CHARACTERIZATION OF HUMIC FRACTIONS IN AMAZON SPODOSOL BY LASER-INDUCED BREAKDOWN SPECTROSCOPY

Organic matter in soils (SOM) usually is not homogeneous, and studies to evaluate the dynamics of this matter are important, especially in soil providing of the Amazon region, what that is considered one of the most important carbon sinks in the world1. The determination of the optical properties of SOM and humic fractions (Humic and Fulvic Acid, Humin) is an important method for understanding their composition elementary. The Laser-induced Breakdown Spectroscopy (LIBS) technique has been shown to be effective in the analysis of SOM by providing fast, sensitive, clean results and can be applied to the sample without pretreatment2. The study area is located in the Barcelos, in the Basin of Demeni River, a tributary of the middle Rio Negro and the soils classified by with Spodosols (0-390 cm). The main objective was characterization of line Al (309.25 nm) for Humic fractions (Humic and Fulvic Acid, Humin) in Amazon Spodosols using LIBS. The spectra obtained by the LIBS were normalized and performed a mathematical treatment, such as Turkey and the Principal Component Analysis (PCA) by Software Matlab R2013a. Preliminary results showed a significant difference (p <0.0001) between of the fulvic acid and whole soil for humic acid in these soils. From results obtained by using the PCA it was possible observe the formation of three groups. The first group was agglomerated by mixture of humic and fulvic acid, the second and third grouping constituting by humin and whole soil, respectively. Thus, the results allowed inferring that the humic and fulvic acid presented similar characteristics of line of Aluminum, whereas humin and whole soil verified a significant variation for this line of the soils. In addition, the LIBS technique presented a simple and quick descriptive analysis of the soils used, which followed the principles of green chemistry.