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Review

Non-Equilibrium Uranium as an Indicator of Global Climate Variations—The World Ocean and Large Lakes

1
Research Park, St. Petersburg State University, 199155 St. Petersburg, Russia
2
N. Laverov Federal Center for Integrated Arctic Research of UB RAS, 163000 Arkhangelsk, Russia
*
Author to whom correspondence should be addressed.
Academic Editor: Elias Dimitriou
Water 2021, 13(24), 3514; https://doi.org/10.3390/w13243514
Received: 5 November 2021 / Revised: 5 December 2021 / Accepted: 6 December 2021 / Published: 9 December 2021
(This article belongs to the Section Water and Climate Change)
In natural water, as a rule, there is a violation of radioactive equilibrium in the chain 238U … → 234U → 230Th →. Groundwater usually has a 234U/238U ratio in the range of 0.8–3.0 (by activity). However, in some regions, the 234U/238U ratio reaches >10 and up to 50. Ultrahigh excesses of 234U can be explained by climatic variations. During a cold period, minerals accumulate 234U as a normal component of the radioactive chain, and after the melting of permafrost, it is lost from the mineral lattice faster than 238U due to its higher geochemical mobility. This hypothesis was tested using data on the isotopic composition of uranium in the chemo- and bio-genic formations of the World Ocean and large lakes, which are reservoirs that accumulate continental runoff. The World Ocean has the most significant 234U enrichments in the polar and inland seas during periods of climatic warming in the Late Pleistocene and Holocene. In the bottom sediments of Lake Baikal, the 234U/238U ratio also increases during warm periods and significantly exceeds the 234U excess of the World Ocean. Furthermore, the 234U/238U ratio in the water of Lake Baikal and its tributaries increases from north to south following a decrease in the area of the continuous permafrost and has a seasonal variation with a maximum 234U/238U ratio in summer. The behavior of 234U in large water reservoirs is consistent with the hypothesis about the decisive influence of permafrost degradation on the anomalies in 234U/238U ratios in groundwater. View Full-Text
Keywords: non-equilibrium uranium; 234U/238U ratio; climate variations; permafrost; World Ocean; Lake Baikal non-equilibrium uranium; 234U/238U ratio; climate variations; permafrost; World Ocean; Lake Baikal
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MDPI and ACS Style

Tokarev, I.; Yakovlev, E. Non-Equilibrium Uranium as an Indicator of Global Climate Variations—The World Ocean and Large Lakes. Water 2021, 13, 3514. https://doi.org/10.3390/w13243514

AMA Style

Tokarev I, Yakovlev E. Non-Equilibrium Uranium as an Indicator of Global Climate Variations—The World Ocean and Large Lakes. Water. 2021; 13(24):3514. https://doi.org/10.3390/w13243514

Chicago/Turabian Style

Tokarev, Igor, and Evgeny Yakovlev. 2021. "Non-Equilibrium Uranium as an Indicator of Global Climate Variations—The World Ocean and Large Lakes" Water 13, no. 24: 3514. https://doi.org/10.3390/w13243514

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