Groundwater origin, age, and flow mechanisms within continuous permafrost environments of Eastern Siberia (Russia) are investigated using tritium data. In this region, permafrost acts as both a barrier and a conduit for hydrological fluxes, influencing groundwater accessibility and quality. The study reveals complex interactions between permafrost dynamics and hydrogeological responses and a significant differentiation in groundwater age. Post-1953 water fractions in continuous-permafrost springs and wells range between 6 and 100

The object of research was the Eruu spring, which is formed by intrapermafrost waters, and the lakes in its catchment area. This article provides an analysis on the chemical composition of surface- and groundwater and how it changes through the year. It is shown that there has been a notable change in the chemical composition of lake Abaga-Kyuel over the last 50 years. It might be attributed to the expansion of the lake and the underlying talik, which caused it to connect with the interpermafrost talik. Lake Krugloye has a chemical composition and salinity similar to that of the waters in the Eruu spring and lakes Abaga- Kyuel and Elgen. This suggests that the interpermafrost waters may discharge subaquatically into the lakes in the floodplain of the Tamma river.

In July of 2023 a groundwater discharge site was discovered in the exposed limestone strata along the Lena river valley, near the settlement of Mokhsogollokh. In order to determine the origin of the spring, the natural conditions of the territory have been researched. This study is based on published materials describing the geological structure of the area and the chemical composition of surface and ground waters, the data taken from the Melnikov Permafrost Institute archive on the hydrogeological and hydrocryological conditions of the area, and on the chemical analysis of water samples taken from the discovered source and the Lena River. Based on a comparative analysis on the chemical composition of various waters in the area it has been determined that the origin of the spring is linked to the thawing of ice wedges. Due to the ongoing change in climate, there is an increasing likelihood that the amount and flow rate of similar springs will grow. Considering that the second flood wave on the Lena River is formed in early summer by the waters of the active layer, a more in-depth study of groundwater springs like the one discovered is required.

In central Sakha (Yakutia) Republic, groundwater icings, primarily formed by intrapermafrost water, are less prone to contamination and serve as a stable freshwater resource. The periodic growth of icings threatens infrastructure such as roads, railways, and bridges in permafrost areas. Therefore, research in this field has become urgently necessary. This study aims to analyze the impacts of various factors on the scale of icing formation using Landsat satellite data, Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow-On (GRACE-FO) data, Global Land Data Assimilation System (GLDAS) data, and field observation results. The results showed that the surface area of icings in the study area showed an overall increasing trend from 2002 to 2022, with an average growth rate of 0.06 km2/year. Suprapermafrost water and intrapermafrost water are the main sources of icings in the study area. The total Groundwater Storage Anomaly (GWSA) values from October to April showed a strong correlation with the maximum icing areas. Icings fed by suprapermafrost water were influenced by precipitation in early autumn, while those fed by intrapermafrost water were more affected by talik size and distribution. Climate warming contributed to the degradation of the continuous permafrost covering an area of 166 km2 to discontinuous permafrost, releasing additional groundwater. This may also be one of the reasons for the observed increasing trend in icing areas. This study can provide valuable insights into water resource management and infrastructure construction in permafrost regions.

The objective of this study was to evaluate subaerial taliks’ geology, configuration, ground temperature and groundwater level in the continuous permafrost environment of Central Yakutia (Eastern Siberia). The study included geophysical surveys, borehole drilling and measurements of ground temperature and groundwater level variation in a talik aquifer in the Shestakovka research watershed. The talik occupies a gentle, sandy slope covered by a sparse pine forest. Its thickness varies from 3 to 17 m. The talik has several water-conducting branches along its slope. The seasonal thaw layer outside the talik and the talik itself form a single aquifer at the end of the summer. Water-saturated deposits in the talik have a temperature of about 0 °C throughout the year and do not freeze because of the constant filtration of water through the pores and convective heat transfer. Although the groundwater level is relatively close to the land surface, at a depth of just 1–3 m, it has very weak response to snowmelt and precipitation events. The maximum groundwater level occurs in February under cryogenic pressure due to deep seasonal ground freezing above the talik aquifer. Complicated relations between the landscape and the groundwater in the given geological conditions lead to the long-term existence of talik aquifers in the continuous permafrost environment.

