Correlation between the natural levels of selenium and soil physicochemical characteristics from the Jequitinhonha Valley (MG), Brazil

Selenium (Se) is a micronutrient of great interest due to the narrow range between its essential and toxic levels. This study was carried out to evaluate the correlations between Se concentrations and soil physicochemical characteristics (sand, silt, clay, organic matter, pH and oxides of Al, Fe and Si) from preserved areas in the Jequitinhonha Valley, Minas Gerais state, Brazil. Total Se was determined in A and B horizons of 12 classes of soils by hydride generation atomic absorption spectrometry (HG AAS) after aqua regia digestion in a microwave oven. Se concentrations in soils ranged from < 0.30 ± 0.03 to 5.97 ± 0.20 mg kg− 1 with the highest concentration reported in Spodosol, followed by the weathered soils (Red and Red-Yellow Latosols). No significant differences in Se concentration were observed between A and B horizons, except for Spodosol. The statistical analysis by Pearson's correlation, principal component analysis (PCA) and hierarchical cluster analysis (HCA) showed that Se concentration correlated significantly and positively with Al2O3 (r = 0.76), Fe2O3 (r = 0.57) and clay (r = 0.64) and negatively with SiO2 (r = − 0.76) and sand (r = − 0.54). There was no significant correlation with organic matter, pH and silt. Significant Se concentration was verified in weathered soils (Red and Red-Yellow Latosols), which are widely distributed throughout Brazil, and they are often used in agriculture. This study also provides useful data for the preparation of maps of Se distribution.