Composition and distribution of organic matter in bottom sediments downstream of the Tumnin river

The distribution of total organic carbon (TOC), hydrocarbons and biotic components (phytopigments, heterotrophic bacteria) was studied in bottom sediments of the Tumnin River downstream. Concentration variability of TOC in bottom sediments is 65, and hydrocarbons - 136 times. The main size fraction of the studied sediments was pelites (up to 988%). According to the content of sedimentary pigments, most of the studied sediments are eutrophic type. According to the currently accepted gradations of hydrocarbon content, the authors estimated the studied silt sediments in the range of "slightly polluted" - "highly polluted". In the absence of a pronounced anthropogenic pressure, hydrocarbons in the sediments have a biogenic genesis, but they can form high levels of background concentrations (up to 680 mg/kg).