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Bottom sediment radioactivity of the six Caucasus lakes located in different altitude zones

Authors:
Natalia Kuzmenkova at Lomonosov Moscow State University
Natalia Kuzmenkova
Valentin Nikolaevich Golosov at Lomonosov Moscow State University
Valentin Nikolaevich Golosov
Maxim Ivanov at Russian State Hydrometeorological University
Maxim Ivanov
Mikhail Alexandrin
Mikhail Alexandrin
Mikhail Alexandrin
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Abstract and Figures

Natural and artificial radioactivity of bottom sediment in the six lakes of the Western and Central Caucasus have been evaluated. It allowed to define the variation of sedimentation rate during the last 100–150 years using technogenic (¹³⁷Cs) and natural (²¹⁰Pb, ²²⁶Ra) radionuclides as a chronomarkers. The studied lakes are located in the contrasting geographic conditions, different orographic positions, and have different origin. The average annual precipitation in the area of each of the lakes has been detected to stay relatively constant during the ¹³⁷Cs fallout period, while the air temperature has markedly increased during the last decades. The detected sedimentation rates are the indirect indicator of climate change in the mountains. They are slightly decreasing owing to the increased protection of soil by vegetation cover in the lower altitude zone; in the upper zones, they are growing due to accelerated glacier retreat. The radioecological situation is estimated as normal. High levels of ¹³⁷Cs (33 kBq m⁻²) and ²⁴¹Am (0.1 kBq m⁻²) in bottom sediments are attributed to the region-specific geographical characteristics.
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https://doi.org/10.1007/s11356-023-25838-4
RESEARCH ARTICLE
Bottom sediment radioactivity ofthesix Caucasus lakes located
indifferent altitude zones
NataliaKuzmenkova1,2 · ValentinGolosov1,3,4· MaximIvanov1,3· MikhailAlexandrin1· IrinaKorneva1·
EvgenyGrabenko1· AlexandraRozhkova2· OlgaBykhalova5
Received: 31 July 2022 / Accepted: 6 February 2023
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023
Abstract
Natural and artificial radioactivity of bottom sediment in the six lakes of the Western and Central Caucasus have been
evaluated. It allowed to define the variation of sedimentation rate during the last 100–150years using technogenic (137Cs)
and natural (210Pb, 226Ra) radionuclides as a chronomarkers. The studied lakes are located in the contrasting geographic
conditions, different orographic positions, and have different origin. The average annual precipitation in the area of each of
the lakes has been detected to stay relatively constant during the 137Cs fallout period, while the air temperature has markedly
increased during the last decades. The detected sedimentation rates are the indirect indicator of climate change in the
mountains. They are slightly decreasing owing to the increased protection of soil by vegetation cover in the lower altitude
zone; in the upper zones, they are growing due to accelerated glacier retreat. The radioecological situation is estimated as
normal. High levels of 137Cs (33kBq m−2) and 241Am (0.1kBq m−2) in bottom sediments are attributed to the region-specific
geographical characteristics.
Keywords Caucasus lakes· Radionuclides· Geochronology· Sedimentation rates
Introduction
The Caucasus mountain massif is a natural barrier to moisture-
laden air masses, which results in intensive deposition of
fallout radionuclides (Efimov and Anisimov 2011; Ivanov
etal. 2022; Kordzadze etal. 2013; Tashilova etal. 2019). As
soon as fallout radionuclides (210Pbex, 137Cs, 241Am) fall onto
the earth surface, they are sorbed by the soils and sediments.
The latter are the most important environmental archive,
recording the information of the environmental changes
within the sedimentation period. Due to the fact that receiving
the results of the direct observations prior to the instrumental
period is impossible, bottom sediments often turn to be the
only source of such data.
Using excessive 210Pb with the adjustment to 137Cs and
241Am for sediment dating is a widely used method for the
evaluation of the sedimentation rate in the natural and artificial
water reservoirs within the last 100–150years (Appleby
and Oldfield 1978; Corbett etal. 2007; Doering etal. 2006;
Putyrskaya etal. 2020; Rose etal. 2011; Semertzidou etal.
2019; Su and Huh 2002; Yamada and Aono 2003).
Nowadays, there are three commonly used models of
assessing the rate of sediment accumulation with the
Responsible Editor: Georg Steinhauser
Highlights
• The climate changes in the last 60 years (temperature
increasing) affected mainly the high-altitude lakes because
sedimentation rates depend on the intensity of melting glaciers.
• The high radionuclide accumulation in the lakes Bolshoe
Khmelevskoe and Khuko is a feature of natural conditions
(origin, location, water regime) and indicated the radioactive
spot in the Caucasus region.
• The detected sedimentation rate is the indirect indicator of the
climate change in the mountains over the last 150 years.
* Natalia Kuzmenkova
kuzmenkovanv@my.msu.ru
1 Institute ofGeography RAS, Moscow, Russia
2 Faculty ofChemistry, Lomonosov Moscow State University,
Moscow, Russia
3 Faculty ofGeography, Lomonosov Moscow State University,
Moscow, Russia
4 Department ofLandscape Ecology, Institute ofEcology
andEnvironment, Kazan Federal University, Kazan, Russia
5 FGBU Utrish State Reserve, Anapa, Russia
/ Published online: 17 February 2023
Environmental Science and Pollution Research (2023) 30:50690–50702
1 3
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... 210 Pb and its parent isotopes 222 Rn and 226 Ra are radionuclides in the 238 U decay series. A fraction of the 222 Rn atoms produced by the decay of 226 Ra in soils escape into the atmosphere where they decay to 210 Pb atoms, which finally fall into lake bottom and are known as excess 210 Pb (Appleby 2001;Kuzmenkova et al. 2023). In surface sediments, 210 Pb activities were much higher than those of 226 Ra, suggesting that a large fraction of 210 Pb atoms should be derived from atmospheric deposition (Fig. 2). ...
... This process probably explains extremely high radioactivities of radionuclides in organic-rich lakes at high elevations (codes 1, 2, 3, 4, 5, and 6; Fig. 4). Furthermore, plentiful rainfall at high elevations could increase the fluxes of radionuclides from the atmosphere into lakes (Appleby 2001), since there is a strong relationship between global radioactive levels and precipitation (Kuzmenkova et al. 2023). ...
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