Gross erosion, net erosion and gross deposition of dust by wind: field data from 17 desert surfaces

Wind erosion measurements were carried out in Nellis Dunes Recreation Area, southern Nevada, USA. Gross erosion (the total mass of sediment effectively blown away from a surface), gross deposition (the total mass of sediment effectively depositing on a surface) and net erosion (the difference in sediment mass before and after an event) were measured for 1 year, on 17 different types of surfaces developed on loose dune sand, compacted sand, loose silt, compacted and/or aggregated silt, rock-covered sands and silts, mixtures of sand, silt and clay, exposed petrocalcic horizons, gravelly substrata and bedrock. Results showed that net erosion, which is the type of erosion measured in field and laboratory experiments, strongly differs from gross erosion. Activity on a surface is much higher than classic net erosion measurements suggest. Future studies on wind erosion should better acknowledge the distinction between the two types of process. Also, a grain diameter of maximum susceptibility to wind erosion ('optimum deflation diameter') near 70 mu m as proposed by the aeolian literature only exists for net wind erosion. No such optimum diameter was found for gross wind erosion within the particle range 0-100 mu m delineating the transport modes of suspension and modified saltation. In addition, desert surfaces predominantly composed of sand did not show an optimum deflation diameter (for net erosion) around 70 mu m. Instead, there was a preferential grain size around 15 mm at which particles were most vulnerable to net emission. Desert surfaces poor in sand showed the classic value of 70 mu m. This suggests that interactions exist between the type of surface and the susceptibility of particles to wind erosion. This study is solely based on field data. Although results are supported by two previous wind tunnel studies, more wind tunnel experiments documenting the interactions between gross erosion and gross deposition are necessary. Copyright (C) 2010 John Wiley & Sons, Ltd.