The Temporal And Spatial Variety Of Atmospheric Dust Fall In The Northeast Margin Of Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau is regarded as a potential dust source region.Especially for Qaidam Basin, the lack of rainfall, the frequent occurrence of sandstorm and severe wind erosion exist pereninally. The results imply that the Qaidam Basin is a majoy source of dust to the Chinese Loess Plateau. In the northeast margin of Qinghai-Tibet Plateau, where is an major dustfall deposition area and necessary passage where Qaidam sandstorm moves towards the east. The characteristic analysis of temporal and spatial variety was carried out on the samples of dust in the northeast margin of Qinghai-Tibet Plateau, which contributes to understand the contemporary process and mechanism for dust transportation in Qinghai-Tibet Plateau region. The dust cylinders are set at Xiaobohu spot by the Qinghai Lake, Duoba spot in Xining city and the roof of Science Building at Qinghai normal university in Xining city and dust is collected by wet trap method between December 2013 and May 2015. In this article, the grain size,the flux and Magnetic susceptibility of samples are applied to study the temporal and spatial variety. The results indicate that:(1)The grain size distributions of all samples are extremely similar and mainly composed of silt(4-63μm).The frequency curve of dust in Xining city under sandstorm weather and non-sandstorm weather exhibits approximately normal distribution.The dust collected under sandstorm weather is more coarse than that under non-sandstorm weather.The mean grain size of all samples in XBH spot,DB spot and KJLD spot are 37μm,34μm and 31μm respectively. The median grain size are 31μm,27μm and 26μm respectively. Comparing with grain size characteristic of sandstorm in Lanzhou city at lower altitude,it shows that the grain sizes possess altitude dependence, which turns coarser with increasing altitude.(2)The dust deposition flux of Xining city is 442-542g/m2·a in 2014. The dust deposition flux of Qinghai lake is 415g/m2·a in 2014. The dust deposition fluxes of all spots have significant variations during the year and seasonal variation trend is consistent. The dust deposition mainly concentrates in the winter and spring. The minimum fluxes of dust deposition appear in the summer.(3)mineral content of dust fall in the three points have the same change characteristic in the same year.magnetic mineral content in heating period is higher than that in No heating period,which ismore prominent in Xining point and Duoba point. The magnetic susceptibility of three points rises gradually.The magnetic susceptibility of Xining point is much more higher than the two other points.What lead to this is that Human activity intensity is more serious in Xining city and the severe pollution.Comparing with the magnetic susceptibility parameter of dust fall in Lanzhou,it shows that inter-annual magnetic susceptibility changes unobviously. The inter-annual mineral content of dustfall of Xining is more abundant than that in Lanzhou.