Characterization of soil dust aerosol in China and its transport and distribution during 2001 ACE-Asia: 1. Network observations

Mass loading, 20 elemental concentrations, and time series of aerosol particles were investigated over the China Dust Storm Research (ChinaDSR) observational network stations from March to May 2001 during the intensive field campaign period of ACE-Asia. Four extensive and several minor dust storm (DS) events were observed. Mass balance calculations showed that 45-82% of the observed aerosol mass was attributable to Asian soil dust particles among the sites, in which Ca and Fe contents are enriched to 12% and 6%, respectively, in the Western High-Dust source regions compared with dust aerosols ejected from the Northern High-Dust source regions. For the latter areas, elemental contents exhibited high Si (30%) and low Fe (4%). For all major source areas and depositional regions, aluminium (A1) comprises 7% of Asian dust. Air mass back-trajectory analysis showed that five major transport pathways of Asian dust storms dominated dust transport in China during spring 2001, all of which passed over Beijing. Measurements also suggest that the sand land in northeastern China is a potential source for Asian dust. The size distribution for estimating vertical dust flux was derived from the observed surface dust size distributions in the desert regions. For particle diameters between 0.25 and 16 μm, a lognormal distribution was obtained from averaging observations at various deserts with a mass mean diameter of 4.5 μm and a standard deviation of 1.5. This range of soil dust constitutes about 69% of the total dust loading. The fractions for particles in the size ranges of <2.5 μm and >16 μm are around 1.7% and 30%, respectively.