ATMOSPHERIC MINERAL DUST EMISSIONS FROM THE BODÉlé DEPRESSION MAY ILLUSTRATE THE KEY TO THE PAST IS THE PRESENT

Atmospheric mineral dust plays an important role in climate that is not entirely understood. The complex meteorological processes, diverse source regions, compositional parameters of emissions, and physical and chemical properties and characteristics of dust emissions make modeling the affects on climate, climate change, and global climate modeling a difficult task. Studies conducted by Koren, et al., (2006), suggest that 240 ± 80 Tg of atmospheric mineral dust is emitted from Saharan Africa to the Atlantic coast between 20° and 30° North Latitude annually. Of that total, an estimated ~120 ± 40 Tg is deposited in the Atlantic Ocean, ~30 Tg is transported to northern Africa and Europe, ~70 Tg reaches the Caribbean in NH summers, and ~50 Tg reaches the Amazon River Basin in NH winters. Of the ~50 Tg of dust deposited in the Amazon River Basin, ~50 percent is emitted from a single source, the Bodélé Depression (Koren, et al., 2006; Kaufman, et al., 2005; Tegan, et al., 2006; Todd, et al., 2005; Washington, et al., 2005).

Identification of mineral types in dust emissions from the Bodélé in NE Chad, Africa, is determined through results from traditional X-ray diffractometers, Scanning Electron Microscope images/chemical analyses, regional geomorphological history and French geological survey maps. In situ samples were supplied by the BodEX 2005 team (Dr. Martin Todd). The sample bulk material was collected at the surface of the Bodélé, and aerosol filters collected material 3 meters above the surface. Samples were collected at four locations between 17.1° North Latitude and 17.6° North Latitude (~60 km distance), by 18.24° East Longitude by 18.15° East Longitude (~88 km distance), with three locations ~20 km apart, and one ~100 km from the location of sample three. Through analyses, the minerals have been identified as ferromagnesian and aluminum silicates, amorphous silica, with limited amounts of calcium carbonate, dolomite, and exotic elements such as titanium and silicon, mixed with 10- 20 percent desiccated diatom structures.