Isotope-Geochemical Studies of Groundwater in the Zapolyarny Region of the Nenets Autonomous Okrug

The aquifer of sandy deposits in the talik zone of the Pechora River valley was studied. The use of information on the distribution of tritium isotopes made it possible to clarify the recharge conditions of groundwater and their genetic structure in different parts of the aquifer. The tritium age of groundwater in coastal wells was 20–25 years, on the basis of which it was concluded that the groundwater that entered the aquifer before 1995–2000 was almost completely replaced. In wells, remote from the river bank, the age of the water is in the range from 20 to 50 years. However, unlike onshore wells, these groundwaters contain “bomb” water and old water that entered the aquifer be- fore 1952. The age of the old water reaches 12.9±2.5 thousand years. It has been established that the ratio between stable 13C and radioactive 14C isotopes of carbon changes with age, indicating an increase in the carbon exchange between dissolved inorganic carbon and soil carbon dioxide caused by permafrost thawing.