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Keywords = chemical characteristics of groundwater

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21 pages, 12439 KB  
Article
Inversion of Groundwater DNAPL Pollution Source Based on DCNN Surrogate Model and Hybrid Homotopy-PSO with Feedback Iteration
by Jiayuan Guo, Tiansheng Miao, Guanghua Li and Han Wang
Water 2026, 18(17), 2185; https://doi.org/10.3390/w18172185 - 3 Sep 2026
Viewed by 197
Abstract
Existing DNAPL groundwater source inversion approaches are confronted with prominent bottlenecks: shallow surrogate models often fail to capture strong nonlinear multiphase flow relationships, traditional heuristic optimizers suffer from premature convergence, and ill-posed equifinality further degrades inversion reliability, together with prohibitive computational costs from [...] Read more.
Existing DNAPL groundwater source inversion approaches are confronted with prominent bottlenecks: shallow surrogate models often fail to capture strong nonlinear multiphase flow relationships, traditional heuristic optimizers suffer from premature convergence, and ill-posed equifinality further degrades inversion reliability, together with prohibitive computational costs from repeated multiphase numerical simulation. Taking a typical chemical-contaminated site in Northeast China as the research object, this study establishes a multiphase flow numerical model that fully reproduces the migration and transformation mechanisms of chlorobenzene-based DNAPLs after systematic generalization of the site’s geological and hydrogeological conditions. To drastically cut the computational burden incurred during iterative inversion, high-quality datasets are generated via parameter sensitivity analysis and Latin hypercube sampling, based on which a deep convolutional neural network (DCNN)-driven high-fidelity surrogate model is constructed and embedded into the optimization framework as an equality constraint. A separated nonlinear programming model is formulated to independently quantify pollution source characteristics and hydrogeological parameters, with the objective of minimizing the residual error between field-measured and numerically simulated contaminant concentrations. A hybrid homotopy-particle swarm optimization (HH-PSO) algorithm is further proposed to address the limitations of conventional optimizers, including strong dependence on initial guesses and susceptibility to local optima. On this basis, a closed-loop feedback iteration scheme is developed, where source identification and parameter calibration are implemented alternately with bidirectional constraints and progressive correction to continuously refine and stabilize inversion outputs. This work presents distinct innovations in the methodology, algorithm, and practical application of DNAPL groundwater source inversion. Results from synthetic benchmark cases and on-site field applications demonstrate that the DCNN surrogate model achieves far higher fitting accuracy than shallow learning approaches (e.g., Kriging and support vector regression), with the coefficient of determination R2 exceeding 0.99. After the feedback correction iteration procedure, the average relative error for retrieved source locations, release histories, and hydrogeological parameters drops to 3.72%, and the overall computational efficiency is elevated by approximately 99.84%. The integrated simulation–optimization inversion framework proposed in this work integrates monitoring signal denoising, multiphase numerical simulation, deep learning surrogate modeling, hybrid intelligent optimization, and feedback iterative correction. This integrated system effectively resolves core technical bottlenecks in DNAPL groundwater source inversion, such as nonlinear ill-posedness, equifinality induced by mutual interference between source terms and aquifer parameters, prohibitive computational costs of multiphase simulations, and premature convergence of traditional optimization algorithms. The established framework can serve as a robust theoretical foundation and technical tool for rapid, precise source tracing, pollution liability confirmation, and remediation design at complex contaminated sites. Full article
(This article belongs to the Special Issue Sustainable Water Resource Management Using Cutting-Edge Technologies)
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19 pages, 3263 KB  
Article
Hydrochemical Characteristics and Controlling Factors of Groundwater in a Typical High-Water-Table Coal Mining Subsidence Area: A Case Study of the Luwa Mining Subsidence Area, Jining City, China
by Shimin Xu, Dianqing Jiang, Xiulei Ren, Yingzhuo Hou, Benyu Bo, Senlin Zheng, Feng Guo and Jianyu Rong
Water 2026, 18(17), 2143; https://doi.org/10.3390/w18172143 - 31 Aug 2026
Viewed by 253
Abstract
Understanding the hydrochemical characteristics of groundwater in coal mining subsidence areas is of critical scientific significance for water environment protection and ecological restoration in mining regions. A systematic hydrochemical campaign was undertaken in the Luwa collapse zone (Jining city, Shandong Province) to decipher [...] Read more.
