Search Results (2,139)

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

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

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

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

The Wadi Al-Ahsaba watershed is an arid to semi-arid catchment situated in southwestern Saudi Arabia, characterized by intermittent surface flow, high evaporation and low rainfall, and a dam reservoir built for flood control. The work aims to assess hydrological and anthropogenic controls on surface and groundwater quality, pollution status, and human health risks using an integrated approach of hydrogeochemical analysis, multivariable statistics, and water quality and contamination indices. A total of 21 water samples (15 surface water, 6 groundwater) were analyzed for general chemistry, major ions, and trace elements. Hydrogeochemical analysis and principal component analysis (PCA) were implemented to differentiate the geogenic from anthropogenic control on water quality. The pollution status and associated risk were evaluated using water quality index (WQI), contamination degree (Cd), Hazard Quotient (HQ), and Hazard Index (HI). Results suggest limited surface–groundwater interaction, with surface water dominated by Ca–Mg–HCO₃ facies, indicating recent recharge and limited water–rock interaction, whereas groundwater exhibits mixed Ca–Mg–Cl and Ca–Na–Cl–SO₄ types, revealing longer residence time and water–rock interaction. Nitrate (9.5–109 mg/L) and TDS (522–1003 mg/L) exceeded drinking water standards in 90% and 95% of tested samples, respectively, and WQI ranged from 43 to 134, reflecting excellent to poor water. High non-carcinogenic risk from nitrate was observed, especially for infants. The study concluded that the geogenic processes (water–rock interaction, evaporation, and mineral dissolution) control the general chemistry of tested water, while anthropogenic input from wastewater and agriculture input are likely contributors to nitrate contamination. The study contributes to the understanding of arid wadi-dam systems by revealing how limited recharge, hydrological connectivity, and episodic flow control contaminant transport and persistence, underscoring the critical role of integrated hydrological analysis and land use management in safeguarding freshwater resources in arid environments. Full article

Coal mining critically affects Shanxi’s economy and national energy security in China, whereas mine water significantly influences regional water quality and ecological stability. However, studies on pollution characteristics and health risks of fluoride and potentially toxic elements (PTEs) remain limited, especially comparative analyses between raw mine water and treated mine drainage. This study comprehensively analyzed the pollution characteristics of fluoride and PTEs, along with water quality evaluation, ecological risks, and human health risks associated with raw mine water and mine drainage. Fluoride concentrations in raw mine water from several mines exceeded the WHO guideline limit of 1.5 mg/L, whereas those in mine drainage were below the WHO standard. The total hazard index (THI) of fluoride in both water types was unacceptable (THI > 1). For PTEs, only arsenic in raw mine water exceeded the Grade III groundwater standard, while all PTEs in mine drainage met standards. Total health risk of PTEs in raw water was approximately one order of magnitude higher than in mine drainage, and both exceeded acceptable levels, mainly contributed by carcinogenic elements, particularly arsenic. These results underscore continuous monitoring and targeted control of arsenic are still required for safe utilization of coal mine water. Full article

Land-use change from natural vegetation to agricultural systems significantly affects watershed hydrology and water quality. This study assesses the long-term effects of historical land-use change on hydrologic processes and nitrogen transport in the Straight River watershed, Minnesota, USA, using the Soil and Water Assessment Tool Plus (SWAT+) model. Three land-use scenarios were created to assess changes in water balance and nitrate levels. These scenarios represent the reconstructed pre-settlement conditions from 1855, established agricultural development from 2006, and current conditions from 2022. Results show a significant increase in water percolation and groundwater recharge. Percolation more than doubled, increasing from about 118 mm under reconstructed pre-colonial conditions to over 256 mm in 2022. Streamflow increased to 2.1 m³s⁻¹ in 2022, indicating improved hydrologic connectivity and groundwater contributions. Nitrate leaching increased from about 1.14 kg N ha⁻¹ to more than 32 kg N ha⁻¹ (1850s–2022), and nitrate export increased by >2000%, indicating strong nitrate loading. The significant increase in nitrate compared to water fluxes points to agriculture as the primary source of groundwater pollution and downstream nutrient loading. These findings highlight the importance of land-use change in affecting water balance and nutrient behavior. They also point out the need to include a historical baseline in watershed assessments. The results show the importance of better land and nutrient management strategies to reduce nitrate losses and protect water resources in intensively managed agricultural areas. Full article

