Journal of the Brazilian Chemical Society
versión impresa ISSN 0103-5053
DICK, Deborah Pinheiro; BURBA, Peter y HERZOG, Helmut. Influence of Extractant and Soil Type on Molecular Characteristics of Humic Substances From Two Brazilian Soils. J. Braz. Chem. Soc. [online]. 1999, vol.10, n.2, pp. 140-145. ISSN 0103-5053. http://dx.doi.org/10.1590/S0103-50531999000200012.
In a previous study it was observed that humic substances (HS) extracted with NaOH solution and with Na4P2O7 solution presented different molecular weights, and also that the extracted HS yield by each method varied between an Oxisol and a Mollisol from South Brazil. In the present study, we further investigated the organic matter in these soils by characterizing HS extracted with 0.5 mol L-1 NaOH and with neutral 0.15 mol L-1 Na4P2O7 solutions from the above mentioned samples, using elemental analysis and nuclear magnetic ressonance spectroscopy (liquid state 1H- and 13C-NMR), and by relating the molecular differences to the extraction method and soil type. HS extracted with pyrophosphate were more humified, showing a higher aromaticity and higher carboxylic content. The NaOH-extracted HS were more aliphatic and contained a higher O-alkyl proportion, which is indicative of a less humified nature than the pyrophosphate-extracted HS.
Palabras clave : humic substances; oxisol; mollisol; aromaticity; ligand exchange.