Understanding the hydrochemical characteristics of groundwater in coal mining subsidence areas is of critical scientific significance for water environment protection and ecological restoration in mining regions. A systematic hydrochemical campaign was undertaken in the Luwa collapse zone (Jining city, Shandong Province) to decipher the composition, evolutionary behavior, and governing factors of groundwater within a high-water-table subsidence context. The analytical protocol comprised three complementary components: conventional hydrochemical profiling, ion-ratio-based source identification, and multivariate statistical modeling. The findings revealed that the groundwater in the study area was weakly alkaline (pH = 7.33 ± 0.217), with total dissolved solids (TDS) ranging from 1180 to 2280 mg/L, and all sampled sites exceeded the Class III groundwater quality standard of China. Na+, SO42−, and Cl were identified as the predominant pollutants, with exceedance rates of 91.3%, 95.7%, and 91.3%, respectively, which were primarily attributed to coal mine drainage and domestic sewage input. The groundwater chemical composition was governed by the combined effects of rock weathering, evaporation–concentration processes, and anthropogenic activities. Specifically, Na+ and Cl originated mainly from the dissolution of silicate minerals and halite, as well as domestic sewage input; SO42− was primarily controlled by evaporite dissolution and industrial wastewater discharge; carbonate and silicate mineral weathering was identified as the primary source of Ca2+ and Mg2+; and NO3 was predominantly influenced by agricultural activities. Principal component analysis (PCA) extracted three major controlling factors shaping the groundwater hydrochemistry in this area, namely: (1) evaporite dissolution and sewage input, (2) carbonate dissolution and pH buffering processes, and (3) agricultural input. This study reveals a dual-driven evolutionary model of groundwater in high-water-table coal mining subsidence areas, characterized by “natural enrichment superimposed by anthropogenic input,” whose work contributes to the knowledge base for sustainable groundwater stewardship and contamination risk reduction in mining-affected areas with analogous conditions. Full article
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21 pages, 2006 KB  
Article
Submarine Groundwater Discharge as a Driver of Biogeochemical Processes in Methane Seep Sediments
by Darya Purgina, Yuliya Moiseeva, Tatyana Malakhova, Andrey Toropov, Andrey Grinko, Tatyana Polivanova, Eva Ugolkova, Andrey Budnikov and Elena Gershelis
Water 2026, 18(16), 1997; https://doi.org/10.3390/w18161997 - 14 Aug 2026
Viewed by 422
Abstract
Submarine groundwater discharge (SGD) is an important pathway of dissolved matter transport to coastal ecosystems, yet its identification in methane seep environments remains challenging because chemical signals are modified by sedimentary biogeochemical processes. This study evaluated hydrochemical tracers of SGD in methane seep [...] Read more.
Submarine groundwater discharge (SGD) is an important pathway of dissolved matter transport to coastal ecosystems, yet its identification in methane seep environments remains challenging because chemical signals are modified by sedimentary biogeochemical processes. This study evaluated hydrochemical tracers of SGD in methane seep sites, bacterial mat areas, and background sediments along the southern coast of Crimea (Black Sea). The studied settings exhibited distinct water chemical characteristics. Chloride concentrations decreased from 10.6 to 11.2 g L−1 in background waters, to 8.7–9.3 g L−1 in bacterial mat pore waters and to 7.7 g L−1 in sediment–water interface waters, indicating the presence of a low-salinity water component. Dissolved silica increased by approximately one order of magnitude relative to background values at methane-associated sites. Methane concentrations ranged from 0.025 to 1058 μM, with the highest values occurring in bacterial mat areas. These zones were further characterized by sulfate depletion (down to 0.9 g L−1), elevated normalized alkalinity, ammonium concentrations reaching 8000 μg L−1, high sulfide contents, and low dissolved Fe concentrations consistent with iron sulfide precipitation. The results demonstrate that no single hydrochemical parameter is sufficient to identify SGD in methane-affected coastal sediments. Instead, the combined use of conservative tracers (Cl and DSi) and reactive constituents (SO42−, alkalinity, NH4+, HS, TDFe, and Mn2+) provides a robust hydrochemical framework for recognizing groundwater influence and evaluating associated biogeochemical transformations. Full article
(This article belongs to the Section Oceans and Coastal Zones)
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22 pages, 18440 KB  
Article
Groundwater Circulation Well Test for Synergistic Remediation of a Heterogeneous Site: Extraction, Tracing and Oxidation
by Han Ke, Xiaowen Wu, Minliang Fei, Shuning Zheng, Ling Li, Tingjun Wang, Jie Hu, Chensheng Zhang and Chaofeng Shen
Water 2026, 18(16), 1967; https://doi.org/10.3390/w18161967 - 11 Aug 2026
Viewed by 289
Abstract
Field tests were conducted at a heterogeneous industrial site using one circulation well and six monitoring wells. Groundwater circulation well (GCW) extraction–injection (30 d), multi-component tracing (6 h), and circulation–oxidation (20 h) tests were performed to investigate the flow-field characteristics and their influence [...] Read more.
