关键词: 河北坝上, 高原, 风蚀物, 垂直分布

Abstract: The sampling and measurement of wind dust over crop land in Bashang plateau,Hebei Province,was conducted.The results show:in 20 cm above soil surface,the concentration of wind dust decreases in exponential function law with the increasing height,which describes the sand flow structure predominated by saltation;and from 20 to 100 cm,the concentration decreases in power function law,which describes the sand flow structure predominated by suspension.With increasing height,the percent of sand decreases,but the percent of silt and clay increases.Futhermore,as the wind velocity and flux increasing,the percent of sand increases other than the percent of silt and clay decreasing.The correlation between the percent of different grain size and height shows:the percent of particles with diameter of 0.25~0.1 mm easy to moved in saltation decreases in power function law;and the percent of particles with diameter less than 0.1 mm increases with increasing height in power function law.In addition,the mean diameter of individual particles decreases with increasing height.At 50 cm height,the diameter of particles is less than 0.1 mm.Consequently,only when soil particles suspended to above 50 cm,they may be transported to great distance.

Key words: Wind dust of soil, Vertical distribution, Bashang plateau in Hebei Province