Search Results (299)

Groundwater is one of the basic requirements for life, economic and social developments in the Bazo River catchment, Rift Valley, Southern Ethiopia. In the study area, availability of water is faced with several problems, such as quality issues due to high levels of fluoride in some samples, spring scarcity in the lowlands, unprotected river water used for drinking, and high demand for good quality water. The aim of this study was to investigate the hydrogeochemical characteristics and to evaluate groundwater quality for domestic and irrigation uses. Thirty-four primary groundwater samples were collected from the field and analyzed in the water quality lab of Arba Minch University. Two water quality indices (WQI and EWQI), a variety of irrigation water quality indices, and GIS-based spatial analysis were utilized in this study. Cations were present in the descending order of Na > Ca > Mg > K > Fe, and anions were HCO₃⁻ > Cl > SO₄ > NO₃⁻ > F. Excepting two samples (BH8 and SP3), the water samples were acceptable for drinking. Sodium, TDS, and fluoride levels were over the limit of drinking water in BH8 and SP3. Rock–water interaction, cation exchange, and silicate mineral weathering were the main hydrogeochemical reactions that controlled groundwater composition in the area, based on Gibb’s diagram, chloro-alkaline indices, and major ions ratios. Groundwater facies were identified as Ca.HCO₃, Na.HCO₃ and mixed Ca-Na/Ca.Mg.Na.HCO₃ types using a Piper plot. The water quality index was computed, and its spatial variations were mapped using GIS. About 82.35% of groundwater samples were excellent for drinking use and 94.12% (SAR) of groundwater were acceptable for irrigation. These study results are useful to help develop inclusive strategies and interventions to address groundwater quality aspects in the study area, underlining the significance of managing and monitoring water resources. The findings underscore the need for effective management and monitoring strategies to ensure sustainable groundwater resources in the Bazo River catchment. Full article

Soil pH is a fundamental geochemical parameter with direct implications for environmental quality, but its spatial drivers in geologically complex mountain regions remain poorly understood. This study investigated surface soil pH across 452 sites in Pingquan City, a semi-arid, lithologically heterogeneous mountainous area of Hebei Province, China. The results show that the soil in Pingquan City is predominantly alkaline, with higher pH in southwestern and northeastern areas and lower pH in the northwest. Soil pH ranged from 4.62 to 9.98, with strong positive spatial autocorrelation. Comprehensive quality assessment indicated that the overall soil quality is moderately low. GeoDetector analysis identified average annual temperature, soil texture, elevation, and bedrock lithology as dominant structural drivers, with bi-factor enhancement interactions. GeoSHAP further uncovered two local effects: precipitation exerts a positive influence on pH in carbonate-rock-dominated areas, reversing the leaching–acidification pattern; and temperature functions as a proxy variable integrating co-varying topography, parent material, and texture rather than a direct thermal driver. The combined application of spatial autocorrelation, GeoDetector, and GeoSHAP provides an effective framework for identifying spatial phenomena, discriminating dominant drivers, and explaining local variations. These findings support regional soil quality assessment and land management, and provide a geochemical baseline for safeguarding groundwater resources in mountainous regions. Full article

In situ leaching (ISL) is the most popular method for uranium mining worldwide, particularly in arid and semi-arid regions. Despite its economic benefits, ISL raises concerns about radioactive migration and groundwater contamination. This review assesses the environmental impacts of ISL uranium mining, focusing on radionuclide transport pathways and key information gaps. This review, focusing on groundwater contamination, radionuclide migration, soil and sediment contamination, atmospheric impacts, vegetation responses, and ecosystem disturbances, summarizes current understanding of the hydrogeochemical, radiological, and environmental impacts of uranium mining. The analysis indicates that groundwater is the environmental component most vulnerable to contamination during ISL operations due to the injection of acidic or alkaline leaching solutions that may mobilize uranium, radium, sulfates, selenium, arsenic, and other potentially hazardous elements. In addition to impacts on groundwater, there have also been reports of soil contamination, airborne dust, radioactive accumulation in flora, and impacts on aquatic and microbiological resources, particularly in arid and semi-arid regions. Although cleanup methods and natural attenuation can minimize contamination to some extent, residual contamination can persist for decades after mine closure. Overall, ISL uranium mining emphasizes the need for effective groundwater management, long-term environmental monitoring, and improved reclamation methods, balancing surface disturbance with long-term hydrogeochemical and environmental concerns. Full article