Рассмотрены особенности гидрогеологического строения и режима подземных вод в пойменной части р. Лены в районе г. Якутска на основе детального анализа опубликованных и фондовых материалов, включая результаты полевых работ авторского коллектива 2013-2021 гг. Для характеристики мерзлотно-гидрогеологических условий территории изучены разрезы более 70 скважин. Режимные наблюдения за уровнем подземных вод проведены на пойменно-намывной территории. Исследование химического состава поверхностных и подземных вод основано на обработке более 250 анализов. Установлено, что на высокой пойме в формировании ресурсов надмерзлотных грунтовых вод, помимо инфильтрации речных вод, участвует транзитный подрусловой поток, гидравлически связанный с пойменными таликами. Отмечена сезонная и пространственная изменчивость химического состава воды в р. Лене и в изучаемых таликах. Минимальная минерализация (0.1-0.3 мг/л) и хлоридно-гидрокарбонатный магниево-кальциевый состав характерны для поверхностных вод и подземных вод четвертичного водоносного горизонта в правобережной части р. Лены. Здесь существуют условия для их питания пресными над- и межмерзлотными водами бестяхской надпойменной террасы реки и подрусловых таликов под малыми реками. У г. Якутска минерализация воды в Лене и четвертичном водоносном горизонте увеличивается до 0.5-1.3 г/л за счет хлорид- и сульфат-ионов, которые обладают хорошей миграционной способностью и поступают с поверхностным и надмерзлотным стоком с надпойменной террасы, где расположен город. This paper reports on the hydrogeological conditions and groundwater regime in the Lena River floodplain near Yakutsk. The published and archive materials, including field data collected by the authors in 2013-2021, were analyzed. Data from more than 70 boreholes were examined to characterize permafrost and hydrogeological conditions in the area. Data on groundwater level monitoring in the reclaimed area of the floodplain were also used. Over 250 sample analyses were interpreted to characterize the chemical composition of surface and ground waters. The results suggest that suprapermafrost waters in the high floodplain are recharged both by infiltration of river water and by a transit water flow under the river channel hydraulically connected to floodplain taliks. The seasonal and spatial variability of the chemical composition of waters was revealed in the Lena River and in the studied taliks. The surface and ground waters of the Quaternary aquifer on the east bank of the Lena River are characterized by the lowest total dissolved solids (TDS) concentration (0.1-0.3 mg/L) and by the magnesium-calcium chloride-bicarbonate composition. These waters are recharged by fresh water of the supra- and interpermafrost taliks of the Bestyakh terrace and by the riverbed taliks under small rivers. In the vicinity of Yakutsk, TDS concentrations in the Lena River and in the Quaternary aquifer increase to 0.5-1.3 g/L due to high mobility of chloride and sulfate ions migrating with the surface and suprapermafrost runoff from the low terrace, where the city is located.

The purpose of the article is to study the influence features of polar-oriented slopes on the near-surface energy and hydrothermal balance in the seasonal cryolithozone. The authors carried out a complex of field observations including measurement of air and underlying surface temperature, soil moisture, solar radiation and wind speed at the hydrological stations of Songling (southern slope) and Luoguhe (northern slope) in the northeast of the Great Xing'an Mountain (China). The analysis of the data obtained allowed to conclude that, on the one hand, the long-term influence of the thermal balance components causes significant differences in the soil structure and properties on differently oriented slopes. The number of daily freeze-thaw soil cycles on the southern slope (100 cycles) significantly exceeds the ones on the northern slope (56 cycles). The soil on the southern soil is 3 °C warmer than that on the northern slope, and its humidity in the area of the Songling hydrological station is lower than that at the Luoguhe station. On the other hand, differences in soil properties control the energy exchange between the atmosphere and the earth's surface, this means that the incoming short-wave solar radiation and heat flux into the soil on the southern slope is greater than on the northern one. Therefore, slope orientation is one of the significant environmental factors affecting the influx of solar energy, temperature and humidity of the soils in the northeastern Great Xing'an Mountain. It also has a decisive role for the spatial distribution and evolution of seasonal permafrost in the region and, accordingly, affects the stability and safety of engineering structures. The performed research is important for understanding the relationship between climate and frozen soil in the mountainous areas with seasonal cryolithozone as well as for optimization of boundary conditions when modeling rock freeze-thaw processes.

The article considers the theory, methods, and some results of four-year field studies of the processes of runoff formation on a small freezing experimental river catchment in a continuous thick (400 m) permafrost zone (the Republic of Sakha (Yakutia)) based on data on natural water chemistry. The analyzed problems include the seasonal and daily dynamics of river flow in the warm season, the concentrations of some dissolved substances in different types of water, as well as the role of channel widenings, supra-permafrost water, and aufeises in flow formation. Various types of relationships between water discharges and the concentrations of some dissolved substances are described under varying hydrothermal conditions. The role of nonfreezing lake-like channel widenings (bochags) in the regulation of freshet flow of water and dissolved matter is evaluated. The efficiency of the automated digital registration of the level, temperature, and specific electric conductance of water with a high time resolution at hydrological gages is discussed, especially, as applied to the rapid processes in a river.

