Effect of wind speed and soil particle size distribution on sediment transport mechanisms due to wind erosion

Wind erosion is one of the aspects of land degradation resulting in some problems especially for arid and semi-arid regions. Recognition of Sediment size Distribution (PSD) as well as transport mechanisms is important in modelling of wind erosion. In the present study، this topic was investigated on two soils taken from cropland and sand dune with different PSD، using wind tunnel. Results showed that compared to the original soil، the collected sediment had finer sizes، indicating a selective mechanism in transporting detachable particles. It was found that for cropland soil، increasing wind speed from 2 to 18 m/s at the height of 20 cm، the PSD of sediment approached to the original soil. This trend was reverse for sandy soil so that، for higher wind velocities، the frequency of fine particles was more than the original soil. The result of transport mechanisms indicated that compared to saltation as well as suspension، creeping was the least important mechanism. The contributing percentage of creeping for cropland and sandy soils was determined less than 10 and 1 %، respectively. For the cropland soil at wind speed of 2 m/s، suspension was the most important mechanism of transport and depends on soil''s PSD، 61. 1- 68. 5 % of particles were transported. Increasing wind speed up to 18 m/s، saltation with 50. 4- 53. 8 % was found as the main transport mechanism. Reversely، in the sandy soil at low wind speed، most of sediment (59. 3 %) was transported through saltation، whereas increasing the speed، suspension with 55. 3 % became the dominant mechanism. The finding of this study brings up the important of soil PSD on the PSD of sediment as well as transport mechanisms.