Espectroscopia de FTIR, aliada a ferramentas quimiométricas, na caracterização estrutural de amostras de solo e ácido húmico

Abstract

Organic matter has fundamental importance for the soil, because it acts positively on several of soil properties. The minerals, along with the organic matter, form the solid phase of the soil, and have influence on the supply of nutrients for plants and soil structure. Therefore, the aim of the present work was to complement the studies about the application of Fourier transform infrared spectroscopy on structural characterization of soil and of organic matter. For this, four samples collected from the surface (0-10 cm) of a typical Oxisol passed by chemical fractionation and 10% hydrofluoric acid treatment to be used on the analysis. The results of the several tests showed that: (1) the amount of potassium bromide used on background pellet interfere on the characteristics of samples spectra; (2) after the chemical fractionation some of mineral impurities stayed on humic acid samples and interfere on the spectra; (3) the 10% hydrofluoric acid treatment, the way it was done, was not efficient to eliminate the minerals of soil samples, since the spectra before and after the treatment were very similar, it was not efficient to eliminate the mineral impurities of humic acid samples too, however, allowed the identification of a important band to calculate the aromaticity index; (4) the baseline adjustment interfere significantly on absorptions intensities and on aromaticity index value too; (5) the use of chemometric tools like the principal component analysis and the paired t test is very important to give consistence to the qualitative evaluation.