Cold Groundwater Research Articles

GEOCHEMISTRY OF GROUNDWATERS AND SURFACE WATERS, AND GROUND ICE OF THE OKA PLATEAU, EASTERN SAYAN (RUSSIA)

The study area is located in the Eastern Sayan hydrogeological folded area. The objects of the study were groundwaters, surface waters and ground ice in the Sentsa River basin on the Oka Plateau. Cold and thermal groundwaters are associated with Proterozoic and Paleozoic metamorphic and igneous rocks. Their discharge as springs occurs in the river valleys along fault zones. Ground ice was studied in mineral frost mounds (lithalsas) composed of clays, clayey silts and silts of lacustrine-alluvial and fluvioglacial genesis. It has been established that thermal and cold groundwaters have HCO3 Ca-Na compositions, river and lake waters, as a rule, have HCO3 Ca-Na compositions, and ground ice melts – HCO3, SO4-HCO3 and NH4-HCO3 Ca. Thermal waters are largely enriched in Li, Be, B, Si, Mn, Ga, Ge, Se, As, Br, Rb, Sr, Cs, Ba and all REE relative to river and rain waters, and have the highest values of trace elements enrichment factor (EFREE). The latter shows that atmospheric precipitation participates in the formation of the composition of groundwaters (cold and thermal) and surface waters. The specificity of the geochemistry of ground ice is determined by the composition of precipitation, the injection of ice-forming groundwater from taliks, the interaction in the water-rock system, and the presence of organic matter in unconsolidated sediments. The participation of river water and groundwater in the formation of the frost mound ice core is also evidenced by similar values of stable isotopes (δ18O, δD) in surface water, groundwater and ground ice. The 3He/4He ratio points to a possible influx of mantle helium into thermal waters, and δ13С points to the magmatic and thermometamorphic mechanisms of carbon dioxide accumulation in thermal waters. The 87Sr/86Sr ratio in travertines indicates a significant contribution of intrusive rocks to the formation of fluid composition.

New insights on the hydrochemistry, geothermometry, and isotopic characteristics of the hydrothermal groundwater of the SASS basin: case study of the Jérid geothermal field, Southern Tunisia.

Chemical and isotopic indicators were used to recognize the origin of hydrothermal groundwater, to assess the mineralization processes and groundwater quality, to identify the source of solutes and the likely mixing with cold, and elucidate the fluid geothermometry in the Jérid field of Southern Tunisia. The results show that the geothermal groundwater is neutral to slightly alkaline. They are characterized by SO4-Cl-Na-Ca water type. The dissolution of evaporates and pyrite-bearing rocks is the dominant mineralization process. The groundwater quality index indicates that the majority of samples are very hard and belong to poor to unsuitable for drinking classes. Applications and calculations of hydrogeochemical parameters, including SAR, %Na, PI, Kr, and MAR, showed that the majority of samples are unsuitable for agricultural practices. The human health risk was assessed based on hazard quotient and total hazard index through ingestion and dermal contact with iron-rich groundwater. The consumption of CI groundwaters does not present non-carcinogenic risk to adults and children. The δ18 O and δ2H signatures indicate that the geothermal groundwater was recharged by ocean precipitation during cold and wet paleoclimatic periods. The slight enrichment of oxygen-18 and deuterium contents suggests a limited mixing effect between geothermal water and cold groundwater within the same aquifer. This mixing effect is confirmed by the Na-K-Mg and the chloride-enthalpy diagrams. The K-Mg and SiO2 geothermometers provided fairly reliable reservoir temperature values, ranging between 69.6 and 99°C. Calculated geothermal potential values, varying between 469 and 16987 kWth, which allow several applications such as domestic and agricultural heating.

Chemical and isotopic constraints on fluid origin and genesis of geothermal systems in the Tingri-Tangra Yumco rift, southern Tibetan Plateau

