The Amazon rainforest presents one of the greater biodiversity in the world and a huge and dynamic carbon reservoir, both in the vegetation and in the soil pools, so it is an attractive subject of study. In the present paper, humic acids from a toposequence of an Oxisol-Spodosol system associated with kaolin was studied using fluorescence emission-excitation matrix combined with parallel factor analysis. The combined techniques allowed to assess the intensities of the two different fluorophores associated with humic acid with core consistency diagnoses of 84.2%. The results for the Humiluvic Spodosol seem to corroborate the model of the supramolecular structure of humic acid, because the intensity ratio of fluorophores does not remain in the profile. Therefore, the use of these combined techniques can provide information about the transformation processes of humic substances in soils, becoming an interesting analytical tool for studying these substances of different soils.
Keywords
humic acid; three-dimensional fluorescence; fluorophores; parallel factor analysis
