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Identification of the hydrochemical characteristics of the groundwater system in the mining area and the controlling factors of the water's chemical components is necessary to protect groundwater resources. In this study, 80 sets of groundwater samples were collected from three aquifers of the Liuzhuang coal mine (northern Anhui Province, China), and a total of eight indicators were selected for quantitative analysis of the chemical components of water. Conventional mathematical and statistical methods and Piper trilinear diagrams show that the cations in the groundwater samples of the mine area are mainly K+ + Na+ (92.4%), while the anions in the Cenozoic and Carboniferous aquifers are mainly Cl−, reaching 57.2% and 55.2%, respectively, and the anions in the Permian aquifer are mainly HCO3- (52.6%). Most of the water chemistry types are Cl-Na, HCO3-Na, and HCO3-Cl-Na. Analysis on the basis of Gibbs plots showed that the aquifer system in the mine area is primarily controlled by the water–rock interaction. The results of ion ratio analysis, principal component analysis, and cluster analysis showed that the dissolution of hydrochloric acid and alternating cation adsorption is more prominent in the Cenozoic and Carboniferous aquifers, while desulfurization is more significant in the Permian aquifer. HIGHLIGHTS This paper is the first to analyze the hydrochemical characteristics and controlling factors of three aquifers in the Liuzhuang coal mine (Northern Anhui Province, China).; The study determines the major cations and anions as well as the types of water chemistry in each aquifer in the study area.; The study shows that the aquifer system in the study area is mainly controlled by water–rock action.; Correlation analysis, ion ratio analysis, principal component analysis and cluster analysis were used to show the hydrochemistry of the three aquifers in the study area and to reasonably infer their genesis.;

Karst aquifers are strategically important as they supply domestic water and are a resource for irrigation and industry in northern China. The heterogeneity of the karst aquifer medium makes it vulnerable to external influences. Here, samples of surface water and groundwater in a typical karst groundwater system of Jinan (China) were collected in December 2021, and the sample data were analyzed to further elucidate the hydrogeochemical processes. Results showed that the predominant water chemical type is HCO3-Ca, with a lesser proportion of type HCO3·SO4-Ca and SO4-Ca. The dominant water–rock interactions comprise the dissolution of carbonate minerals, gypsum, and halite and ion exchange. Dissolution/precipitation of calcite, dolomite, and gypsum determines the concentrations of Ca2+, Mg2+, HCO3-, and SO42-. In terms of spatial distribution, the indirect and direct recharge areas are dominated by calcite dissolution, followed by dolomite dissolution, and are prone to ion exchange. The hydrogeochemical formation mechanism of the discharge area is more complicated by other hydrochemical processes and anthropogenic activities. These results provide guidance for global karst groundwater resource management and pollution prevention. HIGHLIGHTS Study the scientific issues to be solved in the research of hydrogeological characteristics in the process of karst groundwater circulation in Jinan.; Enrich the technical connotation of karst groundwater resource management and pollution prevention.;

The results of hydrochemical studies of Nizhne-Shapinsky (Kipely) CO2-rich thermal (39 °C) springs in 2021 are presented. The springs discharge within the Shchapina graben near active Kizimen volcano. Results include macro- and trace-component composition, isotopic composition of spring water, some gas components and dissolved strontium. The results are discussed using previously published and reported data, taking into account the geological and structural setting of the area, water-rock interactions, and simple thermochemical calculations to explain the rare, but typical for the chemical composition of some CO2-rich waters, predominance of magnesium over calcium. It is shown that waters of Nizhne-Shchapinsky springs are formed as a result of mixing of two components: deeper and more heated sodium chloride water and more superficial, less heated water of Mg-Ca-HCO3- composition, formed due to interaction with carbonate-bearing rocks and CO2 of magmatic origin.

The Sangu Spring Basin is located in an important economic area, and groundwater is the main source of water for local life and industry. Understanding the sources of chemical components in groundwater is important for the development and utilization of groundwater. In this paper, we analyzed the origin of the chemical components of groundwater and their evolution in the Sangu Spring Basin using statistical analysis, Piper diagrams, Gibbs diagrams, ion ratios, and combined hydrochemistry–isotope analyses. The results show that the groundwater in the Sangu Spring Basin is mainly derived from atmospheric precipitation, that the groundwater in stagnant and confined environment zones was formed under colder climatic conditions, and that the surface water (SW) has a close hydraulic relation with the groundwater. Water–rock interaction is the main factor controlling the composition of groundwater. The compositions of groundwater are mainly derived from carbonate weathering, silicate weathering, and dissolution of gypsum. Na+ and K+ in groundwater mainly come from the dissolution of albite and potassium feldspar, rather than rock salt. Ion exchange occurs in karst groundwater (KGW) and fissure groundwater (FGW), and ion exchange is dominated by the exchange of Mg2+ and Ca2+ in the groundwater with Na+ and K+ in the rock or soil. Sulfate in groundwater is derived from dissolution of gypsum, infiltration of atmospheric precipitation, and leakage of SW. Groundwaters with the highest sulfate content are located in the vicinity of SW, as a result of receiving recharge from SW seepage. Groundwaters with higher sulfate contents are located in the stagnant and deeply buried zones, where sulfate is mainly derived from the dissolution of gypsum. SW seepage recharges groundwater, resulting in increased levels of Cl−, NO3− and SO42− in groundwater. These insights can provide assistance in the protection and effective management of groundwater.

During mining, the brittle fracture structure of coal makes it highly susceptible to disturbance, leading to changes in the permeability of the coal seam from non-conductive to water-conductive, which poses a significant threat to the stability and safety of coal pillars in goafs. Therefore, understanding the damage mechanisms of coal during water–rock interactions is crucial for ensuring mine safety. In this paper, based on laboratory seepage tests, the impact of hydrodynamic forces on the microstructure of fissured coal and its subsequent effect on permeability is examined. The study found that increasing confining pressure causes the “closure” of coal fissures, leading to a reduction in permeability. Additionally, during the initial stage of seepage, fine particles within the coal samples are mobilized due to seepage damage, leading to channel blockages and further reductions in permeability. However, as seepage continues, the hydraulic channels eventually open fully, resulting in a sharp increase in permeability. Furthermore, using a two-dimensional fracture seepage model, the study investigated how the scale of fractures in the water-conducting channels influences seepage behavior. A critical fracture width method was proposed to predict permeability surges, offering a new approach for analyzing the stability of coal pillars in mining areas.

Nitrate pollution is a global environmental problem, and mean nitrate levels have risen by an estimated 36% in global waterways since 1990. Tracing nitrate sources is important for water quality management, and nitrate isotopes (δ15N-NO3− and δ18O-NO3−) are commonly used for this purpose because of the different isotopic compositions of different sources. However, the impact of nitrate sorption on matrix and desorption from matrix on N and O isotopic composition of nitrate in liquid phase has not been well clarified. To explore the mechanism for the changes in nitrate concentration and isotopes in liquid phase during sorption and desorption, this study took a shale sample (enriched in clay minerals and commonly exposed in the Earth), conducted a series of laboratory experiments for nitrate sorption and desorption, and studied the impact of sorption and desorption on nitrate N and O isotopic composition in liquid phase. The results showed that the shale sample exhibited a rapid sorption and desorption rate for nitrate in the surface water samples, with the nitrate concentration in the solution decreasing from 14.3 mg/L to 4.1 mg/L within 5 min. The sorption data fit the Langmuir model better than that of the Freundlich model. The maximum possible sorption (Qmax) for the shale sample was estimated to be 46 μg/g. Preliminary laboratory experiments showed that changes in δ15N-NO3− values were not obvious, and changes in δ18O-NO3− values in liquid phase were minor during sorption and desorption of the shale sample, suggesting that nitrogen isotopic fractionation can be neglected, and the sorption of nitrate by the shale sample has a very limited impact on the distribution of nitrate isotopes in liquid phase. However, the impact of nitrate desorption on the nitrate isotopes in liquid phase depends on the isotopic composition of exchangeable nitrate in the solid phase, which may be related to antecedent water–rock interactions. This study provides important information for elucidating the evolution mechanism of nitrate and its isotopic compositions following sorption-desorption, and is conducive to revealing the nitrogen cycle law in the environment.

