Source indicators of humic substances: an elemental composition, solid state 13C CP/MAS NMR and Py-GC/MS Study

Abstract

Humic substances (HS) isolated from swamp water, surface soil, peat and brown coal were characterized using elemental composition, solid state 13C CP/MAS NMR and Py-GC/MS analysis. A substantial amount of information with regard to the source, maturity, depositional environment and degree of degradation of humic substances was obtained. The elemental composition, atomic ratio, 13C NMR spectra and Py-GC/MS results indicated that vascular plant matter is the main contributor to humic substances. Humic substances from swamp water and from soil in the surrounding area of the swamp were found to be identical, suggesting that the swamp humic substances are derived from surrounding soils. Humic substances from brown coal were characterized by a higher degree of humification, including loss of polysaccharides, degradation in lignin content and increase in aromaticity. Compared with humic substances from brown coal, the humic substances from peat showed a lower degree of humification and were considerably more aliphatic in nature.