The article investigates the isotopic characteristics and origin of groundwater within the Quaternary and Neogene aquifers of the Azov-Kuban Artesian Basin (AKAB), Northwestern Caucasus. Isotopic analysis revealed the presence of a distinct "Late Pleistocene fossil groundwater" water component in the deeper sedimentary horizons. These groundwaters are significantly depleted in heavy isotopes, with δ18O values ranging from -17.54‰ to -12.50‰ (mean -14.76‰) and δ2H from -146.1‰ to -89.0‰ (mean -107.4‰). The total absence of tritium and radiocarbon dating results (26-34 ka) confirm that these resources are paleowaters. In contrast, modern groundwater in the recharge areas of the AKAB foothills (200-400 m a.s.l.) exhibits enriched isotopic signatures, with mean values of -10.81‰ for δ18O and -75.5‰ for δ2H. These signatures closely match the weighted mean isotopic composition of local precipitation during the recharge season (-10.7‰ for δ18O and -73.8‰ for δ2H). The presence of tritium and anthropogenic nitrate pollution in the upper geological section further validates the modern origin of these waters. A comparison between the recharge waters and the deep-seated "Late Pleistocene fossil groundwater" component indicates that the latter originated during the cold climatic stage of the Late Pleistocene. The spatial distribution of δ18O and δ2H shows that the proportion of paleowater increases with depth and distance from the foothill recharge zones. These findings provide essential evidence of paleoclimatic imprints on the regional hydrogeological system, highlighting the vulnerability of fossil groundwater reserves.

Six AMS 14C dates from an ice wedge tested in the Holocene wetland on the Pur-Taz interfluve in northwest Siberia are shown here. In the Pur-Taz peatland, peat accumulation started between 11 and 10 cal ka BP, and in the detail studied site, it started after 9.5 cal ka BP. Within the studied peatland, intense ice wedge growth took place between 5.3 and 3.4 cal ka BP. The growth of ice wedges near their southern limit occurred at least 3-4 ka after the formation of the host peat, according to the results of AMS 14C direct dating of ice wedges. Mean January air temperatures ranged from -30 to -27 degrees C during the ice wedge growth phase, which is 2-4 degrees C colder than the current temperature.

This article focuses on a pressing issue in mountainous arid regions: the elevated levels of 222Rn in the natural environment. This phenomenon is related to the endogenous activity of mountainous regions, which gives rise to seismic activity, fluid dynamics and the occurrence of ore mineralisation. Among these areas, the Tian Shan region, which is mainly occupied by the Kyrgyz Republic, deserves special mention. This article presents the results of the calculation of the dose loads and the assessment of the potential radiological impact on the health of the population of different age groups from 222Rn contained in the waters of the Ala-Archa river basin (Kyrgyz Republic). To this end, radioecological and physico-chemical parameters in surface and groundwater were investigated. The highest concentration of 222Rn was observed in groundwater, with values ranging from 1.1 ± 0.5 to 139.2 ± 27.8 Bq dm−3, with a mean value of 21.3 ± 4.3 Bq dm−3. The results of the radon flux density studies led to the conclusion that the increased 222Rn content in the groundwater is of tectonic origin. Dose calculations showed that the mean annual total effective dose was below the WHO recommended reference dose of 100 μSv y−1, except for groundwater for adults (107.86 μSv y−1) and infants (165.98 μSv y−1). The presence of surface water and groundwater with different 222Rn contents and the lack of radioecological studies indicate the potential for further research in the mountainous areas of the Tien Shan.

The current climate warming in the eastern coastal area of Chukotka contributes to deeper seasonal thawing and activation of thermal erosional landslides, leading to the exposure of massive ice bodies. The thawing of exposed massive ice courses the coastline destruction and settlement infrastructure damage. The study of massive ice bodies on the eastern coast of Chukotka, including radiocarbon AMS dating and determination of ice isotopic composition, showed that most of the studied ice bodies were formed in the Late Pleistocene, between 22 and 27.5 thousand calibrated years ago. Relatively high values of the ice isotopic composition and significant variations of the δ18O values of up to 6‰, indicate a predominantly ground origin of massive ice bodies, the formation of which occurred during the freezing of water-saturated sediments in a closed system. The source for the massive ice formation could be water-saturated sediments of sub-lake taliks or supra-permafrost groundwater. However, it is possible that locally massive ice bodies or their peripheral parts could be formed as a result of burial of snow patches or floating ice in the Holocene that may be indicated by a fairly uniform distribution of isotope values and the similarity of isotopic composition of some massive ice bodies and Holocene ice wedges.

