Home – Home – Jornals – Geography and Natural Resources 2021 number 4

The composition, distribution, and genesis of organic components in bottom sediments of the Tumnin river were studied for a comprehensive assessment of their current environmental status. A study of particle size distribution revealed the dominance of the pelitic fraction in the sediments of most of the sites (up to 98.8 %). It was found that the spatial variability in the accumulation organic substances in bottom sediments led to a significant scatter in the minimum and maximum concentrations of organic carbon, by a factor of 65, and in the mass fraction of hydrocarbons, by a factor of 136. According to hydrocarbon content (from 9 to 680 mg/kg), the sediments are estimated in the range of “slightly polluted” - “very dirty”. According to the content of sedimentary pigments (from 16.1 to 39.8 mg/kg), most of the sediments are of the eutrophic type. Correlations between the main sources of organic matter in the sediments under investigation were revealed: hydrocarbons and organic carbon (r = 0.674), the content of pigments and hydrocarbons (r = 0.869), and the content of phytopigments and heterotrophic bacteria (r = 0.888). It is concluded that the value of overload of the self-purification capacity of the bottom sediments from hydrocarbons is closely associated with the presence of phytopigments (r = 0.873) and the number of heterotrophic bacteria (r = 0.959), which is due to their production and destruction activity in relation to hydrocarbons. High concentrations of volatile organic compounds (butanol, methanol, acetaldehyde, acetone, etc.) indicate that bottom sediments contribute to secondary pollution of the river water. The study of the molecular composition of hydrocarbons revealed the dominance of biogenic compounds of terrigenous genesis (53.2-76.7 % of the sum), which is important in differentiating anthropogenic impacts for purposes of environmental monitoring.