Implications of surface properties for dust emission from gravel deserts (gobis) in the Hexi Corridor

Abstract

Gravel deserts (gobis) may be primary dust sources in China, where they occupy almost the same area as sandy deserts. The obvious difference between gravel and sandy deserts is the dominant grain size in the surface sediments: fine in sandy deserts versus coarse in gravel deserts. Potential sand transport, gravel cover, and the mean grain size of the surface sediments of gravel deserts are the main factors that affect dust release. However, little data is available on these properties. In the present study, we estimated gravel cover in surface photographs using ImageJ software, determined the proportion of the total weight accounted for by gravel (diameter>2mm), and described the grain size distribution for study areas in the Hexi Corridor of northern China. We found statistically significant differences between the proportions of total weight as gravel among five sub-regions. This proportion ranged from 22 to 91% of the total (66±17%; mean±SD), and the proportions in most of the samples (73%) ranged from 40 to 80%. The gravel cover ranged from 15 to 87% (52±17%), which was within the range in previous research that produced maximum aerodynamic roughness. The sandy material in the surface sediments was mainly medium sand, which accounted for 52.5% of the total sample. Potential sand transport was >200vector units in most gravel deserts, and 75% of the study sites had a physical soil crust. The high gravel cover and frequency of surface crusts is likely to decrease dust emission from the gravel deserts of the Hexi Corridor.