STUDY MULTI-ELEMENTAR AND ESTRUCTURAL IN AMAZONIAN SOIL USING DIFFERENT SPECTROSCOPIC TECHNIQUES

The Amazonian comprises an extensive and heterogeneous region, in which climatic factors, biotic interactions, landforms and geomorphology give rise to a rich diversity of soil types.1 In amazonian soils, minerals matter and organic matter (OM) can form intrinsic associations through different interactions. This association of OM with mineral surfaces is interesting due to OM retention. Different environmental conditions during its formation and decomposition of soil organic matter (SOM) have a great impact on the structure of the soil (quantity and composition). It is desirable, therefore, to distinguish the intrinsic structural factors governing the rate of decomposition of SOM. X-ray diffraction (XRD), Laser Induced Breakdown Spectroscopy (LIBS) and Fourier Transform Infrared Spectroscopy (FTIR) can be used to perform a qualitative measurement of the chemical changes of SOM functional groups occurring at from the surface to a depth of 4 meters.
The aim of this work is to study the association of mineral and organic matter in amazonian soil, type Humiluvic Spodosol (EH). The XRD quantitative analysis, using Rietveld method showed the Quartz (horizon A1 to Bh) and Kaolinite (horizon Bhs to K1) as major component and small concentrations of Anatase and Montmorillonite phase. According to the elemental analysis (CHN), a gradual decrease of the C concentration of the surface horizon A1 (7.9 g kg-1) was observed for the SPS horizon (4.2 g kg-1). The transformation of the Bhs for the transition horizon (Tr) presents a significant variation of the concentration of C, ~27 g kg-1. This gradual and significant variation can be observed from the FTIR absorption band for each horizon. The absorption of C-H functional groups in EH decreases as a function of depth, this decrease was associated by a relative increase in C=O absorption. This change in absorption intensity reflects the decomposition and mineralization of the soil. From the LIBS spectrum was performed a multi-elemental analysis of the soil profile. Our results suggest that the combination of XRD, LIBS and FTIR and provide a useful method for studying the association of OM and minerals in EH soil.