Search Results (146)

Shiqian County, located within a key geothermal fluids belt in Guizhou Province, China, has abundant underground hot water resources. Therefore, elucidating the hydrogeochemical characteristics and formation mechanisms of thermal mineral water in this area is essential for evaluating and sustainably utilizing regional geothermal fluids. This study focuses on the Shiqian Hot Spring Group and employs integrated analytical techniques, including rock geochemistry, hydrogeochemistry, isotope hydrology, digital elevation model (DEM) data analysis, remote sensing interpretation, geological surveys, mineral saturation index calculations, and PHREEQC-based inverse hydrogeochemical modeling, to elucidate its hydrogeochemical characteristics and formation mechanisms. The results show that strontium concentrations range from 0.06 to 7.17 mg/L (average 1.65 mg/L) and metasilicic acid concentrations range from 19.46 to 65.51 mg/L (average 33.64 mg/L). Most samples meet the national standards for natural mineral water and are classified as Sr-metasilicic acid type. Isotope analysis indicates that the geothermal water is recharged by meteoric precipitation at elevations between 911 m and 1833 m, mainly from carbonate outcrops and fracture zones on the southwestern slope of Fanjingshan, and discharges south of Shiqian County. The dominant hydrochemical types are HCO₃·SO₄-Ca·Mg and HCO₃-Ca·Mg. Strontium is primarily derived from carbonate rocks and celestite-bearing evaporites, whereas metasilicic acid mainly originates from quartz dissolution along the upstream groundwater flow path. PHREEQC-based inverse modeling indicates that, during localized thermal mineral water runoff in the middle-lower reaches or discharge areas, calcite dissolves while dolomite and quartz tend to precipitate, reflecting calcite dissolution-dominated water–rock interactions and near-saturation conditions for some minerals at late runoff stages. Full article

This study evaluates the quality and irrigation suitability of drainage water in the Al-Jouf Region, Saudi Arabia, where water scarcity necessitates the reuse of nonconventional resources. Eighteen drainage water samples were analyzed for physicochemical parameters and irrigation indices, including electrical conductivity (EC), sodium percentage (Na⁺%), sodium adsorption ratio (SAR), magnesium hazard (MH), Kelly’s ratio (KR), permeability index (PS), and irrigation water quality index (IWQI). Multivariate statistical tools were applied to identify dominant hydrogeochemical processes. Inverse Distance Weighting (IDW) interpolation in ArcGIS Desktop 10.8 was employed to map significant physicochemical data and irrigation indicators. Results revealed that while EC values indicated low to moderate salinity (0.74–25.2 μS/cm), most samples showed high Na⁺%, SAR, and KR, classifying them as doubtful to unsuitable for irrigation. The IWQI ranged from 84.47 to 1617.87, indicating poor to inferior quality due to evaporation, fertilizer leaching, and sodium accumulation. Furthermore, the results highlight the importance of precise geographic modeling in determining whether drainage water is suitable for long-term agricultural use in arid regions such as Al-Jouf. Sustainable reuse of such drainage water requires freshwater blending, gypsum application, and the cultivation of salt-tolerant crops, aligning with Saudi Vision 2030 objectives for sustainable water management in arid regions. Full article

Modeling the water cycle in the critical zone requires understanding interactions between the soil–vegetation–atmosphere compartments. Mechanistic modeling of soil water flow relies on the accurate determination of hydrodynamic parameters that control hydraulic conductivity and water retention curves. These parameters can be derived either using pedotransfer functions (PTFs), using soil properties obtained from field samples, or through inverse modeling, which allows the parameters to be adjusted to minimize differences between simulations and observations. While PTFs are widely used due to their simplicity, inverse modeling requires specific instrumentation and advanced numerical tools. This study, conducted at the Hydro-Geochemical Environmental Observatory (Strengbach forested catchment) in France, aims to determine the optimal hydrodynamic parameters for two contrasting forest plots, one dominated by spruce and the other by beech. The methodology integrates granulometric data across multiple soil layers to estimate soil parameters using PTFs (Rosetta). Water content and conductivity data were then corrected to account for soil stoniness, improving the KGE and NSE metrics. Finally, inverse parameter estimation based on water content measurements allowed for refinement of the evaluation of α, Ks, and n. This framework to estimate soil parameter was applied on different time periods to investigate the influence of the calibration chronicles on the estimated parameters. Results indicate that our methodology is efficient and that the optimal calibration period does not correspond to one with the most severe drought conditions; instead, a balanced time series including both wet and dry phases is preferable. Our findings also emphasize that KGE and NSE must be interpreted with caution, and that long simulation periods are essential for evaluating parameter robustness. Full article

