Changes in the composition of humic substances depending on the depth of peat occurrence

The fractional group composition of humic substances and the chemical structure of humic acids isolated from peats of different genesis from different depths of occurrence in peat deposits with the use of two extractants (0.1 N NaOH and 0.1 M Na4P2O7 at pH 7) were studied. Peat from the upper aerated layer of the peat deposits contained more humic substances than peat from the deep layer, which occurred under anaerobic conditions, due to the pyrophosphate fraction of humic acids and fulvic acids. The humic acids of peat isolated from the deep layers of deposits had smaller molecular weights, and they were characterized by lower concentrations of carbohydrate and saturated hydrocarbon fragments and an increased contribution of aromatic polyconjugation systems, as compared with the humic acids of a surface layer.