Search Results (481)

Groundwater contamination by redox-sensitive elements (RSEs) such as arsenic (As), chromium (Cr), vanadium (V), and selenium (Se) pose a critical challenge in alluvial aquifers, where seasonal hydrological forcing drives dynamic hydrogeochemical and redox conditions. This study investigates the seasonal evolution of groundwater hydrogeochemistry and multi-metal behavior in shallow aquifers of the Mid-Gangetic Plain, India, with particular emphasis on the role of seasonal redox decoupling. Monsoon conditions were dominated by strongly reducing environments (ORP: −150 to −70 mV), predominantly Ca–Mg–SO₄ and Na–Cl type facies. Under these conditions, significant correlations among RSEs in particular (As–V, As–Se) indicated coupled mobilization governed by the reductive dissolution of Fe–Mn (oxyhydr)oxides. Monsoon groundwater also exhibited strong associations between RSEs and agronomic indicators (NO₃⁻, SO₄²⁻), suggesting the influence of recharge-mediated agricultural inputs on redox-sensitive geochemical processes. In contrast, post-monsoon conditions showed a clear transition to sub-oxic states (ORP up to +121 mV) and were dominated by Ca–Mg–HCO₃ facies, accompanied by substantial increases in bicarbonate (~372%), electrical conductivity (~62%), and total dissolved solids (~21%). Despite the partial oxidation of the aquifer system, redox-sensitive metals did not respond uniformly. Instead, inter-element correlations weakened or disappeared, indicating a transition from coupled to decoupled contaminant behavior. Arsenic concentrations increased up to 20.8 µgL⁻¹, whereas Cr and V displayed variable enrichment controlled by alkali-induced desorption and carbonate-mediated surface interactions. This transition reflects seasonal redox decoupling, whereby seasonal redox shifts lead to metal-specific rather than coordinated multi-metal behavior. We propose a Seasonal Redox Decoupling Framework (SRDF) to explain the shift from coupled reductive release during monsoon conditions to selective mobilization pathways in the post-monsoon period. These findings demonstrate that seasonal redox shifts control not only metal concentrations but also inter-element relationships, leading to metal-specific risk profiles. This underscores the need for seasonally adaptive monitoring and management strategies in hydrologically dynamic alluvial aquifers. Full article

We present a whole-rock geochemical dataset of late Variscan intrusive rocks and residual anatectic melts from the mid- and lower continental crust exposed in the Serre Massif of Calabria (southern Italy). A total of 74 samples were collected from the main plutonic units and from leucosomes of associated migmatitic metasediments. The composition of intrusive rocks varies from tonalites and quartz-diorites at deeper structural levels, to peraluminous granites at shallower levels. The dataset includes major, trace and rare earth element (REE) analyses obtained using X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). The dataset integrates new and previously published geochemical data into a consistent and reusable format, including sample locations (WGS84), lithological classification and lithostratigraphic attribution. Sampling sites are also provided as a downloadable geospatial (.kmz) file for visualization in GIS platforms. The data are intended to support a wide range of applications, including studies on granitoid magmatism, water–rock interaction processes in crystalline aquifers and raw materials exploration. Therefore, the dataset represents a valuable resource for both fundamental and applied geoscientific research. Full article

Reliable surveillance of dissolved ²²²Rn in arid-region aquifers is challenged by very low natural activity and method-dependent biases, especially humidity sensitivity in electrostatic detectors and air–water partitioning during closed-loop aeration, which can obscure true concentrations needed for defensible drinking-water baselines under preventive frameworks. This study aimed to optimize and field-validate a low-background RAD7 Big-Bottle (RAD H₂O) closed-loop protocol tailored for arid conditions and apply it in a regional survey of groundwater used for potable supply in northeastern Saudi Arabia. Groundwater from wells across the region (shallow and deep completions) was collected and analyzed using isotope-resolved alpha spectroscopy (Po-218 and Po-214 windows) with strict chamber humidity control (≤7% RH), background checks, systematic blanks, duplicates, drift control (±10%), and uncertainty propagation. Air-phase chamber counts were mandatorily converted to water-phase activity using the CAPTURE parameterized by measured loop volumes, temperature, salinity, and humidity, and agreement was evaluated using regression diagnostics and Bland–Altman analysis. The optimized method achieved sub-Bq·L⁻¹ performance, with MDL improving from ~0.1645 Bq·L⁻¹ (30 min) to ~0.0233 Bq·L⁻¹ (1500 min) and ~0.0165 Bq·L⁻¹ (3000 min), and LOQ decreasing from ~0.50 to ~0.0707 and ~0.050 Bq·L⁻¹, respectively. Raw air-phase readings systematically overestimated dissolved radon by ~26% (slope ≈ 1.26), a bias removed by the validated air → water conversion. Surveyed ²²²Rn concentrations were uniformly low (0.03–3.20 Bq·L⁻¹), far below commonly used reference values (e.g., ~11.1 and ~100 Bq·L⁻¹), with no persistent spatial hotspots and broadly overlapping shallow/deep distributions, indicating variability dominated by local lithology and fracture-controlled flow rather than depth. A tiered monitoring scheme is recommended: short screening, routine baselining at ~900–1500 min total counting, and ~3000 min for ultralow verification, providing a transferable template for sustainable baseline programs in arid aquifers. Full article