Zuogong County is located in the southeast of Tibet, which is rich in hot spring geothermal resources, but its development and utilization degree are low, and the genetic mechanism of the geothermal system is not clear. Hydrogeochemical characteristics of geothermal water are of great significance in elucidating the genesis and evolution of geothermal systems, as well as the sustainable development and utilization of geothermal resources. The hydrogeochemical characteristics and genesis of the geothermal water in Zuogong County were investigated using hydrogeochemical analysis, a stable isotope (δD, δ18O) approach, and an inverse simulation model for water–rock reactions using the PHREEQC. The results indicated that the Zuogong geothermal system is a deep circulation heating type without a magmatic heat source. The chemical types present in the geothermal water from the Zuogong area are HCO3 and HCO3·SO4, and the main cations are Na+ and Ca2+. The groundwater is replenished by atmospheric precipitation and glacier meltwater. The salt content of geothermal water mainly comes from the interaction between water and surrounding rocks during the deep circulation process. The reservoir temperature of geothermal water in Zuogong is 120–176 °C before mixing with non-geothermal water and drops to 62–98 °C after mixing with 58 to 79% of non-geothermal water. According to the proposed conceptual model, geothermal water mainly produces water–rock interaction with aluminosilicate minerals in the deep formation, while in shallow areas it interacts mainly with sulfate minerals. These findings contribute to a better understanding of the geothermal system in Zuogong County, Tibet.

The mechanical properties of fissured sandstone will deteriorate under water–rock interaction. It is crucial to extract the precursor information of fissured sandstone instability under water–rock interaction. The potential of each acoustic emission (AE) parameter as a precursor for instability in the failure process of fissured sandstone was investigated in this study. An experimental dataset comprising 586 acoustic emission experiments was established, and subsequent classification training and testing were conducted using three machine learning (ML) models: AdaBoost, MLP, and Random Forest (RF). The primary parameters for identifying the instability risk state of fissured sandstone include acoustic emission ringing count, energy (mV·ms), centroid frequency, peak frequency, Rise Angle (RA), Average Frequency (AF), b value, and the natural/saturated state of fissured sandstone: state. To enhance data utilization, a 10-fold cross-validation method was employed during the model training process. The machine learning models were developed and designed to identify the instability risk of fissured sandstone under the natural and saturated states. The results demonstrated that the established RF model was capable of identifying fissured sandstone instability risks with an accuracy of 97.87%. Feature importance analysis revealed that state and b value exerted the most significant influence on identification results. The Spearman correlation coefficient was utilized to assess the correlation between input features. This study can provide technical support to identify the risk of instability of fissured sandstones under both natural and saturated water conditions. Based on the models developed in this study, it is possible to implement an early warning method for instability in fissured sandstone that meets realistic working conditions. Compared with the traditional empirical and formulaic methods, the machine learning method can more quickly process huge amounts of AE data and accurately identify the damage state of fissured sandstone.

Rare earth elements (REEs) have been used as tracers to reveal the hydrochemical sources and processes in groundwater systems that are usually modified by anthropogenic inputs. However, the REE behaviors in groundwater affected by mining activities have yet to be fully understood. In combination of REE geochemistry with general hydrochemical and isotopic (δ2H and δ18O) methods, this study investigated the concentration and fractionation of REEs in alkaline groundwater from two coal mines with similar aquifer lithology but different mining histories in the Northern Ordos Basin. One of the coal mines started mining in March 2009 (Ningtiaota coal mine, NTT), while the other started mining in December 2018 (Caojiatan coal mine, CJT). Results show that the primary hydrochemical type is HCO3-Ca in NTT groundwater with pH value ranging between 7.68 and 8.60, while CJT groundwater was dominated by the HCO3-Na type with higher pH of 9.09–10.00. The average values of ΣREEs were lower, and the NASC-normalized pattern reflected more intense fractionation in NTT groundwater than those in CJT groundwater. The evident differences are caused by the distinctions in water–rock interaction, complexation of inorganic species, and adsorption of REEs in NTT and CJT groundwater. Furthermore, these processes were closely related to the pH of groundwater that was different in two coal mines, which is likely linked to the different durations of coal mining activities that led to differences in development of rock fractures and pyrite oxidation. It is expected that REEs, combined with other indicators such as pH, can be used to trace and help better understand the hydrochemical changes in groundwater caused by mining. [ABSTRACT FROM AUTHOR]

The wadi dahab delta is in a dry, arid coastal zone within Egypt's south Sinai Peninsula's eastern portion. The primary water source is the Quaternary coastal alluvial aquifer. The groundwater salinity varies from 890 to 8213 mg/L, with a mean value of 3417 mg/L. The dissolved major ions have been used to calculate the seawater mixing index (SWMI) using a linear equation that discriminates the groundwater mostly affected by water–rock interaction (SWMI 1 >) and other samples mixed with Seawater (SWMI < 1). The isotopic composition of groundwater for specifically chosen groundwater samples ranges from −0.645‰ to +5.212‰ for δ18O and from − 9.582‰ to + 22.778‰ for δ2H, where the seawater represented by a Red Sea water sample (δ18O + 1.64‰ − δ2H + 9.80‰) and reject brine water are considerably enriched the isotopic groundwater values. The geochemical NETPATH model constrained by the dissolved significant ions, isotopes, and the rock aquifer forming minerals as phases indicate the mixing percent with the seawater ranges from 9% to 97% of seawater from 91% to 3% of original recharge water. According to the SEAWAT 3-D flow models, seawater has penetrated the Northeastern Dahab delta aquifer, with the intrusion zone extending 1500 m inland. The salt dissolution, upwelling of saline water, recharge from the upstream mountain block, and seawater encroachment are the primary aspects contributing to the deterioration of groundwater quality. These findings may have significance for effective groundwater withdrawal management in arid locations worldwide with similar hydrogeological systems. [ABSTRACT FROM AUTHOR]

The karst geothermal reservoir, Sinian Dengying Formation was investigated from the hydrogeochemical perspective. Integrated techniques including XRD + SEM, isotopes, saturation index and PHREEQC modeling were applied. With 37.3–72 ?, the targeted waters indicate low-mediate temperature geothermal reservoir. The CO2 concentration in the geothermal waters varies from 1.2 mg/L to 52.42 mg/L, and the log(PCO2) value ranges from −2.53 to −1.29, indicating an open carbonate system. A further D-18O stable isotope analysis addresses the geothermal waters are replenished by meteoric water from +815.52 m to +1427.78 m. Strong water-rock interactions are indicated by apparent 18O shift. The dominating hydrochemical type is SO4·HCO3-Ca·Mg with some Cl-Na. The CO2-TDS-SI-Carbonates comprehensive analysis illustrate the origin of Ca2+, Mg2+, and HCO3−, mainly from dolomite. The correlation of 18O-SO42-SI_Gypsum gives sound evidence for the processes of gypsum dissolution. Three inverse models were established and the results showed, that geothermal waters are controlled by two major factors: 1) the adjacent location to salt basin geological profiles with halite dissolution; and 2) the clay minerals such as Na-montmorillonite causing cation exchanges between Na+ and Ca2+ in the geothermal waters, resulting in excess of Na in relation to Cl concentrations. [ABSTRACT FROM AUTHOR]

