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The thermokarst lakes of Western Siberia are important pools of organic and potentially labile organic carbon. These water bodies are also a source of greenhouse gases from the permafrost-prone area. An indirect indicator of organic matter mineralization is the isotope composition of carbon, which reflects the degree of organic matter degradation. We have studied the isotopic composition of carbon (δ13C-DOC и δ13С) in pore water and bottom sediments of three thermokarst lakes of different surface areas. For the analysis of δ13C-DOC, a wet oxidation method was used with sodium persulfate as the oxidizing agent to convert water-soluble organic carbon to CO2 (Zhou et al. Rapid Commun Mass Spectrom 29:1827–1835, 2015). Analysis was performed using a Gas Bench II system connected to a Delta V Advantage isotope mass spectrometer (Gas Bench II + IRMS method). The percentage of carbon in bottom sediments and its isotopic composition were determined by mass spectrometry of isotope ratios of light elements using a DELTA V Advantage isotope mass spectrometer combined with a Flash 2000 elemental analyzer (Thermo Fisher Scientific) equipped with a redox reactor. The distribution of δ13C-DOC in pore water is similar to δ13С in bottom sediments. The isotopic composition of carbon showed a clear dependence on the different lake surface areas. The heaviest composition of carbon isotopes in pore waters (δ13C-DOC) was found in a small lake with an area of 400 m2 (−25.7 ± 0.5‰). Lighter isotope ratios are observed in the middle and large ones (−26.8 ± 0.3 and −26.8 ± 0.5‰, respectively). An important confirmation of the dependence of biogeochemical processes on the different lake surface areas was the distribution of carbon isotopes (δ13С) in the bottom sediments. The heaviest carbon isotopic composition (δ13C) was found in the small lake (−25.6 ± 0.8‰), while the lightest composition was observed in the middle and large lakes (−27.6 ± 0.3‰ and −28.4 ± 0.5‰, respectively). The results of the carbon isotopic composition in thermokarst lakes of the discontinuous permafrost zone of Western Siberia showed different methanogenic activity and mineralization of organic matter in lakes of different surface areas.

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δ13C-DOC and δ13C in Pore Water and Bottom Sediments of Thermokarst Lakes in Discontinuous Permafrost of Western Siberia

  • 会议论文

  • 发表日期：

    2025年

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  • Rinat Manasypov,
  • Tatiana Raudina,
  • Danil Kurashev,
  • Ivan Krickov

摘要

The thermokarst lakes of Western Siberia are important pools of organic and potentially labile organic carbon. These water bodies are also a source of greenhouse gases from the permafrost-prone area. An indirect indicator of organic matter mineralization is the isotope composition of carbon, which reflects the degree of organic matter degradation. We have studied the isotopic composition of carbon (δ13C-DOC и δ13С) in pore water and bottom sediments of three thermokarst lakes of different surface areas. For the analysis of δ13C-DOC, a wet oxidation method was used with sodium persulfate as the oxidizing agent to convert water-soluble organic carbon to CO2 (Zhou et al. Rapid Commun Mass Spectrom 29:1827–1835, 2015). Analysis was performed using a Gas Bench II system connected to a Delta V Advantage isotope mass spectrometer (Gas Bench II + IRMS method). The percentage of carbon in bottom sediments and its isotopic composition were determined by mass spectrometry of isotope ratios of light elements using a DELTA V Advantage isotope mass spectrometer combined with a Flash 2000 elemental analyzer (Thermo Fisher Scientific) equipped with a redox reactor. The distribution of δ13C-DOC in pore water is similar to δ13С in bottom sediments. The isotopic composition of carbon showed a clear dependence on the different lake surface areas. The heaviest composition of carbon isotopes in pore waters (δ13C-DOC) was found in a small lake with an area of 400 m2 (−25.7 ± 0.5‰). Lighter isotope ratios are observed in the middle and large ones (−26.8 ± 0.3 and −26.8 ± 0.5‰, respectively). An important confirmation of the dependence of biogeochemical processes on the different lake surface areas was the distribution of carbon isotopes (δ13С) in the bottom sediments. The heaviest carbon isotopic composition (δ13C) was found in the small lake (−25.6 ± 0.8‰), while the lightest composition was observed in the middle and large lakes (−27.6 ± 0.3‰ and −28.4 ± 0.5‰, respectively). The results of the carbon isotopic composition in thermokarst lakes of the discontinuous permafrost zone of Western Siberia showed different methanogenic activity and mineralization of organic matter in lakes of different surface areas.