Dust emissions from undisturbed and disturbed supply‐limited desert surfaces

Abstract

Aeolian sediment transport systems have been treated frequently as transport limited, where transport is governed by the force of the wind, or as supply limited, where sediment transport is controlled by the availability of surface grains. Although many arid environments are dominated by supply‐limited surfaces, almost all available dust emission and sand transport models are restricted to transport‐limited conditions. To examine the emission of PM 10 (particulate matter ≤10 μ m aerodynamic diameter) and horizontal sand transport from supply‐limited environments, a series of wind tunnel tests were conducted in the Mojave Desert, California. In situ testing was conducted with an open‐floored, portable wind tunnel (12 × 1 × 0.75 m) on a variety of natural soils having disturbed and undisturbed surface conditions. Results indicate that for these supply‐limited environments, PM 10 emissions are primarily driven by the aerodynamic resuspension of loose surface material as opposed to the dynamic entrainment mechanisms associated with saltating grains. Emission rates were directly influenced by wind shear and mechanical disturbance and indirectly influenced by soil texture. In addition, disturbance of the surface was found to increase the potential for multiple emission events, which may affect the temporal accumulation of atmospheric dust.