Hydrothermal circulation around magmatic intrusions affects hazards, critical metal deposition, and heat transfer, however it is often difficult to directly observe. We combine stable isotope and thermochronologic measurements, hydrothermal circulation modeling, and forward thermal history modeling to understand the short-lived hydrothermal circulation system that developed around the Little Devils Postpile, a small-scale mafic intrusion in the eastern Sierra Nevada Mountains of western North America. Bedrock samples collected in transects orthogonal to the intrusion reveal reset and partially reset apatite (U-Th-Sm)/He and zircon (U-Th)/He ages up to ∼13m from the contact. Measurements of hydrogen isotopes in apatite crystals from the same samples show deuterium depletion near the contact; δD values vary between −120‰ and −132‰ within 3m of the contact, −112‰ to −104‰ at 4–6m from the contact, and −85‰ to −95‰ at distances of 12m to 40m from the contact. In contrast, oxygen isotopes do not vary spatially with a δ18O of +6.4 ± 0.4‰. This depletion of δD and consistency of δ18O suggests that short-lived water–rock interaction occurred following the intrusion emplacement, facilitating the exchange of hydrogen isotopes via diffusion rather than dissolution-precipitation processes. Conductive cooling calculations predict an alteration aureole ten times larger than is observed by the low-temperature thermochronometric ages. Numerical models of hydrothermal circulation, for a range of host bedrock permeabilities and magmatic emplacement temperatures, reveal that the geometry of alteration is most consistent with buoyancy-driven hydrothermal circulation and a relatively high crustal permeability. With this case study, we show that combining thermochronology and hydrothermal modeling allows for the opportunity to model hydrogen isotope exchange and predict plausible apatite-water hydrogen fractionation. These new constraints on the geometry of water–rock interactions coupled with hydrothermal circulation modeling provide (1) a rare window into the pressure–temperature evolution of a small magmatic intrusion, (2) constraints on crustal permeability, and (3) a useful tool for interpreting low-temperature thermochronometric data in volcanic settings. [ABSTRACT FROM AUTHOR]

The Pulang super-large porphyry Cu polymetallic deposit, located in the Sanjiang area of Yunnan Province, is one of the largest Cu deposits in China. This deposit hosts Cu resources of ~5 × 106 t and other ore-forming elements, such as Mo, Au, Ag, Pb, Zn, Pt and Pd. Recently, obvious hydrothermal vein-type Pb–Zn mineralization, with a Pb + Zn resource of ~0.4 × 106 t, has been detected in the North Ore Section of the deposit. However, the genesis of these Pb–Zn ore bodies, especially their relationship to the major Cu ore bodies in the South Ore Section, remains controversial. We conducted geologic description, fluid inclusion petrography and microthermometry, and C, H, O and S isotope studies to uncover the genesis of Pb–Zn vein-type mineralization in North Pulang. As a result, three types of Pb–Zn veins were identified: a quartz–pyrrhotite–chalcopyrite–sphalerite–galena vein, a quartz–pyrrhotite–sphalerite–galena vein, and a calcite–quartz–pyrrhotite–galena vein. All fluid inclusions in the quartz from different veins are liquid-rich inclusions, with homogenization temperatures in the range of 184 °C–235 °C and salinities between 10.4 wt.% and 17.8 wt.% NaCl eq., indicating that the Pb–Zn ore-forming fluid was a single-phase fluid with a low temperature and low-to-medium salinity. Hydrothermal quartz in different stages displays δDwater values ranging from −46.9‰ to −120.0‰ (V-SMOW), and the calculated δ18Owater values range from 2.4‰ to 4.3‰ (V-SMOW), implying that the mineralization fluids likely originated from magma, with a minor involvement of meteoric water. The δ13CCal values (−2.3‰ to −7.9‰ V-PDB) of calcite indicate that C likely originated from a deep-seated source. The δ34S values of chalcopyrite, pyrite, pyrrhotite and sphalerite reveal that S was possibly derived from magmatic rocks. Based on the above data, it is suggested that the Pb–Zn mineralization in North Pulang was the result of the northward migration of ore-forming fluids that originated from South Pulang along the NE-trending structural fractures. A strong water–rock interaction occurred during the migration process. However, the involvement of meteoric water and accompanied cooling of fluids were most likely responsible for the precipitation of galena and sphalerite. [ABSTRACT FROM AUTHOR]

The Nuri deposit is the only Cu‐W‐Mo polymetallic deposit with large‐scale WO3 resources in the eastern section of the Gangdese metallogenic belt, Tibet, China. However, the genetic type of this deposit has been controversial since its discovery. Based on a study of the geological characteristics of the deposit, this study presents mineralization stages, focusing on the oxide stage and the quartz‐sulfide stage where scheelite is mainly formed, referred to as Sch‐A and Sch‐B, respectively. Through LA‐ICP‐MS trace element and Sr isotope analyses, the origin, evolutionary process of the ore‐forming fluid and genesis of the ore deposit are investigated. Scanning Electron Microscope‐Cathodoluminescence (SEM‐CL) observations reveal that Sch‐A consists of three generations, with dark gray homogenous Sch‐A1 being replaced by relatively lighter and homogeneous Sch‐A2 and Sch‐A3, with Sch‐A2 displaying a gray CL image color with vague and uneven growth bands and Sch‐A3 has a light gray CL image color with hardly any growth band. In contrast, Sch‐B exhibits a 'core‐rim' structure, with the core part (Sch‐B1) being dark gray and displaying a uniform growth band, while the rim part (Sch‐B2) is light gray and homogeneous. The normalized distribution pattern of rare earth elements in scheelite and Sr isotope data suggest that the early ore‐forming fluid in the Nuri deposit originated from granodiorite porphyry and, later on, some country rock material was mixed in, due to strong water‐rock interaction. Combining the O‐H isotope data further indicates that the ore‐forming fluid in the Nuri deposit originated from magmatic‐hydrothermal sources, with contributions from metamorphic water caused by water‐rock interaction during the mineralization process, as well as later meteoric water. The intense water‐rock interaction likely played a crucial role in the precipitation of scheelite, leading to varying Eu anomalies in different generations of scheelite from the oxide stage to the quartz‐sulfide stage, while also causing a gradual decrease in oxygen fugacity (fO2) and a slow rise in pH value. Additionally, the high Mo and low Sr contents in the scheelite are consistent with typical characteristics of magmatic‐hydrothermal scheelite. Therefore, considering the geological features of the deposit, the geochemical characteristics of scheelite and the O‐H isotope data published previously, it can be concluded that the genesis of the Nuri deposit belongs to porphyry‐skarn deposit. [ABSTRACT FROM AUTHOR]

This work systematically reviews the complex mechanisms of CO2-water-rock interactions, microscopic simulations of reactive transport (dissolution, precipitation and precipitate migration) in porous media, and microscopic simulations of CO2-water-rock system. The work points out the key issues in current research and provides suggestions for future research. After injection of CO2 into underground reservoirs, not only conventional pressure-driven flow and mass transfer processes occur, but also special physicochemical phenomena like dissolution, precipitation, and precipitate migration. The coupling of these processes causes complex changes in permeability and porosity parameters of the porous media. Pore-scale microscopic flow simulations can provide detailed information within the three-dimensional pore and throat space and explicitly observe changes in the fluid-solid interfaces of porous media during reactions. At present, the research has limitations in the decoupling of complex mechanisms, characterization of differential multi-mineral reactions, precipitation generation mechanisms and characterization (crystal nucleation and mineral detachment), simulation methods for precipitation-fluid interaction, and coupling mechanisms of multiple physicochemical processes. In future studies, it is essential to innovate experimental methods to decouple "dissolution-precipitation-precipitate migration" processes, improve the accuracy of experimental testing of minerals geochemical reaction-related parameters, build reliable characterization of various precipitation types, establish precipitation-fluid interaction simulation methods, coordinate the boundary conditions of different physicochemical processes, and, finally, achieve coupled flow simulation of "dissolution-precipitation-precipitate migration" within CO2-water-rock systems. [ABSTRACT FROM AUTHOR]

