月17日北京降尘的粒度分布与磁学特征  

GRAIN SIZE DISTRIBUTION AND MAGNETIC CHARACTERISTICS OF DUST FALL IN BEIJING ON APRIL 17,2006

作　　者：张崧[1] F．Heller 靳春胜[1] 刘平[1] 秦小光[1] 刘东生[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]Institute of Geophysics,ETH Zurich,Switzerland

出　　处：《第四纪研究》2008年第2期354-362,共9页Quaternary Sciences

基　　金：2003年度刘东生国家最高科技成就奖专项项目资助

摘　　要：对2006年4月17日北京降尘的粒度和磁学性质进行深入分析，提出降尘磁化率相对黄土样品较高是现代降尘磁化率的特点，源区表土磁化率普遍较高是本次降尘磁化率值高的主要原因，污染产生的磁性物质对其也有一定的影响。同时通过对比几次降尘的粒度特征和传输方式提出粒度可以有效地指示源区的变化。结合降尘的粒度、磁化率分析与沙尘暴的监测信息和卫星云图，认为此次降尘粒度为0．8～20．0μm的组分可能是来自内蒙古西部的物质；20～70μm与〉70μm的组分可能是来自距离北京较近的河北北部和内蒙古中部发生强烈沙尘暴的地区。Grain size analysis and magnetic method were applied to detect the characteristics of Beijing dust fall on April 17,2006. Similar to others deposition of modern aerosol,Beijing dust fall magnetic susceptibility is higher than the values of glacial loess. Day-plot,which compares the Beijing dust fall with a number of loess/paleosol samples from the central and west Loess Plateau, shows that Beijing dust fall is close to material from the western loess plateau but a little coarser. The component analysis of IRM coercivity by the method of Egli reveals two main components： The component C1 is always constant and has the same magnitude in all samples; while the magnitude of component C2 varies distinctly and becomes more pronounced in the stronger magnetic samples. It is not clear where it comes from; it might be a pollution component of coarser grain size or an oxidized magnetic mineral phase. In this paper,three pretreatment methods were used to analyze grain size of dust fall. There is a difference of about 12% in 〈 10μm component between ultrasonic and non-pretreatment. The difference means that at least 12% fine particles are transported by adhering to coarse particles. In order to clarify the relationship between grain size and transportation, we reviewed the process of several dust fails in Beijing. The result shows that the finer grain sizes usually accord with long and high transportation while the coarser grain sizes usually are components of close and low transportation. Therefore, grain size can be a proxy for the distance of transportation to reflect the change of source. In the cumulative probability curves of dust samples, the grain sizes of dust samples are decomposed to four components. There are two main components： 0.8 - 20.0μm,according to Pye＇s work,are transported in long-term suspension,coming from far sources and 20 -70μm are transported in short-term suspension,from near sources. In the studied dust fall,grain size is coarse then it should be as the analysis of cumulative pro

关 键 词：降尘 粒度 磁化率 磁学特征 

分 类 号：P425.55[天文地球—大气科学及气象学]