Search Results (337)

Rapid and accurate identification of mine water inrush sources is critical for hazard control in underground coal mining. Conventional Fisher discriminant analysis is often limited by feature redundancy and multicollinearity when applied to small-sample, high-dimensional hydrochemical data. To address this, we propose GWO–Fisher, a hybrid model integrating the Grey Wolf Optimizer (GWO) with Fisher discriminant analysis. The model employs correlation-based pre-screening followed by global optimization, using a fitness function that combines Fisher accuracy with a feature-size penalty, to achieve a compact and interpretable feature set. Trained on data from the Xiegou Coal Mine (Shanxi, China), it reduced 17 hydrochemical indicators to 12 key features, achieving 92.98% training accuracy and 86.21% test accuracy—an improvement of 10.35 percentage points over conventional Fisher. When independently validated across four mines in three spring domains, the model maintained over 83% accuracy, consistently selecting TDS, K⁺, and HCO₃⁻ as core features. Misclassification patterns were cross-domain consistent and linked to hydrogeological conditions. The proposed GWO–Fisher model balances predictive accuracy with hydrogeological interpretability, demonstrating reliable performance across both single-mine and cross-spring-domain scenarios. Full article

Located in the northeastern Tibetan Plateau, the Qaidam Basin hosts abundant strategic lithium (Li) and boron (B) salt lake resources crucial for national resource security. Existing studies focus on individual lakes, lacking systematic Li-B geochemical and source–transport–sink research across the geothermal–river–lake system. Based on 40 water samples from 16 lakes and multi-isotope and hydrochemical data, this study explores Li-B spatial distribution, isotopic evolution and enrichment rules. The results reveal prominent spatial heterogeneity of Li and B distributions. The contents of riverine Li and B are higher than the global average level, and terminal salt lakes show the highest enrichment degree. Specifically, southern lakes are Li-dominant, while northern lakes are B-dominant, with both reaching industrial exploitation grades. Significant Li and B isotopic fractionation occurs throughout the hydrological system, with geothermal fluids presenting depleted isotopic compositions and lake waters showing enriched features. H-O isotopic evidence and Gibbs diagram analysis indicate that surface waters in the basin are primarily recharged by atmospheric precipitation, and their hydrochemical compositions are jointly controlled by rock weathering and strong evaporative concentration, accompanied by distinct north–south hydrogeological zonation differences. Source analysis demonstrates that Li is mainly derived from high-temperature water–rock interactions of Li-rich volcanic and granitic rocks in the southern East Kunlun Mountains, whereas B originates from ultrahigh-pressure B-rich metamorphic rocks along the northern North Qaidam margin. The migration and accumulation sequence of Li and B follows the pathway: geothermal fluid emission → fluvial transportation → terminal lake enrichment. Evaporation and mineral precipitation are the dominant factors controlling elemental enrichment and isotopic fractionation. This basin-wide study supplements salt lake critical mineral metallogenic theories and guides efficient Li-B exploration and sustainable development. Full article

Runoff recharge increases during the wet season in arid inland river basins; however, solute inputs along river courses, evaporite salt dissolution, and leaching from saline sediments may still substantially modify the chemical composition of surface waters. To identify the sources of major ions, hydrochemical controlling processes, and salt-enriched river reaches during the wet season in the Cele River Basin, 107 surface water samples were collected from the mainstream of the Cele River and five major tributaries in August 2025. Field and laboratory analyses were conducted for pH, total dissolved solids (TDS), electrical conductivity (EC), dissolved oxygen (DO), and major ions, including Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, SO₄²⁻, and HCO₃⁻. Piper diagrams, Gibbs diagrams, ionic ratios, Spearman correlation analysis, and principal component analysis (PCA) were used to characterize the major-ion composition, hydrochemical facies, and controlling factors. The results show that the surface waters were generally weakly alkaline, with pH values ranging from 7.42 to 8.46. TDS and EC exhibited pronounced spatial heterogeneity, with higher salinity levels in the Buzang River, the Cele River mainstream, and the Uluk Say River, and relatively lower mineralization in the Bostan River and Nur River. SO₄²⁻ and Cl⁻ dominated the anionic composition, together accounting for 80.3% of total anions, whereas Ca²⁺ + Mg²⁺ and Na⁺ + K⁺ jointly controlled the cationic composition, accounting for 57.3% and 42.7% of total cations, respectively. The Piper diagram indicated that the Cl·SO₄–Na·Ca type was the dominant hydrochemical facies, accounting for 67.3%, suggesting a pronounced sulfate–chloride salt-enrichment signature during the wet season. Evidence from Gibbs diagrams, ionic end-member ratios, and PCA further indicates that the hydrochemical composition is primarily constrained by rock weathering and jointly influenced by sulfate and chloride salt dissolution, evaporation–concentration processes, and leaching from saline sediments. These processes reflect the coexistence of runoff dilution and salt reloading during the wet season. The Buzang River, Cele River mainstream, and Uluk Say River should be prioritized for continuous water-quality monitoring and salinity-risk early warning, while TDS, EC, Na⁺, Cl⁻, and SO₄²⁻ can serve as core indicators for diagnosing wet-season water–salt processes and tracking water-quality baselines. This study identifies the key salt-enriched reaches, major ion sources, and hydrochemical control mechanisms of surface waters in the Cele River Basin during the wet season, providing a scientific basis for water-quality protection, oasis agricultural water regulation, and sustainable water–salt management in arid inland river basins. Full article

