Biogeochemistry of dust sources in Southern Africa

Bhattachan, Abinash; D’Odorico, Paolo; Okin, Gregory S.

doi:10.1016/j.jaridenv.2015.02.013

Cited by 14 publications

(14 citation statements)

References 57 publications

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“…For comparison between methods to analyze for Fe (II), the parent soil samples were analyzed following the method used in Bhattachan et al . 's [] study. The samples were run on the same day with the same set of reagents, while the only difference between the two methods is the duration that the sample was soaked in the aliquot (5 min versus shaken for an hour).…”

Section: Methodssupporting

confidence: 80%

“…The dust arriving in the Sierra Nevada Mountains is highly enriched in Fe (II) relative to the fine fraction that is emitted by the source region, and the average enrichment ratio is approximately 15. The higher concentration of Fe (II) in parent soil is consistent with results from dust sources in Southern Africa [e.g., Bhattachan et al, ]: sediments (i.e., parent soil) from the Makgadikgadi and Etosha salt pans and interdunes from the southern Kalahari were found to be richer in Fe (II) than their fine fraction (<45 µm). The analysis of Saharan dust also showed that particles greater than 50 µm were rich in quartz with larger grain size richer in iron [ Kandler et al, ].…”

Section: Discussionmentioning

confidence: 99%

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Soluble ferrous iron (Fe (II)) enrichment in airborne dust

Bhattachan

Reche

D’Odorico

2016

J. Geophys. Res. Atmos.

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The input of soluble iron in dust delivered to the ocean and lakes is critical to their biogeochemistry and phytoplankton productivity. Most iron in soils and sediment deposits is insoluble, while only a tiny fraction is soluble and therefore suitable to meet the phytoplankton's requirements for photosynthesis and nitrogen assimilation. Aerosol deposition constitutes a major source of soluble iron to oceans and lakes, and in some regions the low phytoplankton productivity has been related to limitations in the supply of soluble iron from terrestrial sources. It is suggested that during atmospheric transport part of the insoluble iron is converted into soluble form. While the understanding of increased bioavailability of iron during atmospheric transport is improving, there are only a limited number of studies that actually quantify the increase in iron bioavailability in dust. In this study we compare the soluble ferrous iron, Fe (II) content in dust collected at deposition sites in the high‐altitude mountains of the Sierra Nevada, Spain, to the source of dust in North Africa. We found that the dust is greatly enriched (on average 15 times) in Fe (II) relative to the fine fraction (<45 µm) of the parent soil collected from North African dust sources.

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Section: Methodssupporting

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Soluble ferrous iron (Fe (II)) enrichment in airborne dust

Bhattachan

Reche

D’Odorico

2016

J. Geophys. Res. Atmos.

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“…However, the landscape units from which dust is sourced are highly discrete. The large palaeolake basins of Etosha in Namibia (Hipondoka et al ., ) and Makgadikgadi in Botswana (Burrough et al ., ) are the primary sources of southern African seasonal dust emissions today (Bryant, ; Bryant et al ., ; Bhattachan et al ., ). Physically smaller sources, including salt pans and river valleys, are now also identified as significant contributors to dust flux in the region (Eckardt and Kuring, ).…”

Section: Introductionmentioning

confidence: 97%

Holocene fluvial valley fill sources of atmospheric mineral dust in the Skeleton Coast, Namibia

Thomas

Durcan

Dansie

et al. 2017

Earth Surf Processes Landf

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Western Namibia is a significant global source of atmospheric mineral dust. We investigate the relationship between dust and source sediments, assessing the sustainability of dust flux. Remote sensing studies have highlighted specific ephemeral fluvial systems as important contributors to dust flux, including highlighting sections of valleys that are the origins of dust plumes in the period 2005-2008. Little is known however about the specific within-valley dust sediment sources, particularly whether dust is derived from modern ephemeral channel floors or older valley fill sediments, many of which have been reported in the region. As part of a region-wide analysis of aeolian dust flux, we investigate the sediment properties of atmospheric dust samples and valley sediments from the Huab valley, one of the principal regional dust sources. Trapped dust samples contain up to 88% very fine sand and silt when collected samples are disaggregated prior to analysis. Valley fill surface samples comprise 80% very fine sand and silt, and the surface of the modern ephemeral channel 30%. Valley fill sediments were sampled at depths up to 3.6 m below the present surface and reveal Holocene depositional ages from 0.6 ± 0.03 ka back to 9.79 ± 0.73 ka. These sediments contain 30% to 6% very fine sand and silt, with levels decreasing with depth and age. Aeolian bedforms in the valley system (nebkhas on the fill surface and climbing dunes on valley margins) indicate that aeolian processes under the influence of strong seasonal easterly winds likely result in dust being winnowed out of the valley fill surfaces, with sandy bedforms being constructed from the coarser component of the fill sediments. The volume of valley fill sediment suggests dust sourced from Holocene sediments is likely to continue into the future regardless of flow conditions in the modern channel system. 10 cm depth subsurface sample, S5 and S6 are from the surface of an inner channel terrace and S7, S8, S9 and S10 are modern channel floor samples.

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“…The Fe(II) content in the dust fraction between the sediments from the Mallee interdunes and the southern Kalahari interdunes are equal whereas FeT S is slightly greater in soil in the Mallee44. Because soils in Australia are highly weathered, any iron present in such soils is likely to be in hematite and goethite forms, with low amount of ferrihydrite, which in fact is the most labile form of iron oxide23.…”

Section: Discussionmentioning

confidence: 99%

Can land use intensification in the Mallee, Australia increase the supply of soluble iron to the Southern Ocean?

Bhattachan

D’Odorico

2014

Sci Rep

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The supply of soluble iron through atmospheric dust deposition limits the productivity of the Southern Ocean. In comparison to the Northern Hemisphere, the Southern Hemisphere exhibits low levels of dust activity. However, given their proximity to the Southern Ocean, dust emissions from continental sources in the Southern Hemisphere could have disproportionate impact on ocean productivity. Australia is the largest source of dust in the Southern Hemisphere and aeolian transport of dust has major ecological, economic and health implications. In the Mallee, agriculture is a major driver of dust emissions and dust storms that affect Southeastern Australia. In this study, we assess the dust generating potential of the sediment from the Mallee, analyze the sediment for soluble iron content and determine the likely depositional region of the emitted dust. Our results suggest that the Mallee sediments have comparable dust generating potential to other currently active dust sources in the Southern Hemisphere and the dust-sized fraction is rich in soluble iron. Forward trajectory analyses show that this dust will impact the Tasman Sea and the Australian section of the Southern Ocean. This iron-rich dust could stimulate ocean productivity in future as more areas are reactivated as a result of land-use and droughts.

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Biogeochemistry of dust sources in Southern Africa

Cited by 14 publications

References 57 publications

Soluble ferrous iron (Fe (II)) enrichment in airborne dust

Soluble ferrous iron (Fe (II)) enrichment in airborne dust

Holocene fluvial valley fill sources of atmospheric mineral dust in the Skeleton Coast, Namibia

Can land use intensification in the Mallee, Australia increase the supply of soluble iron to the Southern Ocean?

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