Earth surface processes and landforms vol:26 issue:7 pages:701-720
The dynamics of fine aeolian dust emitted from agricultural land was investigated over 15 months near Gronheim, Lower Saxony, Germany. The following aspects were studied: airborne dust concentration, the ratio of mineral versus organic dust, the vertical distribution of the particles in the atmosphere, horizontal and vertically integrated horizontal dust flux, vertical dust flux, dust deposition at ground level, grain-size distribution of the mineral dust component, and vertical distribution of organic matter in the dust. Standard meteorological parameters (wind speed and direction, precipitation) were measured as well. Dust activity in Gronheim is high in spring (March-May) and autumn (October-November) and low to very low during the rest of the year. There is a strong relationship between the periods of tillage and the intensity of dust activity. Also, there is high dust activity during wind erosion events. For the year 1999, dust emission due to tillage was 6.6 times higher than dust emission due to wind erosion. A dust transport of 15.8 ton km(-1) a(-1) was calculated for the first 10 in of the atmosphere in 1999. Total dust transport (in the entire mixing layer) was estimated between 16 and 20 ton km(-1) a(-1). About 25-30 per cent of this dust is mineral dust, emitted from the fields during tillage or during wind erosion events. In spring and autumn there is a strong vertical stratification in the airborne sediment, with much (coarse) dust in the lower air layers and significantly less (and finer) dust at higher altitudes. In summer and winter, when there is no local dust production, there is no stratification: equal amounts of dust are transported at all heights. The stratification in spring and autumn is exclusively caused by the mineral part of the dust. The organic particles are much better mixed in the atmosphere because of their lower density. Copyright (C) 2001 John Wiley & Sons, Ltd.