Groundwater resources in semi-arid regions are increasingly threatened by agricultural intensification, irrigation expansion, and climate variability. This study investigates the influence of irrigation practices on groundwater recharge and quality degradation in the semi-arid Regueb Basin, Central Tunisia, using an integrated framework combining hydrochemical analysis, irrigation water quality indices, GIS-based spatial modeling, and explainable machine learning (XAI). Thirty groundwater samples were analyzed for major physicochemical parameters and irrigation suitability indicators, including Electrical Conductivity (EC), Total Dissolved Solids (TDS), Sodium Adsorption Ratio (SAR), sodium percentage (%Na), and Irrigation Water Quality Index (IWQI). Hydrochemical facies are dominated by Ca–Mg–Cl, Na–Cl, and Ca–Mg–SO₄ water types, reflecting the combined effects of evaporite dissolution, water–rock interaction, evaporation, and irrigation return flow. Groundwater salinity is generally high, with EC values ranging from 1490 to 8710 µS/cm, while nitrate concentrations frequently exceed the World Health Organization guideline value of 50 mg/L in intensively cultivated zones, indicating significant anthropogenic contamination linked to fertilizer leaching and irrigation practices. GIS-based recharge assessment indicates that irrigation return flow may represent an important component of effective recharge in cultivated areas under semi-arid conditions while simultaneously contributing to salinization and nutrient accumulation within the aquifer system. However, quantitative partitioning of recharge sources requires further investigation using tracer-based approaches and numerical modeling. More than 40% of groundwater samples were classified as unsuitable for irrigation because of elevated salinity and sodicity hazards. To explore the relationships among irrigation water quality indicators, several machine-learning algorithms were evaluated for IWQI estimation and interpretation. Linear Regression achieved the highest performance for IWQI estimation (R² = 0.9839), reflecting the strong internal relationships among irrigation water quality indicators. SHapley Additive exPlanations (SHAP) analysis identified Residual Sodium Carbonate (RSC) as the most influential parameter controlling irrigation water quality. The results highlight the dual role of irrigation as both a recharge-enhancing mechanism and a driver of groundwater degradation. This study provides an integrated hydrochemical–GIS–XAI framework for identifying vulnerable zones and supporting sustainable groundwater management strategies in semi-arid agricultural regions. Full article

Quantitative source apportionment of groundwater contamination is essential for sustainable water resource management, yet the performance of receptor models in complex hydrogeological settings remains debated. This study employed Positive Matrix Factorization (PMF) and PCA-APCS-MLR (Principal Component Analysis–Absolute Principal Component Score–Multiple Linear Regression) models to analyze 16 hydrochemical parameters from 460 groundwater samples (collected at 339 sites), delineating pollution sources and characterizing the groundwater chemistry in the southern recharge zone of Poyang Lake, China’s largest freshwater lake. Both models consistently identified five primary pollution sources: mixed anthropogenic activities (contributing 13.6% and 8.6%, respectively), natural geological processes (28.9% and 45.6%), sewage discharge (23.5% and 24.4%), industrial effluents (13.3% and 12.1%), and agricultural practices (20.6% and 9.3%). Notably, heightened contamination was observed near industrial parks and urban centers through two models. The integrated analysis revealed that anthropogenic activities—particularly sewage discharge, agricultural practices, and industrial effluents—are the dominant drivers of groundwater quality deterioration. These human-induced inputs account for the vast majority of the pollution load (reaching up to ~71%), fundamentally altering the natural hydrochemical regime. Notably, elevated Mn²⁺ and NH₄⁺-N concentrations are intricately linked to a combination of industrial effluents and legacy domestic sewage, which exacerbate the mobilization of natural background elements within the aquifer. These findings provide critical mechanistic insights into the complex interplay between human activities and groundwater hydrochemistry, demonstrating how dual-receptor modeling can unravel overlapping natural and anthropogenic inputs. Ultimately, this study offers a scientific basis for targeted pollution control and the sustainable management of global freshwater lake recharge zones. Full article

