Compositions of n-Alkanes and n-Methyl Ketones in Soils of the Forest-Park Zone of Moscow

Abstract

The seasonal changes in the contents and compositions of n-alkanes and n-methyl ketones have been studied in typical soddy-podzolic soils (Albic Retisols (Ochric)) under lime forests in the Losiny Ostrov National Park, Moscow. In the humus horizons, the reserves (about 370 mg/m²) of odd n-alkanes with the chain length of C₂₅–C₃₅—the biomarkers of terrestrial vegetation—are 4–5 times below their amount entering with the leaf falloff in autumn. A noticeable contribution of microbial biomass hydrocarbons to the lipid fraction in the AY and AYel horizons manifests itself in the increased fraction of odd and medium-chain (25) homologues (OEP = 4–6, LSR = 5–7) in the spectrum of n-alkanes. The lowest content of methyl ketones and odd n-alkanes was observed immediately after the winter period (OEP = 22, A/K = 21–170). In the EL and BT horizons, the n-alkane fraction of organic matter and the relative content of high molecularweight n-alkanes more resistant to microbial destruction (C₃₃, C₃₅) increases by 3–4 times in comparison with that in the abovelying horizons, and the type of distribution of n-alkanes by the carbon chain length changes: the dominance of odd homologues is absent; in the EL horizon, OEP = 1.