Intensive extraction in shallow coal seam groups poses a severe threat to regional hydrogeological stability. This study investigates the evolutionary laws of water-conducting fracture zone (WCFZ) height and phreatic level response at the Wanli No. 1 Mine. Although limited to a two-dimensional physical model and a single-case study, the research integrates field monitoring with similarity simulations to evaluate the efficacy of gangue grouting backfilling (GGB). The results reveal a significant superposition effect in dual-seam mining, where cumulative disturbances trigger the reactivation of upper-seam fractures, causing the WCFZ to penetrate the surface (170 m)—a phenomenon absent in single-seam mining. Scientifically, this work identifies a dual-threshold effect for ecological and structural preservation. While an equivalent filling rate (η) of 35% is sufficient to maintain the ecological water level in single-seam mining, dual-seam extraction requires a minimum η of 65% to restrict phreatic drawdown within the 1.5 m ecological threshold. Notably, while the laboratory model suggests a higher mechanical safety limit of η = 80% to prevent fracture propagation, the 65% threshold provides a balance between backfilling efficiency and environmental protection. The primary scientific contribution of this study is the quantification of the coupling relationship between overburden mechanical stability and long-term ecological functions. By shifting the overburden failure mode from “surface-penetrating fracturing” to “controlled bending subsidence,” this research provides a robust theoretical foundation for decoupling mining intensity from hydrogeological degradation in fragile multi-seam environments. Full article

Shallow coal resources are being gradually depleted, which has led to an increase in mining depth. However, the safe extraction of deep coal seams is increasingly threatened by limestone water hazards. When vertical hydraulic channels such as karst collapse columns (KCCs) develop in limestone strata, high-pressure water may flow into the mine, potentially causing substantial casualties and property losses. In this study, the 1613A stope of the Zhangji coal mine was investigated through comprehensive detection, grouting treatment, and prevention effect evaluation. A numerical model was established to simulate the dynamic changes in groundwater levels within the limestone aquifers throughout the process. The results reveal that a KCC is developed beneath the C₃³ stratum, exhibiting an oval shape with a length of 53 m and a width of 35 m in plan view. A combination of surface and underground methods, including exploration, treatment, verification, and reinforcement, has sealed the hydraulic pathway connected to the Ordovician limestone, thereby eliminating the threat of floor water inrush. These findings are of significant value for the application and dissemination of advanced regional control technologies for water hazards in coal mines. Full article

Vertical land motion in urban areas is a critical manifestation of groundwater, directly affecting infrastructure stability and groundwater sustainability. While land subsidence caused by groundwater extraction has been widely investigated, the opposite process—surface uplift induced by groundwater recovery—remains poorly documented or understood, particularly regarding its hydrological mechanisms and potential hazards. Here, we integrate InSAR time-series analysis of Sentinel-1 imagery (2017–2025) with groundwater well records to quantify the spatial–temporal characteristics of uplift in Xi’an, China, and to evaluate its hydrogeological drivers. Results reveal a persistent surface uplift zone south of the ancient city in Xi’an, with rates up to 20 mm/yr. The uplift correlates closely with rising groundwater levels in the shallow confined aquifer, indicating a strong coupling between aquifer recharge and surface uplift. Calculated storage coefficients and hydraulic diffusivity values highlight marked spatial variations, constrained by some ground fissures that act as both mechanical discontinuities and hydrological barriers controlling pressure diffusion. Time-series analysis further identifies the eastward propagation of subsidence-to-uplift reversal in Yuhuazhai, an urban village with groundwater injection, which is used to quantify the diffusivity coefficients. Field investigations show that rapid groundwater rebound can lead to uplift-related hazards, such as basement seepage, underscoring that surface uplift must be considered alongside subsidence in urban water management. Full article

