Surface Particle Size Characteristics of Dry Lake Beds in Grasslands and Their Effects on Dust Release

Abstract

[Objective] In order to explore the typical surface wind erosion process of the dry lake basin and the mechanism of the formation of saline-alkali dust storm. [Methods] Taking the Chagannaoer dry salt lake in Abaga Banner of Xilin Gol League as the research object, four different surface types (crust surface, broken surface, activated surface and desertification surface) were selected according to the dynamic evolution process of salt lake surface from the lake center to the lake shore. The characteristics of soil particle size distribution, wind speed profile and sediment transport law near the surface from the lake center to the lake shore were analyzed. [Results] (1) Extending from the center of the lake to the shore of the lake, the grain size of 0—2 cm sediment on the surface showed a trend of gradually thickening, and the clay and silt were the main particles. (2) The wind speed from the center of the dry salt lake to the shore of the lake showed a decreasing trend. Wind speed profiles of different surfaces generally followed the logarithmic distribution of Karman’s velocity, and the fitting effect was good (R2>0.90). (3) The amount of sediment transport on the broken surface was the highest, which was about 50 times that of the crust surface, and the sediment transport rate on the crust surface showed a linear law with the change of height due to limited dust supply (R2=0.80), and the sediment transport rate on the other three surfaces showed an exponential function with the change of height (R2>0.97). (4) Near the surface at a height of 0 to 50 cm, the average particle size of sand particles carried in the wind-sand flow ranges from 2 to 8 μm, which falled under the category of silt, with poor sorting. Skewness was predominantly negative, while kurtosis was mainly medium and sharp. [Conclusion] On the whole, the wind erosion effect on the broken surface was the strongest, and the wind erosion effect on the crust surface was the weakest. The wind erosion effect in this area can be weakened by increasing the critical starting wind speed threshold of sand particles and the coverage of underlying surface.

Keywords

• chagannaoer lake
• dry lake basin
• granularity parameters
• wind-sand flow