Mineralogy of the clay fraction of Alfisols in two slope curvatures: III - spatial variability

Revista Brasileira de Ciência do Solo

Livia Arantes Camargo²  José Marques Júnior¹  Gener Tadeu Pereira¹ 

[1] ,Universidade Estadual Paulista - UNESP FCAV Agronomy (Soil Science)Jaboticabal SP ,Brazil

关键词: iron oxides;    kaolinite;    gibbsite;    goethite;    hematite;    relief;    óxidos de ferro;    caulinita;    gibbsita;    goethita;    hematita;    relevo;   

DOI  :  10.1590/S0100-06832013000200001

来源: SciELO

【 摘 要 】

A good knowledge of the spatial distribution of clay minerals in the landscape facilitates the understanding of the influence of relief on the content and crystallographic attributes of soil minerals such as goethite, hematite, kaolinite and gibbsite. This study aimed at describing the relationships between the mineral properties of the clay fraction and landscape shapes by determining the mineral properties of goethite, hematite, kaolinite and gibbsite, and assessing their dependence and spatial variability, in two slope curvatures. To this end, two 100 × 100 m grids were used to establish a total of 121 regularly spaced georeferenced sampling nodes 10 m apart. Samples were collected from the layer 0.0-0.2 m and analysed for iron oxides, and kaolinite and gibbsite in the clay fraction. Minerals in the clay fraction were characterized from their X-ray diffraction (XRD) patterns, which were interpreted and used to calculate the width at half height (WHH) and mean crystallite dimension (MCD) of iron oxides, kaolinite, and gibbsite, as well as aluminium substitution and specific surface area (SSA) in hematite and goethite. Additional calculations included the goethite and hematite contents, and the goethite/(goethite+hematite) [Gt/(Gt+Hm)] and kaolinite/(kaolinite+gibbsite) [Kt/(Kt+Gb)] ratios. Mineral properties were established by statistical analysis of the XRD data, and spatial dependence was assessed geostatistically. Mineralogical properties differed significantly between the convex area and concave area. The geostatistical analysis showed a greater number of mineralogical properties with spatial dependence and a higher range in the convex than in the concave area.

【 授权许可】

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