Dust Emissions from Drylands: Implications for Desertification
Investigators (most current known information)
The loss of fine particles from soils in dryland areas by wind erosion has serious implications for exacerbating desertification. The fine particles (<50 żm dia.) removed from the soil represent a disproportionate amount of nutrients compared with the coarse soil grains. Controlling this loss will be critical for maintaining the sustainability of dryland systems whether they are natural or agricultural. An associated environmental problem is the size and mass concentration of airborne dust particles has been associated with effects on human health. Thus, dust emissions affect the soil, the atmosphere, and the socio-economic conditions of the people living in affected areas.
To assess the impact of airborne dust on dryland systems a simple expression describing the dependence of the emissions on meteorological and surficial parameters is a practical necessity. However, models proposed in the literature for this purpose have, for the most part, remained untested. This provided us with the impetus to develop a dust emission model based on theoretical considerations and the realization that it would need to be validated by detailed empirical field data.
The objectives of our research were twofold. The first objective was to produce a database that characterizes the vertical and horizontal sediment fluxes during dust emissions. The second objective was to develop and test a numerical dust emission model that estimates the vertical flux of dust as a function of easily measurable atmospheric and surficial variables. The model was based on an algorithm developed earlier by Berkofsky and McEwan (1994) to predict dust concentration close to the ground as a function of wind.
The field study was at carried out at the Owens Lake, CA, playa. A validated database that characterizes the wind field and mass concentrations in the bottom 10 meters of the atmosphere during dust emissions was compiled. A tower-based monitoring system was used to make these measurements. The data collected with the tower monitoring system was used to characterize the suspended sediment transport system and the condition of the atmospheric boundary layer. The collected data was used to relate the measured vertical flux of dust with the observed meteorological conditions. In addition a second data set that characterized spatially the dust emissions for two major storm events in May 2001 was also used to compare measured with modeled data.
The modeling component of the proposed research proceeded from theoretical understanding of the dust emission process and be guided by and validated against the observational data. In model performance evaluation we found that the predicted flux compares reasonably well with the measured data in terms of both the spatial distribution of dust flux as well its magnitude. Based on our work the dust model appears to successfully predict dust emission fluxes at Owens Lake in both the magnitude of the flux as well as the evolution of the flux through time.
Article in Journal
Gillies, J.A. and L. Berkofsky. 2004. "Aeolian suspension above the saltation layer, the concentration profile." Journal of Sedimentary Research 74(2):176-183.
Gillies, J.A. and L.B. Berkofsky. 2003. "Aeolian suspension above the saltation layer: The concentration profile." Poster, 2nd workshop on mineral dust, September. Paris, France.
Gillies, J.A., W.G. Nickling and N. Lancaster. 2001. "Aeolian sediment flux characteristics observed at Owens Lake, CA." Presented, 97th annual meeting of the Association of American Geographers, February - 3 March. New York NY.
Nickling, W.G., J.A. Gillies and N. Lancaster. 2001. "Surface controls on dust emissions, Owens (dry) Lake, California." Presented, 97th annual meeting of the Association of American Geographers. February - March. New York NY.
Gillies, J.A., N. Lancaster and W.G. Nickling. 2000. "Dust flux characteristics observed at Owens Lake, CA." Presented, Understanding future dryland changes from past dynamics. Linkages between fluvial, lacustrine and aeolian systems, October. Zzyzx, CA.