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The dust source region in East Asia consists of deserts and gobi-deserts in Northern China and Southern Mongolia. First part of this paper discusses the identification criteria of dust sources. A dust emission mechanism serves as the basis of our analyses and the dust storm frequency is considered the principal criterion. The second part studies Mongolian dust sources. Three types of dust sources in Southern Mongolia are identified and characterized, whose dust emission rates are calculated with US EPA (Environmental Protection Agency) formulas. The dust emission rate increases from north to south across the country by five orders with the strongest dust emission area in the south gobi-area. The third part reveals that the united dust source region in East Asia is comprised of two parts or systems: (a) the Mongolian Plateau dust source system, and (b) the Tarim Basin dust source system. The two systems are related and distinguished not only by topography and the distribution pattern of gobis, deserts and loess lands, but also by soil texture, climate, and dust storm meteorology. For example, M (moving) type dust storms are typical for the Mongolian Plateau system while S (stationary) type dust storms are typical for the Tarim Basin system. Total dust emission from the source region in East Asia is estimated at 10.4 x 10(6) ton yr(-1) for PM10 (dust particles smaller than 10 mum in diameter), 27.6 x 10(6) ton yr(-1) for PM30, and 51.3 x 10(6) ton yr(-1) for PM50. (C) 2004 Elsevier Ltd. All rights reserved.