Mineral dust production in the Bodele Depression, Northern Chad

Aeolian dust studies are of global importance due to the impact of mineral dust on global climate, human health and the environment. Recent research, for example IPCC (2007) highlighted the important effects of atmospheric dust on global climate that has led to an increased interest in wind-blown mineral dust. Despite this increased interest, there is a dearth of field observations from dust sources due to their remoteness and hostility. This has limited the overall understanding of dust emission and led to an over-reliance on model predictions. Thus, there is a strong requirement for field observations to validate model predictions, especially for the Earth's greatest dust source- the Bodele Depression. This study aims to fill this gap by providing a quantitative description of dust emitted at a field study area within the Bodele Depression. This research demonstrates that particle size data can be used to characterise windblown sediments and produce information regarding dust emission mechanisms. The data revealed much evidence of aeolian abrasion that formed the foundation for several research hypotheses that were tested statistically using outputs from a dust emission and sandblasting model. Findings showed that sandblasting is significantly correlated with dust emission and plays a key role in dust emission. The spatial variation in dust emission at the field study area results from spatially heterogeneous aeolian abrasion that is driven by variation in sediment composition (mineralogy) and particle size. The aeolian abrasion of diatomite by quartz grains is a highly efficient mechanism of dust production in the field study area and this was validated by laboratory experiments. This study demonstrates the importance of controls on dust emission that need greater emphasis in dust schemes and makes recommendations for adjustments to models. The findings in this study have important implications for dust schemes that underestimate the roles of mineralogy and particle size since they are so influential in dust production and emission. This research improves the current understanding of dust emission and advances the ability to more accurately predict dust emission.