ORIGIN AND ISOTOPIC COMPOSITION OF PRECIPITATION AT EXTREMELY LOW TEMPERATURES IN YAKUTSK (EASTERN SIBERIA)
A.A. Galanin, M.R. Pavlova, A.N. Vasil'eva, G.I. Shaposhnikov, N.V. Torgovkin
Melnikov Permafrost Institute, SB RAS, Merzlotnaya str. 36, Yakutsk, 677010, Russia
Keywords: stable isotopes of water, atmospheric precipitation, snow, crystalline hoar, ice fog, low temperatures, technogenic sources of precipitation, fractionation, Yakutsk, Eastern Siberia
Abstract
Isotopic (18O, D) and chemical composition of atmospheric precipitation (1-2-cm snow layer on the surface of the snow cover and crystalline hoar), that fell in December 2020-January 2021 at anticyclonic weather, extremely low temperatures from -47 to -52 °C and dense ice fogs, has been studied at 6 sites along a 25-kilometer profile from Yakutsk. Samples from the surface of the snow cover are characterized by the lightest compositions (d18O = -41.04 ± 5.11 ‰, dD = -326.43 ± 34.16 ‰, dexc = 1.91 ± 7.72 ‰) and are noticeably depleted with deuterium. From the outskirts to the center of Yakutsk, a significant weighting of the compositions has been established (by 10 ‰ in d18O, by 80 ‰ in dD), a decrease in dexc (from +10 to -6 ‰), and a 4-fold increase in mineralization due to impurities of calcium carbonate. The isotopic compositions (d18O = = -30.89 ± 5.62 ‰, dD = -285.88 ± 12.82 ‰, dexc = -28.79 ± 32.53 ‰) have been established for samples of crystalline rime, which are not typical for any atmospheric sediments, waters and ice of the region. They experience the greatest variations in d18O (from -24 ‰ in Yakutsk to -37 ‰ at a distance of 25 km from its center); the value of dD varies from -255.4 to -285.9‰, dexc increases from -80 to +11.5 ‰. The isotopic and chemical compositions of the investigated sediments indicate a significant proportion of technogenic water vapor entering the atmosphere during the combustion of hydrocarbon fuel. Based on the model of the Gaussian mixture and deuterium excess of the studied samples, it has been found that in crystalline hoar, the maximum share of technogenic moisture reaches 26-32 % near heat-generating stations, in the central part of the city - 13-18 %, and on the outskirts - 6.5-8.8 %; in the surface layer of the snow cover - 5-6 % in the central part of Yakutsk and decreases to the outskirts to 1 % or less.
|
