Abstract:

The Taklimakan Desert is located in the extreme arid region of our country， which is the largest desert in China and a major dust source region in East Asia. The characteristics of sand transport rate and particle size are the main research contents of aeolian sand activities. However， there have been few actual observations on the transport rate of sand dunes in Taklimakan Desert， so it is difficult to clarify the formation process of sand dunes and the characteristics of dust activities in this desert. In this paper， the transport rates and particle sizes of 6 different dunes （trellis dune and linear dune） in the desert and 2 neighboring regions （scrub dune and gobi） were observed in the field， and their spatiotemporal distributions were investigated. The results are as follows： （1） The sediment transport rates of each station in Taklimakan Desert decreased exponentially with increasing height， from 10.19±6.23 kg·m^-1·month^-1 at a height of 0.25 m to 0.05±0.02 kg·m^-1·month^-1 at a height of 2.5 m， and the decreasing rate slowed down with the increasing height. The fitting coefficients b₁ and the absolute value of c₁ represent the attenuation rate of the sediment transport rates. The maximum and minimum values of b₁ were 82.03 and 0.91 respectively， and the maximum and minimum values of c₁ were -0.61 and -7.83， respectively. （2） The average particle sizes of sand grains in the Taklimakan Desert decreased exponentially with increasing height， from 2.84±0.69 Φ at the surface to 3.94±0.89 Φ at a height of 2.5 m. The average particle size of sand grains in the gobi showed an "elephant trunk" distribution below a height of 0.5 m （the average particle sizes at the surface， 0.25 m and 0.5 m is 2.95 Φ， 2.65 Φ， and 3.07 Φ， respectively）. Above a height of 2 m， the average particle sizes of sand grains decreased significantly in linear dune （3.81 Φ at a height of 2 m and 5.09 Φ at a height of 2.5 m） and gobi （3.92 Φ at a height of 2 m and 5.33 Φ at a height of 2.5 m）， but increased in scrub dune （3.77 Φ at a height of 2 m and 3.16 Φ at a height of 2.5 m）. （3） The particle sizes smaller than 63 µm （from 9.26%±8.29% at the surface to 32.86%±24.88% at a height of 2.5 m） and larger than 125 µm （from 52.76%±20.84% at the surface to 24.5%±11.56% at a height of 2.5 m） varied exponentially with increasing height. The particle sizes of 63-125 µm （37.98%-42.63%） did not change significantly with height. In linear dunes and gobi， the high content of silt and clay at 2.5 m indicated that this is one of the dust-release sources. The increased content of silt and clay implies that the Taklimakan Desert is one of the dust sources compared to other deserts.

Key words: Taklimakan Desert, aeolian sediment transport rate, particle size, distributional law