[1] Simulations of Asian dust emissions over the past 43 years are presented based on a size-dependent soil dust emission and transport model (NARCM) along with supporting data from a network of surface stations. The deserts in Mongolia and in western and northern China (mainly the Taklimakan and Badain Juran, respectively) contribute $70% of the total dust emissions; non-Chinese sources account for $40% of this. Several areas, especially the Onqin Daga sandy land, Horqin sandy land, and Mu Us Desert, have increased in dust emissions over the past 20 years, but efforts to reduce desertification in these areas may have little effect on Asian dust emission amount because these are not key sources. The model simulations indicate that meteorology and climate have had a greater influence on the Asian dust emissions and associated Asian dust storm occurrences than desertification.

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 (Al) 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.

[1] During spring 2002, three dust storm events were monitored by filter sampling in Xi'an near an Asian dust source region of northwest China. The carbonate (CO 3 2À ) fraction was determined by sample acidification and thermal evolution. The CO 3 2À accounted for 8.0 ± 0.8% of particles with aerodynamic diameter 2.5 mm (PM 2.5 ) during dust storms and 4.7 ± 3.0% of PM 2.5 between storms. The ratios of calcium to carbonate carbon were consistent with those of calcite (CaCO 3 ). The d C and d18 O abundances in dust storm samples were À2.7 ± 0.7% and À5.8 ± 1.5%, which differed from À8.3 ± 1.9% for d 13 C and À10.8 ± 2.0% for d 18O during normal conditions. The d 13C is positively correlated with d 18O values (r = 0.78). This first measurement of isotopic abundance in Asian dust indicates the potential to quantify its contribution at distant locations using receptor models. By increasing the alkalinity of ocean water in the Pacific Ocean and buffering the atmospheric acidity of east Asia, the large amounts of airborne CO 3 2À (as high as 44.8 Tg yr À1) entrained by Asian dust may provide an important atmospheric alkaline carbon reservoir for large-scale climatic and environmental changes.