Field tests were conducted at a heterogeneous industrial site using one circulation well and six monitoring wells. Groundwater circulation well (GCW) extraction–injection (30 d), multi-component tracing (6 h), and circulation–oxidation (20 h) tests were performed to investigate the flow-field characteristics and their influence on multi-component solute transport. The results suggested that the extraction–injection circulation mode increased the flow rate of the single well from 0.5 m3/h to 3.5 m3/h, establishing a composite flow field with near-field circulation and far-field outward expansion. Short-term circulation achieved limited concentration attenuation primarily near the well with rebound. Long-term circulation elevated the average concentration attenuation rates of benzene from 13% in the short-term test to 61%, and chemical oxygen demand (COD) from 16% to 47%, expanding the remediation scope of the circulation well. Bromide tracer tests and an advection–dispersion equation characterized the heterogeneous flow field with preferential flow channels and slow migration zones. Furthermore, sulfate tracer transport was governed by adsorptive retardation and advective delivery. Circulation–oxidation tests showed that benzene and COD showed higher concentration attenuation than naphthalene. After cessation, benzene and COD concentration attenuation rates increased by 39% and 29% compared to the short-term test without oxidation. Electrical resistivity tomography (ERT) revealed the downward diffusion of the oxidant, suggesting that the circulation well system enhances oxidant transport and expands the oxidant-affected zone. This research provides field-scale diagnostic evidence and in situ diagnostic methodologies for GCW remediation at complex contaminated sites. Full article
(This article belongs to the Section Hydrogeology)
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17 pages, 4310 KB  
Article
Multi-Year Dynamic Characteristics and Influence Factors of Groundwater Level for Different Karst Groundwater Systems in the Huaibei Region, China
by Zejun Zhu, Shouchuan Zhang and Yan Chen
Sustainability 2026, 18(15), 7758; https://doi.org/10.3390/su18157758 - 31 Jul 2026
Viewed by 216
Abstract
The Huaibei region is a critical grain and energy–chemical base in northern China, characterized by substantial water demand for industrial and agricultural production. Karst groundwater systems constitute the primary water supply source in this area. Under the superimposed impacts of intensive exploitation, climate [...] Read more.
The Huaibei region is a critical grain and energy–chemical base in northern China, characterized by substantial water demand for industrial and agricultural production. Karst groundwater systems constitute the primary water supply source in this area. Under the superimposed impacts of intensive exploitation, climate change, and anthropogenic activities, karst aquifers have encountered a series of geo-environmental problems, including groundwater level decline and expansion of cones of depression. Most previous studies have predominantly focused on water quality assessment and groundwater resource quantification, yet systematic investigations into the multi-scale characteristics and driving mechanisms of karst groundwater level dynamics remain insufficient. In this study, based on long-term groundwater level and rainfall monitoring data (2014–2024) from three monitoring wells representing different types of karst aquifers, continuous wavelet transform (CWT) and wavelet coherence (WTC) approaches are introduced to identify the periodic patterns of karst groundwater levels and reveal the dominant controlling factors of groundwater level dynamics. The results demonstrate that groundwater levels in all types of karst aquifers exhibit distinct multi-scale periodic variations. The groundwater levels of HB01 and HB02 share dominant oscillation periods of 18~19 months and 9 months with regional rainfall, while the groundwater level at HB03 displays a more complex, multi-scale, periodic combination of 41 months, 18~19 months, and 9 months. Periodic variations in regional rainfall serve as the dominant controlling factor for the intra-annual and inter-annual periodic fluctuations of karst water levels, with a prominent resonance relationship identified between the two variables at dominant periodic scales. Distinct heterogeneity is observed in the response magnitude and lag time of different karst aquifer types to rainfall; specifically, the lag time of water level response to rainfall on the annual periodic scale ranges from 2.7 to 2.9 months. The correlation between annual average water level and pumping discharge is moderate for boreholes HB01 and HB03, whereas a strong correlation is detected for borehole HB02, implying that its water level regime is likely subjected to pronounced pumping disturbance. The degree of karst development, aquifer burial depth, and overlying stratum architecture are the key geological factors accounting for such heterogeneous response patterns. For the first time, this study utilizes long-term water level time series data from the karst water exploitation zone of the Huaibei Plain, complemented by synchronous precipitation and pumping records. Integrated with regional hydrogeological settings, wavelet analysis is employed to conduct an in-depth investigation into the dynamic variations in karst water levels in the Huaibei region from the perspective of groundwater recharge–discharge relationships. The results provide a scientific underpinning for the remediation of karst water over-exploitation and the optimal allocation of water resources. Specifically, pumping and artificial recharge schemes can be proactively adjusted based on periodicity forecasts. Zoned management strategies for water resources are put forward: artificial regulation and storage are recommended for zones with sensitive hydrological responses, while preventive protection is prioritized for zones with sluggish responses. By incorporating periodic characteristics and lag durations, targeted pumping strategies for dry and wet seasons can be developed, and a coupled water level–rainfall–pumping early warning system can be established to realize the long-term sustainable regulation of karst water resources. Full article
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15 pages, 3115 KB  
Article
Persulfate Activation by Cobalt-Doped Pyrite Nanoparticles for Oxidative Removal of 4-Chlorophenol
by Mengyang Ni, Fangru He, Chuanjia Jiang and Hongyang Wang
Toxics 2026, 14(8), 663; https://doi.org/10.3390/toxics14080663 - 27 Jul 2026
Cited by 1 | Viewed by 403
Abstract
Persulfate-based Fenton-like oxidation is one of the most promising technologies for in situ chemical oxidation (ISCO) remediation of groundwater contamination, yet the mechanisms affecting persulfate activation efficiency remain underexplored. Herein, we investigated the efficiency and mechanisms of peroxydisulfate (PDS) and peroxymonosulfate (PMS) activation [...] Read more.
