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Registro Completo |
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Biblioteca(s): |
Embrapa Cerrados; Embrapa Solos. |
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Data corrente: |
22/11/2002 |
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Data da última atualização: |
29/09/2004 |
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Autoria: |
MACEDO, J. |
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Título: |
Preferential reduction of hematite over goethite in some oxisols in Brazil. |
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Ano de publicação: |
1988 |
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Fonte/Imprenta: |
1988. |
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Páginas: |
43 f. |
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Idioma: |
Inglês |
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Notas: |
Thesis (Doctor of Philosophy) - Cornell University, [S. l.]. |
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Conteúdo: |
Research was conducted to evaluate iron transformations in a hydrosequence of oxisols from the Central Plateau of Brazil. The best-drained member of the hydrosequence of soils selected for the study classifies as a Typic Acrustox (Dark-Red Latosol) and has codominant hematite and goethite iron oxide mineralogy and reddish hues (2.5 YR). X-ray diffraction and chemical extraction techniques were used to make detailed analyses of the iron oxides. Peak positions for hematite are coincident with those reported for normal hematite. Peak positions for goethite are shifted toward a lower dspacing, which corresponds to 38 mole % of Al00H substituting for Fe00H. Soil samples from the Bo horizon were subjected to reducing conditions in the laboratory over a range of timeperiods, using sucrose as a source of energy to speed yp the activity of the soil microorganisms. Reducing conditions in other samples were induced by citrate-bicarbonate-dithionite treatment at room temperature, using increasing additions of dithionite to achieve a range in reduction of these soils. In both experiments, the observed changes in soil minerologies confirm the preferential reduction and removal of hematite over goethite. The dithionite reduction of aluminum-substituted goethite is temperature dependent. The electrode potential of hematite and aluminum-substituted goethite are 98 and -2 mV respectively. Mineralogies and soil colors after reduction treatments are comparable to that of the Typic Acrustox (Red-Yellow Latosol) found in the wetter section of the hydrosequence. The results of this study support the hypothesis that differences in colors and iron mineralogies of soils in this hydrosequence are the result of the preferential reduction of hematite over goethite in the presence of a seasonally high water table. MenosResearch was conducted to evaluate iron transformations in a hydrosequence of oxisols from the Central Plateau of Brazil. The best-drained member of the hydrosequence of soils selected for the study classifies as a Typic Acrustox (Dark-Red Latosol) and has codominant hematite and goethite iron oxide mineralogy and reddish hues (2.5 YR). X-ray diffraction and chemical extraction techniques were used to make detailed analyses of the iron oxides. Peak positions for hematite are coincident with those reported for normal hematite. Peak positions for goethite are shifted toward a lower dspacing, which corresponds to 38 mole % of Al00H substituting for Fe00H. Soil samples from the Bo horizon were subjected to reducing conditions in the laboratory over a range of timeperiods, using sucrose as a source of energy to speed yp the activity of the soil microorganisms. Reducing conditions in other samples were induced by citrate-bicarbonate-dithionite treatment at room temperature, using increasing additions of dithionite to achieve a range in reduction of these soils. In both experiments, the observed changes in soil minerologies confirm the preferential reduction and removal of hematite over goethite. The dithionite reduction of aluminum-substituted goethite is temperature dependent. The electrode potential of hematite and aluminum-substituted goethite are 98 and -2 mV respectively. Mineralogies and soil colors after reduction treatments are comparable to that of the Typic Acrustox (Red... Mostrar Tudo |
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Palavras-Chave: |
Brasil; Goethita; Hematita. |
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Thesagro: |
Cerrado; Mineralogia; Oxisol; Solo. |
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Categoria do assunto: |
-- |
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Marc: |
LEADER 02370nam a2200217 a 4500
001 1567792
005 2004-09-29
008 1988 bl uuuu m 00u1 u #d
100 1 $aMACEDO, J.
245 $aPreferential reduction of hematite over goethite in some oxisols in Brazil.
260 $a1988.$c1988
300 $a43 f.
500 $aThesis (Doctor of Philosophy) - Cornell University, [S. l.].