Lithium (Li) is a critical metal element in geothermal systems, yet its enrichment mechanism in coastal geothermal waters remains poorly understood. This study focuses on the Xiamen coastal geothermal system, located in the South China granitic reservoir at the front of the Pacific subduction zone. Self-organizing map (SOM) classification, hydrogeochemical analysis, hydrogen–oxygen isotopic constraints, and a three end-member mass balance model were applied to identify the sources and enrichment mechanisms of Li. The geothermal waters are classified into two types: inland low-TDS (Cluster-1) and coastal high-TDS (Cluster-2). Isotopic data indicate a mixture of meteoric water and seawater as the recharge source. The model shows that seawater and groundwater mixing accounts for 2–45% of Li concentration, with over 55% derived from the rock end-member. The leaching of 0.002–0.187 kg of granite per liter of geothermal water explains the observed Li levels. Elevated temperature and low pH enhance Li⁺ release from silicate minerals, and reverse cation exchange further amplifies this process. A strong positive correlation between the CAI-II index and Li⁺ concentration reveals a synergistic effect of ion exchange in high-salinity environments. Overall, the results provide a quantitative framework for understanding Li enrichment and evaluating resource potential in coastal geothermal systems. Full article

The Chiuchiu Pond (CCP) is an inland brackish water body in a pre-Andean scenery in the Atacama Desert, northern Chile. Presently unprotected, the CCP is attractive for tourism and a notable geosite for wildlife characterized by maintaining a fixed water level and chemical composition without surface inlets/outlets. This paper aims to characterize factors accounting for its perennial character by gathering climatic, hydrogeochemical, and morphometric information and microbiological and functional characterization. The CCP is an isolated U-shaped doline with a maximum depth of 17.5 m and vertical walls with more than 80% of soluble salts (halite and calcite) under arid conditions characterized by constant seasonal variation patterns. This is a unique case in that no similar conditions among reported wetlands or ponds have been found in the world. From our studies, it was characterized as an oligotrophic, lentic oligomictic, well-mixed water body, without thermal stratification, stable water level and hydrochemical composition, with water balance conditions from underground flows. Analysis of the microbial community revealed a core composition dominated by Proteobacteria (43.1%), Bacteroidetes (23.5%), and Cyanobacteria (10%). We provide a multidisciplinary contribution to justify urgent actions for the CCP’s conservation, representing a model for other unprotected coastal and inland wetlands in northern Chile and drylands elsewhere. Full article

In this paper, the conceptual hydrogeological circulation model of natural mineral waters from Ribeirinho and Fazenda do Arco hydromineral concession (Castelo de Vide) is updated. These waters are exploited by the Super Bock Group, as bottled waters, and are commercially labeled as Água Vitalis. The physico-chemical data (2004–2024) of these waters were processed regarding their joint interpretation with recent isotopic (δ²H and δ¹⁸O) data. The study region is dominated by the Castelo de Vide syncline, which develops along the southern limit of the Central Iberian Zone. These natural mineral waters have low electrical conductivity (EC) mean values (42.80 < EC_mean < 54.45 μS/cm) and a slightly acidic pH (5.14 < pH_mean < 5.46), making them hyposaline waters. The recharge area of this aquifer system coincides fundamentally with the outcrops of Lower Ordovician quartzites. The updated conceptual circulation model presented in this work is essentially developed on the basis of the chloride–sodium signatures of these waters, explained by the preferential recharge of meteoric waters (δ²H and δ¹⁸O) and low water–rock interaction temperature. Such isotopic results seem to indicate the non-existence of a flow continuity between the two blocks (NW and SE) of the quartzite ridges, separated by a fault with a local orientation approximately N-S, as indicated by the most enriched isotopic values of the waters from borehole AC22 (δ¹⁸O = −5.90‰ vs. V-SMOW) located in the SE block, compared to the average isotopic value of the waters from the other boreholes (Vitalis I, II, III, IV, V and VI) located in the NW block (δ¹⁸O_mean = −6.30‰ vs. V-SMOW). This study enhances the understanding of the hydrogeological and geochemical processes controlling low-mineralized (hyposaline) natural mineral waters, widely used for therapeutic and commercial purposes. Despite their global importance, detailed hydrogeological and isotopic studies of such systems are still scarce, making this conceptual model a valuable reference for their sustainable management. Full article