Numerous geothermal systems are hosted by extensional rifts that transect the Himalayas and Lhasa block in the Himalayan–Tibetan orogen. However, the relationships between hydrogeological processes and geothermal fluid circulation in different tectonic units remain unclear. Here, we report an integrated dataset of chemical and isotopic compositions (including major and trace elements, δD, δ18O, and 87Sr/86Sr) of thermal spring water from the Tingri-Tangra Yumco rift to assess their origins and circulation processes. δ18O (− 21.3 to − 17.0‰) and δD (− 166 to − 135‰) values of thermal springs indicate dominant recharge of meteoric waters from areas with elevation of > 6000 m and minor addition of magmatic fluids. Meteoric water could infiltrate to depths of about 1700–2900 m along the faults, whereby it is influenced by geothermal gradient and/or conductive heat transfer of magmatic fluids. The thermal spring waters are mainly Na-HCO3 type and are controlled by dissolution of silicate and carbonate minerals and mixing with deep fluids. The results of chemical and multicomponent geothermometers indicate reservoir temperatures of 115 − 195 ℃, corresponding to a convection heat flux of 3.96 × 105 J/s to 1.78 × 107 J/s from geothermal systems, which are comparable to that of the low-enthalpy geothermal systems in southern Italy. Geochemical modeling is conducted to assess the water–mineral equilibria in the reservoir. Trace elements and 87Sr/86Sr data suggest spatially variable controlling factors for the rift-related geothermal systems: (1) interaction with granitoid and carbonate in the Himalayas; (2) cold groundwater mixing with that leaching from granite and volcanic rocks in the Lhasa block; (3) the input of vapors from magmatic degassing. The geochemistry of thermal springs associated with extensional rift is largely induced by the interaction between fluid and different reservoir rocks in the Himalayas and Lhasa block. Based on these findings, a genetic model is proposed for exploration and development of geothermal resources in the Tingri-Tangra Yumco rift.

Formation of a Large Cold Groundwater Mantle Helium Anomaly and High Temperature Geothermal Resources in Response to Bimodal Magmatism Near Roosevelt Hot Springs and Utah FORGE, Milford Valley, Southwest Utah

AbstractA large mantle helium anomaly and separate domains of high heat flow are the predominant manifestations of bimodal magmatic activity in the Milford valley. The mantle helium anomaly (1.9–2.6 R/Ra) covers 270 km2 and is subdivided into two separated domains: a cold shallow groundwater regime and high temperature hydrothermal activity. The zone of anomalous heat flow covers >100 km2 and is also subdivided into two adjacent domains, comprising hydrothermal activity at Roosevelt Hot Springs (RHS) (3–7 W/m2) and conductive heat flow (100–180 mW/m2). While the transfer of heat and mantle helium at RHS are coupled, heat and helium transfer are decoupled in the adjacent cold groundwater regime to the west. Both the mantle helium and geothermal anomalies are attributed to recent mafic‐felsic magmatic intrusions of >400 km3, however, the absence of volcanic eruptions <500,000 years indicates magmas stall before rising to shallow crustal level <10 km depth. Deep level magmatism produces a felsic composition melt, which is inferred to be responsible for the widespread and near uniform range of diluted mantle helium values. A thick and impermeable mass of crystalline granitic basement rock at the mid‐crustal level divides the ascent of mantle helium into separate flow paths. It may also impede the rise of buoyant magma trapping thermal energy that facilitates partial melting, slow cooling, and development of a thick thermal aureole. Partitioning of convective and conductive thermal regimes and independent flow paths supplying deeply derived helium characterize the development of a large long‐lived magma‐related geothermal system.

Germanium and its isotopes as indicators of hydrogeochemical conditions in a terrestrial geothermal system (Karkonosze granitoid, Sudetes, Poland)

The germanium content and its isotope ratio in thermal waters, aquifer rocks and main silicate minerals in a terrestrial groundwater system located in a granitic pluton (Karkonosze granitoid, Sudetes, Poland) have been investigated. This is the first extensive Ge isotope study carried out in both groundwater and aquifer rocks to better understand previously the identified enrichment of groundwater relative to rocks. This research also provides the first data on δ74/70Ge for hybrid acid rocks formed by mixing magmas from two different sources (mantle- and crustal-derived) and main silicate minerals. The Ge isotopic composition in different facies of granite (porphyritic, equigranular) is comparable (δ74/70Ge of 0.43–1.23‰) to its hybrid rocks (quartz diorite–granodiorite, microgranular magmatic enclaves, composite dykes) – 0.79–1.27‰. However, the range of variability of this feature is quite wide. The minerals have δ74/70Ge values of 1.01–1.04‰ in quartz, 0.84–0.90‰ in alkali feldspars, 0.76–0.88‰ in plagioclase, and 0.36–0.39‰ in biotite. The thermal waters are enriched in heavy Ge isotopes (δ74/70Ge of 1.21–2.78‰) relative to the aquifer rocks (δ74/70Ge of 0.43–1.27‰). Currently, the most likely explanation for this is the influence of secondary mineral phases formed in the geothermal granitic system. This comprises the preferential incorporation and adsorption of light Ge isotopes in/onto iron oxide/hydroxides and clay minerals. The other theoretical explanation, i.e., sulfide formation, is unlikely due to the unfavourable hydrogeochemical conditions in the studied system. The δ74/70Ge values of thermal waters are similar to those of previously studied continental geothermal waters (1.65–3.29‰; Siebert et al., 2011) and fresh groundwater (2.24–4.02‰; Baronas et al., 2020), confirming that groundwater enrichment in heavy Ge isotopes relative to aquifer rocks may be widespread in the upper continental crust. Variation in the isotopic composition of the studied thermal waters is a result of the aquifer rock mineralogy and, in some cases, mixing of the old deep-circulating thermal water with the shallow modern cold groundwater. The general similarities in the chemical composition of the studied waters are due to the influence of porphyritic granite, which is the dominant rock type in this aquifer system. Some differences in chemical composition, including differences in the Ge isotopic composition, are related to the local distribution of hybrid rocks and sulfides. The δ74/70Ge and Ge/Si ratios have been shown to be sensitive indicators of local hydrogeochemical conditions in an alimentation zone and a near-borehole zone of particular water intakes.

