Publications des scientifiques de l'IRD

Garnier J., Quantin C., Guimaraes E. M., Vantelon D., Montarges-Pelletier E., Becquer Thierry. (2013). Cr(VI) genesis and dynamics in Ferralsols developed from ultramafic rocks : the case of Niquelandia, Brazil. Geoderma, 193, p. 256-264. ISSN 0016-7061.

Titre du document
Cr(VI) genesis and dynamics in Ferralsols developed from ultramafic rocks : the case of Niquelandia, Brazil
Année de publication
2013
Type de document
Article référencé dans le Web of Science WOS:000314193400028
Auteurs
Garnier J., Quantin C., Guimaraes E. M., Vantelon D., Montarges-Pelletier E., Becquer Thierry
Source
Geoderma, 2013, 193, p. 256-264 ISSN 0016-7061
Despite high chromium concentrations in soils developed on ultramafic rocks, Cr availability is generally low, as Cr-bearing minerals are considered stable in supergene conditions. However, KH2PO4 extractions have shown high hexavalent chromium availability in Ferralsols developed on the ultramafic massif of Niquelandia (Brazil). A study combining mineralogical, geochemical, mu SXRF and XANES approaches was performed to assess the solid speciation of Cr and to understand its genesis. Chromium is mostly present in the trivalent form and is included in chromites and Fe-oxides. Nevertheless, a large amount of Cr(VI) is associated with the clay-sized fraction in the mineral horizons. Mn-oxides, the only natural Cr(III) oxidants, are also present in these horizons. Microscale investigations revealed the close association of Cr(VI) with Mn-oxides and strongly suggest that Mn-oxides can oxidize Cr(III) into Cr(VI). The XANES analyses show the occurrence of Cr(VI), which is removed by KH2PO4 extraction, demonstrating that the Cr(VI) is completely sorbed onto the soil matrix, i.e., Fe-oxides. Finally, the high mobility of Cr(VI), associated with the finest Fe-oxide particles mobilized during runoff following rainy events, may have harmful environmental consequences. This approach of combining direct and indirect observations allows us to characterize the total extractable Cr(VI) pool of these soils and to give key information on its mobility and localization.
Plan de classement
Pédologie [068]
Description Géographique
BRESIL
Localisation
Fonds IRD [F B010058969]
Identifiant IRD
fdi:010058969
Contact