This study presents a hydrogeochemical assessment of oilfield formation waters from the Karazhanbas, Zhetybay, and Uzen oil fields in the Mangystau Region of Kazakhstan, with the aim of elucidating lithium distribution, identifying the geochemical factors controlling its accumulation, and providing a preliminary resource-oriented evaluation. The study investigated pH, total dissolved solids (TDS), ionic–salt composition, lithium (Li) concentration, and the relationships between Li, TDS, major cations, and geochemical ratios, including Ca/Li and Mg/Li. Major ions were determined using standard hydrochemical methods, while Li was analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES). The investigated waters were predominantly classified as chloride–calcium type according to their hydrochemical composition. In terms of TDS, the waters follow the sequence Uzen > Zhetybay > Karazhanbas, whereas Li concentrations follow the sequence Zhetybay > Uzen > Karazhanbas. The highest Li concentrations were detected in Zhetybay waters (1.40–1.85 mg/dm³); in Uzen waters, Li reached 1.51 mg/dm³; and in Karazhanbas waters, it ranged from 0.30 to 0.70 mg/dm³. The highest Mg/Li and (Na⁺ + K⁺)/Li ratios were characteristic of Uzen waters, indicating a more complex salt matrix. Compared with internationally reported lithium-enriched brines, the Mangystau formation waters contain relatively low Li concentrations and cannot currently be considered a commercially viable lithium source. The scientific significance of this study lies in establishing a regional hydrogeochemical baseline for oilfield formation waters and demonstrating that maximum mineralization does not necessarily correspond to the highest Li concentration. Full article

Agricultural karst watersheds are highly vulnerable to nutrient loss because strong surface water–groundwater (SW–GW) connectivity can rapidly transfer nitrogen and sulfur species from soils, agricultural activities, and human settlements into aquatic systems. However, the coupled behavior and contrasting controls of nitrate (NO₃⁻) and sulfate (SO₄²⁻) in such agroecosystems remain insufficiently understood, limiting effective nutrient and groundwater-quality management. In this study, a typical karst agricultural watershed in Southwest China was selected to investigate the sources, transformation processes, and transport pathways of NO₃⁻ and SO₄²⁻ under strong SW–GW interactions. During the rainy season, 44 groundwater and 40 surface water samples were collected for major hydrochemical and nitrate–sulfate stable isotope analyses. An integrated framework combining hydrochemical analysis, self-organizing maps (SOM), positive matrix factorization (PMF), and MixSIAR were used to identify dominant sources, quantify source contributions, and clarify controlling processes. The results showed that groundwater was mainly characterized by carbonate-controlled Ca-HCO₃ facies, whereas surface water exhibited higher mineralization and a shift toward Ca-SO₄ facies, indicating stronger external inputs and rapid hydrological responses. Nitrate was primarily controlled by external nitrogen inputs, with manure and sewage and soil nitrogen contributing 39–62% and 16–33%, respectively. Nitrate was also regulated by nitrification under oxic conditions, while denitrification was negligible. In contrast, sulfate was predominantly governed by geogenic processes, with sulfide oxidation contributing 63–83%, while other sources were minor. These contrasting controls resulted in distinct spatial and process behaviors: nitrate showed source-driven variability associated with agricultural and domestic inputs, whereas sulfate displayed process-driven accumulation mainly controlled by water–rock interactions. Strong SW–GW connectivity enhanced the transfer of anthropogenic nutrient signals, while subsurface mixing and buffering regulated their expression in groundwater and surface water. These findings demonstrate a clear decoupling between nitrate and sulfate controls in agricultural karst systems and provide a scientific basis for nutrient pollution control, groundwater protection, and sustainable agricultural water management in vulnerable karst regions. Full article