Heavy metal pollution poses a significant threat to industrial and agricultural ecosystems; however, thorough research on the coupled risks and migration mechanisms of heavy metals within soil-groundwater systems in arid-region industrial parks remains limited. This study systematically collected 312 surface soil samples and 239 groundwater samples from typical chemical industrial parks in Xinjiang, northwestern China. The pollution levels of six typical heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) were quantitatively evaluated utilizing the Single Pollution Index (P_i), Nemerow Pollution Index (P_N), and Potential Ecological Risk Index (RI) for soil and the improved Heavy Metal Contamination Index (HCI) for groundwater. Additionally, GIS mapping and the Positive Matrix Factorization (PMF) model were integrated to delineate spatial distributions and primary emission sources. The assessment results indicated overall moderate pollution risks for Cd, Cu, and Ni in the soil, and for Cd, Pb, Cr, and Ni in the groundwater. Notably, Cd emerged as the primary risk contributor across both media. The RI identified Cd as the element posing the highest soil toxicity risk (with a mean RI of 53.57), while the HCI revealed that specific industrial zones face severe contamination levels (HCI > 4500), predominantly driven by Cd and Pb. GIS analysis illustrated a distinct distance–decay diffusion pattern emanating from industrial point sources. Crucially, PMF source apportionment demonstrated divergent contamination pathways: surface soil heavy metals (e.g., Cr, Cu, Pb, Zn) were primarily governed by top-down local industrial emissions (52.5%), whereas groundwater contamination was largely dictated by regional groundwater flow carrying mixed agricultural and natural geogenic inputs (75%). Furthermore, Pearson correlation analysis revealed a prevalent weak or negative correlation between heavy metal concentrations in the two media, suggesting a spatial “decoupling” of their contamination pathways. This phenomenon is likely driven by a dynamic “retention-leaching” mechanism within the arid vadose zone, where alkaline pH and high clay content act as a hydrochemical barrier impeding vertical migration. These findings underscore that soil and groundwater in arid industrial regions should be managed as distinct hydrochemical systems, providing a robust scientific basis for targeted remediation and the sustainable redevelopment of industrial brownfields. 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

Coral sand dissolution may weaken particle strength and compromise the foundation stability of reclaimed reef islands. However, its dissolution mechanisms and associated effects under saline–freshwater conditions remain poorly quantified. This study combined dissolution experiments, inverse hydrogeochemical modeling, statistical analysis, machine learning, and multiscale characterization to identify dominant mechanisms, quantify their contributions, determine key factors, and evaluate alterations in reef island groundwater. Results demonstrated that the dissolution capacity of coral sand (q) ranged from 0.04 to 0.24 mg, increasing with salinity but decreasing with pH and particle size. Coral sand dissolution was mainly controlled by carbonic-acid-mediated dissolution and Ca-Na cation exchange. The cation exchange contribution (p) reached 63–95% under alkaline conditions and increased with pH, salinity, and particle size. Random Forest accurately predicted q and p, with R² values of 0.875 and 0.980, respectively. SHAP analysis identified salinity and pH as the dominant predictors of q and p, respectively. With increasing q, the relative aragonite content decreased, whereas calcite content increased; particle surfaces became rougher, BET specific surface area and porosity increased by 5–28% and 2–10.5%, respectively, and single-particle compressive strength decreased by 70–87%. These findings provide a theoretical basis for assessing stability and reinforcing coral sand foundations on artificial islands. Full article

Microbial degradation of organic matter is a key driver of iodine enrichment in groundwater. Using stable carbon isotopes (δ¹³C-DIC and δ¹³C-DOC), this study investigates the role of microbial processes and organic matter biodegradation in the formation of high-iodine groundwater downstream of the Kuitun River, China. The groundwater is weakly alkaline and reducing, with Cl⁻ and Na⁺ as the dominant ions, and is mainly slightly saline. I⁻ concentrations range from 51.66 to 552.79 µg/L (mean 177.68 µg/L), with 61.54% of samples classified as high-iodine water. Dissolved inorganic carbon (DIC, 22.97–100.85 mg/L, dominated by HCO₃⁻) originates primarily from microbial degradation of organic matter and silicate weathering. Dissolved organic carbon (DOC, 2.01–4.22 mg/L) is mainly derived from C3 plants. In this reducing, organic-rich aquifer, microbial decomposition of organic matter and reductive dissolution of iron minerals are the primary hydrobiogeochemical processes that release solid-phase iodine into groundwater. The high-iodine groundwater in the study area follows a burial–dissolution genesis model. Full article

