Content of Hydrocarbons in the Sea Bottom Sediments of the Kara Sea North-Eastern Part

The study of the sea bottom sediments (0–5 cm) of the northeastern part of the Kara Sea was carried out during of the voyage of the SRV “Academician Boris Petrov”. Data on the content and composition of hydrocarbons in the sea bottom sediments of the studied water area were obtained. The purpose of this work was the qualitative and quantitative content assessment of hydrocarbons in the sea bottom sediments of the northeastern part of the Kara Sea, as well as the identification of their probable origin. The material for the study were samples of sea bottom sediments upper layer collected by means of a coring tube in the various water areas of the northeastern part of the Kara Sea in the summer of 2022. The determination of qualitative and quantitative hydrocarbon`s composition was carried out by means of gas chromatography (“Crystal 5000.2” chromatograph with flame ionization detector). Diagnostic indices of the origin of hydrocarbons were used to identify the likely sources of organic matter. It was found that the total amount of hydrocarbons in sea bottom sediments of the northeastern part of the Kara Sea varied from 25.8 to 152.4 mg/kg, on average—68.21 ± 7.76 mg/kg. According to the results of chromatograms analysis, the predominance of high-molecular n-alkanes was noted. The most abundant n-alkanes were homologues of n-C25–C29, which are markers of allochthonous organic matter. When considered the diagnostic indices (CPI1, CPI2, ACL, LWH/HWH, TAR, C31/C29, Paq, TMD, ΣC25–3535/ΣC15–21, Pr/Ph), it was found that the increased concentrations of hydrocarbons were mainly due to the natural processes and the predominance of allochthonous organic substances in bottom sediments.