Coastal groundwater in monsoon-dominated regions faces compounding threats from seasonal hydrological extremes and seawater intrusion (SWI), yet the molecular-scale response of dissolved organic matter (DOM) remains poorly understood. We conducted a two-season investigation in Mannar District, Sri Lanka, integrating hydrochemistry, fluorescence spectroscopy, and Fourier-transform ion cyclotron resonance mass spectrometry to characterize DOM dynamics across shallow and deep groundwater. Dry-season chloride averaged 302 mg/L (shallow—5 to 12 m) and 505 mg/L (tube wells—20 to 30 m), then declined by 60–80% during monsoon recharge. Despite this freshening, DOM dynamics were decoupled from salinity: shallow wells showed dry-season DOC peaks (6.64 mg/L) driven by soil concentration, while tube wells exhibited wet-season enrichment (5.02 mg/L). Shallow aquifers maintained consistently high humification indices (around 0.70) and aromatic-rich DOM, indicating sustained buffering by soil-derived inputs. In contrast, wet-season recharge in tube wells appeared to stimulate microbial processing, as indicated by elevated protein-like fluorescence (C2: 26% to 36%) and a higher contribution of nitrogen-bearing formulas (CHONs: 31.4% to 37.1%). Tube wells also accumulated reduced, energy-rich DOM with correspondingly high molecular lability indices. Paradoxically, correlation networks suggested that these saturated aliphatic and halogenated structures persist due to kinetic protection under low oxygen, high-salinity conditions. These findings indicate that aquifer structure and redox conditions control DOM biogeochemistry in coastal groundwater systems. At the molecular level, DOM dynamics are influenced by aquifer depth and seasonal recharge, leading to a decoupling between salinity and organic matter transformation. Full article

Defining the near-surface signal reflecting the deep sub-surface leakage is a critical challenge in the risk assessment of geologic carbon storage (GCS) projects, often exacerbated by decoupled deep-to-shallow modeling. This study quantifies the mass distribution and phase evolution of leaked CO₂ through deep reservoir-caprocks, intermediate aquifer, and near-surface soil, thereby showing the sub-surface retention characteristics and the detectability of near-surface signals. A geological model from the deep reservoir to the soil layer was constructed to simulate CO₂ leakage through the caprock and migration into overlying strata in 1000 years. Using the simulator of GPSFLOW, this study evaluates the evolution of fluid phases and the mass distribution during the injection for 100 years and the post-injection periods. The results indicate that (1) at the moment the injection ceases, 87.43–99.06% of the CO₂ remaining within the system is retained within the reservoirs, with less than 8.42% reaching the intermediate aquifer. Remarkably, although the CO₂ ultimately reaching the near-surface soil is less than 0.00073% of the total mass retained within the system, this mass accumulation translates to a concentration anomaly with a signal-to-noise ratio of 368 relative to the background baseline. (2) Sensitivity analysis reveals that the injection rate affects the timing of fluid transport—a tenfold increase in injection rate (from 3.17 to 31.7 kg/s) accelerates the upward movement of CO₂, advancing its arrival at the near-surface by 15 years without changing the overall mass partitioning. The permeability anisotropy ratio affects CO₂ migration and phase distribution—decreasing the vertical to horizontal permeability ratio (1, 0.5, 0.25, 0.125) reduces connectivity, which delays the upward transfer and increases the amount of the aqueous CO₂. However, specifically in the soil layer, the aqueous CO₂ accumulation reveals a non-monotonic trend that peaks at an intermediate ratio of 0.25. (3) CO₂ shows a cascading distribution across formations where reservoirs provide the primary storage, and the intermediate aquifer reduces the mass available for near-surface accumulation. This attenuation effect significantly reduces the CO₂ mass that reaches the soil layer, thereby controlling the strength and duration of near-surface environmental signals. This work offers a theoretical reference for formulating near-surface monitoring strategies for CO₂ leakage in GCS. Full article