Groundwater is an important water source in China, yet its quality is increasingly threatened by industrial activities, including petroleum exploration. This study assessed seasonal hydrochemical characteristics, groundwater quality, and human health risks of shallow groundwater in the central Jianghan Plain, with emphasis on potential influences of petroleum-related activities. Groundwater samples collected during dry and wet seasons were analyzed for hydrochemical parameters, classified by hydrochemical facies, and evaluated using the water quality index (WQI), non-carcinogenic health risk assessment, and spatial distribution analysis. Groundwater was generally weakly alkaline and mainly hard to extremely hard, with HCO₃–Ca·Mg as the dominant hydrochemical facies and some samples shifting toward mixed HCO₃–Cl–Ca·Mg types. Most parameters had higher mean concentrations in the dry season, indicating wet-season dilution. Rock weathering dominated groundwater chemistry, whereas evaporation had limited influence. Elevated Cl⁻ suggested possible effects of petroleum-related activities. Overall groundwater quality was poor, with mean WQI values of 394.23 and 292.50 in the dry and wet seasons, respectively. Children showed greater vulnerability than adults, and Fe and As were the main contributors to non-carcinogenic risk. WQI and health-risk hotspots were concentrated near Zhouji and adjacent petroleum exploration areas, indicating the need for long-term monitoring and risk management. Full article

Coastal land reclamation is widely implemented to support coastal development, yet its effects on microbial indicators in coupled surface water–groundwater systems remain poorly understood. This study examined the spatiotemporal variability of four microbial indicators and their environmental associations using 46 months of monthly monitoring (April 2016–January 2020) in eastern Guanghai Bay, China. Total bacterial counts, fecal coliforms, Escherichia coli, and total coliforms were analyzed using multivariate statistical methods. Surface water exhibited elevated levels of fecal indicators, with consistently higher pollution levels in the Xiaoma River than in the Dama River and clear seasonal variation associated with climatic and hydrological conditions. Groundwater showed pronounced spatial heterogeneity: Wells 1 and 2 exhibited relatively elevated microbial contamination, whereas Well 3 maintained persistently low microbial levels under high-salinity and high-alkalinity conditions. These patterns suggest that reclamation may be associated with groundwater microbial distribution through changes in groundwater transport pathways and hydrochemical conditions, while anthropogenic pressures also played an important role in shaping contamination patterns. These findings offer practical insights for groundwater protection and sustainable management in reclaimed coastal environments. Full article

Fluoride contamination in groundwater poses a significant public-health concern in most semi-arid areas such as the Punjab alluvial aquifers of Pakistan, with local concentrations exceeding the WHO guideline. Reliable fluoride dynamics prediction and mechanistic interpretation of fluoride is key for targeted monitoring and risk mitigation. This paper built an integrated hydrogeochemical machine learning model to predict the fluoride concentration and classify exceedance risk in the Rechna Doab aquifer Tehsil Jaranwala, Punjab, Pakistan. Nested cross-validation and independent test evaluation were performed on conventional models (linear regression, random forest, XGBoost) and a deep tabular model (FT-Transformer). Model reliability was evaluated using discrimination and probability-calibration metrics, while Shapley Additive Explanations (SHAP) and permutation importance were applied to identify the main hydrogeochemical controls on fluoride prediction. Moreover, the robustness was tested by noise sensitivity experiments. Fluoride concentrations showed a positive skewed distribution with some local exceedances related to the geogenic and hydrochemical influences. Nonlinear models greatly outperformed the linear baseline; XGBoost showed robust regression performance (test R² = 0.878; RMSE ≈ 0.190 mg/L). The FT-Transformer showed strong exceedance-classification performance, with high sensitivity (recall = 0.875) and good probability calibration (Brier ≈ 0.021). Interpretability analyses identified EC/TDS, Mg²⁺, and Ca²⁺ as important predictors, linking fluoride enrichment to chemically evolved groundwater with reduced calcium activity, sodium enrichment, and alkalinity buffering. The proposed framework provides accurate, interpretable, and risk-oriented support for groundwater fluoride monitoring in alluvial aquifer systems. Full article

