Effects of soil moisture and physical sand content on wind erosion modulus in wind tunnel testing

In order to explore the effects of soil moisture and physical sand contents on wind erosion modulus, seven artificial soil type treatments with physical sand contents of 20 %, 30 %, 40 %, 50 %, 60 % and 70 %, eleven treatments with soil moisture contents from 0 to 10 % at 1 % a step, and six wind speed treatments with 5, 6, 9, 12, 15 and 18 m/s, were tested in a instrument of wind erosion tunnel. The wind erosion amount was measured after 10 min wind blowing at 10 different heights of 20, 60, 120, 180, 240, 300, 400, 500, 600 and 700 mm with a cyclone sand collector, which set at placements of 1.2 m away from the wind tunnel. The results were integrated by using cubic spline interpolation method in MATLAB 7.4.0 (R2007) and were computed to wind erosion modulus E. The results showed that the wind erosion amount was very small when the sand content was less than 40%, showed no significant effects for water contents and collecting heights. The amount of wind erosion collected fitted a exponential function at spatial scale when physical sand quality fraction was smaller than 20%, it well fitted both exponential or power functions when physical sand quality fraction was ranged between 20% to 40%, and it fitted a power function when the sand content was higher than 40%. The wind erosion showed an exponential increase against the heights when the wind speed was slower than 9 m/s, and changed to a power function when it was faster than 9 m/s. The total amount of wind erosion in collectors at different heights was exponentially increased with the wind speeds. There were no significant difference in wind erosion accured when the sand content less than 40%. When sand content increased to more than 40%, the wind erosion increased along with increasing sand contents, especially when the soil moisture content was lower than 3%. The E showed an exponential increase against wind speeds. We concluded that the north side region of Yinshan Mountain, Inner Mongolia, China would be an important source of sandstorm with considering the soil moisture contents and physical sand contents, because the soil moisture content, in this region, was often less than 3% to 4 % in spring and winter seasons, the sand contents were more than 50% to 80%.