Óxidos de ferro das frações areia e silte de um Nitossolo desenvolvido de basalto

RESUMOConsiderando as dimensões da região amazônica e a necessidade de estudos que estabeleçam conexões entre os solos e a expressão da paisagem, o objetivo deste trabalho foi estudar as relações solo-paisagem em uma topossequência sobre substrato granítico em Santo Antônio do Matupi, Manicoré, AM. Foi estabelecido um caminhamento de 3.000 m a partir do "espigão" da vertente, no seu sentido mais suave, com identificação dos segmentos da vertente com base na "quebra" do declive do terreno. Foram abertas trincheiras nos segmentos de vertente mapeados, e perfis foram caracterizados morfologicamente, coletando-se amostras de seus horizontes. Foram realizadas análises físicas (textura, ADA e GF, Ds e Dp, Pt e CHSS), químicas (pH em água e KCl, Ca, Mg, K, Na e Al trocáveis, P disponível, H + Al e C orgânico; SiO 2 , Al 2 O 3 e Fe 2 O 3 (método do H 2 SO 4 ) e óxidos de Fe "livres" extraído com ditionito-citrato-bicarbonato e o Fe mal cristalizado extraído com oxalato de amônio) e mineralógicas (frações areia, silte e argila), usando difratometria de raios X. As variações do relevo favoreceram a presença de solos distróficos nos topos e solos eutróficos no sopé de transporte. As variáveis Δ Δ Δ Δ ΔpH, relação silte/argila, V % e relação Fed/Fet indicaram a presença de solos mais intemperizados nas áreas de topo da paisagem e solos com menor grau de evolução na encosta e no sopé de transporte. A composição mineralógica da fração argila

Section: Atributos Mineralógicosunclassified

Relações solo-paisagem em uma topossequência sobre substrato granítico em Santo Antônio do Matupi, Manicoré (AM)

Campos

Ribeiro

Júnior

et al. 2011

“…In the last three decades, Mössbauer spectroscopy (MS) has become an increasingly important analytical tool for the characterization of synthetic and natural Fe-containing materials, and one of the most rapidly growing application areas of this technique is undoubtedly that of soils and sediments (Ferreira et al, 2003). In soils, Al commonly replaces part of the Fe in maghemite (Schwertmann & Fetcher, 1984).…”

Section: Introductionmentioning

confidence: 99%

Structural and magnetic characterization of maghemites prepared from Al-substituted magnetites

Batista

Costa²,

Bigham

et al. 2013

SUMMARYSynthetic aluminum-substituted maghemites were characterized by total chemical analysis, powder X-ray diffraction (XRD), Mössbauer spectroscopy (ME), and vibrating sample magnetometry (VSM). The aim was to determine the structural, magnetic, and hyperfine properties of γ γ γ γ γ-Fe 2-x Al x O 3 as the Al concentration is varied. The XRD results of the synthetic products were indexed exclusively as maghemite. Increasing Al for Fe substitution decreased the mean crystalline dimension and shifted all diffraction peaks to higher o 2θ θ θ θ θ angles. The a 0 dimension of the cubic unit cell decreased with increasing Al according to the equation a o = 0.8385 -3.63 x 10 -5 Al (R 2 = 0.94). Most Mössbauer spectra were composed of one sextet, but at the highest substitution rate of 142.5 mmol mol -1 Al, both a doublet and sextet were obtained at ≈ 300 K. All hyperfine parameters from the sub-spectra were consistent with high-spin Fe 3+ (0.2 a 0.7 mms -1 ) and suggested a strong superparamagnetic component associated with the doublet. The magnetic hyperfine field of the sextets decreased with the amount of Al-substitution [B hf (T) = 49.751 -0.1202Al; R 2 = 0.94] while the linewidth increased linearly. The saturation magnetization also decreased with increasing isomorphous substitution.Index terms: isomorphous substitution, hyperfine parameters, spinel, ferromagnetic.( RESUMO: CARACTERIZAÇÃO ESTRUTURAL E MAGNÉTICA DE MAGHEMITAS PREPARADAS A PARTIR DE MAGNETITAS SUBSTITUÍDAS COM AlMaghemitas sintéticas substituídas com Al foram caracterizadas por meio de análise química total, difratometria de raios-X (DRX), espectroscopia Mössbauer (EM) e magnetometria de amostra vibrante (MAV). Objetivou-se com este trabalho determinar as propriedades estruturais, magnéticas e hiperfinas de γ-Fe 2-x Al x O 3, conforme a variação da concentração de Al.Os resultados de DRX dos produtos sintéticos foram indexados somente para maghemita. Com o aumento da substituição de Fe por Al, o diâmetro médio do cristalito diminuiu e levou todos os picos de difração para maiores ângulos o 2θ. A dimensão a 0 da cela unitária cúbica decresceu com o aumento de Al, de acordo com a equação a o = 0,8385 -3,63 x 10 -5 Al (R 2 = 0,94). A maioria dos espectros Mössbauer foi composta de um sexteto, mas na taxa mais alta de substituição de 142,5 mmol mol -1 Al um doubleto e sexteto foram obtidos a ≈ 300 K. Todos os parâmetros hiperfinos do subespectro foram consistentes com o alto spin Fe 3+ (0,2 a 0,7 mms -1 ) e sugeriram um forte componente superparamagnético associado com o dubleto. O campo magnético hiperfino dos sextetos decresceram com a substituição de Al [B hf (T) = 49,751 -0,1202Al; R 2 = 0,94], enquanto as larguras da linha aumentaram de forma linear. A magnetização de saturação também diminuiu com o aumento da substituição isomórfica.Termos de indexação: substituição isomórfica, parâmetros hiperfinos, espinélio, ferrimagnético.

