Ultraviolet-visible and Infrared Spectroscopic Studies of Soil Humic Acids

Structural characterization of humic acids extracted from surface, below 15 cm depth and 30 cm depth tea garden soils have been studied here. Instrumental analysis of the organic substances were carried out using UV-Visible and IR spectroscopies. The results reveal low level of humification of the humic acids occurring in the soil samples and low condensation of these molecules. The predominant aliphatic characters of the humic acid molecules are evident from this study. The occurrence of hydrogen bonded oxygen containing groups, e.g., hydroxyl, carboxyl, etc., have been observed. The presence of nitrogen containing organic compounds as well as unleachable (in acid and alkali treatments) metal-bonded oxygen and nitrogen species are also indicated. The results obtained in this study would be quite helpful for structural understanding of soil organic matters.