Following adjustments in regional water resource management policies and changes in hydrogeological conditions, significant shifts have occurred in Beijing’s water consumption patterns, which have effectively mitigated land subsidence and triggered a trend of ground rebound. This study systematically analyzed the spatiotemporal characteristics and transition mechanisms of ground deformation (subsidence-rebound) driven by water consumption changes, integrating InSAR, ICA (independent component analysis), and regional hydrogeological data. InSAR time-series analysis derived 2015–2023 Beijing Plain deformation data, with ICA identifying key drivers, supported by hydrogeological interpretation. Three primary patterns emerged: (1) quasi-linear subsidence from persistent deep groundwater overextraction; (2) rebound from Chaobai River basin engineered recharge; (3) “subsidence-to-rebound” dynamics due to reduced shallow groundwater extraction and enhanced precipitation infiltration. The results indicate that a regional rebound emerged 5.5 years after the initiation of the South-to-North Water Diversion Project (SNWDP), which quantifies, for the first time, the direct temporal lag between the initiation of water diversion and the geomechanical deformation response. ICA further revealed that deformation asymmetry (subsidence trend slope > rebound trend slope) correlates with aquifer lithology (clay vs. sand-gravel layers). The results offer a scientific framework for urban groundwater management and subsidence mitigation, not only in Beijing but also in analogous regions globally, highlighting a paradigm shift in ground deformation dynamics under integrated water governance. Full article

Climate change is increasingly affecting groundwater resources in the Carpathian Basin, while rising temperatures are likely to increase irrigation demand and pressure on aquifers. We assessed climate- and pumping-driven impacts on the Nyírség recharge–discharge system (north-eastern Hungary) by combining shallow groundwater monitoring (1970–2022) with hydroclimate indicators from CHIRPS precipitation and ERA5-Land air temperature and snow depth (1981–2024). Using these datasets, we developed and calibrated a MODFLOW groundwater-flow model for representative wet (2010) and dry (2022) conditions, incorporating permitted abstraction and scenario-based estimates of unregistered pumping. We then ran scenario simulations to evaluate mid-century (2050) conditions and managed aquifer recharge (MAR) options. Precipitation exhibits strong interannual variability, but the region shows marked warming and a pronounced decline in snow storage, implying reduced cold-season buffering and higher evaporative demand. Simulations reproduce the observed post-2010 decline in shallow groundwater, with the largest decreases in higher-elevation recharge areas, whereas increased pumping mainly intensifies localized drawdown near major well fields. Scenario results indicate that climate-driven reductions in recharge dominate basin-scale declines by 2050, while MAR provides primarily local benefits; direct subsurface injection performs best among the tested options. These findings support practical groundwater management by prioritizing measurable and enforceable abstraction (including unregistered withdrawals), demand-side irrigation efficiency and adaptive caps in recharge areas, and targeted subsurface MAR where source water and infrastructure are available. Full article

The beneficial reuse of reclaimed water is a legislative objective of the State of Florida and a critical element in the optimization of water management in areas facing scarcity of freshwater. Aquifer storage and recovery (ASR) of reclaimed allows for the balancing of variations in seasonal and longer-term supply and demand. Destin Water Users, Inc. (DWU), which serves a barrier island community in the Florida panhandle, implemented a groundbreaking ASR system that stores reclaimed water in a shallow sand-and-gravel aquifer. Institutional controls were used to provide additional assurance that public health is protected, and natural contamination attenuation processes are taken advantage of to address arsenic leaching into stored water and disinfection byproducts (trihalomethanes) removal. The DWU ASR system eliminated the need for more expensive and environmentally impactful options for the disposal of excess of reclaimed water and increases the reliability of the reuse system, having the benefit of reserving higher-quality fresh groundwater resources for potable use. Full article

This study is based on isotope (δ¹⁸O, δ²H, ¹⁴C), hydrochemical, and groundwater-level data from the past 47 years in the central North China Plain (NCP). It uses methods such as mathematical statistics, Piper diagrams, Gibbs models, and ion ratios to investigate the characteristics of changes in the groundwater flow field, hydrochemistry, and isotopes across various aquifers in the Hengshui funnel area before and after the implementation of groundwater exploitation reduction measures (GWER). Furthermore, it reveals the driving mechanisms of these measures’ effects on hydrochemical characteristics and isotopic variations. The results show the following: (1) The hydrochemical type of shallow groundwater (SG) before GWER was primarily Cl▪SO₄-Na▪Ca, which diversified to Cl▪SO₄-Na and SO₄▪Cl-Na types after GWER; the deep groundwater (DG) type changed from Cl▪SO₄-Na to Cl-Na. (2) Before GWER, the hydrochemical composition of SG and DG was primarily controlled by the dissolution of silicates, salt rocks, and evaporites. After GWER, the hydrochemical composition of DG primarily originated from the dissolution of evaporites and salt rocks, accompanied by enhanced cation exchange. (3) The δ¹⁸O of SG was affected by the recharge of irrigation return water, changing from enrichment to depletion before and after the GWER. The δ¹⁸O value in DG changed from depletion to enrichment, and the groundwater age changed from older to younger after the GWER. The GWER altered the hydrodynamics, weakened the hydraulic connectivity, and led to changes in the evolution of the hydrochemistry. The findings have direct implications for water quality and promoting the sustainable utilization of deep groundwater in the NCP’s central funnel area. Full article

