COMPARING DUST EMISSION PROCESSES AND DUST FLUXES FROM DUNE FIELDS AND ASSOCIATED LANDFORMS

Debate continues on the contribution of eolian dune fields as regional and global dust sources. Specific attention has been given to the role of eolian abrasion of quartz in active dune fields as a source of dust; however, the scale of mapping used to estimate dust fluxes from dune fields at regional and global scales often encompasses an “eolian system”: active dunes, interdunes, adjacent playas, sand sheets and vegetated dunes. We used the Portable in situ Wind Erosion Lab (PI-SWERL) to measure dust (particulate matter <10 μm) emission potential from diverse landforms in two end-member eolian systems: the White Sands dune field in New Mexico, composed of gypsum, and the Monahans dune field in West Texas, composed of quartz. Dust fluxes as well as grain size analysis and surface conditions allow us to interpret dust emission processes including saltation bombardment, aggregate disintegration, and abrasion. White Sands is a hot spot of dust emissions where dunes and the adjacent playa both yield similarly high dust fluxes (0.04-8.3 mg/m²/s) primarily by abrasion of soft gypsum sand grains, saltation bombardment, and aggregate disintegration from the playa. In contrast, portions of active Monahans dunes contain 100% sand and produce low dust fluxes (up to 0.5 mg/m²/s) primarily by abrasion. Stabilized sand sheets and vegetated dunes surrounding the active dunes at Monahans contain 5-20% silt and clay, and if reactivated or disturbed, could produce extremely high dust fluxes (up to 17 mg/m²/s). Sand sheets, as well as many stabilized and active eolian systems in the Great Plains and Southwestern US, store abundant dust-sized sediment, making them potent and unrealized dust sources with potential emissivity of >500 mt/km²/yr if reactivated by 21^st century aridification or anthropogenic disturbance. A better understanding of dust emission fluxes and processes in eolian systems can better inform regional and global emissions estimates and knowledge of dust sources now and into the future.