Home – Home – Jornals – Earth’s Cryosphere 2023 number 2

Based on observations on 12 largest rivers of East Siberia (Lena, Vilyuy, Kolyma, Aldan, Olenek, Vitim, Indigirka, Amga, Olekma, Anabar, Yana, and Chara) during summer low-water runoff in 2007-2011, the main features of the chemical composition and physical properties of river water have been determined. It is found that favorable oxygen regime, higher chemical oxygen demand and color of water, higher concentration of total iron and ammonium ions, and moderate salinity are characteristic of the investigated rivers. The territory of East Siberia is characterized by an ubiquitous distribution of permafrost. The thickness of seasonally thawed layer within river catchments is extremely variable in the studied region. Using canonical-correlation analysis, it was found that concentrations of specific components of ionic constituents (water hardness, calcium, magnesium, bicarbonates, sulfate ions, and salinity) depend on the active layer thickness (ALT). Herewith, the deeper the active layer in a catchment, the higher the concentration of mentioned components of ionic constituents. This pattern is explained by the fact that permafrost serves as a confining barrier that prevents infiltration of surface water through deep mineral horizons thus restricting water saturation with mineral ions. The increase in ALT noted in recent decades in the permafrost zone of the northern hemisphere may continue in the current century. Therefore, knowledge of how the concentration of soluble biogeochemical constituents in the rivers depends on ALT of permafrost in the catchments is valuable for assessment of potential changes in the chemical composition of river water in the permafrost zone in the future.