Stable carbon isotope signature and chemical composition of organic matter in lignite-containing mine soils and sediments are closely linked

The organic matter was most enriched in 13C in the bulk soil of the forest plot and partially submerged plot. The stable isotopic signature (δ13C) was related to the chemical composition of the sample as seen with 13C CPMAS NMR spectroscopy. The ratio (alkyl + aromatic)/(O-alky + carbonyl C) was strongly correlated with the δ13C value regardless of the site conditions (aerobic soil or submerged sediment). Such a correlation was also observed between δ13C and lignin content (V + S + C, where V = vanillyl, S = syringyl, C = cinnamyl oxidation products), as well as parameters indicating lignin diagenetic state [(Ac/Al)V, S/V and C/V, where Ac = acids, Al = aldehydes]. Taking δ13C as an indicator for lignite contribution, we explain the relationships by an increasing influence of lignite contribution not only on bulk chemical composition but also on lignin parameters when the organic matter shows 13C enrichment.