Testing the auto‐abrasion hypothesis for dust production using diatomite dune sediments from the Bodélé Depression in Chad

Abstract

AbstractThis study examines the role of quartz sand in the production of dust using mixtures of quartz sand from the Sahara and diatomite aggregates from the Bodélé Depression in Chad. An aeolian abrasion chamber is used to reproduce the physical processes of aeolian abrasion and test the hypothesis that the breakdown of saltating diatomite flakes as they collide in saltation, and with the surface, is the most prolific mechanism of dust production (auto‐abrasion). This hypothesis is tested against the competing hypothesis that a hard, higher‐density quartz sand impactor is required to abrade fine‐grained sediments to generate dust. The results show that dust can be produced by a mixture of saltating diatomite and quartz sand particles. However, quartz sand is not required for saltating aggregates to produce dust. Indeed, these results, which used a mixture of very coarse‐grained aggregate (1 to 2 mm diameter) with fine quartz sand, indicate that the addition of quartz sand can decrease dust production. For a very coarse aggregate (1 to 2 mm), a pure diatomite aggregate produced the most dust, although using a coarse‐grained aggregate (0·5 to 1·0 mm) with a mixture of 20% quartz and 80% aggregate was found to produce the most dust overall. The results of this study confirm the auto‐abrasion hypothesis for the breakdown of diatomite particles in the Bodélé Depression, which is the single biggest source of atmospheric mineral dust on Earth.