Gel chromatography separation and U.V. spectroscopic characterization of humic-like substances in urban composts

Over a period of 12 months, several experimental protocols were used to follow the evolution of humic-like substances in urban composts. The methodology includes classical humic and fulvic acid extraction and their characterization by their carbon content, and also separation to gel Sephadex G75 and G25 coupled with U.V. spectroscopy. Gel chromatography shows that humic-like substances are characterized by the presence of two main families of compounds and by an increase in organic matter complexity with maturation level. Mineralization processes may also be revealed after a long composting period. Moreover, an index of maturity, based on U.V. spectroscopic measurments, is proposed. This parameter has been validated by a 2-year study of compost evolution.