Emission and redistribution of dust in drylands drive major ecosystem dynamics and provides important biogeochemical connectivity across a wide range of spatial and temporal scales. Wind erosion and dust emissions from drylands are highly variable both spatially and temporally, yet most aeolian transport studies focus only on a particular spatial and temporal scale and the portion of the particle-size spectrum associated with a single instrument. Few aeolian transport studies use multiple instruments to characterize airborne sediment across the broad spectrum of particle sizes and temporal scales, and fewer yet simultaneously characterize the airborne sediment in undisturbed and disturbed environments. Further, there is a lack of time-resolved measurements that allow comparisons (concentration and transport rate) between particles suspended locally during wind gusts and regional “background” aerosols. We measured sediment flux (saltation) and background aerosol PM-10 concentrations (diameters <10µm and total suspended particulate) in both burned and unburned semiarid grassland using four different instruments spanning different combinations of spatial and temporal scales and particle-size resolution: Big Springs Number Eight (BSNE) and Sensit instruments for larger saltating particles, DustTrak instruments for suspended particles with diameters <10 µm, and Total Suspended Particulate (TSP) samplers for measuring the entire range of particle sizes.
Results/Conclusions
Burned and unburned sites differed in vegetation cover and aerodynamic roughness. Time-integrated measurements of saltation using the BSNE samplers were significantly different across the burned and unburned plots, though the one second saltation measurements using the Sensit were not sensitive enough to detect differences. Maximum aerosol concentrations of PM-10 were significantly different between the burned and unburned site suggesting the importance of brief gusts to suspend locally generated dust, but the average background concentrations, which are more indicative of regional dust load, were not different. More generally, our results suggest that interplay between particle-size distribution, temporal resolution, and integration across time and height needs to be considered more explicitly for full characterization of regional and localized background sediment transport and dust characteristics.
