Resumo

MARTINEZ, Claudia X.; BRAVO, Isabel  e  MARTIN, Francisco J.. Molecular composition of humic acids evaluated by pyrolysis - gas chromatography - mass spectrometry and thermally assisted hydrolysis and methylation in high Colombian Andean soils. Rev.Colomb.Quim. [online]. 2013, vol.42, n.1, pp.31-46. ISSN 0120-2804.

It was determined the molecular composition of humic acids (HA) extracted from 'A' horizon in Colombian high Andean soils dedicated to three uses: primary forest, croplands and pastures. The AH were obtained by sequential extraction of humified organic matter (HOM) with tetraborate, pyrophosphate and sodium hydroxide (0.1N) solutions; HA were purified through various analytical processes. Its chemical composition was determined by Py-GC/MS and THMA. Different pyrolysis products were classified in response to the chemical family to which they belong, prevailed fatty acids (FA) as the most abundant in all AH, while phenols, sterols, terpenes and S-compounds were found in lower abundance. There were differences in the percentages of relative abundance of the identified groups, showing that the land use change influences the physical, chemical, and biological propertiers of soils that are perceived at different levels of transformation, affecting the HA composition and its reactivity in the soil.

Palavras-chave : humic acids; High Andes soils; pyrolysis - gas chromatography - mass spectrometry; thermally assisted hydrolysis; methylation.

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