WIND-DRIVEN MINERAL DUST EMISSION RESEARCH: PAST ACCOMPLISHMENTS, RECENT ADVANCES, AND FUTURE CHALLENGES

Mineral dust in Earth’s atmosphere from wind erosion processes plays a critical role in the planet’s radiation balance, biogeochemistry, soils, and ecology. On a regional basis dust can degrade air quality and under extreme storm conditions can result in loss of human and animal life as well as severe environmental degradation. The delivery of dust-sized particles (<70 µm) to the atmosphere is an aerodynamically driven process. There is a complex interplay, however, between the resisting and driving forces that control the release and entrainment of these particles and the vertical flux of dust. Following the pioneering works of R.A. Bagnold and W.S. Chepil that focused on the movement of sand-sized particles, Gillette et al. (1972) marks a critical expansion of scientific inquiry examining the emission of dust from susceptible surfaces. Many of the concepts originating with D.A. Gillette including the links between wind shear, saltation and dust flux and the importance of sediment texture and surface properties guided a generation of dust researchers. Much of the process-based research that followed brought improved and usually investigator-designed instrumentation into the field and laboratory.

Recent avenues of research in dust emission processes are questioning long-held beliefs that emissions of consequence are associated only with vigorous transport events, direct entrainment versus entrainment by saltation bombardment is of lesser importance, and the role of forces, especially electrostatic likely play a more important role than previously thought. Further research is also needed into weathering processes and their role in dust supply. Quantification of the binding energy that causes particles to cohere to one another and create crusts is another area where our knowledge lags. New data are also needed to corroborate recently-developed theories on the scaling relationships of wind shear, magnitude of the flux, and the particle size distribution characteristics of the dust.

The dust cycle is increasingly being recognized as an important part of the Earth system but gaps remain in our understanding of the driving and resisting forces. Hopefully, a new generation of earth scientists will be inspired to pursue knowledge to fill these gaps continuing down the path set by our discipline’s initial innovators.