Geochemical and H–O–Sr–B isotope signatures of Yangyi geothermal fields: implications for the evolution of thermal fluids in fracture-controlled type geothermal system, Tibet, China

High-temperature hydrothermal systems are mainly distributed in the north–south graben systems of southern Tibet as an important part of the Mediterranean–Tethys Himalayan geothermal belt in mainland China. As the largest unit capacity and second stable operating geothermal power station in China, Yangyi is the fracture-controlled type geothermal field in the center of Yadong–Gulu Graben. In this paper, hydrogeological and hydrochemical characteristics, isotope composition (δD and δ18O, 87Sr/86Sr and δ11B) of borehole water, hot springs, and surface river samples were analyzed. From the conservative elements (such as Cl− and Li+) and δD and δ18O values, the geothermal water of the Yangyi high-temperature geothermal field is estimated to be of meteoric origin with the contributions of chemical components of the magmatic fluid, which is provided by partially molten granite as a shallow magmatic heat source. According to logging data, the geothermal gradient and terrestrial heat flow value of the Yangyi high-temperature geothermal field are 6.48 ℃/100 m and 158.37 mW m−2, respectively. Combining the hydrothermal tracer experiment, 87Sr/86Sr and δ11B ratios obtained with gradually decreasing reservoir temperatures from the Bujiemu stream geothermal zone to Qialagai stream geothermal zone, we suggested the deep geothermal waters were mixed with local cold groundwater and then flow northeastward, forming the shallow reservoir within the crushed zone and intersect spot of faults in the Himalayan granitoid. Furthermore, in the process of ascent, the geothermal water is enriched in K+, Na+, and HCO3− during the interaction with underlying Himalayan granitoid and pyroclastic rocks that occur as wall rocks. The detailed description and extensive discussion are of great significance for the further exploitation and utilization of north–south trending geothermal belts in Tibet.

Environmental Adaptation of Psychrophilic Bacteria Subtercola spp. Isolated from Various Cryospheric Habitats.

Subtercola boreus K300T is a novel psychrophilic strain that wasisolated from permanently cold groundwater in Finland andhas also been found in several places in Antarctica including lake, soil, and rocks. We performed genomic and transcriptomic analyses of 5 strains from Antarctica and a type strain to understand their adaptation to different environments. Interestingly, the isolates from rocks showed a low growth rate and smaller genome size than strains from the other isolation sources (lake, soil, and groundwater). Based on these habitat-dependent characteristics, the strains could be classified into two ecotypes, which showed differences in energy production, signal transduction, and transcription in the clusters of orthologous groups of proteins (COGs) functional category. In addition, expression pattern changes revealed differences in metabolic processes, including uric acid metabolism, DNA repair, major facilitator superfamily (MFS) transporters, and xylose degradation, depending on the nutritional status of their habitats. These findings provide crucial insights into the environmental adaptation of bacteria, highlighting genetic diversity and regulatory mechanisms that enable them to thrive in the cryosphere.

Multi-parametric observations of intermittent hydrothermal water discharge in West Crater of Iwo-Yama volcano, Kirishima Volcanic Complex, Japan

