ARS | Publication request: Mineralogical controls on dust emissions in the Bodele Depression, Chad

Submitted to: International Conference on Aeolian Research
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2010
Publication Date: July 9, 2010
Citation: O'Donoghue, A., Zobeck, T.M., Chappell, A., Bristow, C. 2010. Mineralogical controls on dust emissions in the Bodele Depression, Chad. International Conference on Aeolian Research. July 5-9, 2010, Santa Rosa, La Pampa, Argentina. Poster No. 28.

Technical Abstract: Surface mineralogy is critical in the understanding of aeolian processes, however its role in dust production is currently underestimated. Recent research indicates that discrepancies between predicted and observed dust loads by dust models may be attributed to inadequacies within their associated dust production schemes. A particular weakness relates to their representation of the mineralogy of erodible surface sediments. Dust production schemes assume that sediment mineralogy is homogenous across large spatial areas. In addition, little is known about mineralogical controls on dust production in dust source hot-spots such as the Bodélé Depression. This study demonstrates the effect of mineralogical controls on dust emission by quantifying the amounts of dust produced by two of the most abundant minerals (quartz and diatomite) from the surfaces of a study area in the Bodélé Depression. The Lubbock Dust Generation Analysis and Sampling System (LDGASS) at the USDA was used to simulate aeolian abrasion for a range of different “quartz:diatomite” proportions in varying particle sizes. The LDGASS simulates the abrasive breakdown of particles into dust during wind erosion with the physical transfer of kinetic energy to the particles of a source sample . The experiments produced an index of dust yields for a range of mineralogical combinations of sediments from the surfaces of the study area in the Bodélé. Findings showed that there was considerable variation in dust concentrations for the different mineralogical combinations. During the experiments, samples containing greater proportions of quartz particles than diatomite particles produced greater dust yields than samples containing greater proportions of diatomite particles than quartz particles. This was attributed to the differences in density which affected the magnitude of the kinetic energy involved in abrasion. As a result, density was found to be an important controlling factor. Thus, the mineralogy of surface sediments plays an important role in determining the intensity of abrasional sandblasting that occurs during dust production. It is important that dust production schemes account for its significance. The current underestimation of the role of surface mineralogy in dust production may affect the accuracy of regional and global-scale dust flux estimates that are destined for usage in radiative transfer calculations and climate change studies.