Pedogenic Iron Oxides in Iron-Rich Oxisols Developed from Mafic Rocks
Autor(a) principal: | |
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Data de Publicação: | 2017 |
Outros Autores: | , , , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Revista Brasileira de Ciência do Solo (Online) |
Texto Completo: | http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100413 |
Resumo: | 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. |
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Pedogenic Iron Oxides in Iron-Rich Oxisols Developed from Mafic Rockshematitemaghemitecrystallographic characteristicsAl-substitutionselective dissolutionABSTRACT 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.Sociedade Brasileira de Ciência do Solo2017-01-01info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersiontext/htmlhttp://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100413Revista Brasileira de Ciência do Solo v.41 2017reponame:Revista Brasileira de Ciência do Solo (Online)instname:Sociedade Brasileira de Ciência do Solo (SBCS)instacron:SBCS10.1590/18069657rbcs20160379info:eu-repo/semantics/openAccessCamêlo,Danilo de LimaKer,João CarlosFontes,Maurício Paulo FerreiraCorrêa,Marcelo MetriCosta,Antonio Carlos Saraiva daMelo,Vander Freitaseng2017-05-12T00:00:00Zoai:scielo:S0100-06832017000100413Revistahttp://www.scielo.br/scielo.php?script=sci_serial&pid=0100-0683&lng=es&nrm=isohttps://old.scielo.br/oai/scielo-oai.php||sbcs@ufv.br1806-96570100-0683opendoar:2017-05-12T00:00Revista Brasileira de Ciência do Solo (Online) - Sociedade Brasileira de Ciência do Solo (SBCS)false |
dc.title.none.fl_str_mv |
Pedogenic Iron Oxides in Iron-Rich Oxisols Developed from Mafic Rocks |
title |
Pedogenic Iron Oxides in Iron-Rich Oxisols Developed from Mafic Rocks |
spellingShingle |
Pedogenic Iron Oxides in Iron-Rich Oxisols Developed from Mafic Rocks Camêlo,Danilo de Lima hematite maghemite crystallographic characteristics Al-substitution selective dissolution |
title_short |
Pedogenic Iron Oxides in Iron-Rich Oxisols Developed from Mafic Rocks |
title_full |
Pedogenic Iron Oxides in Iron-Rich Oxisols Developed from Mafic Rocks |
title_fullStr |
Pedogenic Iron Oxides in Iron-Rich Oxisols Developed from Mafic Rocks |
title_full_unstemmed |
Pedogenic Iron Oxides in Iron-Rich Oxisols Developed from Mafic Rocks |
title_sort |
Pedogenic Iron Oxides in Iron-Rich Oxisols Developed from Mafic Rocks |
author |
Camêlo,Danilo de Lima |
author_facet |
Camêlo,Danilo de Lima Ker,João Carlos Fontes,Maurício Paulo Ferreira Corrêa,Marcelo Metri Costa,Antonio Carlos Saraiva da Melo,Vander Freitas |
author_role |
author |
author2 |
Ker,João Carlos Fontes,Maurício Paulo Ferreira Corrêa,Marcelo Metri Costa,Antonio Carlos Saraiva da Melo,Vander Freitas |
author2_role |
author author author author author |
dc.contributor.author.fl_str_mv |
Camêlo,Danilo de Lima Ker,João Carlos Fontes,Maurício Paulo Ferreira Corrêa,Marcelo Metri Costa,Antonio Carlos Saraiva da Melo,Vander Freitas |
dc.subject.por.fl_str_mv |
hematite maghemite crystallographic characteristics Al-substitution selective dissolution |
topic |
hematite maghemite crystallographic characteristics Al-substitution selective dissolution |
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. |
publishDate |
2017 |
dc.date.none.fl_str_mv |
2017-01-01 |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100413 |
url |
http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100413 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
10.1590/18069657rbcs20160379 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
text/html |
dc.publisher.none.fl_str_mv |
Sociedade Brasileira de Ciência do Solo |
publisher.none.fl_str_mv |
Sociedade Brasileira de Ciência do Solo |
dc.source.none.fl_str_mv |
Revista Brasileira de Ciência do Solo v.41 2017 reponame:Revista Brasileira de Ciência do Solo (Online) instname:Sociedade Brasileira de Ciência do Solo (SBCS) instacron:SBCS |
instname_str |
Sociedade Brasileira de Ciência do Solo (SBCS) |
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SBCS |
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SBCS |
reponame_str |
Revista Brasileira de Ciência do Solo (Online) |
collection |
Revista Brasileira de Ciência do Solo (Online) |
repository.name.fl_str_mv |
Revista Brasileira de Ciência do Solo (Online) - Sociedade Brasileira de Ciência do Solo (SBCS) |
repository.mail.fl_str_mv |
||sbcs@ufv.br |
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1752126521339805696 |