CHEMICAL-COMPOSITION OF HUMIC ACIDS - A COMPARISON WITH PRECURSOR LIGHT FRACTION LITTER FROM DIFFERENT VEGETATIONS USING SPECTROSCOPIC TECHNIQUES

Humic acids from a range of Italian soils and the residual suspended o rganic material (light fraction litter) associated with them have been studied by pyrolysis gas chromatography mass spectrometry, solid stat e nuclear magnetic resonance spectroscopy, and infra-red spectroscopy. Although the major vegetation types on the soils differ considerably, spectra of humic acids from soils with different major vegetation typ es were similar. Because no relationship between humic acid structure and major vegetation type was observed, gross assumptions about humic acid structure should not be drawn from a knowledge of macro-vegetatio n types on soils. Light fraction litter in the soils from minor vegeta tion may be more significant in affecting the eventual structure of th e humic acids.