Nitrate pollution in aquatic ecosystems has garnered growing attention globally, with particular severity in typical agricultural regions of North China. A typical agricultural area of southern Baoding, North China, is selected as the study area. To address key research questions, hydrochemical analysis is used to characterize the shallow groundwater’s hydrochemical properties, Positive Matrix Factorization (PMF) is utilized to delineate the genetic mechanism of high-nitrate groundwater, and Human Health Risk Assessment (HHRA) is conducted to evaluate potential health risks. Groundwater in the study area is predominantly characterized by the HCO₃-Ca and HCO₃-Mg. Four key factors regulating hydrochemical characteristics are identified via PMF modeling integrated with Pearson correlation analysis. Specifically, Factor 1 (NO₃⁻-dominated) and Factor 4 (SO₄²⁻-dominated) are associated with agricultural and livestock activities. In contrast, Factor 2 (Na⁺- and Mg²⁺-dominated) stems from the dissolution of silicate or carbonate rocks, while Factor 3 (pH- and K⁺-governed) is affected by silicate rock weathering and dissolution. The NO₃⁻ concentrations in groundwater range from 0.2 mg/L to 68.0 mg/L, with 47.54% of samples exceeding 10 mg/L. NO₃⁻ in most groundwater samples originates from mixed sources, including agricultural fertilizers, soil organic nitrogen, and manure-sewage. HHRA results demonstrate that via oral ingestion of groundwater, NO₃⁻ poses non-carcinogenic health risks to 90%, 83%, and 82% of children, adult females, and adult males, respectively. This study provides a hydrogeochemical perspective on nitrogen pollution in groundwater and offers scientific support for sustainable groundwater management in typical agricultural regions worldwide. Full article

Mine water inrush poses a severe threat to coal mine safety, making rapid and accurate identification of water sources essential. Existing methods, including conventional hydrochemical diagrams and machine learning, struggle with high-dimensional, nonlinear hydrogeochemical data characterized by implicit temporal dynamics. This study proposes an intelligent identification model integrating convolutional neural networks (CNNs), long short-term memory (LSTM), and an attention mechanism (CNN–LSTM–Attention). The model employs a CNN to extract local fingerprint features from hydrochemical indicators (K⁺+Na⁺, Ca²⁺, Mg²⁺, Cl⁻, SO₄²⁻, and HCO₃⁻), uses LSTM to model evolutionary patterns, and leverages an attention mechanism to adaptively focus on critical discriminative features. Based on 76 water samples from the Tangjiahui Coal Mine, the model achieved 91% accuracy on the test set, outperforming standalone CNN, LSTM, and CNN–LSTM models. Visualization of attention weights further revealed key diagnostic indicators, enhancing interpretability and bridging data-driven methods with hydrogeochemical mechanisms. This study provides a powerful and interpretable tool for water inrush source identification, supporting the transition toward intelligent and transparent coal mine water hazard prevention. Full article

The Muji Fault Zone (MJF) in the northeastern Pamir Plateau hosts a well-developed non-volcanic geothermal system, characterized by widespread hot springs and mud volcanoes—where core processes of geothermal fluids, including atmospheric precipitation recharge, shallow crustal circulation, carbonate-driven water–rock interactions, and CO₂-rich fluid discharge, are tightly coupled with regional intense crustal deformation and frequent seismic activity. We collected and analyzed 22 geothermal water samples and 8 bubbling gas samples from the MJF periphery, finding that the geothermal waters are predominantly of the HCO₃-Ca·Mg hydrochemical type, with hydrogen (δD: −103.82‰ to −70.21‰) and oxygen (δ¹⁸O: −14.89‰ to −10.10‰) isotopes indicating atmospheric precipitation as the main recharge source. The Na-K-Mg ternary diagram classified the waters as immature, reflecting low-temperature water–rock interactions in the shallow crust (<3 km), while noble gas isotopes (³He/⁴He: 0.03–0.09 Ra, Ra = 1.43 × 10⁻⁶) and carbon isotopes (δ¹³C-CO₂) confirmed fluid origin from crustal carbonate dissolution; SiO₂ geothermometry estimated thermal reservoir temperatures at 67–155 °C. Long-term monitoring (May 2019–April 2024) of Tahman (THM) and Bulake (BLK) springs revealed significant pre-seismic anomalies: before the 2023 Tajikistan Ms7.2 and 2024 Wushi Ms7.1 earthquakes, Na⁺, Cl⁻, and SO₄²⁻ concentrations showed notable negative anomalies (exceeding 2σ of background values) with synchronous trends between the two springs. Integrating these findings, a “Fault-Spring-Mud Volcano-Earthquake” fluid response model was established, providing direct evidence of deep-shallow fluid coupling in mud volcano–geothermal fluid interactions. This study enhances understanding of the dynamic evolution of non-volcanic geothermal systems under tectonic stress and clarifies the mechanisms of hydrogeochemical variations in fault-controlled geothermal systems, offering a robust scientific basis for advancing research on tectonic–fluid interactions in active fault zones of the northeastern Pamir Plateau. Full article