520 $aResearch was conducted to evaluate iron transformations in a hydrosequence of oxisols from the Central Plateau of Brazil. The best-drained member of the hydrosequence of soils selected for the study classifies as a Typic Acrustox (Dark-Red Latosol) and has codominant hematite and goethite iron oxide mineralogy and reddish hues (2.5 YR). X-ray diffraction and chemical extraction techniques were used to make detailed analyses of the iron oxides. Peak positions for hematite are coincident with those reported for normal hematite. Peak positions for goethite are shifted toward a lower dspacing, which corresponds to 38 mole % of Al00H substituting for Fe00H. Soil samples from the Bo horizon were subjected to reducing conditions in the laboratory over a range of timeperiods, using sucrose as a source of energy to speed yp the activity of the soil microorganisms. Reducing conditions in other samples were induced by citrate-bicarbonate-dithionite treatment at room temperature, using increasing additions of dithionite to achieve a range in reduction of these soils. In both experiments, the observed changes in soil minerologies confirm the preferential reduction and removal of hematite over goethite. The dithionite reduction of aluminum-substituted goethite is temperature dependent. The electrode potential of hematite and aluminum-substituted goethite are 98 and -2 mV respectively. Mineralogies and soil colors after reduction treatments are comparable to that of the Typic Acrustox (Red-Yellow Latosol) found in the wetter section of the hydrosequence. The results of this study support the hypothesis that differences in colors and iron mineralogies of soils in this hydrosequence are the result of the preferential reduction of hematite over goethite in the presence of a seasonally high water table.
650 $aCerrado
650 $aMineralogia
650 $aOxisol
650 $aSolo
653 $aBrasil
653 $aGoethita
653 $aHematita
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Registro original: |
Embrapa Cerrados (CPAC) |
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| Registros recuperados : 477 | |
| 1. |  | MACEDO, J. The Brazilian cerrados. In: INTERNATIONAL WORKSHOP ON SOIL, WATER, AND NUTRIENT MANAGEMENT RESEARCH: environmental and productivity dimensions, 1994, Zschortau, Germany. Proceedings: the Zschortau plan for the implementation of soil, water, and nutrient ... . Zchortau: DSE/Bangkok: IBSRAM, 1995. p.78-86.| Biblioteca(s): Embrapa Cerrados. |
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| 2. | | MACEDO, J. Produção de alimentos: o potencial dos cerrados. Planaltina, DF: EMBRAPA-CPAC, 1996. 33 p. (EMBRAPA-CPAC. Documentos, 59). Apresentado no "Workshop de Ecologia e Biodiversidade", com o titulo "Prospectives for the rational use of the Brazilian's Cerrados for food production", Rio de Janeiro, 1994 (CRI4028). Ver CRI3752.| Biblioteca(s): Embrapa Cerrados. |
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| 8. | | MACEDO, J. Os solos da regiao dos cerrados. In: ALVAREZ V., V.H.; FONTES, L.E.F.; FONTES, M.P.F. (Ed.). O solo nos grandes dominios morfoclimaticos do Brasil e o desenvolvimento sustentado. Vicosa: SBCS/UFV, 1996. p.135-155.| Biblioteca(s): Embrapa Cerrados. |
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| 11. | | MACEDO, J. R. de. Erosão em pastagens. Portal Dia de Campo, 18 ago. 2010. Disponível em : < http://www.diadecampo.com.br>. Acesso em: 09 fev. 2011.| Tipo: Artigo de Divulgação na Mídia |
| Biblioteca(s): Embrapa Solos. |
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| 15. | | MACEDO, J. L. V. de. Cultivo de fruteiras em sistemas agroflorestais. In: ENCONTRO DE FRUTAS NATIVAS DO NORTE E NORDESTE DO BRASIL, 1., 2008, São Luís. Frutas nativas: novos sabores para o mundo. São Luís: UEMA: SBF: EMBRAPA: SEBRAE: SEAGRO, 2008. 1 CD-ROM.| Tipo: Artigo em Anais de Congresso / Nota Técnica |
| Biblioteca(s): Embrapa Amazônia Ocidental. |
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| 16. | | MACEDO, J. L. V. de. Atividades de manejo na área experimental. In: SHIFT PROJECT ENV 23 (Manaus-AM). Recuperação de áreas degradadas e abandonadas, através de sistemas de policultivo. Manaus: EMBRAPA-CPAA: University of Hamburg, 1998. p. 1-2.| Tipo: Capítulo em Livro Técnico-Científico |
| Biblioteca(s): Embrapa Amazônia Ocidental. |
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| Registros recuperados : 477 | |
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| Nenhum registro encontrado para a expressão de busca informada. |
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