Persulfate-based Fenton-like oxidation is one of the most promising technologies for in situ chemical oxidation (ISCO) remediation of groundwater contamination, yet the mechanisms affecting persulfate activation efficiency remain underexplored. Herein, we investigated the efficiency and mechanisms of peroxydisulfate (PDS) and peroxymonosulfate (PMS) activation by cobalt-doped pyrite (Co-FeS2) nanoparticles for degradation of 4-chlorophenol (4-CP), a model groundwater contaminant. Notably, the degradation kinetics in the Co-FeS2/PDS system exhibited a unique “three-stage” characteristic, wherein the 4-CP degradation rate underwent a jump during the 3–5 min phase. This kinetic anomaly stems from the specific generation dynamics of ferryl species (FeIV=O), which experienced a 3 min lag phase followed by a rapid burst. Theoretical calculations revealed that surface-accumulated SO42− reduces the thermodynamic energy barrier for FeIV=O formation, which accounts for this rapid generation subsequent to the initial lag phase. Furthermore, while hydroxyl (•OH) and sulfate (SO4•−) radicals were critical in both systems, •OH concentration was higher than SO4•− concentration in the Co-FeS2/PDS system, whereas the Co-FeS2/PMS system exhibited the reverse trend. Moreover, homogeneous persulfate activation mediated by dissolved Fe(II) contributed to 4-CP degradation, but to different degrees in the two systems. This study provides mechanistic insights into persulfate-based ISCO processes for groundwater remediation. Full article
(This article belongs to the Special Issue Oxidative Removal of Emerging Contaminants)
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25 pages, 4178 KB  
Review
Coal Gangue: Sources, Environmental Risks, and Advances in Resource Utilization
by Xiaobin Li, Yongzhe Liang, Fan Chen, Jianing Du, Chaoyue Zhao, Jialong Lv, Yongtao Liu, Jinbo Li, Weiwen Qiu, Vilim Filipovi’c and Hailong He
Sustainability 2026, 18(15), 7572; https://doi.org/10.3390/su18157572 - 24 Jul 2026
Viewed by 385
Abstract
Coal gangue, a major by-product of coal mining, has long posed significant environmental and resource management challenges. With increasing global emphasis on energy transition and environmental sustainability, the comprehensive utilization of coal gangue has emerged as a critical research and policy priority. This [...] Read more.
Coal gangue, a major by-product of coal mining, has long posed significant environmental and resource management challenges. With increasing global emphasis on energy transition and environmental sustainability, the comprehensive utilization of coal gangue has emerged as a critical research and policy priority. This review systematically examines the sources, characteristics, environmental impacts, and integrated utilization pathways of coal gangue. First, the formation mechanisms, mineralogical composition, and physicochemical properties of coal gangue are summarized, with particular attention to hazardous constituents and associated environmental risks, including soil and groundwater contamination, atmospheric pollution, and ecological degradation. Subsequently, current technological approaches for coal gangue management and comprehensive utilization are evaluated, including subsidence areas reclamation and underground backfilling, applications in construction materials and energy conversion, extraction of valuable chemical elements and functional materials, ecological soil engineering, and carbon sequestration. The potential contributions of these pathways to waste reduction, resource efficiency, and low-carbon development are critically discussed. Finally, key environmental, technological, and socio-economic considerations influencing sustainable coal gangue utilization are emphasized. This review provides a comprehensive synthesis of existing knowledge and identifies future research directions aimed at advancing environmentally sound, economically viable, and large-scale utilization strategies. The findings are intended to support researchers, policymakers, and industry stakeholders in promoting circular resource systems and sustainable development. Full article
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21 pages, 3009 KB  
Article
Climate Effects on Water Chemistry in Acid-Sensitive Catchments
by Rolf D. Vogt, Marianne Stave Sekkenes, Magnus D. Norling, Kari Austnes, Heleen A. de Wit and Øyvind Kaste
Water 2026, 18(14), 1731; https://doi.org/10.3390/w18141731 - 17 Jul 2026
Viewed by 425
Abstract
Substantial declines in acidifying emissions across Europe have led to pronounced chemical recovery of Norwegian surface waters. In recent decades, however, changes in water chemistry have increasingly coincided with climate change, complicating the attribution of observed trends to individual drivers. This study assesses [...] Read more.
