Aeolian dust dynamics in agricultural land areas in lower Saxony, Germany

The dynamics of fine aeolian dust emitted from agricultural land was invest igated over 15 months near Gronheim, Lower Saxony, Germany. The following a spects were studied: airborne dust concentration, the ratio of mineral vers us organic dust, the vertical distribution of the particles in the atmosphe re, horizontal and vertically integrated horizontal dust flux, vertical dus t flux, dust deposition at ground level, grain-size distribution of the min eral dust component, and vertical distribution of organic matter in the dus t. Standard meteorological parameters (wind speed and direction, precipitat ion) were measured as well. Dust activity in Gronheim is high in spring (Ma rch-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 durin g 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 o f 15.8 ton km(-1) a(-1) was calculated for the first 10 in of the atmospher e 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 mi neral dust, emitted from the fields during tillage or during wind erosion e vents. In spring and autumn there is a strong vertical stratification in th e airborne sediment, with much (coarse) dust in the lower air layers and si gnificantly 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 spri ng and autumn is exclusively caused by the mineral part of the dust. The or ganic particles are much better mixed in the atmosphere because of their lo wer density. Copyright (C) 2001 John Wiley & Sons, Ltd.