The impact of climate change (CC) includes a decline in agricultural production due to crop damage caused by flooding and drought, which destroys crops before harvest, particularly in small-scale irrigation areas. This has led farmers to look for alternative irrigation methods, i.e., groundwater through dug-wells. However, the volume of water obtained through dug-wells is limited. This has led farmers to select the crops they would cultivate. This study aimed to examine the factors that influence farmers in selecting the crops to be cultivated through multinomial logistic regression (MLR). A total of 118 farmers in Jember and Lumajang were randomly selected and interviewed regarding the use of wells and the selection of crops to be cultivated. The dependent variables consist of three crop pattern categories. The results showed that water access variables—particularly well depth, pumped water volume, pipe length, and pump power—significantly influence crop pattern selection (p < 0.01). Farmers adopting diversified crop patterns (food-other and mixed crop pattern) extracted substantially higher groundwater volumes (>76,659 m³ ha⁻¹ annually) and relied on deeper wells (>90 m) compared with the food-crop-dominated pattern. In contrast, water-use-efficient strategies were characterized by lower extraction volumes (<56,755.99 m³ ha⁻¹ annually), longer distribution pipes, and shallower wells (<90 m). Future research should examine the impacts of CC on aquifer depletion and the consequent implications for agricultural activities. Full article

Urban shallow geothermal systems are increasingly adopted for low-carbon heating and cooling, yet their performance and environmental impact depend on vertical heat transfer processes that are often simplified, particularly across the unsaturated zone that links the urban surface and groundwater. This study quantifies the buffering role of the unsaturated zone and assesses how its explicit representation affects predicted geothermal thermal impacts in an urban alluvial aquifer. We combine multi-depth temperature observations from instrumented piezometers and thermocouple arrays in the Zaragoza alluvial aquifer (NE Spain) with a three-dimensional transient groundwater-flow and heat-transport model implemented in FEFLOW. Model performance was evaluated by comparing simulated temperature profiles against field observations at −2 m, −5 m, and the water table, yielding root mean square errors (RMSE) of 1.24 °C, 0.58 °C, and 0.42 °C, respectively. Scenario simulations show strong damping and phase delay of seasonal signals through the unsaturated zone and indicate that surface heat exchange controls shallow thermal amplitudes (up to approximately 10 °C at approximately 1 m). Simplified configurations that neglect the unsaturated zone and/or surface heat transfer bias impact assessments by increasing simulated aquifer warming (up to 1 °C at the end of summer injection periods) and altering plume intensity and geometry (plume extents on the order of 80 m laterally in the analyzed configuration). These results underline that urban geothermal assessments require field-constrained representations of unsaturated-zone heat transfer and realistic surface boundary conditions to support sustainable subsurface energy planning. Full article

Climate warming and land degradation are reshaping Mediterranean and semi-arid ecosystems, yet their combined effects remain poorly quantified in North Africa. Using four Landsat reference epochs spanning 1984–2024, and four spectral/thermal indices (NDVI, EVI, NDMI, LST), we assessed vegetation dynamics and eco-climatic resilience of Tetraclinis articulata ecosystems in Morocco. Four study sites (Stehat, Merchouch, Tamanar, and Amskroud) distributed along a latitudinal gradient from the northern to southern limits of the species’ Moroccan range were chosen and analyzed. Results reveal a generalized decline in vegetation cover, strongly coupled with increasing land surface temperatures, with threshold-like patterns emerging above 74–75 °C that lead to a rapid reduction in NDVI. The northern site (Stehat) exhibited partial recovery, likely supported by local schist aquifers, whereas the arid southern sites (Tamanar and Amskroud) experienced near-total biomass loss and reduced climate buffering. Moisture indices limited hydrological mediation and suggest that shallow soil water availability constrains T. articulata functioning, amplifying vulnerability under recurrent warming. These findings demonstrate how local edaphic and hydrological conditions modulate the impacts of global change and provide early warning indicators of heightened vulnerability and potential threshold-like behavior in drylands. The study emphasizes the urgent need for targeted management strategies to sustain ecosystem resilience under accelerating climate stress. Full article