Substantial declines in acidifying emissions across Europe have led to pronounced chemical recovery of Norwegian surface waters. In recent decades, however, changes in water chemistry have increasingly coincided with climate change, complicating the attribution of observed trends to individual drivers. This study assesses whether ongoing climate change has produced detectable effects on freshwater chemistry in Norway and how these effects vary among catchments with differing sensitivities to acidification. In this study, the Model of Acidification of Groundwater In Catchments (MAGIC), which is based on current understanding of the processes governing acid–base chemistry in soils and waters, was used to simulate the effects of declining acid deposition. Deviations between observed and modelled water chemistry were provisionally interpreted as climate-related effects. However, these residuals may also reflect model or parameter uncertainty and other unaccounted-for processes. The analysis draws on long-term monitoring data (1986–2022) from 59 acid-sensitive Trend Lakes distributed across Norway, together with four Field Research Stations (1986–2020) representing contrasting hydroclimatic and biogeochemical conditions. Temporal trends were evaluated using the Mann–Kendall test and Sen’s slope estimator, while relationships between inferred climate effects and climatic variables were examined using Pearson’s correlation analysis. Across the Trend Lakes, inferred climate effects were predominantly positive for acid-neutralising capacity (ANC) and weathering-derived cations, suggesting that climate change may contribute to accelerated chemical recovery, particularly in catchments less sensitive to acidification. The inferred climate effects varied substantially among the Field Research Stations. Higher temperatures were generally associated with enhanced recovery, possibly through intensified silicate weathering, whereas increased precipitation and runoff appeared to dampen recovery. Overall, the results suggest that climate change exerts a measurable influence on freshwater chemistry in Norway, although the magnitude and direction of the response are strongly modulated by catchment-specific characteristics. While previous studies have identified climate-related influences on individual chemical variables, quantitative attempts to separate climate- and acid-deposition-related effects across a large number of acid-sensitive catchments remain rare. Here, we use deviations between observed water chemistry and MAGIC simulations of acid deposition recovery as a screening approach to investigate whether climate-related signals can be detected at the national scale and whether these signals vary among catchments with differing sensitivities to acidification. Full article
(This article belongs to the Special Issue Climate, Water, and Soil, 2nd Edition)
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20 pages, 13678 KB  
Article
Chemical Evolution Characteristics and Health Risks Assessment of Surface Water–Groundwater in Large-Scale Coal Mining Areas of the Inner Mongolian Plateau Under Mining Activities
by Yiwei Zhang, Liya Yang, Rui An, Rumeng Tian, Yu Fei, Shengpin Li and Kun Liu
Water 2026, 18(13), 1604; https://doi.org/10.3390/w18131604 - 2 Jul 2026
Viewed by 552
Abstract
Mining can significantly affect the spatial distribution and temporal evolution of groundwater chemistry. From July to August 2024, the research team collected 26 surface water and groundwater samples in the Shengli Coal Mine area of the Mongolian Plateau, conducting comprehensive hydrogeochemical analyses on [...] Read more.
Mining can significantly affect the spatial distribution and temporal evolution of groundwater chemistry. From July to August 2024, the research team collected 26 surface water and groundwater samples in the Shengli Coal Mine area of the Mongolian Plateau, conducting comprehensive hydrogeochemical analyses on surface water flowing through the mining area, groundwater within the mining area, seepage water, and groundwater outside the mining area. The results indicate that groundwater in this region is notably affected by human activities such as mining operations. Specifically, in surface water flowing through the mining area, concentrations of total dissolved solids (TDS), sulfates, nitrates, and nickel showed significant increases. Compared to groundwater systems in other areas of the Mongolian Plateau, nickel levels in the mining area’s groundwater were significantly higher, while nitrate levels exhibited the opposite trend. A significant positive correlation was observed between metal element concentrations in surface water and groundwater. The study found that abnormal distributions of heavy metals such as beryllium (Be), thallium (Tl), and tin (Sn) may originate from point-source pollution caused by mining activities. Furthermore, concentrations of manganese (Mn), arsenic (As), and antimony (Sb) in the groundwater of this area exceeded relevant regulatory limits, with arsenic being particularly prominent. The levels of arsenic in both surface water and groundwater may pose carcinogenic risks to human health. This study shows that nearly half of the sampled water bodies in the area require purification treatment to meet drinking water standards, highlighting the urgent need for further attention to water quality safety issues. The conclusions derived from this research provide theoretical support for understanding the long-term evolutionary mechanisms of groundwater in mining areas, while also offering important insights for improving groundwater environmental management and ensuring water resource security in mining regions. Full article
(This article belongs to the Section Water Quality and Contamination)
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16 pages, 4160 KB  
Article
Hydrochemical Characteristics and Formation Mechanisms of Drinking Natural Mineral Water in Ningbo City
by Yuli Wang, Yi Wei, Shenglei Wang and Yusong Wang
Water 2026, 18(11), 1280; https://doi.org/10.3390/w18111280 - 25 May 2026
Viewed by 667
Abstract
Ningbo City is endowed with abundant mineral water resources. Investigating their chemical characteristics and formation mechanisms is essential for understanding hydrochemical evolution and supporting sustainable resource utilization. Based on hydrochemical data from 12 drinking natural mineral water sources in Ningbo City, this study [...] Read more.