The declining productivity, fertilizer inefficiencies, and rising energy cum production costs are the key issues in crop production, especially in semi-arid regions with alkaline soils. Integration of crop management strategies needs to be adopted to address these issues within the water–energy–food nexus (WEFN). For this purpose, a case study was conducted in semi-arid region of central Punjab, Pakistan, to evaluate the interactive effects of irrigation water source [canal water (CW) and tubewell water (TW)], phosphorus fertilizer source [diammonium phosphate (DAP) vs. phosphoric acid_25% (PA)], and fertilizer application levels [100% and 80% of recommended dose of fertilizer (RDF)] on maize productivity, energy efficiency and economic performance. The experiment comprises eight treatments under raised bed planting (RBP) and one control treatment under ridge-furrow sowing (RFS). Each treatment had three replicates, and the experiment was laid out under a randomized complete block design (RCBD). Maize growth, yield, water productivity, energy efficiency, and economic performance were analyzed using field measurements, energy equivalents, and partial budget analysis. The T1 (RBP+CW+PA+100%RDF) produced the highest maize yield, and it varied from 6.36 to 7.90 t ha⁻¹ under other treatments. CW significantly showed better water productivity (1.14–1.37 kg m⁻³) than that under TW (1.13–1.31 kg m⁻³); however, total energy input was higher under TW-based treatments (29,269–41,033 MJ t ha⁻¹) than that under CW-based treatments (24,129–29,681 MJ ha⁻¹). This results in lower energy productivity under TW-based treatments compared with CW-based treatments (0.17–0.23 kg MJ⁻¹ vs. 0.25–0.31 kg MJ⁻¹, respectively). Moreover, T2 (RBP+CW+PA+80%RDF) produced the highest energy use efficiency (0.59). Economic analysis revealed that production costs were nearly 15–17% higher under TW-based treatments, mainly due to the cost associated with groundwater pumping, and it reduced net profit to USD 1134–1385 ha⁻¹. Better net profits were achieved by CW-based treatments (USD 1244–1593 ha⁻¹), while those produced by BCR ranged from 3.11 to 3.69, with the highest value under T2 (RBP+CW+PA+80%RDF). Overall, irrigation water source emerged as the dominant driver of WEFN performance, while phosphoric acid significantly improved phosphorus availability, energy productivity, and economic returns, particularly under reduced fertilizer input. This study evidenced better maize productivity, less energy consumption, and improved farm profitability in semi-arid irrigated systems through the integration of canal water irrigation with optimized phosphorus management. Full article

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

A one-pot strategy was developed for preparing a chitosan/Mg–Fe layered double hydroxide (LDH) composite by alkaline coprecipitation from an acidic chitosan solution containing Mg(II) and Fe(III) precursors, avoiding separate LDH synthesis and subsequent incorporation into chitosan. X-ray diffraction confirmed LDH formation within the chitosan matrix, and ICP analysis indicated an LDH-equivalent content of approximately 4.1 wt.% on an anhydrous basis. The composite exhibited enhanced chromate adsorption compared with both starting components. The experimental plateau adsorption capacity reached 137.4 mg/g, exceeding those of chitosan (92.2 mg/g) and Mg–Fe LDH (53.5 mg/g). Nonlinear isotherm fitting showed that Mg–Fe LDH was better described by the Freundlich model, whereas chitosan and the composite were better described by the Langmuir model. The kinetic behavior followed the pseudo-second-order equation, while Weber–Morris analysis indicated multistep uptake involving surface interaction and diffusion-related processes. In simulated groundwater containing chloride, bicarbonate, and sulfate, the composite removed 82% of Cr(VI) at 1.0 g/L. It also retained complete chromate uptake over five sorption/desorption cycles, although desorption efficiency decreased from 97.3% to 90.3%. A limitation of this study is that performance was evaluated mainly in batch systems and simplified simulated groundwater; validation with real contaminated waters and dynamic flow conditions is still required. Full article

The evolution of groundwater in the Puhe River Basin is closely related to the ecological security of the Beijing–Tianjin–Hebei water source conservation zone. Based on 122 groundwater samples, this study systematically investigated the hydrochemical characteristics, evolution mechanisms, and water quality of shallow groundwater using mathematical statistics, Piper diagrams, ionic ratio analysis, and a variable fuzzy pattern recognition model. The results showed that shallow groundwater in the middle and upper reaches is generally weakly alkaline, fresh to hard water, with HCO₃–Ca and HCO₃·SO₄–Ca as the dominant hydrochemical facies. Groundwater hydrochemistry is primarily controlled by rock weathering, and the dissolution of silicate and carbonate rocks is the main source of major ions. Calcite and dolomite are in dynamic equilibrium between dissolution and precipitation, whereas gypsum and halite remain undersaturated. Overall, groundwater quality is generally good; however, anthropogenic activities in cultivated and construction lands have altered local hydrochemical composition and caused water quality deterioration in some areas. These findings improved the understanding of groundwater hydrochemical evolution in typical small watersheds of the northern Hebei hilly region and provided a scientific basis for the sustainable management and protection of groundwater resources in the Beijing–Tianjin–Hebei water source conservation area. Full article

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