From April to July 2021, West Crater at Iwo-Yama, Kirishima Volcanic Complex, Japan, was repeatedly filled with hydrothermal water and subsequently evacuated. The overall cycle lasted 14–70 h, and the course of a single cycle followed this sequence of phases: (i) steam effusion disappeared 20–40 min before hydrothermal water discharge; (ii) hydrothermal water discharge occurred, generating a hydrothermal water pool; (iii) steam effusion resumed and gradually increased; and (iv) drain-back (evacuation) of the hydrothermal water occurred 1–1.5 h before the onset of the next hydrothermal water discharge. We used multi-parametric observations (optical camera, thermometer, electric self-potential (SP) electrodes, seismometer, acoustic sensor, and tiltmeter) to investigate the cause of the cyclic hydrothermal water discharge. A change in SP data occurred approximately 2 h before the onset of hydrothermal water discharge. However, the change in SP was small when hydrothermal water discharge did not occur. The temporal change in SP is inferred to have been caused by groundwater flow through the region below West Crater, implying that groundwater flow was occurring 2 h before hydrothermal water discharge. The polarity of SP change suggests that groundwater flowed toward the region underlying the vents. Seismic signals in the frequency range of < 20 Hz decreased 15–45 min after the onset of change in SP. This seismic signal pattern is inferred to have been caused by bubble activity in boiling fluid. We interpret that the inflow of cold groundwater inhibited boiling activity in the conduit, which in turn caused the cessation of both steam effusion and seismic activity. SP data suggest that the inflow of cold groundwater gradually decreased before hydrothermal water discharge. Pressurization sufficient to force the water in the upper part of the conduit to ascend could have built up in the lower part of the conduit owing to a decrease in the input of groundwater into the upper part of the conduit and the continuing supply of steam bubbles and hot water. This increase in pressure finally led to hydrothermal water discharge at the surface. We suggest that the inflow of cold groundwater into the geyser conduit was the key control on the occurrence and cyclicity of hydrothermal water discharge in West Crater at Iwo-Yama.Graphical

Real‐Time Monitoring and Postprocessing of Thermal Infrared Video Images for Sampling and Mapping Groundwater Discharge

AbstractGroundwater discharge along channels can affect stream discharge, chemistry, and ecological communities. Although the spatial distribution of groundwater springs along wide rivers can be investigated by areal thermal infrared (TIR) remote sensing, this technique is difficult to apply to mapping at a high spatial resolution and under riparian tree canopies. We present a real‐time monitoring and postprocessing method of ground‐based TIR video for determining groundwater discharge sampling points and mapping the surface water temperature. We applied this method to mapping two headwater streams in Hokkaido, Japan, in the summer. The first site was a 1.3‐km‐long reach underlain by Pleistocene andesite lava. Almost all of the springs were colder and had a different chemistry compared to that of the stream water, which supports the usefulness of TIR monitoring for determining groundwater discharge zones. Video postprocessing showed that cold groundwater springs were spaced every ∼100 m, and their distribution did not follow the topography. At the second site, cold and warm springs were underlain by Holocene volcanic ash. The cold springs mainly seeped from hyporheic and riparian zones downstream, while warm springs were at the footslope. Some cold springs had much higher solute concentrations than the stream and warm springs, which suggests that the water temperature is useful for inferring sources of groundwater discharge. At this site, the video postprocessing could map not only the locations of the cold springs but also the spatial heterogeneity of the stream temperature associated with groundwater inputs.

Fluoride occurrence in geothermal water of fault zone area, Southeast China

Fluoride (F−) is a common trace component in groundwater, and long-term exposure to high-F− groundwater is harmful to human health. Fluoride concentrations that exceed the World Health Organization guideline for drinking water (1.5 mg/L) have been detected in thermal and non-thermal groundwater from Southeast China, where the causes of the high fluoride occurrence are lack of study. To study the formation and migration mechanism of high fluoride groundwater from Southeast China, we carried out a systemic sampling of water samples in the surrounding area of Heyuan deep fault zone and Zijin-Boluo fault zone, then a comprehensive discussion including water hydrogeochemical, stable isotope composition, as well as hydrogeology analysis was conducted. Fluoride concentrations in geothermal and non-thermal water samples range from 1.11 to 22.76 mg/L and 0.04–8.3 mg/L, respectively. High temperature, alkaline conditions, and the depleted Ca2+ by reverse cation exchange and calcite precipitation would promote the release of fluoride from host rock to geothermal water. The availability of Ca-bearing and F-bearing minerals in host rock causes significant differences in fluoride concentrations between carbonate reservoir and granite reservoir. Hydrochemical diagrams reveal that the composition of groundwater is affected by mixing and that fractures act as the mixing channels in our study area. The addition of cold groundwater limits the fluoride concentrations by lowing temperature and increasing Ca2+ levels of geothermal water. Additionally, the relationship between F− and SiO2 indicates that geothermal water promotes the fluoride enrichment in cold groundwater, especially in confined aquifers which are more susceptible to geothermal water. The direct input of geothermal fluoride and secondary enrichment caused by alkaline condition contribute to the formation of high F− concentrations (7.2−8.3 mg/L) in confined groundwater. Our findings highlight that the natural evolution of geothermal systems in fault zone can result in the formation of geogenic contaminated groundwater.

