半湿润地区农田土壤粉尘释放的风洞模拟研究

Farmland Soil Dust Emission in Semi-humid Areas by Wind-tunnel Simulation

采用风洞模拟手段对地处半湿润区的北京市农田土壤风蚀中的粉尘释放规律进行研究。结果表明,研究区农田粉尘释放强度随风速增大呈指数规律增大,粉尘在风蚀物的含量随风速增大呈指数规律降低。近地表粉尘质量流量随高度增加呈幂函数规律降低,在风蚀物中的含量随高度增加呈线性增大。粉尘粒径随风速增大而变粗,之后达到稳定状态。近地表粉尘粒度组成沿垂直方向的变化可以划分为两段,0～20 cm高度层的双峰态分布和20～60 cm高度层的三峰态分布。随着高度增加,释尘粒度组成变细。

Farmland dust emission law in Beijing area that locates in sub-humid areas is studied in the paper by means of wind-tunnel simulation on the basis of field survey, observation and samples collection. The re- suits show that the intensity of farmland dust emission increases exponentially with wind speed increasing, the dust proportion in wind-erosion particles decreases exponentially with wind speed increasing. Near-surface dust mass flow follows the power function decreasing rule with height increasing. Its proportion in erosion par- ticles increases linearly with height increasing. It has a similar trend of dusts mass flow and its proportion in wind-erosion particles in all layers. So there is a well regularity of dusts movement in near-surface that the dusts mass flow increases exponentially with wind speed increasing and decreases w.ith height increasing, and its proportion in wind-erosion particles decreases exponentially with wind speed incre^sing and increases lin- early with height increasing. The dusts coarsen with wind speed increasing and then reach a steady state. The dust particles become thinner with height increasing. The average particle size decreases linearly with height increasing, which is faster in low wind speed and becomes slower with wind increasing. The change of dust particles composition along the vertical direction in near-surface can be divided into two sections： it presents the bimodal distribution in 0-20cm height layer, and presents the trimodal distribution in 20-60cm height layer.