Comparison of dust emission ability of sand desert, gravel desert (Gobi), and farmland in northern China

Abstract

It is unclear which of the land types of sand desert, gravel desert (Gobi), and farmland acts as the major source of dust emission in northern China. Based on field observations, this study compared the dust emission ability (E) of the three land types and investigated the principal influencing factors, i.e., horizontal mass flux (Q) and dust emission efficiency (μ). Results showed that E was greatest for sand desert, followed by Gobi and then farmland at low friction velocities (u* < 0.23 m s−1). However, with the increase of u*, the exponential rate of increase of E was fastest for farmland, followed by Gobi and then sand desert. This is because the rates of increase of both Q and μ were fastest for farmland and slowest for sand desert. Consequently, as u* increased the E of both Gobi and farmland gradually exceeded that of sand desert. Gobi was found to have the greatest E under most u* conditions (0.23–0.90 m s−1) because of the overlapping effects of the comparatively strong Q and high μ. The E of farmland exceeded that of Gobi under extreme u* conditions (>0.90 m s−1) owing to its lower Q but faster rate of increase of Q and μ as u* increased. The findings of this study illustrate that the effect of wind velocity and dust size should be taken into accountwhen comparing the E of different land types.