Origin of Carbon Compounds in Waters of Drainage Channels of the Tarmansky Marsh Massif (Western Siberia) According to Hydrochemical and Isotope Data

Abstract

The purpose is to study the origin of carbon compounds in the waters of drainage channels of the Tarmansky marsh massif based on the results of analysis of 13С/12С isotopic ratio of dissolved inorganic carbon and hydrochemical data. Materials and methods. The waters of drainage channels of Tarmansky marsh massif located in the Tyumen region and the Bolshoye Tarmanskoye Lake water and groundwater were collected in August 2022 in low-water period. Standard methods of analysis were used to study the chemical composition of water; the isotope mass spectrometry method was used to study the isotopic composition of dissolved inorganic carbon. Results and discussion. According to the results of chemical composition analysis it was found out that drainage channels waters are mainly fed by underground feeding, which is confirmed by increased mineralisation, high chloride ion content, similar pH and temperature values in drainage canal waters and groundwater, unlike the waters of the Bolshoye Tarmanskoe Lake. In drainage channels waters, inorganic carbon form prevails over organic carbon, while in lake waters organic carbon prevails in terms of content. It is established that in lake waters autochthonous organic matter prevails, in groundwater and drainage channels waters this indicator is approximately equal and considerably lower (0.9-1.4 %) than in lake waters (4.8 %). The source of inorganic carbon in the waters of the Bolshoye Tarmanskoe Lake is mineralisation of organic matter (δ13C- DIC= -11.78 ‰), while dissolution of carbonate minerals plays a significant role in the formation of the carbonate system of groundwater (-2.56 ‰) and drainage channels waters (-2.52 ‰, -7.74 ‰), which is confirmed by isotope analysis data. Conclusion. Pressure groundwater plays a significant role in drainage channels feeding during low-water period, which is confirmed by physico-chemical characteristics of water (temperature, chemical composition) and isotopic characteristics of dissolved inorganic carbon. According to a rough estimate, the content of inorganic carbon entering with groundwater exceeds 60 % in one of the sampled drainage canals, and in the other it is 6-7 %. Organic carbon in drainage canal water is mainly of allochthonous origin.