塔克拉玛干沙漠腹地复合型纵向沙垄区近地层沙尘水平通量及粒度特征

Dust Horizontal Flux and Grain Size Characteristics of the Near-Surface on Compound Longitudinal Dunes in the Hinterland of Taklimakan Desert

利用BSNE梯度集沙仪采集塔克拉玛干沙漠腹地复合型纵向沙垄区近地层80m高度内秋季不同高度的沙尘物质,探讨沙尘天气下水平输沙通量差异及沙尘的粒度特征。结果表明：由于受到复合型纵向沙垄的影响,沙尘天气过程近地层沙尘水平通量并不遵循幂函数或指数函数分布,在20m以下随高度增加而降低,在32~63m随高度增加而增大,并且在24m和63m两个高度处出现转折点。各层沙尘平均粒径64~80μm,以极细沙为主,分选系数0.96~1.12,分选性中等偏差。粒径频率曲线呈双峰分布,主峰值出现在80~110μm,次峰值在10~12μm,反映了沙尘组成的复杂性,远源沙尘在各高度层的变化幅度较小,以局地和区域源为主。沙尘水平通量与沙尘粒度变化表明沙尘天气主导风速风向、强烈的上升运动及纵向沙垄是影响沙尘水平通量垂直差异的重要因素。

In the hinterland longitudinal dunes of the Taklimakan Desert, in order to explore the differences of dust horizontal flux and grain size characteristics of the near-surface in dust weather, we use BSNE sam- plers to gather sand-dust of different heights within 80 meters above the surface in the fall of 2014. The results show that the horizontal sand-dust flux of the near-surface is neither in power function distribution nor exponential function distribution during dust weather processes due to the influence of the compound longitu- dinal dunes. It decreases with the height below 20 meters, while increases with the height of 24--63 meters, and 24 m and 63m are the turning points. The mean particle size of each layer is between 64--80 t,m, dominated by very fine sand. The sorting coefficient is between 0. 96--1.12, belonging to general sorting. The grain size frequency curve shows double peaks in the distribution. The main peak appears between 80-- 110 μm, the second peak in 10--20 μm. Multi peak reflects the complexity of the dust composition. Remote dust in each layer changes small, the major sand are local and regional sources. The variety of dust horizon- tal flux and grain size suggests that the leading wind speed and direction, strong rising motion and longitudi- nal dunes are the main reasons to the vertical differences.