Groundwater is an essential freshwater resource in the Western Himalayas, where increasing anthropogenic pressure and environmental variability are raising concerns regarding groundwater quality and water security. However, regionally integrated assessments of groundwater-quality variability across the Western Himalayan states remain limited. This study evaluates groundwater quality across Jammu and Kashmir, Himachal Pradesh, and Uttarakhand using groundwater-monitoring data obtained from the Central Ground Water Board (CGWB). A total of 338 observation wells monitored during 2019–2022 were analyzed using the weighted arithmetic Water Quality Index (WQI) based on Bureau of Indian Standards (BIS) and World Health Organization (WHO) drinking-water guidelines. Spatial and temporal variability were examined through hydrochemical, correlation, and geospatial analyses. The results reveal substantial regional and district-level variability in groundwater quality across the Western Himalayas. Groundwater in Himachal Pradesh and Uttarakhand is predominantly classified as excellent to good, whereas Jammu and Kashmir exhibit greater hydrochemical heterogeneity and localized groundwater deterioration. Elevated WQI values are concentrated within foothill and valley-transition districts, while high-altitude recharge zones generally maintain lower WQI values. Hydrochemical analyses indicate that groundwater-quality variability is primarily associated with mineralization processes, lithological controls, and localized anthropogenic influences. Temporal analysis further indicates moderate groundwater-quality improvement between 2019 and 2022, particularly in parts of Jammu and Kashmir. Overall, the findings demonstrate that groundwater systems across the Western Himalayas remain largely controlled by hydrogeological conditions but are increasingly modified by localized anthropogenic pressures. Strengthened groundwater monitoring, protection of recharge zones, and targeted management of vulnerable foothill and valley-transition environments will be essential for sustaining long-term water security in this climate-sensitive mountain region. Full article

Shallow aquifers in intensively managed alluvial plains worldwide are increasingly impacted by inorganic nitrogen, yet the simultaneous occurrence and interconversion of nitrate (NO₃⁻–N), nitrite (NO₂⁻–N) and ammonium (NH₄⁺–N) often confound source attribution when single indicators are used. Here, we present a transferable, process-linked framework for diagnosing “tri-nitrogen” (tri-N) pollution that integrates hydrogeochemical evolution, data-driven pattern discovery and receptor-model apportionment. We analyzed 409 shallow-groundwater samples from Shijiazhuang City (central North China Plain) for major ions and tri-N species, interpreted within Piper facies and salinization gradients, and then applied a Gaussian mixture model (GMM) to resolve multivariate hydrochemical–nitrogen end-members. Six clusters (I–VI) depict an interpretable progression from background Ca–HCO₃/Ca·Mg–HCO₃ waters to agricultural NO₃⁻–N enrichment under oxic conditions and a distinct NH₄⁺–N-rich point-source end-member under reducing conditions. An attention-based attribution model indicates that total tri-N, Na⁺, NO₃⁻–N, the NO₂⁻ fraction and SO₄²⁻ are the primary discriminators of cluster structure. Species-resolved positive matrix factorization (US EPA PMF 5.0) quantifies dominant controls, with agricultural leaching–nitrification explaining most NO₃⁻–N (Factor 6, 87.9%) and sewage/manure inputs dominating NH₄⁺–N (Factor 3, 95.3%), while NO₂⁻–N reflects mixed contributions consistent with redox-interface transitions. Beyond this case study, the combined GMM–interpretability–PMF workflow provides a general template for separating non-point versus point tri-N inputs and for prioritizing management actions in shallow aquifers where isotope or tracer data are limited. Full article

Overexploitation of groundwater resources poses a critical challenge in major agricultural regions worldwide, yet how confined and unconfined aquifers respond differentially to governance interventions remains poorly understood. This study presents a comparative assessment of hydrochemical evolution and nitrate contamination dynamics in the Weishan Irrigation District, Shandong Province, China, contrasting pre-governance conditions (2011) with post-governance status (2022–2023) following comprehensive overexploitation control. By integrating hydrochemical characterization with stable isotope tracers (δ¹⁸O, δD, δ¹⁵N-NO₃⁻, δ¹⁸O-NO₃⁻) and Bayesian mixing models (MixSIAR), we reveal fundamentally contrasting aquifer responses to regulation. The unconfined aquifer exhibited continued degradation under persistent agricultural influence, characterized by elevated sodium, nitrate, and bicarbonate concentrations. In sharp contrast, the confined aquifer demonstrated substantial recovery, with major ion concentrations declining markedly, hydrochemical facies restored toward a pristine state, and overall water quality improving significantly to achieve full compliance with the highest-quality standards by 2023. These divergent trajectories indicate that regulatory interventions effectively restored aquitard barrier integrity, thereby shielding the confined aquifer from surface contamination, whereas the unconfined aquifer remained vulnerable to agricultural pollution. Isotope-constrained Bayesian modeling identified soil organic nitrogen, chemical fertilizers, manure/sewage, and industrial wastewater as dominant nitrate sources, with isotopic evidence confirming that the unconfined aquifer receives mixed recharge from Yellow River water and precipitation under contemporary contamination, while the confined aquifer maintains independent, pollution-free recharge. These findings demonstrate that overexploitation control can effectively rehabilitate confined aquifer systems by reestablishing natural hydrogeological barriers, but unconfined aquifers require targeted agricultural pollution mitigation. The contrasting responses highlight the necessity of aquifer-specific management strategies in irrigation-dependent regions, advancing theoretical understanding of how regulatory measures differentially affect multi-layered groundwater systems and providing a scientific basis for precision groundwater governance. Full article

