Investigating the impact factors of dust emission efficiency over gobi with portable wind tunnel field experiments

The contribution of the gobi to dust emission in arid northwestern China is largely uncertain due to the lack of studies on the surface properties of gobi. The dust emission efficiency (eta) as a comprehensive characterization of surface properties is an essential parameter for quantifying dust emission. However, the main influencing factors of dust emission efficiency are still unclear, as it is a big challenge to do a comprehensive field experiment and get the long-term continuous field data in gobi due to its harsh environment. Here, we are aiming at quantitively identifying the main factors of dust emission efficiency by using a portable wind tunnel for field experiments over the gobi surface in Dunhuang Mogao grottoes. Results showed that (1) the abundance of bombardment sand regulates the relationship between eta and friction wind velocity (u(*)). The eta decreases as a power function with increasing u(*), and the correlation is weak (R-2 = 0.41, P < 0.05) in the shortage of bombardment sand. In contrast, eta increases with u(*) following a power function, and the correlation is strong (R-2 = 0.91, P < 0.05) when bombardment sand is enriched. (2) The surface dust content of the gobi dominates the eta, which increases exponentially with the increased dust content. Relative to u(*), the surface dust content has a bigger contribution to eta. (3) The gobi in Northwest China could be an underestimated dust source, as it has an enriched dust content and a higher eta than sandy desert. Therefore, the quantitative monitoring and further research of dust emissions in the gobi should be strengthened.