Background: Access to safe drinking water remains a critical public health concern in rural Ghana, particularly in climatically vulnerable and underserved settings. This study assessed the microbiological and chemical quality of drinking water and evaluated nitrate-related health risks in the North Gonja and North-East Gonja Districts of the Savannah Region. Methods: A cross-sectional study was conducted between January and March 2025. A total of 460 water samples were collected from groundwater sources and household storage containers. Microbial analyses targeted total coliforms and Escherichia coli. Physicochemical and chemical parameters included nitrate-nitrogen, pH, residual chlorine, major ions, and trace metals. Data was analyzed using descriptive statistics, chi-square tests, spatial interpolation, and non-carcinogenic health risk assessment based on the hazard quotient (HQ) approach. Results: Widespread microbial contamination was observed, with 91.5% of household water samples positive for total coliforms and 46.6% for E. coli. Contamination of source water was significantly higher in North Gonja than in North-East Gonja. Overall, 49.1% (n = 55) of groundwater sources exceeded the World Health Organization guideline value for nitrate-nitrogen, with exceedances predominantly occurring in North Gonja. Additionally, 67.0% (n = 75) of samples were outside the acceptable pH range (6.5–8.5), including 74 samples below 6.5 and one above 8.5. Residual chlorine was not detected in any of the samples. Health risk assessment indicated potential non-carcinogenic risks associated with nitrate exposure, particularly among infants and children. Conclusions: The study demonstrates significant microbial contamination and nitrate-related health risks in the study area, particularly in North Gonja. Interventions such as improved source protection, routine water quality monitoring, chlorination, household water treatment, and implementation of Water Safety Plans are recommended to enhance drinking water safety and reduce associated public health risks. Full article

Urban water insecurity is an increasingly critical challenge in rapidly urbanizing regions of the Global South, driven by population growth, environmental degradation, infrastructure limitations, and institutional constraints. Kathmandu Valley, Nepal, exemplifies these interconnected pressures. This study presents a systematic review of 45 peer-reviewed and selected grey literature sources published between 2000 and 2025, conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were included if they examined drinking water contamination, public health risks, household coping practices, wastewater-related exposure, or governance dynamics in Kathmandu Valley, Nepal. Findings were synthesized using a narrative thematic approach. The review identifies widespread contamination across municipal supply systems, groundwater, tanker water, traditional water sources, and household-stored water. Microbial contamination, particularly total coliforms, fecal coliforms, and Escherichia coli, emerged as the most consistently reported and immediate public health concern. Chemical and physicochemical contaminants, including ammonia, iron, arsenic, nitrate, and turbidity, were also widely reported, especially in shallow and deep groundwater systems. Seasonal dynamics further influenced exposure risks, with increased microbial contamination during monsoon periods and greater dependence on alternative and less regulated water sources during dry seasons. The findings further indicate that unsafe water exposure is associated with a substantial burden of waterborne diseases and emerging risks such as antimicrobial resistance. Although household water treatment practices reduced contamination in some cases, risks often persisted due to recontamination during storage and handling. These burdens disproportionately affected marginalized and peri-urban populations with limited access to safe and reliable water infrastructure. The review also highlights persistent governance challenges, including institutional fragmentation, weak regulatory enforcement, inadequate infrastructure investment, and growing dependence on informal water supply systems. Together, these conditions contribute to a hybrid urban water system in which formal and informal sources coexist without consistent quality control. Overall, the evidence demonstrates that water insecurity in Kathmandu Valley is a systemic condition shaped by the interaction of environmental contamination, unequal exposure, household coping limitations, and fragmented governance. By integrating environmental, public health, and governance evidence, this review advances understanding of urban water insecurity in rapidly urbanizing contexts and highlights the need for integrated, equity-oriented, and governance-informed interventions. These findings have broader relevance for cities across the Global South experiencing similar environmental and infrastructural pressures. Full article