Extreme disequilibrium in uranium isotope ratios (234U/238U > 10 by activity) in groundwater is rare, as most groundwaters generally exhibit a moderate excess of 234U (234U/238U = 1–3). One hypothesis attributes 234U/238U > 10 to past permafrost conditions. To test this hypothesis, groundwaters were investigated along the contact between the Baltic Shield and the East European Platform, in the Leningrad region and western Karelia, northwest Russia, where permafrost existed during the Wichlesian Ice Age. Groundwater 234U/238U ratios were found to reach 25.8. To link the extreme excess of 234U in groundwater to past permafrost conditions, the major ion, isotopic (δ18O, δ2H) composition and tritium (3H) abundance of groundwater were also determined. Groundwaters were found to contain four different components. The first component, with 234U/238U 1, corresponded to fresh groundwater derived from modern recharge, containing 3H and stable isotope compositions reflecting modern precipitation. The second component, with 234U/238U 1 corresponded to fresh groundwater with a recharge age of 50 years or slightly older, as stable isotope compositions were close to modern precipitation, but 3H activity was below the limit of detection. The third component, with 234U/238U = 1–3, corresponded to postglacial groundwater recharge derived from the melting of the Scandinavian ice sheet, reflecting an extremely depleted stable isotope composition. The fourth component, with 234U/238U ≤ 25, corresponded to “revived” groundwater formed during the permafrost thawing in the Holocene. This classification of groundwater origin corroborates with regional paleogeographic reconstructions and supports the hypothesis that long-term permafrost conditions influence excess 234U in groundwater.

The metamict fergusonite-(Y) with the formula (Y0.70Ln0.20Ca0.13U0.02Th0.02)∑1.07(Nb0.72Ta0.17W0.06Ti0.04)∑1(O3.97(OH)0.11F0.08Cl0.03) · 2.12H2O from the Blyumovskaya Pit, Ilmeny Mountains (Russia) was studied by the means of high-temperature X-ray diffraction, thermal analysis, Raman spectroscopy and microprobe analysis. Thermal expansion was studied for both tetragonal (α-fergusonite) and monoclinic (β-fergusonite) polymorphs. The expansion of β-fergusonite is anisotropic and strongly negative along the α33. In contrast, α-fergusonite exhibits a relatively isotropic thermal expansion upon heating. The volume CTE (αV) for β-fergusonite varies in the range 22.87(94)–75.4(2.5) × 10–6 ºC−1, whereas α-fergusonite has αV = 32.33(57)–31.66(49) × 10-6 ºC−1 in the temperature range 850–1200 °C. After heating to 1100 °C, the mineral develops a porous texture, and the radioactivity is reduced by 37

The isotopic composition (δ 2 H and δ 18 O) and unstable parameters (temperature, Eh, pH) of the natural waters in this area were obtained to clarify the features of the formation of the thermal water. The nitrogen thermal (72 °C) and relatively cold (20–25 °C) groundwater as well as surface water was studied in 2022. The isotopic composition of the surface water in the Kuldur River varies from δ 18 O≈−13.30‰ and δ 2 H≈−95.8‰ to δ 18 O≈−12.53‰ and δ 2 H≈−90.5‰ and fits on the approximation line δ 2 H = 7.14 × δ 18 O–1.2 ( R 2 = 0.91), which is close to the Local Meteoric Water Line (LMWL δ 2 H = 7.24 × δ 18 O + 0.5). Thermal groundwater has the isotope composition from δ 18 O≈−13.83‰ and δ 2 H≈−100.6‰ to δ 18 O≈−12.29‰ and δ 2 H≈−95.1‰ and it is approximated by equation δ 2 H = 3.23 × δ 18 O–56.2 ( R 2 = 0.84). The initial isotopic composition of the recharge water is about δ 18 O≈−14.1‰ and δ 2 H≈−102‰, which was found as intersection of the approximation line and LMWL. A comparison of the water temperature and its isotopic composition shows that thermal waters are most likely the result of a mixture of three components. The first end-member is the modern recharge water (it is obviously from tritium content), the second end-member is thermal fluid, and the third one is thawed permafrost, as the authors suggest. This assumption is supported by water from one of the observation boreholes noticeably shifts from the main area of the isotopic composition of the thermal water towards the isotopic enrichment. Apparently, this deviation is attributed to the isotopic fractionation during the groundwater freezing, when aquifer was turned into permafrost in last ice age, which is now thawing under the climate influence. The contribution of meltwater cannot yet possible to assess. Data on the tritium content and the isotopic composition of the dissolved noble gases makes it possible to estimate characteristics of the modern recharge water. Calculation gives an age of the modern component about 55 years and initial tritium concentrations of about 98 TU, which is fully consistent with field observations.

