Abstract: We monitored the structure of wind-sand flow in nine types of sites in the dry bottom of Qingtu Lake by sand accumulation instrument and analyzed the variations of sediment transport rate, grain size composition and grain size parameters of windsand flow at the height of 0-30 cm in different sites. The results showed that the sediment transport rates and fluxes of seven site types had negative power function relationship with height of 0-30 cm. The sediment transport fluxes of different sites were mainly concentrated in the nearsurface area of 0-20 cm height. Except for fixed-dune Nitraria tangutorum shrub, the sediment transport fluxes of other types accounted for more than 80% of the total sediment transport fluxes at the 0-30 cm height. The sand transport rates of wind-sand flow were high in the height range of 0-30 cm among lake shoal,Kalidium foliatumcommunity in lakebed, and moving-duneNitraria tangutorum shrub. The grain content of wind-sand flow in the three types of sites with higher sand transport rate was mainly composed of fine sand, followed by coarse sand and silt. With increasing height, the content of coarse sand in the three types of sites increased slightly at first and then decreased, while the content of fine sand decreased slightly at first and then increased, and the content of silt increased slightly. The grain size classification of the three types of sites was under the levels of good moderate. The skewness value shifted from near symmetry to positive deviation with the increasing height, while the kurtosis value belonged to medium kurtosis distribution.

Key words: Qingtu Lake, wind-sand flow, sediment transport rate, structure, grain size parameter.