Aeolian salts in Gobi deserts of the western region of Inner Mongolia: Gone with the dust aerosols

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 SO42 − 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 22 m/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.