Comparison of Two Different Dust Emission Mechanisms over the Horqin Sandy Land Area: Aerosols Contribution and Size Distributions

Dust aerosols (PM₁₀) emission fluxes due to convective turbulent dust emissions (CTDE) and saltation-bombardment and/or aggregation-disintegration dust emissions (SADE) events over the Horqin Sandy Land area in Inner Mongolia were comparatively studied. The annual cumulative dust fluxes released by SADE and CTDE events from 2011 to 2015 were approximately of the same order of magnitude (10³~10⁴ µg m^-2 s^-1). The particle (PM₂₀) size distributions (PSDs) during CTDE and SADE events were also simulated. These PSDs during SADE and CTDE events over the Horqin Sandy Land area were simulated based on the fragmentation theory. The results indicated that an improved version of fragmentation theory could be applied to describe the PSD over the Horqin site and that was more applicable to SADE which could be explained by the different dust emission mechanisms involved. The number-related mean aerosol diameters (D_N) barely varied under different friction velocity () for SADE events, while the volume-related mean aerosol diameters (D_V) changed distinctly with the change in . For CTDE events, the and had no obvious relationship with the change of because of the mechanism involved. The mass-related PSDs during SADE events mostly tended to have one peak between , while for CTDE events there was a wide peak in the range of . The results suggest that should be not be used as an individual parameter to describe the PSD. However, the mass-related PSD could be used to effectively distinguish the SADE and CTDE events.