河北坝上高原土壤风蚀物垂直分布的初步研究

根据河北坝上高原农田土壤风蚀物的观测与采样分析结果,风蚀物含量随高度的增加,在0~20 cm高度内以指数函数规律递减,反映了以跃移质为主的风沙流结构;在20~100 cm高度内以幂函数规律递减,反映的是悬移质为主的风沙流结构。在风蚀物粒度组成中,随高度增加,砂级颗粒含量减少而粉砂及粘土含量增多;随风速与输沙率的增加,砂级颗粒含量增多而粉砂及粘土含量减少。对风蚀物各粒级含量与高度的相关分析表明:易以迁移形式运动的粒径0.25~0.1 mm土粒百分量以幂函数形式向上递减;沉降速度较低的粒径<0.1 mm土粒百分含量成幂函数形式向上递增。此外,风蚀物平均粒径随高度变细且在50 cm处细于0.1 mm,因此,土壤颗粒成为悬移物质而上升到50 cm以上高度时可能搬运到较远的地区。

PRELIMINARY STUDY ON THE VERTICAL DISTRIBUTIONS OF WIND DUST OVER BASHANG PLATEAU, HEBEI PROVINCE

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.