{"title":"Multicriteria decision making for sustainable groundwater development and management in basaltic terrain of Upper Bhima basin, Maharashtra, India","authors":"Abhilash Kumar Paswan , Ayushi Agarwal , V Ajay Kumar , Satish Chandra Verma","doi":"10.1016/j.gsd.2025.101511","DOIUrl":"10.1016/j.gsd.2025.101511","url":null,"abstract":"<div><div>Climate change has exacerbated freshwater challenges, leading to groundwater depletion and threatening food security. As demand increases amid shrinking supplies, advanced technologies and methodologies are essential for sustainable groundwater management. This study employed a multi-criteria decision-making approach by coupling the Analytic Hierarchy Process (AHP) with nine thematic layers and 36 morphometric parameters to identify groundwater potential zones (GWPZ) and manage water resources in the Upper Bhima Basin, predominantly characterized by basaltic aquifer systems. Using AHP, five zones were delineated within the basin and categorized as very poor (6.7 %), poor (24.6 %), moderate (34.9 %), good (23.9 %), and very good (9.9 %). The thematic layers' weights demonstrated a high level of reliability, with a consistency index of 0.00051 and a consistency ratio of 0.00035. GWPZ was also validated with the Area Under the Curve (AUC = 0.707). Morphometric analysis further supports the identification of low potential zones in the steep slope region. The mean bifurcation and circularity ratios for the basin, highlighting minimal geological influence on the drainage pattern and varying infiltration capacities. Furthermore, the hypsometric analysis reveals a concave shape with an integral value of 0.19, indicating the potential for developing stable recharge zones for sustainable groundwater management. Besides this, evapotranspiration and NDVI have shown strong seasonality, highlighting the agricultural response of the region and exhibiting a strong connection with ENSO events. Increasing urbanization and agrarian expansion drive water demand, necessitating effective regional groundwater management. Measures like check dams, rainwater harvesting, and cultivating less water-intensive crops can enhance water security.</div></div>","PeriodicalId":37879,"journal":{"name":"Groundwater for Sustainable Development","volume":"31 ","pages":"Article 101511"},"PeriodicalIF":4.9,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145057252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fethi Lachaal , Geoffroy Duporté , Christian Leduc , Elena Gomez
{"title":"Combining piezometry, isotopes, and emerging contaminants to assess aquifer recharge operations: case studies of Korba and Kairouan sites (Northeast and Central Tunisia)","authors":"Fethi Lachaal , Geoffroy Duporté , Christian Leduc , Elena Gomez","doi":"10.1016/j.gsd.2025.101514","DOIUrl":"10.1016/j.gsd.2025.101514","url":null,"abstract":"<div><div>In many semi-arid and Mediterranean regions, scarce water resources face an ever-increasing demand for water. A possible response is to complement the natural groundwater recharge by infiltrating treated wastewater, but this addresses the question of the future of this water, in quantitative and qualitative terms. Two contrasting artificial recharge sites with treated wastewater were chosen at the centre and northeast of Tunisia. The study was focused on field measurements (water table level, total mineralisation) and groundwater sampling (stable isotopes of the water molecule, emerging contaminants). Data from 2020 were compared with historical records. A suspect-screening analysis of 137 organic compounds was also performed at the first site. The hydrodynamic survey and the total mineralisation of groundwater underline a common feature of the two sites: the strong heterogeneity of the hydrogeological information, especially disturbed by agricultural pumping. The positive piezometric effect of groundwater artificial recharge is not clearly, observed due to the combined effects of intense pumping and the relatively small recharge volume. A slight increase in groundwater salinity is observed at both sites. In the coastal area of Korba, the isotopic data show that the recharged area is less vulnerable to seawater intrusion compared to other parts of the coastal aquifer. Stable isotope analysis showed an evaporative water only at the site where the water is transferred over a long distance and spread over the ground surface. Emerging compounds, especially carbamazepine, provided a much finer definition of the recharge plumes. The results of the suspect screening and non-target analysis were consistent with the historical location of the sites and the relocation of the discharge point for the first site. Together, the results underlined the limitation of the classical tools of hydrogeology (hydrodynamics, major ions, stable isotopes) and the significant added value of integrating emerging compounds in the analysis.</div></div>","PeriodicalId":37879,"journal":{"name":"Groundwater for Sustainable Development","volume":"31 ","pages":"Article 101514"},"PeriodicalIF":4.9,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145099687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wang Wang , Jiaqi Chen , Jian Sheng Chen , Yitong Zhang
