Aeolian dust transport represents an important component of Earth's biogeochemical cycles, as is convincingly demonstrated by the formation of China's Loess Plateau and other loess deposits around the world over millions of years (Goudie and Middleton, 2006 A.S. Goudie and N.J. Middleton, Desert Dust in the Global System, Springer Press, Germany (2006).[Goudie and Middleton, 2006], [McTainsh and Strong, 2007] and [Liu, 2009]). The strong dust transport that occurs during dust storms often creates a serious hazard for humans (Zhao, 1993). Consequently, the significance of aeolian dust for geomorphology, climatology, meteorology, ecology, and environmental science has received widespread attention in recent decades (Stout et al., 2009).

The effects of aeolian dust depend on the amount of dust being transported, as well as on its particle-size distribution. A wide variety of techniques have therefore been developed to measure the amount of aeolian dust (Middleton, 1997). The process of aeolian dust transport is composed of several sub-processes, including the emission of dust particles into the air, horizontal transport of the dust particles in the air, and their deposition (Pye, 1987). Dust particles emitted into the air are transported by the wind for different distances, depending on the particle size and wind conditions, before being deposited again as dustfall. As a result, differences are observed in the amounts of dust emission (defined as the “emission flux”), transport (defined as the “horizontal flux”), and deposition (defined as the “deposition flux” or the “dustfall flux”). Data on the horizontal dust flux are only available for a few places around the world, even though records of dustfall events date back to the ancient history ([Zhang, 1985] and [Offer and Goossens, 2001]).

In studies of aeolian dust, the most important parameter is the amount of dust transported in the air (i.e., the horizontal dust flux). However, measuring this flux remains a difficult task, even though many efforts have been made since the 1980s to monitor the concentrations of airborne particulates (Yang et al., 2005). The majority of these attempts have estimated dust transport indirectly by measuring dustfall using dust gauges (Pye, 1987). Relatively few reports have been published about direct measurement of the horizontal aeolian dust flux. Hence, obtaining measurements of horizontal aeolian flux will significantly increase our understanding of wind erosion and dust problems.

The main sources of aeolian dust are located in the world's arid and semi-arid regions, although desiccated sediments in any environment can produce dust ([Prospero, 1981] and [Middleton, 1997]). Desertified lands resulting from adverse human behaviors such as excessive land reclamation for agriculture and over-grazing are becoming more important dust sources. The dirty 1930s (“dust bowl”) in America, black dust storms in the former Soviet Union in the 1950s that blanketed Middle Asia, and the serious dust storms in the Sahel region of North Africa between the late 1960s and early 1970s are classic examples of human impacts on the production of aeolian dust.

The deserts and desertified lands of China's arid and semi-arid regions are currently considered to be the main sources of Asian dust (Liu, 2009). The Hexi Corridor in northwestern China, which stretches over 1600 km, is an important dust source and corridor for dust transport due to the area's “funneling effect” and the vast expanse of deserts and desertified lands (Zhang et al., 1998b). The sand and dust storm that occurred on 5 May 1993 in the Hexi Corridor, especially in the eastern part of the corridor, caused an estimated economic loss of 500 million RMB (about 74 million US dollars) and killed many people and livestock (Zhao, 1993). Meteorological records (1952 to 2000) reveal that the Minqin area, in the eastern Hexi Corridor, is a place where the frequency of severe sand and dust storms is higher than in any other part of China (Qian et al., 2002). As a result, the area is a key source area for Chinese dust storms. Minqin is also an area where desertified lands have expanded rapidly both during historical periods and during the last five decades due to adverse human activities (Song et al., 2003). A pessimistic view is that Minqin will become China's second Lop Nur, another famously degraded area in Northwest China. Minqin's dust directly affects areas to the east, including much of the Asian and Pacific Ocean regions ([Wang et al., 1995], [Qian et al., 1997], [Zhang et al., 1997] and [Zhang et al., 1998a]). Thus, it is important to understand the amount of dust being transported from the Minqin area.

Although research designed to provide guidance for rehabilitating the degraded environment of Minqin started in the 1950s, few studies of aeolian dust have been conducted until the last few years. To support such studies, we mounted aeolian dust samplers on a 50 m monitoring tower in the Minqin area in May 2007 to provide measurements of the horizontal aeolian dust flux at different levels. The present paper presents some results for the amount of horizontal aeolian dust flux and its variation with height and time based on continuous observations from May 2007 through April 2008.

Minqin has become one of the key dust source areas in China due to its severely degraded eco-environment. However, little is known about how much dust is emitted and transported in this area. Aeolian dust samplers were mounted at 15 heights on a 50 m monitoring tower in Minqin in May 2007 to monitor the horizontal aeolian sediment flux. The monitoring data suggests that the total annual horizontal aeolian sediment flux over Minqin is about 8700 kg m− 1. Of that annual total, the flux in the PM63, PM20, and PM10 size classes amounted to 1730, 780, and 580 kg m− 1 respectively. The flux in May and June accounted for 64% of the annual total, with a minimum in October. The horizontal aeolian sediment flux, including dust flux, decayed rapidly with increasing height following a modified power function, in agreement with the results of several previous studies. The sediment flux in Minqin depends primarily on the wind's characteristics, especially the maximum wind speeds (which create strong aeolian transport). Precipitation in this arid region had limited significance for reducing aeolian sediment transport. The mean diameter, standard deviation, skewness, and kurtosis of the aeolian sediments varied with height, but varied most significantly within 9 m above the surface. The mean diameter of the aeolian sediment ranged from 20 µm (5.6 ø) to 95 µm (3.4 ø), and thus primarily represents suspended dust, even though coarse particles of organic and salt aggregates are also present.