Bulk composition of northern African dust and its source sediments — A compilation

Scheuvens, Dirk; Schütz, L.; Kandler, Konrad; Ebert, Martin; Weinbruch, Stephan

doi:10.1016/j.earscirev.2012.08.005

Cited by 321 publications

(468 citation statements)

References 174 publications

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“…5), also reported in Table 3, ranged from 2.8 % (Namibia) to 7.3 % (Australia). These are in the range of values reported in the literature, taking into account that differences might be also due to the method (direct measurement/calculation) and/or the size fraction over which the total dust mass concentration is estimated (Chiapello et al, 1997;Reid et al, 1994;Derimian et al, 2008;Formenti et al, 2001Formenti et al, , 2011Formenti et al, , 2014aScheuvens et al, 2013). The agreement of MC Fe% values obtained by the XRF analysis of polycarbonate filters (Eq.…”

Section: Elemental Composition and Iron Oxide Contentsupporting

confidence: 53%

“…For samples from areas other than northern Africa, the largest variability is observed for the Fe / Ca values, ranging from 0.1 to 8, whereas the Si / Al ratio varied only between 2.5 and 4.8. In this case, values are available in the literature for comparison (e.g., Cornille et al, 1990;Reid et al, 1994;Eltayeb et al, 2001;Lafon et al, 2006;Shen et al, 2007;Radhi et al, 2010Radhi et al, , 2011Formenti et al, 2011Formenti et al, , 2014aScheuvens et al, 2013, and references within). Values in the PM 2.5 fraction are very consistent with those obtained in the PM 10.6 : their linear correlation has a slope of 1.03 (±0.05) and a R 2 equal to 0.97, suggesting that the elemental composition is relatively size independent.…”

Section: Elemental Composition and Iron Oxide Contentmentioning

confidence: 99%

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Spectral- and size-resolved mass absorption efficiency of mineral dust aerosols in the shortwave spectrum: a simulation chamber study

et al. 2017

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Abstract. This paper presents new laboratory measurements of the mass absorption efficiency (MAE) between 375 and 850 nm for 12 individual samples of mineral dust from different source areas worldwide and in two size classes: PM 10.6 (mass fraction of particles of aerodynamic diameter lower than 10.6 µm) and PM 2.5 (mass fraction of particles of aerodynamic diameter lower than 2.5 µm). The experiments were performed in the CESAM simulation chamber using mineral dust generated from natural parent soils and included optical and gravimetric analyses.The results show that the MAE values are lower for the PM 10.6 mass fraction (range 37-135 × 10 −3 m 2 g −1 at 375 nm) than for the PM 2.5 (range 95-711 × 10 −3 m 2 g −1 at 375 nm) and decrease with increasing wavelength as λ −AAE , where the Ångström absorption exponent (AAE) averages between 3.3 and 3.5, regardless of size. The size independence of AAE suggests that, for a given size distribution, the dust composition did not vary with size for this set of samples. Because of its high atmospheric concentration, light absorption by mineral dust can be competitive with black and brown carbon even during atmospheric transport over heavy polluted regions, when dust concentrations are significantly lower than at emission. The AAE values of mineral dust are higher than for black carbon (∼ 1) but in the same range as light-absorbing organic (brown) carbon. As a result, depending on the environment, there can be some ambiguity in apportioning the aerosol absorption optical depth (AAOD) based on spectral dependence, which is relevant to the development of remote sensing of light-absorbing aerosols and their assimilation in climate models. We suggest that the sample-to-sample variability in our dataset of MAE values is related to regional differences in the mineralogical composition of the parent soils. Particularly in the PM 2.5 fraction, we found a strong linear correlation between the dust lightPublished by Copernicus Publications on behalf of the European Geosciences Union. 7176 L. Caponi et al.: Spectral-and size-resolved mass absorption efficiency of mineral dust aerosols absorption properties and elemental iron rather than the iron oxide fraction, which could ease the application and the validation of climate models that now start to include the representation of the dust composition, as well as for remote sensing of dust absorption in the UV-vis spectral region.

