不同类型农田地表粉尘起动摩阻风速的野外观测

Field Observation of Dust Threshold Friction Velocity on Different Types on Farmland Surfaces

[目的]为北方城市空气污染控制提供依据。[方法]选择不同地表类型,观测起尘差异,分析表土微团粒粒度,计算起动摩阻风速。[结果]沙化农田的光滑地表空气动力学粗糙度(Z0s)为0.001 2 cm,小麦地为0.002 1 cm,果树苗地的为0.002 5 cm。有植被覆盖的地表粉尘起动摩阻风速明显高于裸露地表,且随着植被高度增加而增大。延安果树苗地地表起动摩阻风速达到了139.15 cm/s。裸露小麦地和果树苗地地表粉尘起动摩阻风速大于裸露沙化农田(7.39 cm/s)。小麦返青期、成熟期、收割后地表粉尘起动摩阻风速分别为46.85、98.93、29.05 cm/s,裸露地表和幼苗期果树苗地地表粉尘起动摩阻风速分别为26.01和139.15 cm/s。[结论]植被高度和土壤结构性质是影响地表粉尘起动摩阻风速的重要因素。

[ Objective] The study was to provide the basis to control the air pollution in northern city. [ Method] Different types of land surfaces were collected to observe the difference of dust explosure. The size of micro - aggregates in surface soil was analyzed and threshold friction velocity was calculated. [ Result] The smooth surface aerodynamic roughness of desertification farmland （Z0s） was 0. 001 2 cm, that of wheat land was 0. 002 1 cm and that of fruit seedling land was 0. 002 5 cm. The dust threshold friction velocity on soil surface covered by vegetation was obviously higher than that of exposed surface and it increased with the rise of vegetation height. The dust threshold frictional velocity on fruit seedling land in Yanau reached 139.15 cm/s. The dust threshold friction velocity on the exposed wheat land and fruit seedling land was bigger than that of the exposed desertification farmland（7.39 cm/s）, that on wheat land surface at returning green stage and mature stage, after wheat harvesting was 46.85, 98.93, 29.05 cm/s resp. and that on the exposed surface and the land of fruit seedling in seedling stage was 26.01 and 139.15 cm/s rcsp. [ Conclusion] Vegetation height ad soil structure property was the main factors influencing threshold frictional velocity.