Underlying geology and climate interactively shape climate change refugia in mountain streams

AbstractIdentifying climate‐change refugia is a key adaptation strategy for reducing global warming impacts. Knowledge of the effects of underlying geology on thermal regime along climate gradients and the ecological responses to the geology‐controlled thermal regime is essential to plan appropriate climate adaptation strategies. In the present study, the dominance of volcanic rocks in the watershed is used as a landscape‐scale surrogate for cold groundwater inputs to clarify the importance of underlying geology in stream ecosystems along climate gradients. First, using hundreds of monitoring stations distributed across multiple catchments, we explored the relationship between watershed geology and the mean summer water temperature of mountain streams along climate gradients in the Japanese archipelago. Mean summer water temperature was explained by the interaction between the watershed geology and climate in addition to independent effects. The cooling effect supported by volcanic rocks reached up to 3.3°C among study regions, which was more pronounced in streams with less summer precipitation or lower air temperatures. Next, we examined the function of volcanic streams as cold refugia under contemporary and future climatic conditions. Community composition analyses revealed that volcanic streams hosted distinct stream communities composed of more cold‐water species compared with nonvolcanic streams. Scenario analyses based on multiple global climate models and Representative Concentration Pathways (RCPs) revealed a geology‐related pattern of thermal habitat loss for cold‐water species. Nonvolcanic streams rapidly declined in thermally suitable habitats for lotic sculpins even under the lowest emission scenario (RCP 2.6). In contrast, most volcanic streams will be sustained below the thermal threshold, especially for low‐ and mid‐level emission scenarios (RCP 2.6, 4.5). However, the distinct stream community in volcanic streams and geology‐dependent habitat loss for lotic sculpins was not uniform and were more pronounced in streams with less summer precipitation or lower air temperatures. These findings highlight that underlying geology, climate variability, and their interaction should be considered simultaneously for the effective management of climate‐change refugia in mountain streams.

Formation of the hydrothermal system from granite reservoir for power generation in igneous rock areas of South China

Hydrothermal systems occurring in granite reservoir widely exist over the world, but those can continuously supply large quantities of hot water with certain temperature for power generation are rare, e.g., TangKeng geothermal system in South China. It is unclear how the granite reservoir keeps this kind of large natural yield of geothermal water with stable temperature and the genesis study is of great importance to find similar geothermal fields for further exploitation. This paper aims to discuss the formation of TangKeng geothermal system in granite of Cretaceous period, with emphasis on heat sources, geothermal fluid circulation and reservoir temperature. Results show that average regional heat flow of 72.2 mW/m2 is composed by almost equal contribution from heat production of radioactive elements in crust and conductive heat of mantle. Extension and thinning processes of lithosphere and upwelling of magma in the asthenosphere caused the thermal erosion of the upper mantle and lower crust but doesn't induce the formation of magma chamber or partial molten in the upper crust and had very limited influences on the regional thermal state. Heat flow of the crust is mainly composed by intrusive granite pluton with high heat production value in the surface and the felsic upper crust. Geothermal fluid is recharged by the local precipitation from the surrounding mountains through regional developed NE and NW faults system. The crushed fine-middle grained biotite granite or granite with fractures and fissures of Mesozoic period provide excellent reservoir for water circulation. Interactions between regional faults and fractures in granites provide excellent conduits for additional recharge from shallow groundwater which is continuously recharged by the Rong Jiang River water during the ascending process. Reservoir temperature is calculated to be about 140–143 °C with correction of slightly CO2 degassing and mixing. Missing of caprock for most of the areas and mixing with cold groundwater during ascending process led to the occurrence of geothermal water with lower temperature of 92 °C collected at the surface.Fractured granite reservoir with high heat productivity from radioactive elements, well developed NE and NW oriented faults system and continuous recharge from local precipitation and surface water nearby are essential for the formation of this kind of hydrothermal system.

Creation of geomechanical block model of Severomuysky Tunnel area in Micromine Origin &amp; Beyond

In 2016 Russian Railways made a decision to reconstruct the upper structure of the track and drainageand-transport adit in Severomuysky Tunnel in order to mitigate the impacts of adverse factors and to increase the tunnel capacity. As a rule, such work goes with the creation of a 3D model of subsoil in the area of reconstruction. The area of Severomuysky Tunnel features difficult geological and geotectonic conditions. The seismically active zones, subvertical tectonic delamination of granitoid rock mass in the Baikal Mega Dome, as well as the thermal and cold groundwater complicate operation and require special control activities to be undertaken. Creation of the geomechanical model is discussed, the modeling stages are described, the source data of the modeling are given, and the calculation procedure to find geomechanical determinants for the modeling is delineated. The modeling is performed in geological and mining information system Micromine Origin &amp; Beyond. Visualization of distribution of quantitative data on rock mass quality and real-time updating of the model when new geomechanical observations arrive allow enhancing quality of project solutions, including designs of tunnel lining and new underground openings. With the block model at hand, it is possible to identify hazardous areas in rock mass and to predict rock mass damages in three and in two dimensions. The geological and mining information systems are usable both in solid mineral mining and in construction / reconstruction of various-purpose underground structures. At the comparatively low labor cost of modeling, specialists gain an offing to improve essentially the computational accuracy and to minimize the risks associated with construction and operation of objects in difficult geotechnical conditions.