Sustainable Urban Drainage Systems (SuDSs) represent a contemporary and eco-friendly method for managing surface water, with the goal of reducing flooding impacts while preserving the environment and enhancing water quality and biodiversity. In Bari, recurrent flooding stemming from water stagnation, extreme weather, and urban development poses challenges to sustainable growth. This study applies the ‘Sponge city’ concept to address these issues through an evaluation of current urban permeability and the implementation of Nature-Based Solutions (NBSs) to reduce runoff and manage underground flows. By assessing the climatic conditions and hydrological factors contributing to urban stagnation, this project seeks to create a resilient urban environment capable of adapting to climate change and effectively mitigating both significant and minor rainfall events. It aims to reduce runoff, while also promoting groundwater recharge and alleviating saline contamination effects in coastal areas, ultimately enhancing the safety and livability of urban landscapes. Full article

With the rapid urbanization of China, environmental risks posed by informal landfills, particularly those dominated by agricultural waste, are an urgent yet understudied concern. This study systematically monitored groundwater quality surrounding five typical informal agricultural waste landfills in a coastal Chinese city. Eight major pollutants were analyzed using pollution index evaluation, the health risk model and multivariate statistical methods. The results indicate one landfill as a high-priority concern, exhibiting a combined multi-index pollution pattern with an exceedance rate of 87.5%, where NO₃⁻-N, F⁻, COD_Mn, and total hardness are the dominant indicators. Another landfill showed high background levels and anthropogenic impacts. Total non-carcinogenic risk of all landfills is below 1 (negligible). Children face approximately twice the health risk of adults. The exposure risk through drinking water ingestion is three orders of magnitude higher than that from dermal contact, with NO₃⁻-N contributing >90% of the total risk. Groundwater deterioration is primarily affected by geological conditions and seawater intrusion (52.31%), followed by agricultural activities and soil characteristics. Given these findings, priority attention should be directed to nitrogen-driven landfill and multi-index composite pollution landfill, with reinforced source tracing and control of NO₃⁻-N, alongside long-term monitoring for regional groundwater protection. Full article

Groundwater quality assessment in urban and peri-urban environments is often constrained by incomplete monitoring records, irregular sampling frequencies, and heterogeneous environmental datasets. The primary objective of this study is to predict the Water Quality Index (WQI) in the Attica River Basin, Greece, using advanced machine learning (ML) techniques. A groundwater quality dataset comprising 958 observations from 80 monitoring stations was analyzed using six physicochemical parameters, namely electrical conductivity, ammonium, nitrate, nitrite, chloride, and sulphate. Three modeling approaches, namely TabNet (with Winsorization), SVM, and Gradient Boosting Machines (GBM), were implemented to estimate groundwater quality conditions. To address the challenge of missing data, Multiple Imputation by Chained Equations (MICE) with Predictive Mean Matching (PMM) was implemented and systematically compared against conventional imputation approaches, including smoothed averages, interpolation, and forward-fill methods. The novelty of this study lies in the integration of open-access groundwater chemistry data, advanced multivariate imputation (MICE-PMM), and attention-based deep learning (TabNet) for groundwater quality prediction in a Mediterranean peri-urban area under data-scarce conditions. Using a multi-year groundwater monitoring dataset, the results indicate that the integrated MICE-PMM and TabNet framework achieved the highest predictive performance, with R² = 0.91, NSE = 0.91, RMSE = 52.21, and MAE = 25.68. Feature importance and sensitivity analyses identified nitrate as the dominant driver of WQI variability, highlighting the strong influence of anthropogenic nutrient loading on groundwater quality. Overall, the proposed framework provides a transferable, data-driven approach for groundwater quality prediction, environmental monitoring, and groundwater resource management in urban and peri-urban aquifer systems characterized by incomplete environmental datasets. Full article