This study investigates geothermal waters in the Xinjiang region through hydrogeochemical methods, including cluster analysis, ionic ratios, and isotopic analysis. Cluster analysis categorized the geothermal water samples into three distinct groups (G1, G2, and G3). The predominant hydrochemical facies are SO₄-HCO₃-Na, SO₄-Cl-Na, and Cl-Na types, whose formation is controlled by multiple factors. Evidence from molar ratios of major ions suggests that geothermal waters in Group G1 are predominantly governed by water–rock interactions, whereas Groups G2 and G3 are mainly influenced by evaporative concentration. Hydrogen and oxygen isotopic signatures confirm that meteoric water serves as the primary recharge source for these geothermal waters. The spatial correlation between regional tectonic features and most geothermal discharge points demonstrates a consistent relationship between geothermal water occurrence and structural distribution in Xinjiang. Additionally, a conceptual circulation model is proposed wherein meteoric water undergoes deep circulation following local recharge, ascends along fault zones under tectonic pressure, and mixes with shallow groundwater. This research primarily elucidates the hydrogeochemical characteristics and recharge mechanisms of geothermal resources in Xinjiang, thereby providing a scientific basis for their future development and utilization. Full article

Groundwater chemical composition often exhibits complex characteristics under the combined influence of anthropogenic activities and natural geological conditions. Accurately distinguishing between human-derived and naturally occurring constituents is crucial for formulating effective pollution control strategies and ensuring sustainable groundwater resource management. However, conventional hydrogeochemical analytical methods often face challenges in quantitatively differentiating these overlapping influences. In this study, 66 groundwater samples were collected from the midstream section of the Dawen River Basin, an area subject to significant anthropogenic pressure. An integrated approach combining hydrogeochemical analysis, Self-Organizing Map (SOM) clustering, and Positive Matrix Factorization (PMF) receptor modeling was employed to identify sources of chemical constituents and quantify the proportional contributions of various factors. The results indicate that: (1) The predominant groundwater types in the study area were Cl·SO₄·Ca. (2) SOM clustering classified the groundwater samples into five distinct groups, each reflecting a dominant influence: (i) natural geological processes—samples distributed within the central geological mining area; (ii) agricultural activities—samples located in intensively cultivated zones along both banks of the Dawen River; (iii) hydrogeochemical evolution—samples concentrated in areas with impermeable surfaces on the eastern and western sides of the study region; (iv) mining operations—samples predominantly found in industrial zones at the periphery; (v) domestic wastewater discharge—samples scattered relatively uniformly throughout the area. (3) PMF results demonstrated that natural geological conditions constituted the largest contribution (29.0%), followed by agricultural activities (26.8%), consistent with the region’s extensive farming practices. Additional contributions arose from water–rock interactions (23.9%), mining operations (13.6%), and domestic wastewater (6.7%). This study establishes a methodological framework for quantitatively assessing natural and anthropogenic impacts on groundwater quality, thereby providing a scientific basis for the development of protection measures and sustainable management strategies for regional groundwater resources. Full article

Although many studies have examined reaction zones in groundwater–seawater mixing areas, little attention has been given to how subsurface processes drive changes in iron (Fe) precipitation over time and space. This gap has limited our understanding of the “iron curtain” phenomenon in coastal aquifers. To address this, this study developed a reactive transport model to investigate how porosity evolves during the oxidative precipitation of Fe(II) in porous media. The model incorporates the dynamic effects of tortuosity, diffusivity, and surface area as minerals accumulate. Validation experiments, conducted with syringe tests that simulated Fe precipitation during freshwater–saltwater mixing, showed that precipitates formed mainly near the inlets, reflecting the development of a geochemical barrier at the groundwater–seawater interface. Scanning electron microscopy confirmed that Fe precipitates coated the surfaces of spherical particles. Numerical simulations further revealed that high Fe(II) concentrations drove pore clogging near the inlet, creating a dense precipitation zone akin to the iron curtain in coastal aquifers. At 10 mmol/L Fe(II), local clogging was observed, while at 100 mmol/L Fe(II), outflow rates (i.e., discharge) were substantially reduced. Together, the experiments and simulations highlight how hydrogeochemical processes influence hydraulic properties during the oxidative precipitation of Fe(II) in mixing zones. Full article

