1. Unravelling zinc and lead distributions in dolomitic and metapelitic soils of the Brazilian Central Plateau: insight from physical fractionation, optical microscopy and X-ray microfluorescence
- Author
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D. Lang Burak, F. van Oort, Eddy Foy, M. P. Ferreira Fontes, Thierry Becquer, Unité de recherche Science du Sol (USS), Institut National de la Recherche Agronomique (INRA), Federal University of Espírito Santo, Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Departamento de Solos, Universidade Federal de Santa Maria (UFSM), Brazilian-French Cooperation Programme Capes-Cofecub [514-05], EMBRAPA Cerrados/IRD [0203205], Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), and Universidade Federal de Santa Maria = Federal University of Santa Maria [Santa Maria, RS, Brazil] (UFSM)
- Subjects
Sols tropicaux ,iron oxide ,Ferralsol ,Dolomite ,métaux en trace ,Soil Science ,Mineralogy ,chemistry.chemical_element ,Weathering ,Zinc ,Fractionation ,010501 environmental sciences ,01 natural sciences ,Sesquioxide ,plomb ,0105 earth and related environmental sciences ,2. Zero hunger ,Cambisol ,lead ,Dolomitic ,Chemistry ,contamination métallique ,zinc ,Sorption ,04 agricultural and veterinary sciences ,heavy metal ,oxyde de fer ,[SDE.ES]Environmental Sciences/Environmental and Society ,metal contamination ,Tropical soils ,Lead ,Metapelitic soils ,Environmental chemistry ,Soil water ,040103 agronomy & agriculture ,0401 agriculture, forestry, and fisheries - Abstract
International audience; Large zinc and lead concentrations occur in strongly weathered soils of Cambisol–Ferralsol toposequences in the Paracatu-Vazante area (Central Plateau, Brazil). Weathering of the mineralized dolomite parent material of the Cambisols is hypothesized to be the geogenic source of zinc (Zn) and lead (Pb), with dissemination downslope into the Ferralsols. This leads to different metal distribution patterns in the two soils. We studied Zn and Pb distributions in selected A and B horizons of two typical profiles to examine this hypothesis and assess the contribution of sesquioxides to the retention of these metals. Physical separation into 200–2000, 50–200, 20–50 and < 20-µm size fractions in water without chemical dispersants was carried out before (F1) and after (F2) ultrasonification. The fractions were analysed for total and extractable Zn and Pb concentrations and studied by X-ray diffraction and optical microscopy. Microscale Zn and Pb distribution maps were obtained by using micro-X-ray fluorescence on thin sections. For the Cambisol, the composition, morphology and large Zn and Pb concentrations of coarse-sized F2 fractions were consistent with a geogenic metal origin. In both soils, < 20-µm fractions contained the largest amounts of Zn and Pb. In the Cambisol, this < 20-µm fraction included poorly crystalline Mn-rich material, encouraging strong Pb sorption. The Ferralsol < 20-µm fractions contained more Al- and Fe-oxide-rich microaggregates, which also enhanced strong metal retention. Large sesquioxide contents in these and similar tropical soils reduce metal mobilities. This limits the risk of toxicity when such soils, with metal contents exceeding guidelines, are used for agriculture.
- Published
- 2013