The perennially unfrozen zones (taliks) in the Eruu area of central Yakutia have a complex stratigraphic structure, and the dynamic characteristics of groundwater in this region have been insufficiently studied. This study analyzed the results of the explorations and geophysical studies conducted by the Melnikov Permafrost Institute of the Siberian Branch of the Russian Academy of Science. In addition, we simulated and analyzed the dynamic characteristics of groundwater in the area based on hydro-meteorological data, snow data, and remote sensing data. During the process, the dynamic changes in the attributes of aquifers due to the seasonal freeze–thaw processes of soils, including the active layer, were also taken into account. The results showed the following: (1) According to the analysis of the measured data on water levels in hydrogeological observation well 14E/2014, the difference between the simulated and measured values of groundwater levels in monitoring wells for over 99% of the measurements was less than 0.1 m. The average difference between the measured (excluding missing values) and simulated values of groundwater level in the monitoring wells was 0.028 m/d. (2) The annual average water level in the study area declined. The simulated value dropped at a rate of 0.10 m/a, with only a gap of 0.01 m/a with the measured value. Meanwhile, the simulated water head was greatly influenced by the terrain, especially in the central area, where the head decreased rapidly from the perimeter toward the lakes (8.9 m/km on average). (3) From 1 September 2014 to 31 August 2015, the mean value of the simulated discharge in the study area was 3888.39 L/d, which was in line with the results of previous monitoring (the average flow was 4147.20 L/d and 3715.20 L/d in 2014 and 2015, respectively). This study can provide a reference for the reasonable exploitation and utilization of groundwater under the influence of the distribution of perennially unfrozen zones, or taliks, and provides an effective three-dimensional modeling method for quantifying the analysis of groundwater dynamics in permafrost regions.

In this study, we reviewed and summarized the data on permafrost and groundwater areas of Central Yakutia to understand the formation and distribution of subpermafrost mineral waters of sodium bicarbonate and chloride-bicarbonate types, and to evaluate their potential use for medical purposes. Analysis of the data indicated that these low-mineralized groundwaters are basic analogues to the Maykop and Karachi mineral waters, with no particular bioactive components. These mineral water types contain 400 to 1200 mg/dm3 bicarbonates, 100 to 600 mg/dm3 chlorides, 50 to 250 mg/dm3 (Karachi) and <50 mg/dm3 (Maykop) sulfates, 400 to 800 mg/dm3 sodium, and <10 mg/dm3 calcium and magnesium. The formation of sodium bicarbonate and chloride-bicarbonate type water in Central Yakutia is influenced by permafrost which promotes concentration of major chemical components under the cold temperatures and slow groundwater circulation. The study of minor and trace constituents indicates that the subpermafrost waters in the study region contain fluorine and lithium in excess of the drinking water standards but are potentially appropriate for balneotherapy. Further research on the bio-physiological effects of subpermafrost waters with elevated fluorine and lithium concentrations contribute to the development of the spa and health resort industry in Yakutia. Moreover, the study will expand the balneological spectrum of disease prevention and treatment for the benefit of residents of Yakutia and the adjacent regions.

Степень изученности процессов миграции воды и растворенных веществ в арктических и субарктических мерзлотных ландшафтах крайне низкая. В нашем исследовании на основе гидрохимических данных, полученных в ходе экспедиций в 2019 и 2020 годах, делаются выводы об источниках питания и механизмах формирования стока трех ручьев в арктической тундре в низовьях реки Лены. Исследованные природные воды контрастны по химическому составу. Максимальные концентрации химических веществ, вплоть до солоноватого типа вод, характерны для высачиваний подземных вод, состав которых формируется при длительном взаимодействии с материнскими породами. Наиболее пресные воды приурочены к органогенным горизонтам почвенного профиля. Воды в истоках ручьев ультрапресные, холодные и иногда показывают слабокислую реакцию, что говорит об их формировании в обедненном минеральными веществами органогенном почвенном горизонте сезонно-талого слоя по контакту с кровлей многолетнемерзлых пород. На участках активного врезания русла в коренные породы воды ручьев обогащаются минеральными соединениями. Ниже по течению происходит прогрев воды в русле и приток ультрапресной воды со склонов, сформированной в верхней грубогумусной части сезонно-талого слоя. Истоки и слабоминерализованные притоки ручьев формируются за счет вытаивания льда сезонно-талого слоя. Взаимодействие воды и горных пород определяет химический состав воды исследованных ручьев. Сведения о химическом составе природных вод позволяют делать выводы об источниках и путях движения воды на водосборах, что необходимо для разработки моделей и прогнозирования природных процессов.