Косейсмические временные вариации термофильного элемента Si подземных вод западного побережья оз. Байкал в 2012–2022 гг.

The results of monitoring concentrations of the thermophilic element Si in fresh subthermal and cold groundwaters from the Kultuk polygon with a temperature range at the output from ca. 0 to 20 °C are presented. A stepwise zonal increase in the Si concentration is recognized in groundwaters of the polygon centered at station 40. In this center of the Kultuk hydrothermal reservoir, the minimum temperature of 25 °С on September 17, 2014 (before the earthquakes of 2014–2015) and the maximum temperature of 60 °С on January 23, 2021 (11 days after the strongest Khubsugul earthquake Mw=6.8) is obtained using the chalcedony geothermometer. It is proposed that groundwater came from the deep Kultuk reservoir with elevated temperature during the strong Kultuk seismic reactivation (August 27, 2008 – January 04, 2011) and changed to those with a lower temperature during the weak Tolbazikha one (June 24, 2011 – October 11, 2012) reaching a temperature minimum by 2014. Then the inflow of groundwaters with elevated temperature was revived again during the preparation and implementation of the Baikal-Khubsugul seismic reactivation that was marked by strong earthquakes in 2020–2022.

Горячинская активизация Ямбуйской зоны транстенсии в 2013–2015 гг.: Косейсмическая химическая гидрогеодинамика подземных вод на ЮВ побережье Среднего Байкала

Variations of Si, Na, Li, 234U activity, and 234U/238U activity ratio in thermal and cold groundwaters, as well as cooled hydrotherms from active faults in the SE coastal area of Middle Baikal are considered. For the Maksimikha area, hydrogeochemical monitoring data of 2013–2015 with interpretation in terms of chemical hydrogeodynamics: temperature, depth of water reservoir and opening–closing of microcracks for circulating water. When comparing series of hydrogeochemical monitoring with a series of earthquakes K = 10.5–12.7 of the Goryachinsk seismic reactivation in Middle Baikal, an increased sensitivity of responses to earthquakes at the station of cooled hydrotherms from the transition zone of the lower hydrogeodynamic floor is revealed in comparison with the responses of fracture-derived cold water from the upper floor. The Maksimikha groundwater reservoir is considered as a representative reservoir located along the in the Yambuy transtension zone that is lateral structure of the South Baikal basin. Coseismic hydrogeodynamics of the Maksimikha reservoir in 2013–2015 is referred to the time interval preceding the landmark Goloustnoye earthquake on September 05, 2015, which corresponded to the conditions of maximum compression of the crust of the Kultuk reservoir, localized at the main structural line of the Baikal Rift System, in the 2008–2020 seismogeodynamic cycle.

Hydrogeochemical pattern and environmental isotope hydrology of coastal Bademli geothermal area (BGA) in western Turkey (Dikili-İzmir): A new geothermal prospect

Bademli geothermal area (BGA) is located on the coastline of Dikili-İzmir province and consists of Bademli spring and Hayıtlı areas with 36.8-51°C discharge temperatures, respectively. The waters of Hayıtlı borehole have remarkable seawater mixing ratios like Bademli spring and have Na-Cl water type. Dikili group pyroclastic volcanic units constitute the reservoir rock in the entire geothermal area. The heat source is relatively elevated geothermal gradient caused by extensional tectonics forming E-W trending grabens. Bademli thermal water is plotted in the "immature waters" area in the Na-K-Mg triangular diagram with a calculated seawater contribution of 18%. Therefore, some cation geothermometers are considered unreliable. On the other hand, the silica-enthalpy diagram showed an anticipated reservoir temperature of approximately 240 °C. Hayıtlı borehole water sample is plotted on the "partially equilibrated waters" area in the same triangular diagram and shows a reservoir temperature of 208 °C. The seawater contribution in the Hayıtlı area (16%) is less than the Bademli spring. On the other hand, based on the K/Mg geothermometry, the reservoir temperatures for Bademli spring and Hayıtlı borehole waters are 129 °C and 138 °C, respectively. B, Fe, Mn, and Sb concentrations exceed the tolerance limits of the EPA and Turkish drinking water standards in the area. In addition, due to silica-rich volcanic rocks, Ge solubility increased with temperature in thermal waters and reached 34-45 μg/L. Enrichment of δ1818O and δ2D values can be observed in Bademli spring and Hayıtlı with -3.70‰ and -4.63‰, and -34.5‰ and -37.9‰, respectively. From the chemical and isotopic results, it can be clearly said that this coastal geothermal area is high enthalpy, as evident from the equilibrium temperatures. However, when the thermal water rises to the surface, it mixes with both cold groundwater and modern seawater resulting in a decrease of the discharge temperatures of the springs. Moreover, according to the isotopic and hydrogeochemical data, the area has a high potential for thermal heating of the settlements in the area.