Groundwater quality in arid and semi-arid regions is increasingly affected by salinization, evaporation, abstraction, and agricultural return flow. This study evaluates the hydrochemical evolution, isotopic characteristics, ²²²Rn activity, and water-use suitability of groundwater and associated waters in Karbala Governorate, central Iraq. Seventeen groundwater, lake water, and municipal supply water samples were analyzed for physicochemical parameters, major ions, δ¹⁸O, δ²H, and ²²²Rn. Hydrochemical, isotopic, and water-quality assessment methods were applied to evaluate groundwater evolution, salinization, and suitability for drinking and irrigation. The waters are near-neutral, with pH values of 6.18–7.35, but are strongly mineralized. Electrical conductivity ranges from 1440 to 16,305 µS/cm, and total dissolved solids (TDS) range from 592 to 10,191 mg/L. Most samples belong to a Ca–Mg–SO₄–Cl facies, indicating sulfate- and chloride-rich hard water evolution. The highest mineralization occurs near Karbala proper and lake-influenced sites. Ion ratios and chloro-alkaline indices indicate that evaporite dissolution, gypsum/anhydrite dissolution, carbonate interaction, evaporation, and local ion exchange jointly control groundwater chemistry. Stable isotopes indicate meteoric origin with variable evaporative enrichment; however, highly saline but isotopically depleted water, particularly W8, shows that evaporation alone cannot explain salinization. ²²²Rn activities range from below detection to 11.28 Bq/L and mainly reflect local aquifer contact and degassing. High TDS, sulfate, chloride, and very high hardness limit suitability for drinking-water use. For irrigation, the sodium hazard is low, but salinity, hardness, magnesium hazard, and permeability constraints make most samples unsuitable or restricted. Management should prioritize salinity and hardness control, treatment or blending before domestic use, restricted irrigation of the least saline wells under drainage and soil-salinity monitoring, protection of less mineralized recharge zones, and long-term monitoring of lake-adjacent and agriculturally influenced wells. Full article

Groundwater quality remains insufficiently characterized in the rural agriculture–residential interface of the Huaibei Plain, particularly with respect to nitrate (NO₃⁻) occurrence, hydrochemical controls, source contributions, and population-specific health risks. In this study, multivariate statistical analysis, source apportionment models, and health risk assessment models were applied to investigate the hydrochemical characteristics of groundwater and related non-carcinogenic risks to different populations. NO₃⁻ content exceeded the World Health Organization (WHO) guidelines for drinking water in 60.0% and 62.5% of wet- and dry-season groundwater, respectively. Groundwater NO₃⁻ was mainly influenced by agricultural non-point inputs and domestic sewage, whereas major-ion composition was primarily governed by water–rock interactions. Our deterministic health risk assessment model reveals that the hazard index (HI) exceeded the acceptable threshold of 1.0 in 76.25%, 65.00%, 66.25%, and 56.25% of groundwater samples for infants, children, adult females, and adult males, respectively. These results indicate that continuous monitoring, improved sewage collection, and more controlled nitrogen management are required in the rural agricultural–residential interface of the Huaibei Plain with regard to shallow domestic groundwater. Full article