This study examines the impact of physicochemical and geological factors on radon concentrations in groundwater throughout the Mexican Altiplano. Geological diversity, uranium deposits, seismic zones, and geothermal areas with high heat flow are all potential factors contributing to the presence of radon in groundwater. To move beyond local-scale assessments, this research employs spatial prediction methodologies that incorporate geological and geochemical variables recognized for their role in radon transport and geogenic potential. Certain properties of radon enable it to serve as an ideal tracer, viz., short half-life, inertness, and higher incidence in groundwater than surface water. Twenty-five variables were analyzed in samples from 135 water wells. Geostatistical techniques, including inverse distance weighted interpolation and kriging, were used in conjunction with multivariate statistical analyses. Salinity and geothermal heat flow are key indicators for determining groundwater origin, revealing a dynamic interplay between geothermal activity and hydrogeochemical evolution, where high temperatures do not necessarily correlate with increased solute concentrations. The occurrence of toxic trace elements such as Cd, Cr, and Pb is primarily governed by lithogenic sources and proximity to mineralized zones. Radon levels in groundwater are mainly influenced by geological and structural features, notably rhyolitic formations and deep hydrothermal systems. These findings underscore the importance of site-specific groundwater examination, combined with spatiotemporal models, to account for uranium–radium dynamics and flow paths, thereby enhancing radiological risk assessment. Full article

Natural radionuclides may occur in groundwater and pose health risks when present in elevated concentrations. This study evaluates the quality of shallow groundwater in Nysa County (SW Poland) based on the activity concentrations of natural radionuclides radon (²²²Rn) and radium (²²⁶Ra) and estimates the associated radiological risk from water ingestion. Twenty-three groundwater samples were collected from private wells located within two distinct geological units: the Fore-Sudetic Block and the Opole Trough. Activity concentrations of ²²²Rn and ²²⁶Ra were measured using the liquid scintillation counting method. A spatial distribution model for ²²²Rn was developed using inverse distance weighting in QGIS. Local hydrogeochemical background levels were determined using the Q-Dixon test, interquartile range, and Shapiro–Wilk normality test. The background ranged from 2.6 to 3.9 Bq·L⁻¹ in the Opole Trough and from 0 to 10.7 Bq·L⁻¹ in the Fore-Sudetic Block. The lower detection limit (0.05 Bq·L⁻¹) for ²²⁶Ra activity concentration measurements was not exceeded. Effective dose rates were calculated in accordance with the recommendations of the International Commission on Radiological Protection and United Nations Scientific Committee on the Effects of Atomic Radiation. Doses ranged from <1 µSv to over 120 µSv·y⁻¹. Although all samples met national regulatory standards (≤1 mSv·y⁻¹), the World Health Organization reference level (0.1 mSv·y⁻¹) was exceeded in two cases. The results support the need for the radiological monitoring of unregulated private wells and provide a scientific basis for the refinement of legal frameworks and health protection strategies. Full article

Strontium, a key trace element regulating bone development and cardiovascular function, has seen growing research interest in its groundwater accumulation and resource potential. The unique geological structure of the northern Lushan Mountain slope provides an ideal setting to investigate strontium migration and enrichment. We systematically collected 21 groundwater samples and analyzed strontium occurrence characteristics and formation mechanisms using hydrochemical analysis, PHREEQC simulations, Gibbs diagrams, and cation exchange adsorption models. Analysis revealed that 71.4% of samples (15 groups) exceeded the GB 8537-2018 standard (≥0.4 mg/L), significantly higher than typical groundwater systems. Spatial distribution showed marked geological differentiation: average strontium concentration in Cambrian-Ordovician fractured-karst water reached 2.79 mg/L (range: 0.207–12.41 mg/L), 109.8% higher than in bedrock fissure water (1.33 mg/L). Structural control was evident, with samples near fault zones exhibiting generally higher concentrations than non-fault areas. Multivariate statistics indicated significant positive correlations between Sr²⁺ and TDS, Na⁺, Ca²⁺, and SO₄²⁻, suggesting synergistic enrichment mechanisms. Hydrogeochemical simulations confirmed that multiphase leaching of strontium-bearing silicate rocks provides the primary source, while rock weathering-driven ion exchange reactions constitute the key enrichment mechanism. This study elucidates the structural-lithological coupling-controlled hydrogeochemical cycle of strontium, providing theoretical support for delineating high-quality mineral water targets and developing health-beneficial geo-resources in the Lushan region. Full article