Concentration, size-distribution and deposition of mineral aerosol over Chinese desert regions
Zhang, Xiao Y.
Zhu, G. H.
Zhang, G. Y.
- Publisher: Tellus B
(issn: 1600-0889, eissn: 0280-6509)
The mass-particle size distributions (MSDs) of 9 elements in ground-based aerosol samples from dust storm (DS) and non-dust storm (N-DS) periods were determined for 12 sites in 9 major desert regions in northern China. The masses of the 9 elements (Al, Fe, K, Mg, Mn, Sc, Si, Sr and Ti) in the atmosphere were dominated by local mineral dust that averaged 270 μg m−3, and the MSDs for the elements were approximately log-normal. On the basis of Al data, the < 10 μm particles account for ∼84% of the total dust mass over the deserts. Model-calculated (“100-step” method) dry deposition velocities (Vd) for the 9 dust-derived elements during N-DS periods ranged from 4.4 to 6.8 cm s−1, with a median value of 5.6 cm s-1. On the basis of a statistical relationship between D99% (the dust particle diameter corresponding to the uppermost 1% of the cumulative mass distribution) and Vd, one can also predict dry velocities, especially when D99% ranges from 30 to 70 μm. This provides a simple way to reconstruct Vd for dust deposits (like aeolian loess sediments in the Loess Plateau). The estimated daily dry deposition fluxes were higher during DS vs. N-DS periods, but in most cases, the monthly averaged fluxes were mainly attributable to N-DS dust. Two regions with high dust loading and fluxes are identified: the “Western High-Dust Desert” and the “Northern High-Dust Desert”, with Taklimakan Desert and Badain Juran Desert as their respective centers. These are energetic regions in which desert-air is actively exchanged, and these apparently are the major source areas for Asian dust.DOI: 10.1034/j.1600-0889.1998.t01-3-00001.x