GEOCHEMICAL CHARACTERISTICS OF ORGANIC MATTER IN BOTTOM SEDIMENTS IN IVASHKINA LAGOON, (BYKOVSKY PENINSULA, LAPTEV SEA)

Studying Arctic biogeochemical ecosystem with various methods and approaches is of vital importance to further predict future global climate changes. Organic matter of modern bottom sediments, which accumulates heterogeneous signals of various processes of carbon transport and transformation, acts as the unique indicator of initial depositional environment of sediment and its diagenetic history. Using high-precision geochemical instruments allows us to obtain important information on potential input of both allochthonous and autochthonous components to organic matter, and thus to further promote understanding of the modern Arctic carbon cycle. The aim of the research is to study the lithological and organo-geochemical features of the sediments accumulated in the specific lagoon conditions of the coastal part of the Laptev Sea (Ivashkina Lagoon, Bykovsky Peninsula). Materials and methods. Precipitation in the area of ​​the Lena river delta was selected as an object of the study. To assess the variability of molecular composition of organic matter in accumulation of sediments, the 18-meter interval of the VD-13 well, drilled in the central part of the Ivashkina lagoon during the 2013 spring Arctic expedition, was investigated. For the samples, their granulometric characteristics were determined, and pyrolytic and chromatography-mass spectrometric studies were conducted as well. It is shown that the increased content of organic carbon in the section is confined to the pelitic fraction of sediments. The distribution of n-alkanes is characterized by the dominance of high molecular weight odd homologues, which indicates the ubiquitous contribution of higher terrestrial vegetation to formation of organic matter accumulated in sediments. However, the contribution of the potentially migratory organic component is not excluded, since the presence of a low molecular weight fraction of n-alkanes is noted for a number of samples. The results of the pyrolytic analysis of the samples indicate a sharp variability in the content of Corg and volatile organic compounds with depth.