Granulometry is an initial factor to be considered in soil research as it plays a fundamental role in physical and chemical properties. The objective of this study was to characterize the granulometric fractions of soil, obtained using the screening and sedimentation method. The Dynamic Light Scattering (DLS), Mid-Infrared (MIR), and Scanning Electron Microscopy with Field Emission Gun (SEM-FEG) techniques were used for this purpose. The quantitative results showed that this soil presents high percentage of clay, followed by fine sand fraction, silt fraction and, finally, the coarse sand fraction. The results obtained by DLS qualify this technique as a procedure to evaluate the quality of the granulometric fractionation of the clay fraction. The MIR analyzes detected characteristic vibrational states of minerals such as kaolinite, halloysite, gibbsite, and quartz. Few works in the literature characterize the clay fraction of the soil without chemical treatment using the SEM-FEG technique. Thus, in this work, pseudo-hexagonal structures were identified, typical of the kaolinite mineral and, to a lesser extent, structures with a filamentous needle-like morphology, which can be ascribed to illite and/or halloysite, whose inorganic functional groups were identified by MIR in the clay fraction of the soil.

A espectroscopia de Ressonância Paramagnética Eletrônica (EPR) foi aplicada em sete amostras de solos (Gleissolos), com o objetivo de quantificar o grau de humificação da matéria orgânica destes solos e comparar com as suas respectivas frações físicas. O sinal dos radicais livres do tipo semiquinona foi detectado e quantificado identificando o grau de humificação da matéria orgânica do solo inteiro que correlacionou com a humificação da matéria orgânica de suas frações.

Electron Paramagnetic Resonance (EPR) spectroscopy was applied in whole soil samples (Gleysoil). The objective of this work was to quantify the degree of humification of the organic matter of the soil, whole soil (Gleysoils) without any chemical treatment, and to compare with its organic-mineral fractions. The signal of semiquinone free radical was detected and quantified showing close relationship with its organic-mineral fractions.