Wind erosion: mechanics of saltation and dust generation
Singh, Udai Bhan
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Soil erosion by wind and associated dust generation cause major social and economic problems in many parts of the world. There is a high cost associated with on-site and off-site damages due to wind erosion. Wind erosion of top soil causes loss of essential plant nutrients and soil productivity, resulting in loss of agricultural production. Visibility reduction on highways during dust storms can cause severe accidents. Fine dust particles suspended in air deteriorate the environmental air quality. Particulate matter smaller than 10 jim in size (PM,o) are also recognized as health hazards to human and animals. Off-site costs of wind erosion are much higher than on-site costs. The reference saltation height and ref erence concentration in the saltation zone must be determined to accurately predict dust concentrations and visibility at different heights in the atmosphere. The rate of dust generation depends on kinetic energy from saltating particles during the wind erosion process and dust potential in natural soil. The mechanics of saltation and dust generation and the relationship between kinetic energy of saltating particles and dust generation are not very well understood. An experiment was carried out in a wind tunnel to collect mean saltation height and maximum transport data for three different uniform particle sizes and a physically based model was developed to predict mean saltation height as a function of particle size, wind velocity, and material properties. Data on soil particle concentration with height in the saltation zone were analyzed to develop a general equation to predict soil particle concentration with height as a function of friction velocity and particle size. A methodology was also developed to connect dust generation to the wind erosion process. A controlled energy dust generator (CE/DG) was designed and developed to relate dust generation to the wind erosion process. The device was tested with seven different soil types to investigate the relationship between dust emission and kinetic energy from abrasion during wind erosion.