Complex permeability distribution is frequently encountered in weathered rocks with inherited heterogeneities, such as networks of discontinuities that impact fluid flow and water‐rock interactions. Reactive transport modeling is a powerful tool for analyzing fractured media's chemical weathering dynamics. In this study, two different ways to model the fracture‐matrix interaction were explored. A 1D dual‐porosity simulation of reactive transport is designed to study the global impact of fractures on the weathering progression front, compared with a Single Porosity (S.P.) (unfractured) reference model. Then a 2D discrete model using a Discrete Fracture Matrix (DFM) representation is built to highlight the importance of medium geometry and fracture connectivity on weathering. The relevance of such models was evaluated in the case of weathering processes affecting ultramafic units in New Caledonia. Comparing the average behavior of the dual and S.P. models reveals a similar trend in both global mineralogical evolutions. Yet differences occur when confronting the weathering rates. By extending the weathering over a greater depth, the fractures favor a smoother transition between the saprolite horizon and the oxide ore. Furthermore, a partition of the newly formed phyllosilicates occurs in fractures and matrix: Ni‐phyllosilicates preferentially precipitate in fractures, while Mg‐phyllosilicates remain trapped within the matrix due to differences in residence time and liquid‐to‐solid ratio. The DFM modeling highlights the effect of the connectivity of a complex fracture network on the dissolution‐precipitation processes. Depending on the permeability and geometry, fluid flow is modified, favoring the formation of weathering heterogeneities typically observed on the field. Key Points: Dual Porosity modeling of a fractured rock mass recreates weathering heterogeneitiesWeathering heterogeneities originate from the physico‐chemical differentiation of the fractures and the matrixDiscrete Fracture Matrix modeling reveals the impact of the geometry and permeability of fractures on weathering heterogeneities [ABSTRACT FROM AUTHOR]

Groundwater resources in Mahdia‐Ksour Essef region, located in the central‐eastern part of Tunisia, suffer from intensive exploitation and degradation of water quality. The assessment of groundwater vulnerability, the well‐understanding of geochemical processes and the investigation of groundwater quality variations are of particular importance for water resources management in this semi‐arid region. The results of this multi‐disciplinary investigation show that groundwaters of Mahdia‐Ksour Essef region are flowing from El Jem and Boumerdes regions in the South, towards the Mediterranean Sea and the sebkha of Moknine in the North. The groundwaters are classified as either Na‐Cl or Ca‐SO4. Stable oxygen and hydrogen isotope compositions (δ18O and δ2H) confirm a recharge by rapid water infiltration, evaporate surface water and water‐rock interaction processes in the salinity increase. The rock‐water interaction processes of the mineralization of groundwaters include the cation‐exchange reactions and the dissolution of carbonates and evaporate. The high values of the water quality index (WQI) and of the total dissolved solids (TDS) (3.7–11 g/L) of these groundwaters indicate their unsuitability for drinking purpose. Moreover, the combination of the WQI, TDS and nitrate results prove the vulnerability of the studied groundwater to the anthropogenic pollution linked to agriculture and domestic activities and to the salt water contamination. [ABSTRACT FROM AUTHOR]

The western U.S. is experiencing shifts in recharge due to climate change, and it is currently unclear how hydrologic shifts will impact geochemical weathering and stream concentration–discharge (C–Q) patterns. Hydrologists often use C–Q analyses to assess feedbacks between stream discharge and geochemistry, given abundant stream discharge and chemistry data. Chemostasis is commonly observed, indicating that geochemical controls, rather than changes in discharge, are shaping stream C–Q patterns. However, few C–Q studies investigate how geochemical reactions evolve along groundwater flowpaths before groundwater contributes to streamflow, resulting in potential omission of important C–Q controls such as coupled mineral dissolution and clay precipitation and subsequent cation exchange. Here, we use field observations—including groundwater age, stream discharge, and stream and groundwater chemistry—to analyse C–Q relations in the Manitou Experimental Forest in the Colorado Front Range, USA, a site where chemostasis is observed. We combine field data with laboratory analyses of whole rock and clay x‐ray diffraction and soil cation‐extraction experiments to investigate the role that clays play in influencing stream chemistry. We use Geochemist's Workbench to identify geochemical reactions driving stream chemistry and subsequently suggest how climate change will impact stream C–Q trends. We show that as groundwater age increases, C–Q slope and stream solute response are not impacted. Instead, primary mineral dissolution and subsequent clay precipitation drive strong chemostasis for silica and aluminium and enable cation exchange that buffers calcium and magnesium concentrations, leading to weak chemostatic behaviour for divalent cations. The influence of clays on stream C–Q highlights the importance of delineating geochemical controls along flowpaths, as upgradient mineral dissolution and clay precipitation enable downgradient cation exchange. Our results suggest that geochemical reactions will not be impacted by future decreasing flows, and thus where chemostasis currently exists, it will continue to persist despite changes in recharge. [ABSTRACT FROM AUTHOR]

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The northern part of Zhangqiu district in Jinnan City has developed a thick sedimentary formation from the late Paleozoic to the Cenozoic. In this district, relatively well-developed fault structures and magmatic rocks provide good geothermal conditions. Abundant geothermal resources have been discovered in the study area, with three geothermal wells located near the fault zone. Therefore, establishing the genesis model of geothermal resources is significant for their future sustainable development and utilization. Based on hydrochemical and isotopic data of the study area, hydrochemical characteristics, water-rock interaction process, recharge source and formation age of geothermal water have been analyzed in this study. Besides, the elevation of the recharge area, thermal reservoir temperature, and depth of hot water circulation have also been calculated. Research findings show that geothermal water in the study area is composed of Cl·SO4-Na·Ca or SO4·Cl-Ca·Na, whose hydrochemical components mainly come from water-rock dissolution in the similar hydrogeochemical process. The source of water recharge is supplied by atmospheric precipitation, at an elevation from +563 m to +616 m. The 14C apparent age ranges from 5.55 ka to 29.71 ka. The geothermal water is mixed with modern water and ancient water. The chalcedony temperature scale shows that the temperature of geothermal reservoir is at 41.9-52.4 °, with the circulation depth of geothermal water at 622-1,565 m. The study area is a small-opened karst hot reservoir with deep circulation, during which geothermal water is heated up. Formation and enrichment of geothermal water are significantly controlled by fault structures. The geothermal reservoir is of stratified and banded type, belonging to geothermal resources at medium-low temperature. [ABSTRACT FROM AUTHOR]

In order to study the influence of water–rock interaction on the mass time-varying characteristics of coal rocks, coal was selected as the research object and subjected to chemical immersion tests with different pH aqueous solutions for 12 days. By experiment, the time-varying patterns of mass change fraction in coal samples, pH value in solution, and ions concentration of calcium and magnesium were obtained. Based on the gray correlation theory, the correlation degree between the mass change fraction and four influencing factors was analyzed. The gray prediction models for the mass time-varying characteristics of coal rocks have been established. The research shows that: (1) the influence ways and degree of different pH aqueous solutions on the mass changes of coal rocks are different, (2) during the process of water–rock interaction, the change law of pH value, ions concentration of calcium and magnesium in solution are obvious, (3) the multiple regression models can be used to predict the mass change of coal rocks accurately under water–rock interaction. [ABSTRACT FROM AUTHOR]

