Estimativa da caulinita e gibbsita por técnicas de difração de raios x e espectroscopia de reflectância difusa dos solos do Planalto Ocidental Paulista
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Data
2017-02-23
Autores
Fernandes, Kathleen Lourenço [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Planalto Ocidental Paulista (POP) é uma das principais áreas de cultivo de citros do país, representando cerca de 80% da produção nacional, tendo ainda grande participação na produção de açúcar e álcool. A caracterização e quantificação mineralógica dos solos desta região torna-se importante para melhor entendimento dos processos pedogênicos do solo, e uso de melhores práticas de manejo. Por meio de ferramentas como a geoestatística é possível entender a relação entre a mineralogia do solo e as formas da paisagem, indicando a variabilidade espacial dos dados e a dependência entre os atributos pedogênicos e os geomórficos da região. Assim, o presente trabalho teve como objetivos: a) caracterizar os teores e a cristalinidade da caulinita (Ct) e gibbsita (Gb), e suas relações com os diferentes compartimentos geológicos e geomorfológicos do POP; b) e avaliar o potencial de diferentes metodologias aplicadas às curvas espectrais, dada pela técnica de espectroscopia de reflectância difusa (ERD), para estimativa da razão entre Ct e Gb, e caracterizar a variabilidade espacial da razão para o POP. Foram coletadas 600 amostras de solo georreferenciadas, próximas às principais rodovias do estado de São Paulo. Para quantificação dos teores e cristalinidade da Ct e Gb foi utilizada a técnica de difratometria de raios X (DRX) e a metodologia de Rietveld. A quantificação não convencional pela técnica de ERD, foi feita por três metodologias aplicadas às curvas espectrais: contínuo removível, relação direta do vale e regressão mínima por quadrados parciais. Os dados foram submetidos a análises de estatística descritiva, análise de regressão (para comparativo entre as técnicas) e análises geoestatísticas, pela krigagem simples. Os compartimentos geológicos e geomorfológicos influenciam na distribuição dos teores de Ct e Gb, e na formação cristalográfica destes. Ambientes de geologia Arenítica apresentam maiores teores de Ct, menos cristalinas, e ambientes de Basalto maiores teores de Gb de maior cristalinidade. A ERD mostrou-se como uma técnica eficiente para a estimativa não convencional dos minerais, tendo a metodologia do contínuo removível apresentado os melhores parâmetros estatísticos, entre a comparação de valores dados pela DRX e pela ERD. A variabilidade espacial da razão entre Ct e Gb, apresentou padrões semelhantes entre os mapas de dados da DRX e ERD, para ambas as metodologias.
The Ouest Paulista Plateau (POP) is one of the main areas of citrus cultivation in the country, accounting for about 80% of the national production, with a large share of sugar and alcohol production. The characterization and mineralogical quantification of the soils of this region becomes important for a better understanding of the soil pedogenic processes, and the use of better management practices. Through tools such as geostatistics, it is possible to understand the relationship between soil mineralogy and landscape forms, indicating the spatial variability of the data and the dependence between the pedogenic and geomorphic attributes of the region. Thus, the present work had as objectives: a) to characterize the contents and crystallinity of kaolinite (Kt) and gibbsite (Gb), and its relations with the different geological and geomorphological compartments of POP; B) and to evaluate the potential of different methodologies applied to the spectral curves, given by the diffuse reflectance spectroscopy (DRS) technique, to estimate the ratio between Ct and Gb, and to characterize the spatial variability of the ratio for the POP. A total of 600 georeferenced soil samples were collected near the main highways in the state of São Paulo. The X-ray diffraction (XRD) technique and the Rietveld methodology were used to quantify the Ct and Gb contents and crystallinity. The unconventional quantification by the DRS technique was done by three methodologies applied to the spectral curves: removable continuous, direct ratio of the valley and minimum regression by partial squares. Data were submitted to descriptive statistics analysis, regression analysis (for comparison between the techniques) and geostatistical analysis, by simple kriging. The geological and geomorphological compartments influence the distribution of Kt and Gb contents and their crystallographic formation. Environments of sandstone geology have higher levels of Ct, less crystalline, and environments of basalt greater Gb levels of greater crystallinity. DRS proved to be an efficient technique for the unconventional estimation of minerals, and the methodology of the removable continuum presented the best statistical parameters between the comparison of values given by the XRD and the DRS. The spatial variability of the ratio between Kt and Gb presented similar patterns between the XRD and DRS data maps for both methodologies.
The Ouest Paulista Plateau (POP) is one of the main areas of citrus cultivation in the country, accounting for about 80% of the national production, with a large share of sugar and alcohol production. The characterization and mineralogical quantification of the soils of this region becomes important for a better understanding of the soil pedogenic processes, and the use of better management practices. Through tools such as geostatistics, it is possible to understand the relationship between soil mineralogy and landscape forms, indicating the spatial variability of the data and the dependence between the pedogenic and geomorphic attributes of the region. Thus, the present work had as objectives: a) to characterize the contents and crystallinity of kaolinite (Kt) and gibbsite (Gb), and its relations with the different geological and geomorphological compartments of POP; B) and to evaluate the potential of different methodologies applied to the spectral curves, given by the diffuse reflectance spectroscopy (DRS) technique, to estimate the ratio between Ct and Gb, and to characterize the spatial variability of the ratio for the POP. A total of 600 georeferenced soil samples were collected near the main highways in the state of São Paulo. The X-ray diffraction (XRD) technique and the Rietveld methodology were used to quantify the Ct and Gb contents and crystallinity. The unconventional quantification by the DRS technique was done by three methodologies applied to the spectral curves: removable continuous, direct ratio of the valley and minimum regression by partial squares. Data were submitted to descriptive statistics analysis, regression analysis (for comparison between the techniques) and geostatistical analysis, by simple kriging. The geological and geomorphological compartments influence the distribution of Kt and Gb contents and their crystallographic formation. Environments of sandstone geology have higher levels of Ct, less crystalline, and environments of basalt greater Gb levels of greater crystallinity. DRS proved to be an efficient technique for the unconventional estimation of minerals, and the methodology of the removable continuum presented the best statistical parameters between the comparison of values given by the XRD and the DRS. The spatial variability of the ratio between Kt and Gb presented similar patterns between the XRD and DRS data maps for both methodologies.
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Palavras-chave
Pedometria, Curva espectral, Geoestatística, Arenito, Basalto