Locus  

Pedogenic iron oxides in iron-rich oxisols developed from mafic rocks

Show simple item record

dc.contributor.author Ker, João Carlos
dc.contributor.author Camêlo, Danilo de Lima
dc.contributor.author Fontes, Maurício Paulo Ferreira
dc.contributor.author Corrêa, Marcelo Metri
dc.contributor.author Costa, Antonio Carlos Saraiva da
dc.contributor.author Melo, Vander Freitas
dc.date.accessioned 2017-12-01T17:35:13Z
dc.date.available 2017-12-01T17:35:13Z
dc.date.issued 2016-11-01
dc.identifier.issn 18069657
dc.identifier.uri http://dx.doi.org/10.1590/18069657rbcs20160379
dc.identifier.uri http://www.locus.ufv.br/handle/123456789/14233
dc.description.abstract Despite the considerable amount of information on the mineralogical characteristics of pedogenic Fe oxides in Brazilian soils, there are few studies on Fe-rich soils developed from mafic rocks with taxonomic identities at lower categorical levels. This study evaluated the mineralogical characteristics of pedogenic Fe oxides in B horizons (Bw) of Fe-rich Oxisols developed from several mafic rocks in the state of Minas Gerais, Brazil. The Bw horizons were sampled at a 0.8-1.0 m depth in 13 Ferric and Perferric Rhodic Oxisols along with a Mesoferric Typic Oxisol originating from basalt, gabbro, tuffite, amphibolite and itabirite in Minas Gerais. The selected soils have taxonomic identities up to the fourth categorical level of the Brazilian System of Soil Classification. In the laboratory, the following analyses were made: a) powder X ray diffraction (XRD) of the clay fraction before and after selective concentration of Fe oxides by silicate alkaline dissolution (5 mol L^-1 NaOH); b) selective chemical dissolution of the clay fraction by citrate-bicarbonate-dithionite (CBD), acid ammonium oxalate (AAO), and sulfuric acid (H2SO4 1.8 mol L^-1); c) quantitative estimation of minerals in the clay fraction through allocation of phases from the XRD patterns, magnetic susceptibility of the clay fraction, and quantification of elements after sulfuric acid digestion (H2SO4 1:1) of the air-dried fine earth and treatment of the clay fraction with CBD; and d) estimation of the mean crystal size (MCS), specific surface area (SSA), and isomorphic Al-substitution (IS) of hematite, goethite, and maghemite from the XRD patterns obtained from concentrates of Fe oxides. The results showed that estimation of Fe content of maghemite by selective dissolution with 1.8 mol L^-1 H2SO4 may not be accurate enough to realistically reflect the maghemite contents in the soil sample. The Al content extracted may also be influenced by other minerals that are sources of this element. Hematite crystals were predominantly placoid in shape in all Rhodic Oxisols and had smaller SSA compared to goethite, which showed both isodimensional and asymmetric habit. Higher crystallinity of maghemite and the IS values generally lower than those of hematite and goethite suggest that in well-drained soils derived from mafic rocks, the IS phenomenon in maghemites seems to result from pedogenetic advancement after its formation from magnetite oxidation. en
dc.format pdf pt-BR
dc.language.iso por pt-BR
dc.publisher Revista Brasileira de Ciência do Solo pt-BR
dc.relation.ispartofseries v.41, e0160379, Abril 2017 pt-BR
dc.rights Open Access pt-BR
dc.subject Hematite pt-BR
dc.subject Maghemite pt-BR
dc.subject Crystallographic characteristics pt-BR
dc.subject Al-substitution pt-BR
dc.subject Selective dissolution pt-BR
dc.title Pedogenic iron oxides in iron-rich oxisols developed from mafic rocks en
dc.type Artigo pt-BR


Files in this item

This item appears in the following Collection(s)

  • Artigos [634]
    Artigos Técnico-científicos na área de Solos

Show simple item record

Search DSpace


Browse

My Account