青藏高原东北部降尘通量及粒度特征分析

Dust Flux and Grain Size Variation Analysis inNortheast Qinghai-Tibet Plateau 

中文关键词:  青藏高原东北部  降尘通量  降尘粒度

英文关键词::Northeast Tibetan Plateau  Dust flux  Dust grain size

中文摘要:

      青藏高原东北缘是柴达木沙尘暴东移的必经之道和沉降区,对青藏高原东北部降尘时空分异特征进行分析,有助于认识青藏高原区域粉尘输送的现代过程和机制。2013年12月至2015年5月分别在青海湖小泊湖(XBH)、西宁多巴(DB)、西宁青海师大科技楼顶(KJLD)设置降尘缸,进行湿法收集。对其降尘通量和粒度特征进行了时空分异特征分析,结果显示,1)西宁地区2014年降尘通量为442~542 g/m²·a,青海湖XBH采集点指示的2014年降尘通量为415 g/m²·a,降尘通量年际变化较大,各站点降尘通量季节变化趋势一致,降尘主要集中在冬春季,夏季降尘通量最低；2)各站点降尘粒度组成特征非常相似,以粉砂为主(4~63 μm),西宁地区尘暴与非尘暴降尘粒度频率曲线呈近似正态分布,尘暴期间降尘粒径较非尘暴时段大；3)XBH、DB和KJLD 3点所有样品平均粒径分别为37 μm、34 μm和31 μm,中值粒径分别为31 μm、27 μm和26 μm；对比低海拔兰州尘暴粒径特征,发现降尘粒径存在一定的海拔依赖性,即粒度随海拔增高逐渐变粗。

英文摘要:

      :Qinghai-Tibet Plateau (QTP) is regarded as a potential dust source region, especially for Qaidam Basin, which is characterized by extreme low precipitation, high frequency of sandstorm and severe wind erosion. According to previous study Qaidam Basin is a majoy source of dust to the Chinese Loess Plateau,and the northeast margin of QTP should be an potential dustfall deposition area and passage. The temporal and spatial variation analysis was carried out on the collected modern dust samples, contributing more knowledge to the land surface process and mechanism for dust transportation in QTP. Three dust collection devices are set at Xiaobohu site east of the Qinghai Lake,Duoba site in Xining rural zone andQHSDKJLD site at Qinghai normal university in Xining urban area, respectively. Dust is collected by wet trap method from December 2013 to May 2015. In the present work,the flux and the grain size of samples are applied to analysis the temporal and spatial variations. Results indicate that:1)The dust deposition flux of Xining area is 442~542 g/m²·a in 2014, and 415 g/m²·a for Qinghai Lake.Dust deposition fluxes of the three sites show a consistent variation trend, and significant variations on the annual intervals. The dust deposition mainly concentrates in winter and spring, and the minimum fluxes of dust deposition appear in summer.2)The grain size distributions of all samples are similar, and mainly composed of silt(4~63 μm).The grain size frequency distribution curve of dust in Xining city under both sandstorm weather and non-sandstorm weather exhibits an approximately Gussian distribution. The dust collected under sandstorm weather is coarser than that under non-sandstorm weather.3)The mean grain size of all samples in XBH,DB and KJLD are 37 μm, 34 μm and 31 μm,respectively.The median grain size is 31 μm, 27 μm and 26 μm,respectively.Comparing with grain size characteristic of sandstorm in Lanzhou city at lower altitude, it presents an altitude dependence, i.e. the dust grainsize increases with the increased altitude.