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During the establishment of the coal mine goaf reservoir, the strength of the coal pillar dam was weakened by various water–rock interactions triggered by water movement. To explore the influence of the water-bearing state on the shear characteristics of coal pillar dams, the 2–2 coal seam of Shangwan Coal Mine in the Shendong Mining area was taken as the research object and was prepared to coal samples with different moisture contents and different drying-saturation cycles, and the variable angle shear test of coal samples was carried out. The law of water absorption of coal samples under natural and pressurized conditions is obtained. The research results show that the shear characteristics of coal samples change significantly under the action of water, with the increase of moisture content and drying-saturation cycles, the lower the shear strength of coal samples is, the larger the peak shear strain is, and the cohesion and internal friction angle of coal samples decrease linearly. According to the relationship between cohesion, internal friction angle, moisture content, and drying-saturation cycle times, the Mohr–Coulomb model of coal samples considering moisture content and immersion times is established, which contributes to the load-bearing capacity estimation of water-bearing coal mass. Additionally, scanning electron microscope analysis revealed significant changes in the microstructure of coal samples under different moisture states: as the moisture content and dry-saturation cycles increase, the microstructure of the coal samples gradually transforms from orderly and compact to disordered and murky, elucidating the mechanism by which moisture weakens the mechanical properties of the coal samples. The research results provide a useful reference for engineering problems related to the stability evaluation of coal bodies involving the repeated erosion effect of water. [ABSTRACT FROM AUTHOR]

The geochemical characterization and evolution of shallow groundwater in the Zihe River source area is a key issue that needs to be addressed. In this study, a combination of traditional geochemical techniques and geochemical modeling was used to explain the geochemical processes and major ion sources in the chemical evolution of shallow groundwater in the Zihe River source area, Northeast China. Fifty-seven water samples were collected in June 2020 for chemical analysis, and the results showed that the main groundwater chemistry types in the three major aquifers are HCO3·SO4-Ca·Mg-type pore water from loose quaternary rocks, HCO3·SO4-Ca·Mg-type karstic fissure water from carbonate rocks, and HCO3·SO4-Ca-type weathered fissure water from massive rocks. Water–rock interactions in alkaline environments were the main causes of changes in groundwater chemistry. Rock weathering dominated the geochemical evolution of each aquifer. The analysis of ion concentration ratios and modeling revealed that the aquifer's chemical components are mainly derived from the dissolution of dolomite and calcite and partly from the infiltration of pollutants containing C l − and N O 3 − , as well as from the dissolution of quartz. Mg2+ is derived from the dissolution of dolomite. H C O 3 − is primarily derived from the co-dissolution of calcite and dolomite, and to a lesser extent, its content is also influenced by the recharge of rainfall. S O 4 2 − has two sources: it mainly originates from the dissolution of gypsum and the anhydrite layer, followed by atmospheric precipitation. The synthesis showed that the groundwater quality in the source area of Zihe River is good, all the indices reached the standard of class III groundwater quality, and the overall degree of human pollution is low. The results of this research will provide a scientific basis for the local authorities to delineate karst groundwater protection zones in the Zihe River source area and to formulate resource management strategies for the development, utilization, and protection of karst groundwater. [ABSTRACT FROM AUTHOR]

Understanding the hydrological processes of dissolved organic matter (DOM) in the surface karst zone is crucial for the utilization and safety of groundwater resources. However, research on DOM in drip water from karst caves is limited. In this study, continuous monitoring was conducted for four years at four drip water monitoring sites (MP1, MP2, MP3, and MP9) in Furong Cave, Southwest China. The three-dimensional fluorescence excitation–emission spectroscopy (3D-EEM) and fluorescence region integration (FRI) methods were employed, along with correlation analysis, to investigate the spectral characteristics, composition, sources, and influencing factors of the DOM in the drip water of Furong Cave. The results indicated that (1) the three-dimensional fluorescence peaks in the drip water were classified into six categories: A, B, C, T, Ti, and M. (2) The dominant source of the drip water DOM is endogenous organic matter. (3) The FRI analysis indicates a relatively high proportion of Type II substances in the drip water, predominantly composed of tryptophan-like substances. (4) The DOM in the drip water of Furong Cave was influenced by various factors, including the mixing effect of "new" and "old" water, water residence time in karst systems, and water–rock interactions (WRI), resulting in the complex responses of drip rates and DOM to surface precipitation and temperature at different drip water sites. This study provides a reference for comparative research on DOM in cave drip water in karst regions, which contributes to a better understanding of the migration mechanism of DOM in karst aquifers under different climate and karst ecological conditions. [ABSTRACT FROM AUTHOR]

Both igneous and sedimentary rocks affected by water–rock interaction commonly form rhythmic Fe‐oxide bands that provide information on palaeo‐groundwater. This study investigated the formation of Fe‐oxide banded patterns of concentrically banded concretions from the Jurassic Navajo Sandstone (United States) and banded claystone 'zebra rock' from the Neoproterozoic Johnny Cake Shale Member (Western Australia). Micro‐X‐ray fluorescence imaging of both samples revealed uniformly banded patterns of asymmetrical Fe content peaks. This study proposes that their formations were caused by diffusion, with a pH buffering reaction of Fe2+ and O2 due to dissolution of earlier materials by acidic fluids. Based on the model, it is suggested that the acid fluids for Navajo diffused towards the inner side of the concretion, and that for Kimberley they penetrated oblique or perpendicular to bedding. In addition, the Fe‐oxide precipitation has resulted from pH rises of acidic fluids because of diagenetic alteration of earlier calcite concretion in Navajo and that of earlier pyrite‐bearing claystone in Kimberley. The interpretation for Kimberley is based on the δ34S values (<−20‰) of zebra rock, suggesting that the alunite and Fe‐oxide resulted from the supply of SO42− and Fe2+ produced as a result of pyrite oxidation in earlier rocks. The formation rate of the Fe‐oxide band was estimated from the constant width of the Fe peaks and the expected diffusion coefficient for Fe2+ through the rock matrix, and it was found to be on the order of years for Navajo and on the order of tens of years for Kimberley. [ABSTRACT FROM AUTHOR]

Investigating deformation behavior of fractured reservoir bank slopes during impoundment plays an essential role in safety control of high arch dams. Because of changes in water levels during impoundment, the fractures are subjected to varying water pressure and cyclic wetting–drying conditions. In this numerical study, mechanical, physical, and chemical water–rock interactions in rock fractures are incorporated into discrete element modeling of fractured reservoir bank slopes, and effects of mechanical, physical, and chemical water–rock interactions on deformation of fractured reservoir bank slopes are investigated based on a case study of valley deformation at the Xiluodu Hydropower Station. The mechanical water–rock interaction is considered by the effective stress law, while the physical and chemical water–rock interactions are modeled by some empirical deterioration laws. The results showed that the modeled and monitored deformation behaviors of fractured reservoir bank slopes are in good agreement. The slip of shear zones due to water pressure elevation and mechanical parameter weakening is the main reason of impoundment-induced valley contraction. Discrete element method considering water–rock interactions can serve as a robust and reasonable tool to predict the deformation magnitude of fractured reservoir bank slope. Highlights: Mechanical, physical and chemical water–rock interactions in rock fractures are incorporated into discrete element modeling of fractured reservoir bank slopes. Four scenarios are designed to understand the role of mechanical, physical and chemical water–rock interactions on deformation of fractured reservoir bank slopes. The slip of shear zones due to water pressure elevation and mechanical parameter weakening is the main reason of impoundment-induced valley contraction. [ABSTRACT FROM AUTHOR]

The study deals with the hydrochemistry (EC, DO, pH, HCO3-, SO4-2, Cl-, Ca2+, Mg+, Na+, and K+) and isotopic studies (18O, 2H, and 3 H) of the groundwater of the Thal Doab, between River Indus and Jhelum, to delineate the sources of recharge and quality of groundwater. The groundwater based on isotopic data is recharged by two sources: the Indus River and rainfall shown by the depleted and enriched isotopic concentrations. The tritium concentrations revealed the short residence time of shallow groundwater as compared to the deeper groundwater. Furthermore, a deep groundwater upwelling zone has also been identified. Furthermore, it was found that the groundwater evolved in response to rock-water interaction, evaporation, precipitation, land use changes, and other anthropogenic activities. The groundwater system in the Chashma area is relatively safe for consumption. Future planning for the groundwater recharge zones should be the priority areas for protection, by the government water management and public health departments. [ABSTRACT FROM AUTHOR]

