Study On Blown Dust Characteristics Of PM₁₀ And PM_2.5 From Bare Agricultural Soils Based On Wind Tunnel Experiment

Soil wind erosion dust is one of the main sources of ambient PM10 and PM2.5,which causes serious harm to human and environment.In this study,indoor wind tunnel experiments were carried out to study the threshold wind velocities of PM10 and PM2.5 of five bare farmland soils in Tianjin,analyze the vertical characteristics of PM10 and PM2.5 during wind erosion and use integral formulas to calculate the emission rate at different heights and wind speeds.Meanwhile,Hourly meteorological data,emission rate and emission area were used to estimate the dust emission of PM10 and PM2.5 in Tianjin,and the results of emission rates and dust emission in wind txinnel experiments were compared with those estimated by wind erosion prediction and monitoring system and emission factor method,respectively.The main conclusions were as follows:(1)The threshold wind velocities of PM10 and PM2.5 were in the range of 4-7 m/s at height 10 m.It was mainly caused by the difference of soil physical and chemical properties.(2)At the same wind speed,the average concentration of PM10 and PM2.5 released generally decreases and trend slowed down with the increase of height.At the same height,the average concentration increased with the increase of wind speed.(3)Emission rates and wind speeds increased with exponential function.Emission rates of PM10 and PM2.5 were in the range of 0.7-450?g/m2·s and 0.3-233?g/m2·s,respectively.(4)The annual total emissions of PM10 and PM2.5 from soil dust were 23080 t and 15279 t,the emissions per unit area were 0.62-7.38 t/km2·a and 0.21-5.07 t/km2·a,respectively.(5)Compared with the results of wind tunnel experiment and emission factor method,the annual total emission difference of PM10 was small,the result of wind tunnel experiment was 0.7 times that of the emission factor method,while the result of PM2.5 was 2.3 times higher that of the emission factor method.The results between wind tunnel experiment and field monitoring showed that the wind erosion rates of PM10 and PM2.5 obtained by wind erosion prediction and monitoring system were 0.12 and 0.05 times as much as those of wind tunnel experiment,respectively.