The long-term dynamics of tritium content in atmospheric precipitation and in surface and ground water of the Lena River basin is characterized on the basis of new data obtained in 2019 and 2020 and historical information. The relationship between the tritium content and the concentration of dissolved chemicals is analyzed. In 2019 and 2020, during the periods of winter and summer low water, 44 water samples were taken from the Lena River, its large, medium, and small nonfreezing tributaries, intrapermafrost and subpermafrost groundwater, snow cover, and liquid precipitation. Data on tritium concentrations in the upper and middle Lena River and its tributaries are given for the first time. The element content in samples from river water, snow cover, and rain corresponds to its long-term descending curve. The tritium concentration in river waters during the winter low-water period is smaller than in the summer period, when its content in the rivers approaches its values in atmospheric precipitation. This testifies to the contribution of groundwater to river recharge in spite of the wide spread permafrost. Statistically significant correlations of the tritium content with the redox potential and the contents of bicarbonate, lithium, and sodium ions, total dissolved solids, and pH have been revealed.

SignificanceRussian rivers are the predominant source of riverine mercury to the Arctic Ocean, where methylmercury biomagnifies to high levels in food webs. Pollution controls are thought to have decreased late-20th-century mercury loading to Arctic watersheds, but there are no published long-term observations on mercury in Russian rivers. Here, we present a unique hydrochemistry dataset to determine trends in Russian river particulate mercury concentrations and fluxes in recent decades. Using hydrologic and mercury deposition modeling together with multivariate time series analysis, we determine that 70 to 90% declines in particulate mercury fluxes were driven by pollution reductions and sedimentation in reservoirs. Results suggest that Russian rivers likely dominated over all other sources of mercury to the Arctic Ocean until recently.

Степень изученности процессов миграции воды и растворенных веществ в арктических и субарктических мерзлотных ландшафтах крайне низкая. В нашем исследовании на основе гидрохимических данных, полученных в ходе экспедиций в 2019 и 2020 годах, делаются выводы об источниках питания и механизмах формирования стока трех ручьев в арктической тундре в низовьях реки Лены. Исследованные природные воды контрастны по химическому составу. Максимальные концентрации химических веществ, вплоть до солоноватого типа вод, характерны для высачиваний подземных вод, состав которых формируется при длительном взаимодействии с материнскими породами. Наиболее пресные воды приурочены к органогенным горизонтам почвенного профиля. Воды в истоках ручьев ультрапресные, холодные и иногда показывают слабокислую реакцию, что говорит об их формировании в обедненном минеральными веществами органогенном почвенном горизонте сезонно-талого слоя по контакту с кровлей многолетнемерзлых пород. На участках активного врезания русла в коренные породы воды ручьев обогащаются минеральными соединениями. Ниже по течению происходит прогрев воды в русле и приток ультрапресной воды со склонов, сформированной в верхней грубогумусной части сезонно-талого слоя. Истоки и слабоминерализованные притоки ручьев формируются за счет вытаивания льда сезонно-талого слоя. Взаимодействие воды и горных пород определяет химический состав воды исследованных ручьев. Сведения о химическом составе природных вод позволяют делать выводы об источниках и путях движения воды на водосборах, что необходимо для разработки моделей и прогнозирования природных процессов. The degree of knowledge about migration of water and dissolved substances in arctic and subarctic permafrost landscapes is extremely low. In our study the water sources and the mechanisms of streamflow formation of the small Arctic tundra rivers in the lower Lena River are described on the basis of hydrochemical data. Studied natural waters are contrasting in chemical composition. The maximum concentrations of chemicals, up to the brackish type of water, are characteristic of groundwater seeps, the composition of which is formed during long-term interaction with parent rocks. The freshest waters are confined to the organic layers of the soil profile. The sources of streams are ultra-fresh, cold and sometimes show a slightly acidic reaction, which indicates their formation in the organic part of the active layer at the contact with the permafrost top. Downstream where the channel is actively cut into the bedrock, the streams' waters are enriched with mineral compounds. Downstream, water warms up in the channel and ultra-fresh water flows from the slopes and dilute the stream water. The sources and low-mineralized tributaries of the small streams are formed due to the thawing of the ground ice in the active layer. The interaction of water and rocks determines the chemical composition of the water of the studied streams. Information about the chemical composition of natural waters allows drawing conclusions about the sources and water pathways in the watersheds, which is necessary for developing models and predicting natural processes.

