| Summary: | The relevance of the research is related to the intensive economic development of the Arctic part of the European North of Russia, which entails a sharp increase in anthropogenic pressure on vulnerable ecosystems of the Far North. At climate warming, melting of permafrost can provoke the formation of new thermokarst lakes and subsidence, which in its turn facilitates the removal of organic matter from peat into natural environments. The main aim is to reveal the features of composition of dissolved organic matter and its possible sources in the waters of thermokarst lakes of the Bolshezemelskaya tundra (near Naryan-Mar), with different water-mirror areas and at different stages of evolution. Methods. Analysis of the dissolved organic matter content in the waters of thermokarst lakes was carried out in the laboratory of georesources and the environment of Toulouse by the method of complete burning of dissolved organic carbon. In the laboratory of physicochemical methods of analysis of the Institute of Petroleum Chemistry of the SB RAS (Tomsk), by a three-step extraction at various pH the chloroformed concentrates were obtained. They contain dissolved organic matter. Organic structures were studied by Infrared spectroscopy. The structural-group composition of dissolved organic matter was determined by gas chromatography-mass spectrometry method. Results. Organic compounds in the waters of thermokarst lakes of Bolshezemelskaya tundra are mainly represented by hydrocarbons of aliphatic structure, carboxylic acid esters and aromatic compounds belonging to three homologous series. It was found, that low-molecular n-alkanes predominate in the small acid lake BZ-12, the main sources are bacteria, lower plants (unicellular algae) and phytoplankton. In the more mature and less acidic lake BZ-13, the main contribution belongs to higher terrestrial plants and coast marine algae. Phytoplankton also plays an important role in enriching water with dissolved organic matter. Accordingly, with evolution of the lake ecosy stem ...
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