{"title":"Spatial distribution of Chinese baijiu driven by groundwater recharge processes: Insights from hydrochemical analysis","authors":"Wang Wang , Jiaqi Chen , Jian Sheng Chen , Yitong Zhang","doi":"10.1016/j.gsd.2025.101513","DOIUrl":"10.1016/j.gsd.2025.101513","url":null,"abstract":"<div><div>Baijiu companies located along the Chishui River contribute significantly to the local economy. This area lies within China's highest output value of baijiu region, known as the Baijiu Golden Triangle. This study performed geochemical analyses on groundwater and surface water from the Chishui River Basin and other well-known baijiu-producing areas in China. Findings show that water-rock reaction characteristics in brewing water greatly influence the aromatic profiles of various baijiu flavors, with key chemical elements of sulfate (S) and strontium (Sr). Isotope analyses of δ<sup>18</sup>O and δ<sup>2</sup>H isotope identified the source of the brewing water as recharge from leakage water in the Tibetan Plateau. As groundwater passes through distinct geological layers—such as carbonate, gypsum, and celestite formations—it significantly affects the flavor characteristics of high-quality baijiu.</div></div>","PeriodicalId":37879,"journal":{"name":"Groundwater for Sustainable Development","volume":"31 ","pages":"Article 101513"},"PeriodicalIF":4.9,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145060238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yussef Ricardo Abud-Russell , Gonzalo Hatch-Kuri , María del Carmen Carmona Lara , Tatiana Aguilar-Castillo
{"title":"Environmental evidence of surface manifestations of regional groundwater flows in the lower Colorado River Basin: the case Mexicali Valley, Mexico","authors":"Yussef Ricardo Abud-Russell , Gonzalo Hatch-Kuri , María del Carmen Carmona Lara , Tatiana Aguilar-Castillo","doi":"10.1016/j.gsd.2025.101510","DOIUrl":"10.1016/j.gsd.2025.101510","url":null,"abstract":"<div><div>Transboundary water in the Lower Colorado River Basin, shared between Mexico and the United States, demands robust, collaborative governance frameworks to address drought and increasing water demands. Although groundwater resources have become increasingly strategic for meeting water demands in both countries, they rarely receive formal consideration in official studies. Through geospatial analysis, this research delineates for the US portion of the Lower Colorado River Basin, the spatial distribution of recharge and discharge zones within the interconnected groundwater and surface water systems to characterize the regional components of groundwater flow. Employing a methodology based on the Tóthian framework of gravity-driven groundwater flow systems, the study emphasizes the interconnection of groundwater with perennial surface water, soil taxonomy, land use and land-forms as indirect evidence of its surface manifestation throughout this basin. The results are represented in discharge and recharge zones related to regional groundwater flow. Results highlight the need for binational data homologation and integration process to strengthen the available groundwater assessment tools for sustainable management in the U.S.-Mexico border.</div></div>","PeriodicalId":37879,"journal":{"name":"Groundwater for Sustainable Development","volume":"31 ","pages":"Article 101510"},"PeriodicalIF":4.9,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145220221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gabriel T. Colledge, John G. Outram, Graeme J. Millar
{"title":"Control of Al2O3/TiO2 sorbent synthesis parameters to enhance fluoride remediation of impaired water resources","authors":"Gabriel T. Colledge, John G. Outram, Graeme J. Millar","doi":"10.1016/j.gsd.2025.101512","DOIUrl":"10.1016/j.gsd.2025.101512","url":null,"abstract":"<div><div>Alumina is widely used for fluoride ion removal due to its high affinity but is limited by low uptake capacity and structural instability. To overcome these issues, innovative alumina-titania sorbents were developed using co-precipitation. These sorbents maintained a surface area of ∼260 m<sup>2</sup>/g and pore volume of ∼0.21 cm<sup>3</sup>/g regardless of feed flow rate. However, low NaOH molarity significantly increased surface area, peaking at 343 m<sup>2</sup>/g with 1 M NaOH. Aging also enhanced surface area, reaching ∼315 m<sup>2</sup>/g.</div><div>Equilibrium isotherms showed that a feed flow rate of 25 mL/min achieved the highest fluoride uptake (0.19 meq/g). NaOH concentrations ≤4 M produced favourable isotherm profiles, while ≥4 M resulted in unfavourable outcomes. Aging the synthesis mixture for 1–2 h was optimal, as extended aging reduced isotherm performance.</div><div>The Al<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> sorbents also removed calcium, magnesium, barium, strontium, potassium, and silica from groundwater. Optimal synthesis conditions were identified as a 25 mL/min feed flow rate, 2 M NaOH concentration, and a 2-h aging time. The sorption mechanism combined electrostatic attraction and ligand exchange, highlighting the potential of these materials for multifunctional water treatment.</div></div>","PeriodicalId":37879,"journal":{"name":"Groundwater for Sustainable Development","volume":"31 ","pages":"Article 101512"},"PeriodicalIF":4.9,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145049071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Milad Barzegar , Saba Gharehdash , Faysal Chowdhury , Ming Liu , Wendy Timms