Yakutsk, the largest city in the continuous permafrost zone, is used as a case study for examining natural and modified environmental conditions that control the character and intensity of water-logging in the active layer in relation to topography and drainage. Interpretation of aerial photography and satellite imagery was carried out, along with analysis of drilling and long-term hydrogeochemical monitoring data, in order to determine the response of natural landscapes to human impacts and to assess the probability of suprapermafrost cryopeg development with city expansion. The role of vegetation cover in controlling the temperature and moisture regime of the active layer was examined. Results suggest that the neighborhoods with chaotic development patterns and impeded drainage have high risk of cryopeg formation. Puddle water in these areas is characterized by high dissolved-solids levels (2-4 g/dm3). As puddles evaporate, salts settle on the underlying soil surface and then migrate into the active layer, increasing its salinity (up to 1.3%). Suprapermafrost water that forms in these soils has dissolved-solids concentrations as high as 8–10 g/dm3. Continuous supply of dissolved solids and their cryogenic concentration promote the formation of hydrochemical taliks and cryopegs. Remote sensing and mathematical modeling demonstrate that changes to the soil moisture and hydrogeochemical regimes cause forest degradation, which, in turn, promotes deeper seasonal thaw. This provides favorable conditions for the formation of subaerial water-bearing taliks and later anthropogenic cryopegs

The experience of inwashed soil development under the conditions of permafrost is considered for various engineering structures: the foundations of gas-oil, industrial and civil facilities, soil hydraulic facilities, roads, etc. Particular attention is paid to the technology of construction of the foundation of inwashed soil on the low floodplain of the Lena river for the residential complex of the Yakutsk city (quarters No. 202 and 203).The results of studies into the dynamics of the geocryological conditions over this territory during the long-term operation of buildings and engineering structures are presented.It was revealed that in the major part of the territory of quarter No. 202 in Yakutsk, which was constructed in the 1980-90s according to the 1st principle, at present the ground has a positive temperature at a depth of 10 m and deeper.At the territory of quarter No. 203,, suprapermafrost aquiferous taliks, were formed during hydromechanical works in the 1990s, and they still exist everywhere after 30 years.The factors that contribute to the preservation of suprapermafrost taliks in the body and base of the inwashed soil are considered.The main factors determining the formation of the soil temperature field include distinct thermophysical properties of dry inwashed sands in the upper part of the section and the hydrogeological conditions of the territory.The features and prospects of inwashed soil exploitation as the structure foundations and the principles of construction on them are analyzed.To control and develop robust recommendations for ensuring the sustainability of structures, it is necessary to organize comprehensive geocryological monitoring, including ecological aspects of the interaction between technogenic systems and the environment.

俄罗斯萨哈(雅库特)共和国属于典型高纬度寒区,是世界地下水溢流积冰问题最严重的地区之一,布鲁斯位于萨哈共和国汉加拉斯基区东部,是地下水溢流积冰现象的代表性区域.在实地勘测的基础上,采用Geo-stu-dio软件结合气象数据对不同时期山谷边坡的温度场、渗流场的分布特征进行耦合模拟并分析其对地下水溢流积冰发育的影响.结果 表明:(1)研究区长达192 d稳定的负温环境,使得边坡内部过水通道温度环境维持地下水接近冻结-未冻结的临界状态,有效地提高了其溢流到地表(或积冰体表面)后的冻结效率.坡体外部最低可达-43℃的超低温度,也为其冻结提供了足够的冷量.(2)寒武纪碳酸盐岩的强风化带是坡体内为溢流积冰供水的主要过水通道,其地下水渗流速度最高可达1.23 m/d,较其他岩层水流速率(一般不超过0.05 m/d)明显加快.(3)同时充足的地下水补给为地下水溢流积冰的形成提供物质条件,形成较高的地下水水位为地下水渗流提供驱动力.本研究可为中国及其他国家和地区的地下水溢流积冰相关研究提供科学参考.

The results of long-term studies of a group of aufeis-forming Buluus groundwater sources are given. A stow, which has been formed by the spring, contains the drainage area of the suprapermafrost–intrapermafrost aquifer, which is widespread in the sand deposits of the bestyakhskaya terrace of the Lena River in Central Yakutia. The analysis of observations of 1964–2017 showed stable water chemistry in Buluus spring at the long-term scale. Considerable seasonal variations of water chemistry are typical of low-discharge springs, which start functioning after becoming free of aufeis. The spring water also shows higher concentrations of lithium and fluorine. The possible causes of the different chemistry of spring water are discussed, with special attention paid to the local activity of rock freezing and thawing processes in the aufeis valley. It is shown that groundwater samples are to be taken from all springs in the areas of their group discharge with the aim to assess the effect of natural and technogenic factors on the permafrost–hydrogeochemical conditions.