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Section: Elemental Composition and Iron Oxide Contentsupporting

confidence: 53%

Section: Elemental Composition and Iron Oxide Contentmentioning

confidence: 99%

Spectral- and size-resolved mass absorption efficiency of mineral dust aerosols in the shortwave spectrum: a simulation chamber study

et al. 2017

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“…The combination of methods described herein document (1) the dominance of goethite over hematite in the examined source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Considering the intensity of recent research on the occurrences of hematite and goethite in dust and dust-source sediments, it is important to note that identifications of these minerals depend on their concentrations and variable sensitivities of different methods (e.g., Scheuvens et al, 2013), such that apparent inconsistencies arise with respect to determining their absolute and relative amounts. For example, our results differ importantly from recent magnetic and diffuse reflectance spectroscopic investigations by Oldfield et al (2014) of many of the same samples that indicated the presence of hematite only in a few of the samples.…”

Section: Discussionmentioning

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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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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“…Dust is first uplifted by local winds, transported by an increased vertical velocity to higher latitudes (Engelstaedter and Washington, 2007) and then transported over hundreds to thousands of kilometers along three main transport pathways (Goudie and Middleton, 2001) (see SM1). Most of the dust is carried westward over the North Atlantic Ocean by the trade winds (D'Almeida, 1986;Kellogg and Griffin, 2006;Scheuvens et al, 2013). However, due to peculiar meteorological conditions (e.g., low pressure systems, creation of easterly waves - White et al, 2012;Scheuvens et al, 2013), an eastward or a northward flow may punctually bring dust across the Mediterranean Sea to adjacent Table 1. countries.…”

Section: Introductionmentioning

confidence: 99%

“…Most of the dust is carried westward over the North Atlantic Ocean by the trade winds (D'Almeida, 1986;Kellogg and Griffin, 2006;Scheuvens et al, 2013). However, due to peculiar meteorological conditions (e.g., low pressure systems, creation of easterly waves - White et al, 2012;Scheuvens et al, 2013), an eastward or a northward flow may punctually bring dust across the Mediterranean Sea to adjacent Table 1. countries. Occasionally dust is even deposited north of the Alps, transported by anticyclonic cells and washed out by rain (see Stuut et al, 2009 for a review).…”

Section: Introductionmentioning

confidence: 99%

Deciphering human–climate interactions in an ombrotrophic peat record: REE, Nd and Pb isotope signatures of dust supplies over the last 2500years (Misten bog, Belgium)

Fagel

Allan

Roux

et al. 2014

Geochimica et Cosmochimica Acta

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, et al.. Deciphering human-climate interactions in an ombrotrophic peat record: REE, Nd and Pb isotope signatures of dust supplies over the last 2500 years (Misten bog, Belgium). Geochimica et Cosmochimica Acta, Elsevier, 2014Elsevier, , vol. 135, pp. 288-306. 10.1016Elsevier, /j.gca.2014 To cite this Fagel, Nathalie and Allan, Mohammed and Le Roux, Gaël and Mattielli, Nadine and Piotrowska, Natalia and Sikorski, Jaroslaw AbstractA high-resolution peat record from Eastern Belgium reveals the chronology of dust deposition for the last 2500 years. REE and lithogenic elements in addition to Nd and Pb isotopes were measured in a 173 cm age-dated peat profile and provide a continuous chronology of dust source and intensity. Calculated dust flux show pronounced increases c. 300 BC, 600 AD, 1000 AD, 1200 AD and from 1700 AD, corresponding to local and regional human activities combined with climate change.The Industrial Revolution samples (1700-1950 AD) are characterised by a significant enrichment in Sc-normalised REE abundance (sum REE/Sc > 25) due to intensive coal combustion. For the pre-Industrial Revolution samples, the Sc-normalised REE abundance (10 < Sum REE/Sc < 25) and the eNd variability (À13 to À9) are interpreted by a mixing between dust particles from local soils and long-range transport of desert particles. Three periods characterised by dominant-distal sources (c. 320 AD, 1000 AD and 1700 AD) are consistent with local wetter-than-average intervals as indicated by a lower degree of peat humification. Local erosion prevails during the drier (higher humification) intervals (100 AD, 600 AD). On a global scale, more distal supplies are driven during colder periods, in particular during the Oort and Maunder minima, suggesting a potential link between dust deposition and global climate. Combining REE abundance, fractionation between Light REE and Heavy REE and Nd isotope data in ombrotrophic peat allows one to distinguish between dust flux changes related to human and climate forcings.

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Bulk composition of northern African dust and its source sediments — A compilation

Cited by 321 publications

References 174 publications

Spectral- and size-resolved mass absorption efficiency of mineral dust aerosols in the shortwave spectrum: a simulation chamber study

Spectral- and size-resolved mass absorption efficiency of mineral dust aerosols in the shortwave spectrum: a simulation chamber study

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

Deciphering human–climate interactions in an ombrotrophic peat record: REE, Nd and Pb isotope signatures of dust supplies over the last 2500years (Misten bog, Belgium)

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