The Genesis Mechanism and Health Risk Assessment of High Boron Water in the Zhaxikang Geothermal Area, South Tibet

The natural discharge of geothermal water containing harmful components affects the water quality of the surrounding environment and brings security risks to drinking water safety. The geothermal water in Tibet is characterized by high boron content, but the water pollution caused by the discharge of this high boron geothermal water is not clear. In this study, we collected geothermal water and surface water from the Zhaxikang geothermal system in southern Tibet to investigate the causes of high boron geothermal water and the water pollution of water quality by its discharge. The results indicate that the hydrochemical type of geothermal water was HCO3-Cl-Na, while that of cold spring water, mine water, river water, and lake water was SO4-HCO3-Ca-Mg. Hydrogen and oxygen isotopes show that the recharge source of cold groundwater was mainly snow-melting water and meteoric water, while in addition to that, there is magmatic water for hot springs. The boron content of geothermal water in the study area is as high as 42.36 mg/L, far exceeding the World Health Organization limit for drinking water (0.5 mg/L). The analysis of ion components and PHREEQC modeling indicated that the dissolution of silicate minerals and cation exchange controlled the composition of groundwater, and the boron in groundwater mainly came from the volatilization of magmatic components and the leaching of shallow sediments. The entropy weight water quality index was used to evaluate the water quality of the study area; about 42.9% of the groundwater samples are of good quality and can be used for drinking, mainly cold water that has not been mixed with geothermal water in the upstream. With the discharge of geothermal water into the river (with a mix ratio of ~20%), the downstream water quality gradually deteriorated. The health risk assessment of drinking water in the study area showed that the hazard index (HI) of drinking water in the mixed area was higher than 1 (with an average of 1.594 for children and 1.366 for adults), indicating that children are at a higher health risk than adults. Geothermal water with high boron content has been found all over the world, and the adverse effects of its natural drainage cannot be ignored.

Effect of Mineral Carriers on Biofilm Formation and Nitrogen Removal Activity by an Indigenous Anammox Community from Cold Groundwater Ecosystem Alone and Bioaugmented with Biomass from a "Warm" Anammox Reactor.

Simple SummaryDuring more than 50 years of exploitation of the sludge repositories near Chepetsky Mechanical Plant (Glazov, Udmurtia, Russia) containing solid wastes of uranium and processed polymetallic concentrate, the soluble compounds entered the upper aquifer due to infiltration. Nowadays, this has resulted in a high level of pollution of the groundwater with reduced and oxidized nitrogen compounds. In this work, quartz, kaolin, and bentonite clays from various deposits were shown to induce biofilm formation and enhance nitrogen removal by an indigenous microbial community capable of anaerobic ammonium oxidation with nitrite (anammox) at low temperatures. The addition of a “warm” anammox community was also effective in further improving nitrogen removal and expanding the list of mineral carriers most suitable for creating a permeable reactive barrier. It has been suggested that the anammox activity is determined by the presence of essential trace elements in the carrier, the morphology of its surface, and most importantly, competition from rapidly growing microbial groups. Future work was discussed to adapt the “warm” anammox community to cold and provide the anammox community with nitrite through a partial denitrification route within the scope of sustainable anammox-based bioremediation of a nitrogen-polluted cold aquifer. In this unique habitat, novel species of anammox bacteria that are adapted to cold and heavy nitrogen pollution can be discovered.The complex pollution of aquifers by reduced and oxidized nitrogen compounds is currently considered one of the urgent environmental problems that require non-standard solutions. This work was a laboratory-scale trial to show the feasibility of using various mineral carriers to create a permeable in situ barrier in cold (10 °C) aquifers with extremely high nitrogen pollution and inhabited by the Candidatus Scalindua-dominated indigenous anammox community. It has been established that for the removal of ammonium and nitrite in situ due to the predominant contribution of the anammox process, quartz, kaolin clays of the Kantatsky and Kamalinsky deposits, bentonite clay of the Berezovsky deposit, and zeolite of the Kholinsky deposit can be used as components of the permeable barrier. Biofouling of natural loams from a contaminated aquifer can also occur under favorable conditions. It has been suggested that the anammox activity is determined by a number of factors, including the presence of the essential trace elements in the carrier and the surface morphology. However, one of the most important factors is competition with other microbial groups that can develop on the surface of the carrier at a faster rate. For this reason, carriers with a high specific surface area and containing the necessary microelements were overgrown with the most rapidly growing microorganisms. Bioaugmentation with a “warm” anammox community from a laboratory reactor dominated by Ca. Kuenenia improved nitrogen removal rates and biofilm formation on most of the mineral carriers, including bentonite clay of the Dinozavrovoye deposit, as well as loamy rock and zeolite-containing tripoli, in addition to carriers that perform best with the indigenous anammox community. The feasibility of coupled partial denitrification–anammox and the adaptation of a “warm” anammox community to low temperatures and hazardous components contained in polluted groundwater prior to bioaugmentation should be the scope of future research to enhance the anammox process in cold, nitrate-rich aquifers.