In order to reveal the characteristics of groundwater circulation in a typical basin in the mine area, the groundwater of different aquifers in Fuyuan Laochang Town, east of Qujing City, Yunnan Province, was taken as the research object. The recharge characteristics of groundwater in the study area were determined, and the material sources of the main constituents of groundwater were identified. Also, the water-rock interaction processes occurring in the study area were identified by analyzing conventional water chemistry and hydrogen and oxygen isotopes. The results show that the anions of water samples in the study area are mainly SO42- and HCO3-, while the cations are mainly Na+, Ca2+ and Mg2+. The groundwater in the study area is mainly recharged by local atmospheric precipitation, and water vapor condensation may exist in the pit water and some underground water samples. The water-rock interaction in the study area is dominated by the lixiviation of carbonate and sulfate minerals, accompanied by silicate lixiviation and ion exchange, and the groundwater is mainly controlled by rock weathering. Domestic sewage and coal mining activities lead to the content increase of NO3- and SO42- in groundwater, as well as the excess of iron and manganese ions. The corresponding results can provide a scientific basis for the protection, development, and utilization management of local groundwater resources. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nitrate contamination in groundwater is widespread, and studying the extent of contamination and its health risk effects on the population is beneficial for groundwater protection. In this study, 130 groundwater samples collected from the western Sichuan Basin were analyzed for hydrochemical spatial distribution, groundwater quality, and probabilistic health risk. Piper diagram showed that the hydrochemical type of groundwater samples was Ca-HCO3. The hydrochemical components were mainly controlled by carbonate dissolution, silicate weathering and cation exchange based on ion ratios and saturation index. The statistical and spatial analysis showed that the concentration of NO3− exceeded the permission limit for drinking purpose in the central and eastern parts of the study area. The EWQI results showed that about 90.84% of the water samples were of excellent and good quality for drinking purpose. The HI-total values showed that, about 37.40% of samples yielded health risks above the limit value 1 for children. And the percentages of samples were 22.90% and 29.77% for adult females and adult males, respectively. Spatial analysis indicated the samples unsuitable for drinking were concentrated on the cultivated areas of low-hill landform where nitrogen fertilizers were used. Therefore, more attention of groundwater protection should be paid in the central and eastern cultivated areas of low-hill landform. The achievements would provide a vital reference for groundwater management in Sichuan Basin and other similar areas in the world. [ABSTRACT FROM AUTHOR]

The Hutuo River Drinking Water Source Area is an important water source of Shijiazhuang (North China Plain). Knowing the characteristics of groundwater chemistry/quality is essential for the protection and management of water resources. However, there are few studies focused on the groundwater chemistry evolution over the drinking water area. In this study, total of 160 groundwater samples were collected in November 2021, and the spatial distribution of groundwater chemistry and related controlling factors were analyzed using hydrological and multivariate analysis. The entropy-weighted water quality index (EWQI) was introduced to assess the groundwater quality. The results show that the hydrogeochemical types of groundwater are Ca-HCO3 (78.1%), mixed Ca-Mg-Cl (20%), and Ca-Cl (1.9%) in the area. Graphical and binary diagrams indicate that groundwater hydrochemistry is mainly controlled by water–rock interaction (i.e., rock weathering, mineral dissolution, and ion exchange). Five principal components separated from the principal component analysis represent the rock–water interaction and agricultural return, redox environment, geogenic sources, the utilization of agricultural fertilizer, the weathering of aluminum silicates, and dissolution of carbonates, respectively. More than 70% of the samples are not recommended for irrigation due to the presence of high salt content in groundwater. EWQI assessment demonstrates that the quality of the groundwater is good. The outcomes of this study are significant for understanding the geochemical status of the groundwater in the Hutuo River Drinking Water Source Area, and helping policymakers to protect and manage the groundwater. [ABSTRACT FROM AUTHOR]

The study determines the major ion chemistry of the Teesta River catchment in the Eastern Himalayan region and evaluates hydrochemical processes controlling water composition of the catchment area. Water of the Teesta River basin was in neutral to alkaline condition. HCO3−, Ca2+, Na+, Mg2+ and SO42- were identified as the dominant ionic species in the Teesta catchment water composition and Ca-Mg-HCO3 as the dominant hydrochemical facies. Higher contribution of (Ca2++Mg2+) and HCO3− towards the TZ+ and TZ−, high ionic ratios of (Ca2++Mg2+)/(Na++K+), HCO3−/(Cl−+SO42-) and low (Na++K+)/TZ+ ratio suggest carbonate weathering as a major contributor of dissolved ions in the Teesta basin water. Under-saturation with respect to both carbonate and sulphate phase minerals suggests that water can dissolve these minerals during water-rock interaction. Concentration of the analysed water quality parameters were well below the specified drinking and irrigation water limits. [ABSTRACT FROM AUTHOR]

Uranium extraction through the in situ leaching method stands as a pivotal approach in uranium mining. In an effort to comprehensively assess the repercussions of in situ uranium leaching on groundwater quality, this study collected 12 representative groundwater samples within the Bayan-Uul mining area. The basic statistical characteristics of the water samples showed that the concentrations of SO42− and total dissolved solids (TDS) were relatively high. Through the use of cluster analysis, the water samples were categorized into two distinct clusters. Seven samples from wells W-d, W-u, N01, W10-2, W08-1, W10-1, and W13-1, situated at a considerable distance from the mining area, were grouped together. Conversely, five samples from wells W08-2, W13-2, W01-1, W02-2, and the pumping well located in closer proximity to the mining area, formed a separate cluster. A decision tree-based machine learning approach was employed to discern the influence of various hydrochemical indicators in forming these clusters, with results indicating that SO42− exerts the most substantial influence, followed by Ca2+. The mineral saturation indices from geochemical modeling indicated that, as the distance from the mining area increased, the trend of calcium minerals changed from dissolution to precipitation; iron minerals were in a precipitation state, and the precipitation trend was gradually weakening. In light of these findings, it is clear that in situ uranium leaching significantly impacted the groundwater in the vicinity of the mining area. The prolonged consumption of groundwater sourced near the study area, or its use for animal husbandry, poses potential health risks that demand heightened attention. [ABSTRACT FROM AUTHOR]

The purpose of the present study is to fundamentally investigate the micro-meso-macroscale correlation mechanism of red-bed soft rocks failure within static water, based on energy analysis. Through a series of experimental studies, changes in the micro-meso-macroscale characteristics of the rocks were characterised by measuring ion concentrations in and pH of water, the pore structure and crack propagation. Based on the experimental measurements, theoretical modelling of micro-meso-macroscale energy conservation was carried out to determine the micro-meso-macroscale correlation mechanism of red-bed soft rocks failure. The results show that the microscale dominant effect of red-bed soft rocks is determined as chemical effects. The failure mechanism of red-bed soft rocks under static water saturation involves chemical, physical and mechanical dominant effects at the micro-meso-macroscale. It was demonstrated that the dominant chemical effect of clay minerals and water comprises a series of chemical energy changes in the microscale water–rock interface. This can induce the energy changes in both mesophysical and macromechanical levels. During the first month after the water saturation, there was a significant decrease in Na+ and K+ concentrations in aqueous solution, whereas there was little change in Ca+ and Mg2+ concentrations. The scanning electron microscope (SEM) images indicated an obvious change in microstructure of the red-bed soft rocks after 3 months of water saturation. A decrease in pore number and increase in total pore surface area could be seen after 6 months of water saturation. Furthermore, the theoretical results suggest that chemical effects at the microscale dominate the softening process of the rocks. During the water–rock interaction, nearly 80% of the energy dissipation results from the microscale change, and the meso-macroscale change accounts for the remaining 20%. As a uniform measure of material evolution, energy can correlate the micro-meso-macro dominant effect of red-bed soft rocks softening appropriately. [ABSTRACT FROM AUTHOR]

