Susceptibilidade magnética para o agrupamento e análise da variabilidade espacial em solos tropicais

Abstract

Due to its potential in attributes prediction, the magnetic susceptibility is currently considered an effective for survey and quantificate soil properties, and can also be effective to distinguish soils in the landscape. This study aimed to (i) determine the mass magnetic susceptibility (XBF) of different classes of soils from Guarapuava/PR and group them according to their common characteristics through principal component analysis (PCA), and (ii) conduct a spatial variability survey of the volumetric magnetic susceptibility (K) values in tropical soils using the MSZD probe. For this issue, were collected 33 soil samples (ADFE) belonging to different geochemical landscapes (Serra Geral and Rio do Rasto Formation) in the region of Guarapuava/PR (POLISELI, 2007) and determined the XLF and frequency-dependent susceptibility (XFD), the chemical, physical and mineralogical soil attributes. Based on the results, two PCA were generated, one with the chemical and physical variables and other with the mineralogical data. In the city of Maringa/PR were determined the K values and the heavy metal contents through sulfuric digestion. The variability map was obtained by geostatistics analysis, using semivariograms and ordinary kriging. The obtained values in Guarapuava/PR samples revealed a high correlation between XLF before and after-CBD treatment (r = 0.97, p < 0.0l) and between pedogenical and total Fe contents (r = 0.43 and 0.65, respectively). The average values of Serra Geral Formation XLF were larger (691 X l0'8m3l<g'l) than those on Rio do Rasto Formation (44 x l0'8m3l<g'1), demonstrating the influence of parent material in the presence of ferrimagnetic minerals. The PCA with mineralogical variables explains better the total variation of the sample set (84.55 %), being the Xu: the variable that most contributed to distinct the formed groups, allowing to differentiate Gleysols and samples belonging to Rio do Rasto Formation. The K values of Maringa/PR showed a strong spatial dependence, due to its relationship with the parent material, ranging from 3 l6 x l0'5 Sl in the region of Arenito Caiua to 6,945 x l0'5 SI in the basaltic material region. The values determined by MSZD probe correlates (r = 0.93, p < 0.01) with those obtained by MSZB sensor, showing the inexistence of anthropogenic pollution on soil surface. Regarding heavy metals, higher correlations (p < 0.0l) were obtained between K and the elements Al, Cu, Fe and Mn. The relationship between Fel and Fed contents (r = 0.90) are due to the high weathering degree of soils. Due to the equipment Magnetic susceptibility for grouping and spatial variability analisys in tropical soils high sensitivity to quantificate the magnetic susceptibility, it is recommended use this variable to group soils in different geochemical landscapes and identify different lithologies along the landscape, according to their magnetic properties.