Dust Emission From Types Of Loessal Soil And Verification Of DPM Model

This article take the young fruit tree cultivates base in Yan'an Ansai as the main object , uses the value simulation and the observed value contrast analysis method to compare the aerodynamic roughness length and threshold frictional velocity of farmland surface at different crop growing stage(seeding cultivate stage and transplanted stage); the dust emission was observed and the authentication of DPM model was verified at transplanted stage. The parameter scheme for computed dust emission flux was established, and the modification of DPM model which can be used on farmland of lou soil was also discussed. The main Conclusion are as follow:(1) According to the result of soil dry sieving, the micro-aggregates size distribution was can be expressed as a mixture of two lognormal mass size distribution populations, the mass median diameters were 210μm and 736μm, and the standard deviation of them were 1.40 and 1.35, the ratio of the micro-aggregates mass was 35:65.(2) The average value of roughness length in seeding cultivate stage and transplanted stage were 28.3758cm and 0.0647cm. The presence or absence of vegetation cover on the surface roughness has a significant influence.Wind friction velocity by the impact of Wind speed and surface roughness . The average wind speed friction range is 23.9442-30.8256cm/s, The threshold frictional velocity in seeding cultivate stage and transplanted stage were 139.15/cm sand 26.01cm/s.(3) The measured and computed vertical fluxes were 6-23μg/m~2·s and 41-63μg/m~2·s respectively, both at the range of 10~1-10~2μg/m~2·s.(4) The parameter scheme for computed dust emission flux was established, and the modified model of farmland of loessal soil at transplanted stage:(5) According to starts the mechanism of the dust particle combines with DPM model the analysis of parameters,explore the effects factor of dust release flux and the corresponding measures to suppress dust. By increasing the surface roughness threshold frictional velocity and weakens the wind speed will be able to effectively control the release of dust. Through to the Yan'an Returning farmland to forest project's dust suppression effect preliminary quantification, under the perfect condition take the Returning farmland to forest area 873.06 million mu as the example, every year can suppress the dust release quantity is 1.4 million tons, the dust suppression effect is more obvious, has the good ecological benefit.