In order to study the water-rock interaction of red-bed soft rock, triaxial compression tests of red-bed soft rock with different water content were carried out, the effects of water content on mechanical properties, failure forms, microstructure and damage mechanism were analyzed, and the statistical damage constitutive model of red-bed soft rock with water content was constructed. The results show that the peak strain increases linearly with the increase of water content, and the peak strength and elastic modulus decrease linearly and exponentially respectively. Water content has obvious influence on the failure mode of red-bed soft rock. When the water content is low, the failure mode is shear failure. With the increase of water content, the failure mode changes to shear-tension composite failure. Under the water-rock interaction, the pore particles of the soft rocks in the red-bed of South China are adsorbed to each other and form a sheet structure. In the saturated state, the lamellar and scaly structures further increase, and the overall structure becomes more loose and fragmented. Considering the water-rock interaction, the damage correction coefficient is introduced to improve the constitutive model. The calculated results of the improved statistical damage constitutive model are consistent with the experimental results, which can better describe the influence of water-rock interaction on the mechanical properties of red layer soft rock. [ABSTRACT FROM AUTHOR]

Red-layer mudstone is a typical expandable rock, that is, it easily expands and deforms in water. This study focused on the dynamic quantitative analysis of the mudstone hygroscopic process and development of strain caused by the hydration expansion of clay, by combining a self-designed simple self-imbibition device with the digital image correlation method. The mudstone samples were self-imbibed in deionized water and salt solutions of different concentrations under the same atmospheric conditions (25°C and 50% humidity). The effects of the salt type and salt concentration on the water absorption quality, expansion rate, crack initiation and expansion, matrix deformation, and water migration of mudstone over time were analyzed. The change in the water absorption capacity of mudstone with time was determined from the water absorption characteristic curve. The location and strain development of the local high-strain area during the water–rock interaction was captured from the full-field strain cloud image. The migration of water on the rock surface at different times was observed using camera photographs. Finally, water absorption was combined with strain, water migration, and crack propagation. The effect of saltwater on the hygroscopic expansion of mudstone was evaluated. [ABSTRACT FROM AUTHOR]

Geological explorations have revealed plentiful Neogene formation waters in anticlines in the central Qaidam Basin (QB). However, the hydrochemistry and origin of these waters are obscure. In this study, the hydrochemistry and D‐O‐S‐Sr isotopes of these formation waters were determined to study their origin and evolution. The formation waters are enriched in Na‐Ca‐Cl, and depleted in Mg‐K‐SO4‐HCO3 ions with elevated Li‐B‐Br‐Sr elements. The D‐O isotopes prove that the formation waters originated from weak‐evaporated meteoric waters, and experienced water‐rock interactions. Ion comparisons and Caexcess–Nadeficit diagrams suggest that solute sources of these waters include evaporite dissolution, water‐rock interaction, and minor residual lake brines. Bacterial sulfate reduction and water‐rock interactions are supported by the high S‐Sr isotopes. The enriched Li‐B‐Br‐Sr concentrations of these waters are in accord with the high geochemical background values of the QB. Regarding the genesis of the formation waters, it can be concluded that meteoric waters from the southern Kunlun Mountains were discharged into the basin, weakly evaporated, and then infiltrated into the Neogene strata through faults leaching the soluble ions and mixing with residual lake brines, and all experienced water–rock interactions and a sulphate reduction process. [ABSTRACT FROM AUTHOR]

This study focuses on assessing hydrochemical characteristics and non-carcinogenic health risks associated with fluoride contamination in groundwater within the Palacode and Pennagaram taluks of Dharmapuri district. The presence of fluoride in drinking water is a significant concern due to its potential health impacts on both adults and children. We collected a total of 158 groundwater samples during both the summer (SUM) and monsoon (MON) seasons in 2021 to evaluate the suitability of water for drinking purposes in this region. During the SUM season, groundwater exhibits alkaline characteristics with a pH range of 6.70 to 8.73 and a mean value of 7.43, while the MON season falls within the neutral pH range with values ranging from 6.60 to 7.60 and a mean of 7.00. Hydrogeochemical analysis reveals that fluoride concentrations during the SUM season range from 0.13 to 2.7 mg/L, with a mean of 0.82 mg/L, whereas the MON season exhibits concentrations ranging from 0.08 to 1.6 mg/L, with a mean of 0.5 mg/L. Spatial distribution analysis indicates a gradual increase in fluoride concentrations from the northeast to the central and southern parts of the study area during both seasons. Residents in these areas have been exposed to high fluoride levels for an extended period, leading to health issues related to fluorosis. Our hydrogeochemical analysis attributes fluoride dominance to the Cl--SO42- water type in both seasons. Furthermore, the relationship between fluoride and pH, HCO3-, Ca2+, and Na+ suggests the influence of geological factors in fluoride dissolution under alkaline conditions, while a reverse cation exchange process and increasing calcium concentration inhibit fluoride concentration. Saturation indices indicate that the unsaturated state of gypsum dissolution contributes to elevated fluoride levels in groundwater. Additionally, Gibbs plots highlight rock-water interactions as a significant factor influencing groundwater chemistry in the study area. Based on our hazard quotient (HQ) investigation, children are at a higher risk during both seasons compared to adults, with the central and northern regions showing alarming HQ values. These findings underscore the urgent need for enhanced groundwater quality monitoring and a comprehensive assessment of health risks, providing valuable insights for groundwater safety management in vulnerable areas of this region. [ABSTRACT FROM AUTHOR]

Elucidating the hydrogeochemical processes and quality assessment of groundwater holds significant importance for its sustainable development. In this paper, 53 groundwater samples were collected from a typical agricultural area in the northeastern Chongqing municipality in SW China. The integration of multivariate statistical analysis, ion ratio analysis, geomodelling analysis, the entropy water quality index, health risks assessment, and sensitivity analysis was carried out to explore the hydrochemical processes and quality assessment of groundwater in this study. The statistical results reveal that the cationic concentrations followed the order of Ca2+ > Mg2+ > Na+ > K+, while the anionic components were in the order of HCO3− > SO42− > NO3− > Cl−. Based on the Piper trilinear diagram, the hydrochemical types were shown as Ca-HCO3 and Ca-Mg-HCO3 types. Hierarchical cluster analysis indicated that the groundwater samples could be categorized into three groups. The hydrochemical compositions were primarily influenced by water–rock interactions (e.g., carbonate dissolution and silicate weathering). In terms of irrigation suitability, the sodium adsorption ratios (SARs) ranged from 0.05 to 1.82, and the electrical conductivity (EC) varied from 116 to 1094 μs/cm, indicating that most groundwater samples were suitable for irrigation. The entropy-weighted water quality index ranged from 15 to 94, suggesting that the groundwater samples were suitable for drinking purposes. Non-carcinogenic human health risks followed the order of children > adult females > adult males, within the average values of 0.30, 0.21, and 0.18, respectively. Sensitivity analysis showed that the parameters had the weight order of NO3 > body weight (BW) > ingestion rate (IR) > exposure frequency (EF). Hence, we recommend prioritizing the management of areas with high salinity levels, while avoiding the excessive use of nitrogen fertilizers, raising awareness among local residents about safe groundwater, and providing robust support for the sustainable development of groundwater in typical agricultural areas. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present study investigates the role of varying subglacial drainage distribution, discharge patterns and reactive mineralogy in switching the chemical weathering mechanism and altering CO2 drawdown in distinct hydromicroclimate. Catchments with less glacierized area (Stok and Phutse in cold-arid zones) bestow high (ablation/accumulation)area ratio and large spatial extent of channelized subglacial conduits and, thus permit high specific discharge. Conversely, Chhota Shigri (CS) acquires large glacierized portion covered under accumulation zone. The low (ablation/accumulation)area ratio promotes the development of lesser channelized and more distributed subglacial drainage, allowing low specific discharge in CS basin. As a consequence of distinct drainage characteristics, carbonation reaction processed through atmospheric CO2 and calcite dissolution becomes the locus of solute generation in Phutse and Stok. Correspondingly, carbonate weathering mediated CO2 drawdown override and remains on the higher side than silicate weathering and thus makes the system potential sink to atmospheric CO2. Meltwater draining in Phutse and Stok shows neutral pH, low sulphate mass fractionation (SMF) and low pCO2. In contrary, Chhota Shigri augments predominant sulphide oxidation and carbonation via atmospheric CO2 as a major source of H+ for chemical weathering during low and high ablation seasons, respectively. Elevated role of sulphide oxidation in chemical weathering promotes high SMF, high pCO2 and lowered alkalinity during low ablation, which may act as a source of atmospheric CO2 in Chhota Shigri. [ABSTRACT FROM AUTHOR]