The results of the study of bottom sediments and water of the estuary of the Grøndalen River (Grøn-Fjord, West Spitsbergen) are presented. The stratigraphic features of the sedimentary strata are determined. The chronology of changes in geoecological environmental conditions has been established using radioisotope dating methods. The main factors influencing sedimentation in the study area are air temperature and precipitation during the period of predominance of low temperatures. It is shown that climate fluctuations determine the chronological sequence of the sedimentation rate and the change of the lithotype of the bottom sediment toward fine fractions.

Small intermountain river basins are most suitable for developing new methods to estimate water balance due to their well-defined catchment boundaries, relatively rapid runoff processes, and accessible landscapes for study. In general terms, dissecting the hydrograph of a small mountain river requires calibration of the flow model against multi-year data sets, including (a) glacier mass balance and snow water content, (b) radiation balance calculation, (c) estimation of the groundwater contribution, and (d) water discharge measurements. The minimum primary data set is limited to the precipitation and temperature distributions at the catchment. This approach postulates that the conditions for the formation of all components of river flow are known in advance. It is reduced to calculating the dynamic balance between precipitation (input part) and runoff, ablation, and evaporation (output part). In practice, accurately accounting for the inflow and outflow components of the balance, as well as the impact of regulating reservoirs, can be a challenging task that requires significant effort and expense, even for the extensively researched catchments. Our studies indicate the potential benefits of an approach based on one-time, but detailed, observations of stable isotope composition, temperature, and water chemistry, in addition to standard datasets. This paper presents the results of the 2022–2023 work conducted in the basin of the small mountain river Ala-Archa, located on the northern slope of the Kyrgyz Range in Tien-Shan, which was chosen as an example due to its well-studied nature. Our approach could identify previously unknown factors of flow formation and assess the time and effectiveness of work in similar conditions.

Excess of uranium-234 in natural water (ratio 234U/234U 1 in comparison to the equilibrium value as 1 by activity) correlates with global climate variations, increasing during warm and decreasing during cold periods. The hurricane disequilibrium of 234U/234U 10 are found in groundwater. Based on mathematical models, it is shown that such anomalies are the result of a geologically long stay of aquifers in a frozen state in the past and the subsequent melting of ground ice with the formation of “revived” water. Non-freezing film moisture present in permafrost rocks make a decisive contribution to the formation of hurricane 234U excess.

AMS radiocarbon ages of organic matter from ice wedges and enclosing peat were determined for the polygonal peatland at the Lorino site on the eastern coast of the Chukchi Peninsula. The study's goal was to fill a knowledge gap about the dynamics of polygonal peatlands with ice wedges and winter climate conditions during the Holocene in this easternmost region of the Russian Arctic. It has been found that peatland accumulated during the Younger Dryas and early Holocene, mostly between 14 and 9.9 cal ka BP, while ice wedges were dated from 7.7 to 6.6 cal ka BP. Since ice wedges have features of syngenetic growth, the discrepancy in the age of ice wedges and enclosing peatland may result from the significant presence of early and pre-Holocene peat. It is assumed that the older polygonal peatland deeply thawed during the Holocene optimum, and subsequently, when the permafrost aggraded, a new generation of ice wedges was formed. The AMS C-14 age (18.1 cal ka BP) of the ice wedge exposed below the peat indicates the presence of a Late Pleistocene generation of ice wedges at the study site. Paleotemperature reconstructions based on the stable isotope composition of ice wedges show that the mean January air temperature during the Northgrippian stage of the Holocene varied from -27 to -23 degrees C, and at the end of the Late Pleistocene, from -32 to -26 degrees C.