Soil water availability, salinity dynamics, and nitrate transport are key factors controlling agricultural sustainability in arid environments characterized by limited water resources and high evaporative demand. This study evaluated the combined effects of soil texture, nitrate–nitrogen application, and sawdust mulching on soil water retention, evaporation losses, salinity redistribution, and nitrate movement in loamy sand and sandy clay loam soils under controlled greenhouse conditions. Results showed that soil texture was the dominant control on hydrochemical behavior, with sandy clay loam exhibiting higher water retention and lower drainage than loamy sand. Sawdust mulching significantly improved soil water conservation by reducing evaporation and stabilizing moisture distribution, while the 4 cm mulch treatment achieved the highest overall CSI performance. Evaporation strongly governed salinity accumulation in surface layers, whereas mulching reduced salt build-up and promoted a more uniform salinity profile. Nitrate transport closely followed water fluxes, resulting in higher leaching in loamy sand and greater retention in sandy clay loam. Increasing nitrogen application enhanced nitrate mobility and leaching in both soils. A Composite Sustainability Index (CSI) was developed to integrate soil water conservation, evaporation reduction, salinity control, and nitrate retention into a unified metric. Sensitivity analysis demonstrated that treatment rankings were largely unaffected by alternative weighting schemes, confirming the robustness of the CSI framework. The CSI identified mulch application, particularly the 4 cm mulch treatment, as the most effective management option based on overall sustainability performance. The CSI framework provides an integrated decision-support tool for evaluating coupled water–salt–nitrate interactions and improving water use efficiency and salinity management in arid agricultural systems. This study offers a novel integrated CSI-based framework for simultaneously quantifying hydrological and hydrochemical soil responses under mulch management in arid environments. Full article

Shallow groundwater systems of rural municipalities are highly vulnerable to long-term contamination from former on-site sanitation systems, while the hydrochemical response of the aquifer after sewerage network development may be delayed by several factors. In the present study, a total of 147 shallow groundwater samples collected during the summer sampling campaigns of 2018, 2019, 2023, and 2024 were analyzed for general water-quality parameters including pH, EC, NH₄⁺, NO₂⁻, NO₃⁻, PO₄⁻, Cl⁻, SO₄²⁻, microelements, and potentially toxic elements, including As, Pb, Cd, Ni, Cu, Zn, Fe, and Mn. The dataset was evaluated using descriptive statistics, Piper, Wilcox, and Gibbs diagrams, hierarchical cluster analysis, principal component analysis, and GIS-based spatial interpolation. The results indicate that, more than ten years after sewerage network development (2014), shallow groundwater in the study area still shows considerable contamination, primarily characterized by elevated mean concentrations of ammonium (0.836 mg/L), nitrate (177.43 mg/L), and chloride (313.26 mg/L), accompanied by high electrical conductivity (3115 µS/cm) and sodium enrichment (378.12 mg/L). Spatial and boxplot analyses of SAR further indicated increasing sodium-related heterogeneity after 2018, with higher local SAR values in 2023–2024. Hydrochemical diagrams revealed a shift towards Ca-Cl type to Na–Cl types, while multivariate analyses confirmed that salinity enrichment, nitrate contamination, water–rock interaction and redox-sensitive trace element mobilization act as overlapping but partly separable controls. The nitrate–chloride source plot indicated mixed contamination origins, dominated by residual sewage influence and manure-related inputs, with diffuse agricultural nitrogen leaching. Arsenic was used as a supporting indicator of mixing with wastewater; however, As was no longer detectable in most of the investigated wells, suggesting a marked reduction in the former wastewater leakage. These results support the slow attenuation of contamination in the shallow groundwater system affected by former wastewater infiltration and highlight the need for continuous monitoring. Full article

Karst terrains hold vital global groundwater reserves, underpinning regional water security and ecological stability. To elucidate groundwater hydrochemical patterns and formation mechanisms in Wuhan’s karst zone, this study adopted the Gibbs model, correlation analysis, principal component analysis and positive matrix factorization to explore water–rock interactions, hydrochemical origins, element migration, hydrogeochemical facies and genetic processes. The results show that water in both confined porous loose rock aquifers (CPLRAs) and karst fissure carbonate rock aquifers (KFCRAs) is mainly of HCO₃–Ca and HCO₃·SO₄–Ca types. Carbonate dissolution dominates hydrochemical evolution, with Ca²⁺, Mg²⁺, and HCO₃⁻ as major ions. Natural water–rock interactions control the ionic characteristics of both groundwater types. Silicate weathering exerts a greater influence on water in the KFCRA, while water in the CPLRA has more complex ion sources. Anthropogenic activities contribute 17.52% and 17.61% to their hydrochemical variations, suggesting moderate human influence. Water in the CPLRA is mainly affected by domestic sewage and soil organic nitrogen, locally superimposed with industrial and mining disturbances. Water in the KFCRA is primarily influenced by agricultural pollution, with minor domestic sewage input. These findings provide a scientific basis for sustainable development, protection, and targeted pollution control of groundwater resources in the Wuhan karst area, and offer a reference for hydrochemical studies in comparable karst regions. Full article