Size distribution of mineral dust emissions from sparsely vegetated and supply-limited dryland soils

Authors: WEBB, NICHOLAS - New Mexico State University; LEGRAND, SANDRA - Non ARS Employee; COOPER, BRADLEY - New Mexico State University; Courtright, Ericha; EDWARDS, BRANDON - New Mexico State University; FELT, CHRISTOPHER - Non ARS Employee; Van Zee, Justin; ZIEGLER, NANCY - Non ARS Employee

Submitted to: Journal of Geophysical Research Atmospheres
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2022
Publication Date: 11/8/2021
Citation: Webb, N., LeGrand, S., Cooper, B., Courtright, E.M., Edwards, B., Felt, C., Van Zee, J.W., Ziegler, N. 2021. Size distribution of mineral dust emissions from sparsely vegetated and supply-limited dryland soils. Journal of Geophysical Research Atmospheres. 126(22):Article e2021JD035478. https://doi.org/10.1029/2021JD035478.
DOI: https://doi.org/10.1029/2021JD035478

Interpretive Summary: The size of dust particles emitted into the air during wind erosion determines how soils are affected and how dust influences air quality and climate. However, much remains unknown about how wind speed, soil properties, and vegetation influence the size of emitted dust at different locations. Some studies suggest that when land is unvegetated and soils are loose, the size of emitted dust does not change with wind speed. We measured the size of dust emitted from vegetated landscapes with soils that are crusted and have changing amounts of loose erodible sediment. We found that wind speed has a strong effect on the size of emitted dust particles. Stronger winds produced finer dust at sites with weaker soil crusts and more loose erodible sediment. Predictive models need to consider the changing size of emitted dust particles in different environments in order to more accurately assess wind erosion and dust impacts.

Technical Abstract: Controls on the particle size distribution (PSD) of mineral dust emissions remain poorly understood. Under near-idealized conditions, dust PSDs can appear invariant with wind friction velocity. However, dryland vegetation and soil crusting attenuate friction velocities, supply of loose erodible material, and surface resistance to abrasion by saltating grains. Under such conditions, variability in saltation bombardment efficiency and intensity could have a large effect on dust PSDs. We present dust emission measurements from vegetated, supply-limited aeolian systems that indicate dependence of emission-flux PSD on wind friction velocity. We find the fine fraction (<5 µm) of dust particles increases with friction velocity and saltation intensity. Results suggest models that assume wind-invariance of the emission-flux PSD may only be valid for conditions that enable steady-state saltation. There is a need for dust models to represent variability in emission-flux PSDs for land management, air quality, and climate applications across vegetated and sediment supply-limited drylands.