Groundwater serves as a vital source of domestic and agricultural water in rural areas of the Songnen Plain. Its chemical composition and water quality directly impact public health and regional sustainable development, making them subjects of significant concern. This study employed a comprehensive analytical framework, integrating Piper trilinear diagrams, ionic ratio analysis, the Water Quality Index (WQI), and the Human Health Risk Assessment (HHRA) model, to preliminarily evaluate groundwater conditions in a rural township of the Songnen Plain. The multi-method approach was designed to provide scientific insights for groundwater pollution prevention and remediation strategies in the region. Results indicate that the predominant groundwater chemical type in the study area is HCO₃-Ca. The hydrochemical process is primarily controlled by weathering and dissolution of silicate and carbonate minerals, accompanied by cation exchange. The WQI ranged from 84.78 to 192.82, with an average of 132.68, indicating overall moderate water quality. Fe and Mn are significant factors affecting water quality. The potential non-carcinogenic risks posed by groundwater to children, females, and males (0.988, 0.701, 0.534) and carcinogenic risks (1.77 × 10⁻⁵, 6.27 × 10⁻⁵, 4.81 × 10⁻⁵) are both below the USEPA recommended threshold (1.0, 1 × 10⁻⁴), indicating that the health risks were generally acceptable, though the HI for children approached the threshold. The results underscore the need for targeted mitigation of elevated Fe/Mn concentration (e.g., via aeration biofilters) while highlighting the region’s low health risks under current conditions. This work provides a template for integrating geochemical and health risk paradigms in groundwater management. Full article

Nitrogen applied in excess of plant demand in intensive agricultural systems can be lost through runoff and leaching into surface and groundwater, with potentially negative effects on water quality. Zeolites, due to their high cation exchange capacity and internal porosity, can adsorb ammonium (${NH}_4^{+}$) and help mitigate excessive nitrate (${NO}_3^{-}$) leaching. Owing to such properties, zeolites can play an important role in reducing the potential negative impact associated with the extensive use of nitrogen-based fertilizers. In this study, we investigated the effects of two commercial natural zeolites on selected hydraulic properties, water storage, and solute transport parameters of three sandy-loam soils with different pedological characteristics. Laboratory experiments were conducted on disturbed soil columns. The leaching of ${NO}_3^{-}$ and ${NH}_4^{+}$ ions was monitored using ion-selective electrode analysis. The results indicate that zeolite application reduces the mobility of nitrate and ammonium. This effect can be attributed to changes in the original pore size distribution of the investigated soils, characterized by a reduction in macropore regions and a corresponding increase in meso- and micropore regions. In the case of ammonium, adsorption mechanisms are also involved, which further contribute to retarding its mobility. These effects were consistently observed across the investigated soils. For a given soil, the magnitude of the observed effects depended on both the type of zeolite used and the amount of zeolite mixed with the soil. Finally, ANOVA tests and multivariate analyses were applied to the full dataset to provide statistical support for the observed changes in the selected parameters. Full article

Disinfection of drinking water prevents waterborne diseases but can lead to the formation of trihalomethanes (THMs), which are linked to an increased risk of cancer. This study examined the association between water source allocation and THM levels in Israel. A retrospective analysis of water quality reports, published by the Israeli Ministry of Health, was conducted, including only samples collected from the water distribution system between 2015 and 2024. To assess temporal and geographic variability, monthly and annual averages were calculated. Trends were evaluated using interrupted time series regression. Overall, 16,268 samples were included, with a study-wide mean THM level of 30.41 µg/L, mainly due to Bromoform. Elevated THM levels were observed in northern districts, particularly before 2020, with seasonal peaks in the summer months. After 2020, as surface water utilization increased, THM levels also rose in central Israel, with no discernible seasonal pattern. Southern regions, supplied mainly by desalinated water, showed consistently low levels. This analysis indicates that the water source influences THM formation, as increased surface-water use is associated with higher THM concentrations. Mixing surface and groundwater with desalinated water may reduce exposure in areas with high THM levels, highlighting the need for informed water management policies. Full article