Phreatic volcanic eruption preceded by observable shallow groundwater flow at Iwo-Yama, Kirishima Volcanic Complex, Japan

It is difficult to forecast phreatic eruptions because they are often characterised by an abrupt onset at shallow depths beneath volcanoes. Here we show that temporal changes in the tilt, tremor, and horizontal electric field have occurred repeatedly near the vent of a small phreatic eruption at Iwo-Yama, Kirishima Volcanic Complex, Japan. Such geophysical changes were observed 13 times, with one of these events occurring immediately before the onset of the 2018 phreatic eruption. These observations suggest that shallow hydrothermal intrusions, which are observed as tilt changes with tremors, commonly induce near-surface cold groundwater flow, which is observed as electric-field changes. Near-surface groundwater flows towards the active vent, potentially inhibiting a phreatic eruption. However, explosive phreatic eruptions occur when the intrusion is shallow and cold groundwater flow is depleted. The near-surface groundwater is key in controlling the occurrence of phreatic eruptions and can be monitored using electric-field measurements.

Hydrogeochemical characteristics and evaluation of the geothermal fluids in the Gazlıgöl geothermal field (Afyonkarahisar), Western Anatolia, Turkey

The Gazlıgöl geothermal field located in 20 km northern of Afyonkarahisar in Western Anatolia region of Turkey is one of the most important geothermal areas in the Afyon-Akşehir Graben on the basis of potential. The present study has been performed to investigate the hydrogeochemical and isotopic characteristics and evaluate the origin, reservoir temperature and processes controlling the chemical composition of thermal waters of the Gazlıgöl geothermal field. Discharge temperature, electrical conductivity and pH of the thermal waters vary from 58.5 to 74 °C, 3910 µS/cm to 4050 µS/cm and, 7.05 to 7.54, respectively. The Gazlıgöl thermal waters are chemically of Na-HCO3 type, with high salinity, while the cold waters have mainly Ca-Mg-HCO3, Ca-Na-HCO3 and Ca-Mg-HCO3-SO4 types, with low salinity. Geochemical processes controlling chemical composition of the thermal waters are mainly water-rock interactions including dissolution and/or weathering of mostly silicates and partially carbonates and ion-exchange reactions. Besides, the bacterial sulfate reduction is another main process leading to the depletion of SO4 in the thermal water. Higher contents of some minor elements in the thermal waters, such as F, B, Li, As and Sr, are probably derived from enhanced water-rock interaction, and the minor elements can be regarded as indicator of residence times and flow paths.Geothermometer applications including quartz geothermometers and SiO2-K2/Mg, mineral saturation state and silica enthalpy mixing models provide the most reliable estimations of reservoir temperature in the varying of 100-150 °C for the Gazlıgöl thermal waters. Accordingly, the Gazlıgöl geothermal system can be classified as a low-moderate geothermal resource. The isotope data (δ18O, δ2H and 3H) of the thermal waters point to their deep circulating meteoric origin, and let estimating of recharge elevation varying from 1300 to 1400 m.a.s.l. These elevations suggest the mountainous region in the north-northeastern of the study area as the recharge area of the geothermal system. Long-term circulation of meteoric waters within the aquifer is confirmed by low tritium ratios (< 1 TU) of the thermal waters although the fluids do not achieve thermodynamic equilibrium. Based on the all gathering data, a conceptual model of the functioning of geothermal system has been constructed. Accordingly, geothermal fluid is heating at deep zones due to the high geothermal gradient caused by active fault systems and heated waters rise toward the shallow levels through faults and fractures. During moving to the surface, they undergo conductive cooling by mixing with the cold groundwater at shallow depths and during contacting with the colder rocks.