Search

A series of experiments to determine the direct emission of dust-sized particles from Gobi surfaces by clean wind (wind without sand), and the potential for aeolian abrasion of Gobi surfaces and beds of gravel and mobile sand to produce fine (<100 μm) and dust-sized (<10 μm, PM) particles under sand-laden winds were conducted. Parent material was obtained from Gobi areas of the Ala Shan Plateau, the region with high dust emissions in arid China. The fine particles produced by aeolian processes were collected using sand traps and sieved the captured materials to exclude particles >100 μm in diameter and then PM by sedimentation was acquired. The Gobi surface provided most of the emitted fine particles during the initial dust emission processes, but subsequently, release of the clay coatings of particles by abrasion becomes the dominant source of fine materials. Under sand-laden winds, PM production rates produced by aeolian abrasion of Gobi surfaces ranged between 0.002 and 0.244% of blown materials. After removal of sand, silt, or clay with low resistance to erosion from the Gobi surfaces by the wind, the PM production rates caused by aeolian abrasion were similar to those from gravel and sand beds. The results also indicated that after the dust-sized particles with low resistance to erosion were removed, the production of dust-sized particles was unrelated to wind velocity. Under aeolian processes, Gobi deserts in this region therefore play a major role in dust emissions from arid and semiarid China. [ABSTRACT FROM AUTHOR]

Abstract: Gobi deserts of the western region of Inner Mongolia are potential dust source area and a dominant source of soluble salts that are transported into eastern Asia and the western Pacific. Currently, the salt species, their emission magnitudes, and their spatial trends in this source area are poorly understood. In the present study, we used intact surface samples and wind tunnel experiments, combined with salt and particle size data, to estimate the spatial trends of ionic species and the contents of terrestrial-derived soluble salts in this region. The salt contents in the surface materials range between 0.28 and 14.78‰ (by mass). However, the salt contents in materials transported by the wind ranged between 1.55 and 16.95‰. In this region, the soluble salts in the PM50 and PM10 fractions ranging between 0.008 and 0.913‰ and between 0.004 and 0.583‰, respectively, with SO4 2− and Ca2+ contents far higher than those observed in previous studies in East Asia and the western Pacific. Areas with the highest salt emissions were located in the western Ala Shan Plateau and in southwestern Mongolia, and the contents decreased moving towards the southeastern Ala Shan Plateau. In addition, wind tunnel experiments showed that under wind velocities ranging from 8 to 22m/s, the soluble salts ranged between 0.64 and 8.49%, with a mean of 3.45%. Given the significance of western Inner Mongolia for global dust emissions, the emissions of terrestrial-derived soluble salts from these areas should be carefully evaluated in future dust aerosol studies. [Copyright &y& Elsevier]