Dust-raising in the dustiest place on earth

Warren, Andrew; Chappell, Adrian; Todd, Martin C.; Bristow, Charlie S.; Drake, Nick; Engelstaedter, Sebastian; Martins, Vanderlei; M'Bainayel, S; Washington, Richard

doi:10.1016/j.geomorph.2007.02.007

Cited by 84 publications

(69 citation statements)

References 34 publications

(42 reference statements)

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“…The Bodélé Depression (north-central Africa) is Earth's most prolific dust producer and may be key component to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon rainforest (e.g., Prospero et al, 2002;Washington et al, 2003;Giles, 2005;Goudie and Middleton, 2006;Warren et al, 2007;Bristow et al, 2009Bristow et al, , 2010Hudson-Edwards et al, 2014;Yu et al, 2015). The Bodélé dust-source region consists mainly of diatomaceous lake beds overridden by dunes and other aeolian deposits (e.g., Warren et al, 2007;Bristow et al, 2009), which are driven by dominant northeasterly winds (Washington and Todd, 2005;Washington et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

“…The Bodélé dust-source region consists mainly of diatomaceous lake beds overridden by dunes and other aeolian deposits (e.g., Warren et al, 2007;Bristow et al, 2009), which are driven by dominant northeasterly winds (Washington and Todd, 2005;Washington et al, 2006). These diatom-rich lake beds and their derived aeolian sediments are white and therefore very bright.…”

Section: Introductionmentioning

confidence: 99%

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Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

et al. 2016

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Atmospheric mineral dust can influence climate and biogeochemical cycles. An important component of mineral dust is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of dust plumes and thus affect the radiative forcing of global dust. Here we report on the iron mineralogy of dust-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth's most prolific dust producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in dust-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral dust aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellowreddish dust-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that dust plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002-0.57 wt. %) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM<0.1m. For all examined samples, the average iron apportionment is estimated at about 33% in ferric oxide minerals, 1.4 % in magnetite, and 65% in ferric silicates. Structural iron in clay minerals may account for much of the iron in the ferric silicates. We estimate that the mean ferric oxides flux exported from the Bodélé Depression is 0.9 Tg/yr with greater than 50% exported as ferric oxide nanoparticles (<0.1m). The high surface-to-volume ratios of ferric oxide nanoparticles once entrained into dust plumes may facilitate increased atmospheric chemical and physical processing and affect iron solubility and bioavailability to marine and terrestrial ecosystems.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

et al. 2016

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“…By analysing Total Ozone Mapping Spectrometer data, Middleton and Goudie (2001) and Middleton, (2001, 2006) showed that the major African dust sources include southern Algeria, western Mali, eastern Mauritania and the Bodélé Depression. The latter is located at the southern edge of the Sahara Desert, is the lowest point in Chad, was the floor of a much larger Mega-Lake Chad and has been called 'the dustiest place on earth' (Giles, 2005;Engelstaedter et al, 2006;Warren et al, 2007). Winds that sweep between the Tibesti and the Ennedi mountains in northern Chad are funnelled across this depression.…”

Section: Introductionmentioning

confidence: 99%

Microbial hitchhikers on intercontinental dust: catching a lift in Chad

et al. 2012

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Ancient mariners knew that dust whipped up from deserts by strong winds travelled long distances, including over oceans. Satellite remote sensing revealed major dust sources across the Sahara. Indeed, the Bodélé Depression in the Republic of Chad has been called the dustiest place on earth. We analysed desert sand from various locations in Chad and dust that had blown to the Cape Verde Islands. High throughput sequencing techniques combined with classical microbiological methods showed that the samples contained a large variety of microbes well adapted to the harsh desert conditions. The most abundant bacterial groupings in four different phyla included: (a) Firmicutes—Bacillaceae, (b) Actinobacteria—Geodermatophilaceae, Nocardiodaceae and Solirubrobacteraceae, (c) Proteobacteria—Oxalobacteraceae, Rhizobiales and Sphingomonadaceae, and (d) Bacteroidetes—Cytophagaceae. Ascomycota was the overwhelmingly dominant fungal group followed by Basidiomycota and traces of Chytridiomycota, Microsporidia and Glomeromycota. Two freshwater algae (Trebouxiophyceae) were isolated. Most predominant taxa are widely distributed land inhabitants that are common in soil and on the surfaces of plants. Examples include Bradyrhizobium spp. that nodulate and fix nitrogen in Acacia species, the predominant trees of the Sahara as well as Herbaspirillum (Oxalobacteraceae), a group of chemoorganotrophic free-living soil inhabitants that fix nitrogen in association with Gramineae roots. Few pathogenic strains were found, suggesting that African dust is not a large threat to public health.

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“…As a result, the number of studies that use digital earth imagery to visualize, map or analyse landforms is increasing. For example, Google Earth images were used to visualize and inspect dunes in Chad (Warren et al 2007), karst phenomena in Slovenia (Podobnikar et al 2009), and glacial landscapes in Tibet (Heyman et al 2008). Qualitative observations are frequently complemented by quantifying landforms on-screen, like measuring dune size in Peru (Hesse 2009), pre-landslide topography in Taiwan (Tsou et al 2011), or treeline elevation in Ethiopia (Jacob et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Transferring Google Earth observations to GIS-software: example from gully erosion study

Frankl

Zwertvaegher

Poesen

et al. 2013

International Journal of Digital Earth

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High-resolution images available on Google Earth are increasingly being consulted in geographic studies. However, most studies limit themselves to visualizations or on-screen measurements. Google Earth allows users to create points, lines and polygons on-screen, which can be saved as KML files. Here, the use of R statistics freeware is proposed to easily convert these files to the shapefile format [or '.shp file format'], which can be loaded into GIS-software (ESRI ArcGIS 9 in our example). The geospatial data integration in GIS strongly increases the analysis possibilities.

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Dust-raising in the dustiest place on earth

Cited by 84 publications

References 34 publications

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

Microbial hitchhikers on intercontinental dust: catching a lift in Chad

Transferring Google Earth observations to GIS-software: example from gully erosion study

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