Wind Tunnel Experiments on Volcaniclastic Dust Emission and Dispersion Initiated by Water Droplet Impact

Abstract

AbstractIceland contains active dust regions within high‐latitude, cold‐climate environments. An abundant supply of particulates <10 μm in diameter (PM10) is available within its extensive glacial outwash plains and through widespread transport and deposition of volcanic ash with hydrophobic tendencies. The climate is notably wetter than dust regions located in hot deserts, so that additional processes governing dust emission must be considered, inclusive of rain splash. Field workers in Iceland report that dust emission events sometimes overlap with precipitation. This study used high‐speed photography in wind tunnel experiments to assess the influence of water droplet impact and wind shear on the detachment and suspension of particulates collected from several active dust source regions within Iceland. Concentrations of PM10 sampled downwind of a single water droplet impact reached values as high as 104 μg m−3 and were positively correlated with increasing wind speed, droplet impact velocity and angle. Our measurements demonstrate that wind shear in a turbulent flow is important for the dispersion of aerosols ejected via water droplet impact from the surface of dry sediment, and that these coincident mechanisms can be highly effective agents of erosion, especially in light winds that are normally incapable of dust entrainment. Foremost, this study provides further evidence of the complexity of dust emission in cold environments and the importance of examining this phenomenon over a wide range of temporal and spatial scale.