Earth’s Cryosphere, 2022, Vol. XXVI, No. 2, p. 34-41.

FLUORIDE DISTRIBUTION IN SUBPERMAFROST GROUNDWATER IN CENTRAL YAKUTIA

N.A. Pavlova, S.V. Fedorova

Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Sciences, Merzlotnaya str. 36, Yakutsk, 677010 Russia; na-pavlova@yandex.ru

We studied the distribution of fluoride (F^–) in fresh and moderately mineralized waters of subpermafrost aquifers in Central Yakutia. We analyzed the data archive of 296 water samples collected by the Melnikov Permafrost Institute staff members during hydrochemical surveys between 1984 and 2019. The average fluoride concentrations varied between 5 and 10 mg/L. Highest concentrations (up to 15.5 mg/L) were determined in waters of the terrigenous aquifers over the crystalline basement. The sources of fluoride can likely be the various fluorine-bearing minerals of aluminosilicate rocks. The high fluoride concentrations in these aquifers are associated with geochemistry (alkaline medium and sodium bicarbonate water type) resulting from cryogenic metamorphism of rocks. Lowest concentrations (0.4–0.8 to 2–3 mg/L) were found in subpermafrost water samples collected from boreholes near the Lena River channel. These low concentrations indirectly indicate the presence of open taliks under the channel and the infiltration of stream water into the subpermafrost aquifers.

Artesian basin of Yakutia, subpermafrost water, permafrost, low groundwater circulation zone, chemical composition, fluoride