Genesis of Organic Matter in Bottom Sediments

Data on the contents of inorganic (IC) and organic carbon (OC), the genesis of organic matter (OM) and its digenetic transformation in bottom sediments of the Il ' d River and bordering areas of the river-reservoir contact zone were obtained. The concentrations of IC and OC along the longitudinal profile of the studied water area varied over a wide range. The maximum concentration of IC was confined to the zone of free flow of the river (0.8-1.0% DW), and for OM it was confined to the zone of the receiver (similar to 10% DW). Based on an analysis of n-alkanes in bottom sediments, three types of OM have been identified: autochthonous, mixed, and predominantly terrigenous, which successively change in the longitudinal profile of the Il ' d River and areas of bordering systems. All types of OM are closely related to the specifics of sedimentation and hydrodynamics of the waters of a given water area. The contributions of different groups of aquatic and near-aquatic photoautotrophs to the formation of the autochthonous component of OM in bottom sediments are discussed. The geochemical indices (Pr/Ph, OEP17-19, CPI) reflect the influence of oxidative conditions on the formation of OM and the active microbiological transformation of its autochthonous part.