Composition of organic compounds in bottom sediments of lakes in the taiga and steppe zones in Siberia

Resumo

The paper presents chromatographic–mass spectrometric data on the individual composition of organic compounds in sapropel-like deposits of lakes in the steppe, forest–steppe, and three taiga natural climatic zones (NCZ) in Khakassia and western Siberia. Data on the individual composition of n-alkanes, carboxylic acids and their esters, thiophenes, phytol, phytone, steroids, and di- and triterpenoids and on their distribution in the sediments show systematic variations in the composition of the organic matter (OM) with increasing ambient temperature and the aridity of the climate. The concentrations of all groups of the compounds in lacustrine sediments decrease southward, and simultaneously esters with long (up to С₂₀) alkyl substituents appear. The concentrations of oxygen-bearing compounds increase among the acyclic structures and triterpenoids, as also do the concentrations of structures ketonic substituents among the steroids. The dominance of the carboxylic acids and their esters by high molecular weight homologues gives way to the dominance of palmic acid and its derivatives. Among n-alkanes, the dominance of С₂₇ and С₂₉ hydrocarbons typical of terrestrial plants gives way to a higher percentage of homologues С₂₁–С₂₅ (macrophytes) and С₃₁ (herbaceous plants). Among the tocopheroles, the concentration of the oxidized form of α-tocopherol (acetate) increases.