Ningbo City is endowed with abundant mineral water resources. Investigating their chemical characteristics and formation mechanisms is essential for understanding hydrochemical evolution and supporting sustainable resource utilization. Based on hydrochemical data from 12 drinking natural mineral water sources in Ningbo City, this study investigates the hydrochemical features and genesis of mineral water by integrating statistical analysis, hydrochemical diagrams, ionic ratios, and mineral equilibrium modeling. The results indicate that metasilicic acid (as H2SiO3) and strontium (Sr) are the principal characteristic components of the drinking natural mineral water in Ningbo City, with concentrations of 32.87–60.8 mg/L and 0.05–4.59 mg/L, respectively. The mineral waters are neutral to slightly alkaline and weakly mineralized, with the pH values ranging from 6.70 to 8.16, and total dissolved solids (TDS) contents of 76.8–767.2 mg/L. The predominant hydrochemical facies are HCO3-Ca-Na, HCO3-Ca, HCO3-Na-Ca. Their chemical composition is mainly governed by rock weathering, whilst also being influenced by cation exchange and mineral dissolution–precipitation equilibrium. H2SiO3 is mainly derived from the weathering and hydrolysis of silicate minerals such as plagioclase. Sr enrichment is associated with the dissolution of Sr-bearing silicate minerals and certain sulphate minerals, as well as prolonged water–rock interaction. The Sr- and Si-rich aquifers provide the material basis for the enrichment of Sr and H2SiO3 in groundwater. Structural fractures and weathering fractures provide transport pathways and storage spaces for groundwater, facilitating the migration and enrichment of these characteristic components. The mechanism of mineral water emergence can be summarized as of the tectonic fracture-controlled circulation-leaching type. Full article
(This article belongs to the Section Hydrogeology)
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25 pages, 5919 KB  
Article
Groundwater Springs in Young Glacial Areas and Their Role in Sustainable Environmental Development (Case Study—North Poland)
by Izabela Chlost, Stanisław Chmiel, Roman Cieśliński, Joanna Fac-Beneda, Ivan Kirvel and Alicja Olszewska
Sustainability 2026, 18(11), 5245; https://doi.org/10.3390/su18115245 - 22 May 2026
Viewed by 751
Abstract
This article presents the results of a field study conducted in 2022 on groundwater outflows located at the edge of the Kashubian Lake District and the Reda-Łeba Proglacial Stream Valley in northern Poland. The recharge of numerous springs was found to occur from [...] Read more.
This article presents the results of a field study conducted in 2022 on groundwater outflows located at the edge of the Kashubian Lake District and the Reda-Łeba Proglacial Stream Valley in northern Poland. The recharge of numerous springs was found to occur from the first aquifer, locally supported by a deeper aquifer connected to the first one near the bowl of Lubowidzkie Lake. Groundwater drainage occurs by gravity. It is relatively abundant for young glacial areas and averages 82 dm3·s−1, making the springs capable of acting as a drinking water reservoir. This assessment is based on major ions and nutrients only; microbiological and trace-organic/metal analyses are required before any drinking-water designation. Spring water is important in the lake’s supply, accounting for 18.0% of the total inflow to the basin. The hydrochemical characteristics of these waters keep the lake in ecological balance. The waters from the springs are characterized by little variation in chemical composition, with the Ca-HCO3 hydrochemical type. They represent young infiltration waters associated with direct recharge from precipitation (the average age of the water is 60 years). Currently, low nitrate and chloride suggest limited agricultural and urban influence, but phosphate levels and observed human activities warrant caution. Forest management is gradually developing in its catchment, which may result in a reduction of the spring yield and a deterioration of their quality in the future. This may result in a disturbance of the hydrological balance of structures hydraulically connected to spring recharge and to groundwater inflow (river, lake). Although the springs studied are local hydrological phenomena, their functioning and the need for protection are closely linked to global challenges in the field of sustainable development. This primarily concerns the protection of groundwater-dependent ecosystems and, more broadly, water security and increased resilience to climate change. Full article
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21 pages, 10483 KB  
Article
Geological Characteristics and Groundwater Health Risk Assessment in Nanshu Area, Eastern China
by Guang Yang, Chao Zhang, Sichu Bai, Bo Wang, Jing Sun, Jing Li, Quanbao Su, Chao Ma and Gang Wang
Water 2026, 18(10), 1136; https://doi.org/10.3390/w18101136 - 9 May 2026
Viewed by 713
Abstract
Located in eastern China, the Nanshu area is abundant in groundwater resources with favorable water quality, acting as a critical water supply source for the region. In recent years, the regional groundwater environment has been significantly disturbed by continuous anthropogenic activities, which has [...] Read more.
