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Solid-phase phosphorus speciation in Saharan Bodélé Depression dusts and source sediments

DOI: 10.1016/j.chemgeo.2014.06.014 DOI Help

Authors: Karen Hudson-edwards (Birkbeck College) , Charles Bristow (Birkbeck, University of London) , Giannantonio Cibin (Diamond Light Source) , Gary Mason (Birkbeck, University of London) , Caroline Peacock (University of Leeds)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemical Geology , VOL 384 , PAGES 16 - 26

State: Published (Approved)
Published: September 2014
Diamond Proposal Number(s): 1986 , 7527

Open Access Open Access

Abstract: Phosphorus (P) is one of the most important limiting nutrients for the growth of oceanic phytoplankton and terrestrial ecosystems, which in turn contributes to CO2 sequestration. The solid-phase speciation of P will influence its solubility and hence its availability to such ecosystems. This study reports on the results of X-ray diffraction, electron microprobe chemical analysis and X-ray mapping, chemical extractions and X-ray absorption near-edge spectroscopy analysis carried out to determine the solid-phase speciation of P in dusts and their source sediments from the Saharan Bodélé Depression, the world’s largest single source of dust. Chemical extraction data suggest that the Bodélé dusts contain 28 to 60% (mean 49%) P sorbed to, or co-precipitated with Fe (hydr)oxides, < 10% organic P, 21-50% (mean 32%) detrital apatite P, and 10-22% (mean 15%) authigenic-biogenic apatite P. This is confirmed by the other analyses, which also suggest that the authigenic-biogenic apatite P is likely fish bone and scale, and that this might form a larger proportion of the apatite pool (33+/-22%) than given by the extraction data. This is the first-ever report of fish material in aeolian dust, and it is significant because P derived from fish bone and scale is relatively soluble and is often used as a soil fertilizer. Therefore, the fish-P will likely be the most readily form of Bodélé P consumed during soil weathering and atmospheric processing, but given time and acid dissolution, the detrital apatite, Fe-P and organic-P will also be made available. The Bodélé dust input of P to global ecosystems will only have a limited life, however, because its major source materials, diatomite in the Bodélé Depression, undergo persistent deflation and have a finite thickness.

Journal Keywords: Bodélé Depression; Sahara; Dust; Phosphorus; Fish; Apatite

Subject Areas: Environment, Chemistry

Instruments: B18-Core EXAFS

Other Facilities: No