Quantification of the dry aeolian deposition of dust on horizontal surfaces: an experimental comparison of theory and measurements



    1. Physical and Regional Geography Research Group, Katholieke Universiteit Leuven, Redingenstraat 16 bis, B-3000 Leuven, Belgium (E-mail: dirk.goossens@geo.kuleuven.ac.be); Erosion and Soil & Water Conservation Group, Wageningen University and Research Centre, Nieuwe Kanaal 11, NL-6709 PA Wageningen, The Netherlands; Laboratoire Interuniversitaire des Systèmes Atmosphériques, Université de Paris 12, 61 av. du Général de Gaulle, F-94010 Créteil, France
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Eight techniques to quantify the deposition of aeolian dust on horizontal surfaces were tested in a wind tunnel. The tests included three theoretical techniques and five measurement techniques. The theoretical techniques investigated were: the gradient technique, the inferential technique without grain-shape correction, and the inferential technique corrected for grain shape. The measuring techniques included the following surrogate surfaces: a water surface, a glass surface, a metal surface, a vertical array of metal plates, and an inverted frisbee filled with glass marbles. The efficiency of the techniques was investigated for the sediment as a whole (all grain sizes together) as well as for a large number of grain sizes extending from 1 to 104 μm. The surrogate surfaces showed more or less comparable catch efficiencies, although the water surface nearly always caught the highest quantities of dust and the marble-filled frisbee and the vertical array of metal plates the lowest quantities of dust. The dust fluxes calculated by theoretical methods were markedly different from those obtained by direct measurements. The fluxes calculated by the inferential technique approximated those of the direct measurements only for grain sizes between 30 and 40 μm. For smaller and coarser grains, deviations from the measured fluxes were high. The gradient method, in its turn, provided extremely low calculated fluxes for grains in all size classes investigated. The latter technique was not considered very reliable for the dust used in the tests.