Located in eastern China, the Nanshu area is abundant in groundwater resources with favorable water quality, acting as a critical water supply source for the region. In recent years, the regional groundwater environment has been significantly disturbed by continuous anthropogenic activities, which has aroused widespread concern. In this study, correlation analysis, principal component analysis, hydrochemical methods, the Entropy Weight Water Quality Index, and the Human Health Risk Assessment model were comprehensively applied to systematically investigate groundwater in the Nanshu area. The research objectives are to determine the health risk levels of regional groundwater and provide a scientific basis for the protection and rational utilization of groundwater resources. The results indicate that groundwater in the study area is weakly alkaline freshwater, dominated by the HCO3-Ca hydrochemical type. With favorable groundwater circulation conditions and weak evaporative concentration effects, it generally exhibits the typical natural hydrogeochemical characteristics of shallow groundwater in the piedmont regions of northern China. The chemical composition of groundwater is mainly controlled by water–rock interactions. The dissolution of silicate minerals, gypsum, halite and sepiolite, together with significant reverse cation exchange, collectively shape the hydrochemical composition, and natural hydrogeological conditions form the basic pattern of regional water quality. The overall potability of groundwater in the study area is moderate. Approximately 30% of the groundwater is unsuitable for direct drinking due to anthropogenic pollution, and agricultural activities and domestic sewage discharge have become key factors causing local water quality degradation. Non-carcinogenic health risks posed by groundwater nitrate vary significantly among different populations. The risk level for infants and young children is much higher than that for adults, posing a substantial health threat to sensitive populations. According to the findings, it is recommended to focus on controlling the groundwater risk sources in the central area, strengthen the dynamic monitoring of water quality in water source zones, and strictly regulate regional development activities, so as to achieve the sustainable utilization of groundwater resources. Full article
(This article belongs to the Topic Water-Soil Pollution Control and Environmental Management)
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33 pages, 5466 KB  
Review
Carbonate-Induced Self-Sealing of Near-Field Granite Fractures in Geological Disposal of High-Level Radioactive Waste: Coupled THMC Precipitation–Dissolution Mechanisms and Long-Term Performance Evaluation
by Xiao Tian, Jia-Wei Wang, Ju Wang, Zhichao Zhou, Jiebiao Li, Xianzhe Duan, Nan Li, Wentao Xu and Biao Wang
Appl. Sci. 2026, 16(10), 4651; https://doi.org/10.3390/app16104651 - 8 May 2026
Viewed by 469
Abstract
Deep geological disposal is widely recognized as the most reliable strategy for the long-term isolation of high-level radioactive waste (HLW). In granitic host rocks, fractures in the near-field represent the primary pathways for groundwater flow and potential radionuclide migration. The self-sealing capacity of [...] Read more.
Deep geological disposal is widely recognized as the most reliable strategy for the long-term isolation of high-level radioactive waste (HLW). In granitic host rocks, fractures in the near-field represent the primary pathways for groundwater flow and potential radionuclide migration. The self-sealing capacity of carbonate-filled fractures, along with its long-term effectiveness, plays a critical role in maintaining the integrity of the multi-barrier system and ensuring repository safety. Near-field fractures undergo complex thermo–hydro–mechanical–chemical (THMC) coupled evolution driven by excavation-induced disturbances, decay heat, groundwater saturation, and ongoing water–rock interactions. Within the confined fracture spaces, carbonate minerals may persistently undergo precipitation–dissolution cycling and micro- to nanoscale structural reorganization, resulting in progressive reductions in fracture connectivity and hydraulic transmissivity. However, existing studies have largely focused on short-term sealing effects, with limited systematic understanding of the long-term safety functions. In this context, this study comprehensively investigates carbonate-induced self-sealing in granitic fractures within the near-field of a repository under realistic THMC-coupled conditions. We elucidate the micro- and nanoscale heterogeneous precipitation characteristics governed by non-classical nucleation pathways, reveal how dynamic precipitation–dissolution equilibria facilitate ongoing reductions in fracture transmissivity, and propose a multi-dimensional framework for long-term hydraulic, mechanical, and chemical performance assessment. Our findings demonstrate that carbonate self-sealing operates as a dynamic, reorganizing, and multi-mineral cooperative mechanism rather than a static, one-directional process. Its core safety function lies in the sustained suppression of fracture transmissivity. The mechanistic insights and evaluation framework proposed in this study provide a foundation for integrating natural carbonate self-sealing with engineered barrier system design, thereby improving fracture control, advancing long-term safety assessment, and optimizing the design of HLW deep geological repositories. Full article
(This article belongs to the Special Issue Radioactive Waste Treatment and Environment Recovery)
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20 pages, 3972 KB  
Article
Case Study on the Assessment of Leaching and Migration Risks of Contaminants in Tailings Backfill at an Open-Pit Gold Mine: Leaching Characteristics, Long-Term Release Patterns, and Migration Modeling
by Peng Li, Yang Sun, Wenwen Meng, Zhe Hu, Zhengcan Li, Qilin Liu and Yushuang Li
Minerals 2026, 16(5), 491; https://doi.org/10.3390/min16050491 - 7 May 2026
Viewed by 478
Abstract
Flotation tailings, the primary solid waste generated during gold extraction, may pose issues such as land occupation, environmental pollution, and geological hazards in open-pit mining areas. This study systematically investigated the environmental characteristics, long-term pollutant release patterns, and migration risks associated with flotation [...] Read more.