“…In addition to the close relationship between parent material and soil properties (Brilhante et al, 2017;Neves et al, 2018), the relief plays a key role in pedodiversity, since along the slopes, there may be mixtures of parent materials, conditioning the formation of soil with peculiar properties. It is possible to find the occurrence of Nitossolos distinct from those previously studied in other regions of Brazil (Cooper and Vidal-Torrado, 2000;Ferreira et al, 2003;Silva et al, 2009;Melo et al, 2010) The southern coastal region of Pernambuco, in addition to the estuarine environments, is formed by the Atlantic forest ecosystem, the natural vegetation of which is practically nonexistent. The area is mainly used for sugarcane cultivation, a large industrial park, and dense urban areas with a population of approximately 500,000 inhabitants (IBGE, 2010).…”

Section: Introductionmentioning

confidence: 83%

“…Nitossolos commonly presents low clay fraction activity (Santos et al, 2013) as a consequence of the kaolinitic and oxidic mineralogical composition (Ferreira et al, 2003). However, the high activity identified along P3 is related to the smectites (Table 5 and Figure 2).…”

Section: Soil Properties and Their Relation To Pedogenesismentioning

confidence: 99%

Genesis and Classification of Nitisols from Volcano-Sedimentary Lithology in Northeastern Brazil

Costa

Araújo

Neves

et al. 2019

On the southern coast of Pernambuco State (PE), Brazil, lithotypes of the Cabo Basin (volcanic and sedimentary rocks), in association with the relief, allow the determination of the dynamics of the formation of Nitossolos Háplicos (Nitisols), including those with high levels of exchangeable aluminum. The objective of this study was to evaluate the influence of lithological diversity (basalt and sedimentary siliciclastic rocks) on the morphological, physical, chemical, and mineralogical properties of Nitossolos Háplicos along a slope (P1-summit, P2-backslope, P3-footslope) on the southern coast of PE, in order to consider its genesis and the relation of soil properties to adjacent environments and to evaluate its framing within the Brazilian Soil Classification System (SiBCS). The interaction of lithology/soil permeability and climate indicate significant differences in the mineralogical composition and dynamics of soil chemical elements. The profiles P1 and P2 are subject to monosialitization, ferralitization, and alitization processes. All profiles showed high Fe contents (ferric soils) and clay fractions, consisting primarily of kaolinite, goethite, hematite, and gibbsite, as well as quartz and feldspar in the sand and silt fractions. However, smectite minerals (P3) are probably inherited from the sedimentary source material. In the conglomerate samples, under P3, biotite, muscovite, and plagioclase were identified. Allytic characteristics (P3) are probably associated with the weathering of aluminous smectite minerals. These properties distinguish these soils from adjacent Nitossolos and other Nitossolos in Brazil. For the classification of soils according to SiBCS, considering the high levels of Fe and Al, Nitossolo Háplico distroférrico (P1 and P2) and Nitossolo Háplico alitiférrico (P3) are suggested, and according to the World Reference Base of Soils (WRB), the soils are classified as Ferritic Nitisols.