This study was carried out with the objective of quantifying the concentrations of various physicochemical parameters of the groundwater (GW) and evaluating the interactions between the GW and the carrier rocks. Forty-two (42) GW samples were collected from different tube wells distributed in and around the Jashore University of Science and Technology (JUST) campus. The result showed that the cations and anions follow the order of Ca2+, Mg2+, Na+, K+, and HCO3-, Cl-, and SO42-, respectively, for most cases. In general, the GW was found to be slightly alkaline and hard to very hard. More than 50% of samples exceeded the permissible limit of arsenic and manganese contents. The Water Quality Index (WQI) represented that 60% of waters are good to excellent in categories as per World Health Organization (WHO) guidelines. The Pearson correlation showed statistically significant correlations between each pair of parameters, with maximum positive and negative r values of 0.80 and -0.54, respectively. The Principal Component Analysis (PCA) produced the six principle components among the 21 tested parameters (20 physicochemical and 1 is biological), which accounted for more than 81% of the total variance. Varius plots such as Piper, Durov, and Stiff Patterns suggested that the hydrogeochemical facies was dominated by the Ca-Mg-HCO3 water type. Finally, it was observed that the GW quality parameters in the Southwestern region of Bangladesh were governed mostly by the geochemical process of rock-water interaction, whereas the chemical weathering (dissolution) of calcite minerals was followed by the weathering of silicate minerals. [ABSTRACT FROM AUTHOR]

Water immersion significantly influences the mechanical characteristics of rock materials, with the degradation of these properties often leading to engineering hazards. Understanding the micro mechanism of rock-water interaction is crucial when evaluating the mechanical behavior of a rock mass. A series of multiscale tests were conducted to investigate the micro and macro behaviors of Plagioclase amphibolite, sourced from Gansu, China, under water immersion conditions. The results indicated that the micro particles transitioned from a flake-dispersed structure in a dry state to floc clusters after 20 days of immersion. The surface micro morphology was analyzed using a laser scanning machine, revealing a transformation from a smooth state to roughness, attributed to the emergence and swelling of numerous micro humps. The evolution of parameters such as the standard deviation of the height distribution (Sq), profile area ratio(Sdr), and the root mean square of the first derivative of surface (Sdq) demonstrated that the rock expanded uniformly, with the micro grains swelling to varying degrees. NMR-based porosity testing suggested an exponential increase in damage, leading to the interconnectedness of newly formed micro-pores with neighboring ones due to water immersion. Ultimately, the water-induced porosity doubled compared to the original porosity. Additionally, the axial swelling rate exhibited a corresponding increase in tandem with the growth in porosity, with an average value of 0.141 %. Finally, linear functions were established between uniaxial compressive strength, elastic modulus, and axial swelling rate. These findings offer a comprehensive understanding of the multiscale evolution characteristics of Plagioclase amphibolite under water intrusion.

Chemical weathering of silicate minerals is an important source for Ca, Mg, Na and K. However, in comparison with other major elements (e.g., Ca, Mg and Na) in waters, how K behaves during water-rock interaction remains poorly understood. Recent studies have shown that large K isotopic fractionation could occur during various processes of low-temperature water-rock interaction such as chemical weathering and adsorption, making K isotopes gradually become a powerful tracer for the sources, migration and transformation of K cycling in the subsurface. This overview summarizes K isotopic compositions of major reservoirs at the Earth’s surface, including upper continental crust, hydrosphere and other reservoirs (plants and fertilizers). We conclude that 41K is enriched in hydrosphere than upper continental crust, providing an opportunity to identify the K source in groundwater.The magnitudes and mechanisms of K isotope fractionation during common water-rock interaction processes are also summarized (i.e., silicate dissolution, secondary mineral formation, adsorption, cation exchange), demonstrating that limited K isotope fractionation occurs during silicate dissolution, while clay formation results in enrichment of 41K in waters and adsorption and cation exchange leads to depletion of 41K occurring in waters. These different behaviors of K during these water-rock interactions provide an opportunity for tracing the migration and transformation process of K in groundwater. This paper presents the latest research that applied K isotopes to trace silicate weathering and water pollution. Since K isotopes are an excellent tracer for silicate weathering, they can be used to reveal the sources, migration and transformation of K cycling in aquifers with abundant CO2. Additionally, the distinguishable behavior of K isotopes during chemical weathering, clay adsorption and cation exchange can be used to identify various water-rock interactions. Future K isotopic studies in the field of hydrogeochemistry should focus on: (1) constraining the contribution of multi-endmember control on sources of potassium in groundwater; (2) quantifying K behavior during long-term groundwater circulation; and (3) using multiple isotopes to trace carbon cycle-related processes.

Research on the dissolution effect and the water purification mechanism of fractured coal and rock mass in the goaf area of underground reservoir is the key to realizing the safe and efficient operation of underground reservoir in mine.This paper takes the underground water reservoir formed by the mining of 31409 working face in Jinjie coal mine as example, and selects the broken coal rock mass in the mining area and deionized water for the experimental study of pollutant release law.We analyse the law of dissolution action of broken coal rock mass in the mining area, and explore the mechanism of the influence broken coal rock mass exerts on the characteristics of the water body.We discover the law of pollutant release of broken coal rock mass under different temperature and weathering degrees, and analyse precipitation and dissolution that occurs during the water purification process in underground water reservoir.The water-rock interaction of dissolution, the adsorption and precipitation of clay mineral surfaces and soluble organic matter in the rock body constitute the water purification characteristics of the groundwater reservoir, with dissolution, adsorption and precipitation each playing a dominant role in influencing mine water quality at different time scales.

Objective The permeability of coral sand is the key factor determining the groundwater reserves of coral islands. For a long time, the research on the influence of different salinity filtrates on the permeability of coral sand during the formation of freshwater lenses is quiet few. Methods In this study, three kinds of solutions with different salinities were designed to represent freshwater, transition zone water and seawater to conduct dissolution and permeation tests on coral sand. Based on X-ray diffraction analysis and PHREEQC reverse simulation, the possible causes of water-rock interactions and permeability changes in coral sand in different salinity solutions were discussed. Results Results showed that the permeability of coral sand was highly related to its dissolution in water bodies. The higher the salinity of the solution, the stronger the dissolution and the greater the permeability coefficient of the coral sand. The permeability coefficient of coral sand was almost unchanged in pure water. In saltwater, coral sand has undergone water-rock interactions, including carbonate dissolution and Na+-Ca2+ ion exchange, and the water-rock interaction is stronger with increasing salinity. After 360 hours of reaction under NaCl solutions with concentrations of 0.2 mol/L and 0.4 mol/L, the coral sand permeability coefficient changed from 0.58 m/d to 0.64 m/d and 0.74 m/d, respectively. It was inferred that dissolution could increase the overall porosity and thus the permeability coefficient by changing the sand particle size. Conclusion The results provide a scientific reference for the accurate assessment of freshwater reserves and the sustainable development of water resources on coral islands.