Flotation tailings, the primary solid waste generated during gold extraction, may pose issues such as land occupation, environmental pollution, and geological hazards in open-pit mining areas. This study systematically investigated the environmental characteristics, long-term pollutant release patterns, and migration risks associated with flotation tailings by taking a specific backfill project as a case study and employing short-term leaching tests, long-term column leaching experiments, and multi-model numerical simulations. Short-term leaching tests indicated that tailings leachate exhibited weak alkalinity (pH 8.21−8.45) with low pollutant leaching concentrations, meeting the fundamental requirements for open-pit backfilling. Notably, leaching characteristics varied significantly among tailings from different sources, and an extended storage duration enhanced chemical stability. Long-term leaching tests identified nine characteristic pollutants, including fluoride and sulfate, with their release patterns categorized into three types: continuous slow release, initial rapid leaching, and delayed/complex release. Furthermore, simulation results from the HYDRUS and MODFLOW/MT3DMS models indicated that the maximum predicted concentrations of characteristic pollutants in the surrounding soil and groundwater will remain at low levels for 50 years post-backfilling. The site’s “micro-to-weakly permeable” strata exhibited significant pollutant retention capabilities. Based on these experimental and simulation results, a three-tier risk management system—”source control, process monitoring, and end-point surveillance”, was developed to provide technical support for the long-term environmental safety of the flotation tailings backfill project. This study revealed the environmental risk characteristics associated with the storage of flotation tailings, including land occupation, environmental pollution, and the potential for geological hazards in open pits. Furthermore, the leaching characteristics, long-term release patterns, and migration mechanisms of tailings used to backfill open pits have been elucidated, providing theoretical references and practical guidance for similar solid waste resource recovery and backfilling projects. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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24 pages, 2685 KB  
Article
Multi-Dimensional Method Innovation and System Construction for Synergistic Damage Assessment of Multi-Media Pollution
by Zhengda Lin, Jifeng Wang, Bingjie Yan, Jun Zhang, Yu Wang, Lingling Fan and Caoqingqing Li
Water 2026, 18(9), 1068; https://doi.org/10.3390/w18091068 - 29 Apr 2026
Viewed by 643
Abstract
To address issues existing in current multi-media pollution assessment, such as data mismatch, parameter conflicts, and inadequate characterization of nonlinear effects, this study developed a multi-factor synergistic assessment methodological system encompassing “data preprocessing-parameter calibration-damage quantification-model coupling”. A three-stage parameter calibration system of “inheritance-linkage-sensitivity [...] Read more.
To address issues existing in current multi-media pollution assessment, such as data mismatch, parameter conflicts, and inadequate characterization of nonlinear effects, this study developed a multi-factor synergistic assessment methodological system encompassing “data preprocessing-parameter calibration-damage quantification-model coupling”. A three-stage parameter calibration system of “inheritance-linkage-sensitivity screening” was established to achieve cross-media parameter synergy; an Environmental Damage Entropy (EDE) model was constructed based on information entropy to quantify the nonlinear coupled damage of multiple factors; and the optimal governance threshold was determined by combining the coupling theory of marginal damage and governance cost. Taking a multi-media pollution incident (atmosphere-soil-surface water-groundwater) caused by a chemical plant explosion as a case study, pollution chain identification, damage quantification, ecological risk cascading effect analysis, and health risk assessment were conducted. The results show that this method can accurately identify key pollution pathways. Based on the calculation of Environmental Damage Entropy (EDE = 0.604) and the synergy coefficient (δ = 1.32), the comprehensive damage value was quantified as 8.21 million yuan. Additionally, the threshold exceedance characteristics of various media were identified, reflecting the cumulative and lagging nature of ecological risk cascading effects. The method proposed in this study can accurately identify key pollution pathways and quantify comprehensive damage as well as ecological risks, providing scientific support for the allocation of multi-media pollution governance responsibilities and precise prevention and control. Full article
(This article belongs to the Section Water Quality and Contamination)
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