The study aims to evaluate the shares of primary waters (Atlantic, river, meltwater, and sea water withdrawn for ice formation) in the resulting water masses in the eastern part of the Barents Sea at the end of the hydrological winter. Moreover, the study compares the outcomes achieved by using salinity-518O and salinity-52H values. The study was based on the data on water temperature and salinity and 518O and 52 & Ncy; stable isotopes values. We implemented field studies in March and April 2021 at the Dalnie Zelentsy research vessel, providing the only known and available source of data on 518O and 52 & Ncy; for the eastern part of the Barents Sea between 700 N and 790 N at the end of the hydrological winter. The results allow for estimating the shares of the primary waters, namely Atlantic, river, meltwater, and sea water, withdrawn for ice formation in the sea water during this period of the year in various water masses meltwater. Moreover, they allow for estimating the influence of each of the primary waters on the salinity of the resulting water masses. However, when we calculate the average Atlantic and ice water shares using the 52H isotopic parameter, they are somewhat higher than those calculated using 518O. Conversely, the river water share is somewhat lower. A 0.36 ps mu (0.34-0.51 ps mu) change (decrease) in salinity in the Atlantic water mass is due to mixing with river waters and 0.04 ps mu (-0.05 to 0.10 ps mu) with mixing with meltwater. In the Barents Sea winter water mass these values are 0.63 (0.53-0.71 ps mu) and 0.31 (0.27-0.42 ps mu), respectively. In the water mass called 'Surface waters of the Arctic seas, winter', the processes of ice formation prevail over the processes of ice melting. The average decrease in salinity due to the content of river waters alone could be 0.66 ps mu (0.59-0.74 ps mu). However, it is only 0.46 ps mu (0.41-0.57 ps mu) due to salinisation during ice formation. The quantities of meltwater volumes and volumes of water withdrawn for ice formation serve as specific characteristics of << memory >>, describing the ice formation/ice melting processes.

ABSTRACT Accelerator mass spectrometry radiocarbon (AMS 14 C) dating was used for determining the age of wedge ice. It has been found that between 11,270 and 6420 cal BP, or the Greenlandian and Northgrippian stages of the Holocene, ice wedges grew syngenetically in sandy deposits with gravel in the Chara River valley. The variations of δ 18 O values in the ice wedges are about 8‰, from –25.5‰ to –18.8‰. Based on the stable isotope composition of ice wedges, paleotemperature reconstructions revealed that the mean January temperature was as low as –38°C during the coldest periods of the early half of the Holocene and as high as –28°C during the warmer periods.

The article is devoted to assessing the radiation quality formation of groundwater with anomalous excesses of 234 U on example the Pre-Volga region (European part of Russia). It was found that exceeding the reference values of groundwater radiological toxicity in a number of cases is associated with anomalously high activity of 234 U. Isotopic ( 2 H, 18 O) and chemical data indicate that the anomalous 234 U/ 238 U ratios are of cryogenic origin related to the effects of past climatic fluctuations on the aquifers. Such groundwater formed from thawed permafrost at extremely low uranium concentrations may have unsatisfactory radiological quality due to anomalous excesses of 234 U.

In 2009–2018, the isotopic composition of oxygen and hydrogen in the atmospheric precipitation, groundwater and river and lake water of Lake Onega basin was studied. The weighted annual isotope composition of precipitation at Petrozavodsk was δ18O = −11.7‰ and δ2H = −84‰ and varied from −30.9 to −4.1‰ for δ18O and from −23 to −22‰ for δ2H. The isotopic composition of the water in Lake Onega was relatively uniform from −11.5 to −9.3‰ for δ18O and from −85 to −71‰ for δ2H. In the bays, the isotopic composition of the water varied more substantially than in the central part of the lake due to the river runoff during springtime flooding. In late summer, the concentrations of deuterium and oxygen-18 increased in the lake water, and figurative points on the δ2H vs. δ18O diagram shifted above the meteoric line. The absorption of the isotopically heavy summer precipitation and disequilibrium isotope fractionation during evaporation led to the enrichment of the lake water by heavy isotopes. Experiments were conducted to estimate the evaporation influence on the isotope enrichment of the residual water, and a comparison of the obtained isotope data with the experimental function showed that commonly, about 4% and up to 12% of water was lost during the spring and summer, respectively. In the water of the tributaries, the abundance of the deuterium and oxygen-18 varied in a wider scale than in the lakes, from −14.4 to −9.1‰ for δ18O and from −102 to −73‰ for δ2H. An evaporation loss of up to 35% was found for the rivers in late summer, and this value was proportional to the area of lakes and wetlands in the elementary watershed. The initial isotope composition of the water in the tributaries prior to evaporation was estimated to be δ18O ≈ −14.1‰ and δ2H ≈ −103‰ on average and crossed the approximation and meteoric lines. This estimation was close to the average composition of the groundwater, i.e., δ18O ≈ −13.4‰ and δ2H ≈ −94‰ on the Lake Onega catchment. The slightly increased isotope depletion of the calculated composition in the initial river water in comparison with the groundwater was the result of the contribution of the spring snowmelt water, which had a significant influence on the lake water balance.

