Chemical characterization and infrared spectroscopy of soil organic matter from two southern brazilian soils

Revista Brasileira de Ciência do Solo

D. P. Dick²  J. H. Z. Santos²  E. M. Ferranti¹ 

[1] ,Universidade Federal do Rio Grande do Sul - UFRGS Instituto de Química Porto Alegre RS

关键词: hydrophobicity;    organo-mineral interactions;    HF-treatment;    humic substances;    hidrofobicidade;    interação organo-mineral;    tratamento com HF;    substâncias húmicas;   

DOI  :  10.1590/S0100-06832003000100004

来源: SciELO

【 摘 要 】

Soil organic matter from the surface horizon of two Brazilian soils (a Latosol and a Chernosol), in bulk samples (in situ SOM) and in HF-treated samples (SOM), was characterized by elemental analyses, diffuse reflectance (DRIFT) and transmission Fourier transform infrared spectroscopy (T-FTIR). Humic acids (HA), fulvic acids (FA) and humin (HU) isolated from the SOM were characterized additionally by ultraviolet-visible spectroscopy (UV-VIS). After sample oxidation and alkaline treatment, the DRIFT technique proved to be more informative for the detection of "in situ SOM" and of residual organic matter than T-FTIR. The higher hydrophobicity index (HI) and H/C ratio obtained in the Chernosol samples indicate a stronger aliphatic character of the organic matter in this soil than the Latosol. In the latter, a pronounced HI decrease was observed after the removal of humic substances (HS). The weaker aliphatic character, the higher O/C ratio, and the T-FTIR spectrum obtained for the HU fraction in the Latosol suggest the occurrence of surface coordination of carboxylate ions. The Chernosol HU fraction was also oxygenated to a relatively high extent, but presented a stronger hydrophobic character in comparison with the Latosol HU. These differences in the chemical and functional group composition suggest a higher organic matter protection in the Latosol. After the HF treatment, decreases in the FA proportion and the A350/A550 ratio were observed. A possible loss of FA and condensation of organic molecules due to the highly acid medium should not be neglected.

【 授权许可】

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