Influence of the humification process on the properties of peat humic acids

Comparative and complex characterisation of peat humic acids (HAs) isolated from peat profiles of different origin in Latvia was conducted. Elemental and functional analysis of the isolated HAs was made and their acidity and molecular weight were estimated. Spectral characterisation included UV-Vis, IR, electron spin resonance and fluorescence spectra. Structural characterisation of HAs was by both ¹H and¹³C nuclear magnetic resonance spectra. Properties of HAs isolated from the Latvian peat were compared with HA from other sources (soil, water, coal and synthetic humic substances). Major properties of peat HAs depended on their origin, indicating the importance of humification processes. HAs isolated from peat of more recent origin were more similar to soil Has, while there was a greater degree of humification in part from older sources.