An isotope–hydrochemical study of the surface and groundwater was carried out in the basin of the Ala-Archa River located on the Northern slope of the Kyrgyz ridge, Kyrgyzstan. The results of studies of stable isotopes of δ2H and δ18O, the isotope composition of uranium and the physicochemical parameters were used to carry out the diagnostics of runoff components of the mountain river basin Ala-Archa and to determine river runoff components in the zone of development of modern glaciation. The contribution of buried ice to river flow was determined.

This paper presents the results of seasonal observations of the geochemical composition of the waters of the large tributaries of Lake Onego. The mineralogy and geochemistry of the suspended matter and the isotopic composition (oxygen-18 and deuterium) of the river waters were studied for the first time. The dependence of the chemical and isotopic compositions of the tributary water on the season and characteristics of the catchment area (swampiness and lacustrine) was revealed. It is shown that the river waters belong to the bicarbonate class of the calcium group and have low mineralization, high color and a similar composition to the main minerals of the suspended matter. It is determined that the difference between the multielement spectra of the water and suspended matter of the different rivers is closely related to the geological and geomorphological structures of river basins. It is established that the quantitative characteristics of the mineral and organic parts of the suspended matter, the ratios of the different minerals andthe size and patterning of the particles of detrital material in the tributaries differ. The change in the mineralogical and geochemical compositions of the suspended matter of each individual river over the year is insignificant. The influence of the river runoff on the formation of lake waters is manifested in the chemical composition of the lake waters. The quantitative ratios of the main ions, biogenic elements and microcomponents in lake water mainly correspond to their ratios in river waters. The mineral part of the dispersed sedimentary matter of the lake in its geochemical characteristics is close to the suspended matter of the river waters.

The article gives the results of isotopic analysis of the composition of Karelian snow cover, which formed in winter of 2015/2016, and atmospheric precipitation in Petrozavodsk. It is shown that snow composition varies from –15.7 to –21.1‰ for δ 18 О and from –118 to –158‰ for δ 2 Н, and the isotopic composition becomes lighter in the direction from south to north in accordance with air temperature drop. The isotopic composition of winter precipitation can be approximately reconstructed by the isotopic composition of snow cover.

Modern permafrost conditions of the Subpolar Urals are characterized by the example of peat bogs of the lateral moraine in the vicinity of Narodnaya mountain area (Polar Urals, Russia). Changes in permafrost conditions due to warming, studied by georadar survey and radiocarbon dating. The depth of thawing in these bogs was also determined by measuring the depth of the seasonally thawed layer and the temperature of the rocks using a thermometer and a metal probe 1.5 m long along a 100 m profile with a step of 10 m. It was found that the depth of the STL ranged from 10 to 140 cm at a permafrost surface temperature of 0 degrees C. The structure of the peat deposit was checked on a dry section of the swamp using a pit 40 cm deep. It was found that the peat bog is underlain by frozen clay-loam. In the peatland itself, several boundaries of peat and gley accumulation are visible in the layers directly above the underlying loam, which indicates a repeated change in the conditions of peat accumulation at the beginning of warming or the movement of rocks as a result of solifluction flows from nearby slopes.

For the first time, AMS radiocarbon dating was used to date microinclusions of organic material extracted directly from Holocene syngenetic ice wedges in the Noprthern European part of Russia, on the coast of Baydarata Bay near the village of Yarynskaya, 500 m south of the mouth of the Ngarka-Tambyakha River (68°51′20.27″ N, 66°52′6.51″ E). Dated ice wedges formed about 6.4, 5.0, and 1.9 ka BP. According to isotope oxygen data, the average January air paleotemperature in the Middle and Late Holocene on the coast of Baydarata Bay was calculated. It is shown that the average January air temperature during this period here varied from about −20 to −25°C. However, during milder winters it could have been about −18°C.