{"title":"Hybrid machine learning for predicting groundwater level: A comparison of boosting algorithms with neural networks","authors":"Milad Barzegar , Saba Gharehdash , Faysal Chowdhury , Ming Liu , Wendy Timms","doi":"10.1016/j.gsd.2025.101508","DOIUrl":"10.1016/j.gsd.2025.101508","url":null,"abstract":"<div><div>This study proposes a novel hybrid machine learning framework that integrates gradient boosting (XGBoost, LGBM) and neural network models (LSTM, MLP) with Basin Hopping Optimization (BHO) to improve groundwater level forecasting. The approach simultaneously optimizes input lag times and model hyperparameters, addressing a key limitation in previous studies. Four hybrid models (XGBoost-BHO, LGBM-BHO, LSTM-BHO, MLP-BHO) are evaluated for daily one-to seven-day-ahead predictions, incorporating meteorological inputs. Results showed that all models achieved high predictive accuracy (R<sup>2</sup> > 0.98), with LSTM-BHO yielding the lowest MAE and RMSE across both boreholes. Boosting models, particularly XGBoost-BHO, demonstrated strong short-term performance with narrow residual distributions and significantly lower computation time. These findings highlight the effectiveness of combining machine learning and metaheuristic optimization for robust groundwater forecasting.</div></div>","PeriodicalId":37879,"journal":{"name":"Groundwater for Sustainable Development","volume":"31 ","pages":"Article 101508"},"PeriodicalIF":4.9,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144926193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Siddhartha Roy , Michael B. Fisher , Solomon Minyila , Zakaria Seidu , Kaida Liang , Aaron A. Salzberg
{"title":"Preventing lead (Pb) contamination in rural community water systems in LMICs through analytical screening, policy and standards enforcement, and supply chain interventions","authors":"Siddhartha Roy , Michael B. Fisher , Solomon Minyila , Zakaria Seidu , Kaida Liang , Aaron A. Salzberg","doi":"10.1016/j.gsd.2025.101509","DOIUrl":"10.1016/j.gsd.2025.101509","url":null,"abstract":"<div><div>Lead (Pb) is a neurotoxic metal that can leach into potable water from plumbing components. This study investigated Pb contamination in rural community water systems in Ghana to inform strategies for reducing its occurrence in low- and middle-income countries (LMICs). We screened 101 systems, including 83 borehole handpumps and 17 mechanized piped systems, installed across seven districts during 2019–22, using a handheld X-Ray Fluorescence (XRF) analyzer. Despite manufacturer assurances that components were lead-free, 57 % of tanks in borehole handpumps and 100 % of taps in mechanized systems exceeded the international “lead-free” standard of 0.25 % Pb w/w. Other components like riser pipes, rods, cylinders, and foot valves generally met standards. There were no significant differences in Pb content (p > 0.05) for systems across districts or installation years. Consequently, we engaged original equipment manufacturers (OEMs) to source truly lead-free alternatives. Stainless steel taps from one manufacturer replaced leaded brass taps, and a second manufacturer custom-fabricated stainless steel handpump tanks and spouts to replace lead-containing galvanized steel components. These were verified lead-free via XRF before installation. Despite initial claims from multiple OEMs that sourcing lead-free components would be prohibitively difficult or expensive, the switch was logistically feasible and increased overall installation costs by only 2 % or less. Our findings highlight vulnerabilities in global plumbing supply chains and manufacturing practices that can introduce Pb and harm consumers, and illustrate the value of independently verifying OEM assurances and specifications for lead-free components. We offer guidance for implementers to mitigate water Pb contamination, with some measures also limiting iron corrosion-related system failures. This includes adherence to product quality standards, analytical screening considerations, supply chain interventions, water quality monitoring, and progressive remediation of existing systems. This case study suggests that eliminating Pb from rural water systems is feasible and cost-effective in Ghana and other LMIC settings.</div></div>","PeriodicalId":37879,"journal":{"name":"Groundwater for Sustainable Development","volume":"31 ","pages":"Article 101509"},"PeriodicalIF":4.9,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144917545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fida Hussain , Lan Hee Kim , Sang-Eun Oh , Sungpyo Kim
{"title":"Neutralization of pH and removal of heavy metals from acid mine water by using low-cost biosorbents in batch and column studies","authors":"Fida Hussain , Lan Hee Kim , Sang-Eun Oh , Sungpyo Kim","doi":"10.1016/j.gsd.2025.101506","DOIUrl":"10.1016/j.gsd.2025.101506","url":null,"abstract":"<div><div>The present research explored raw oyster shell (RO), oyster shell biochar (OB), and ginkgo leaves biochar (LB) as low-cost biosorbents for heavy metal removal and pH neutralization from acid mine water. Five adsorbents were tested in batch mode. The results showed that OB, RO, and LB effectively removed Cd<sup>2+</sup> (57–98 %), Cu<sup>2+</sup> (93–99 %), and Fe<sup>2+</sup> (96–99 %), while Mn<sup>2+</sup> (7–57 %) and Zn<sup>2+</sup> (18–97 %) exhibited lower removal efficiencies. RO and OB also increased solution pH to ∼6.3 due to their alkaline buffering capacity. LB, OB, and RO were further tested in series columns. RO and OB with 31.1, 93.5, and 185 min HRTs were tested in primary columns. A hybrid column with LB, OB, and RO was tested at 93.5 min HRT to enhance removal efficiency. Increasing HRT improved both metal removal and breakthrough times. RO and OB with 185 min HRT removed ∼71 % Cd<sup>2+</sup>, ∼93 % Cu<sup>2+</sup>, ∼6 % Mn<sup>2+</sup>, ∼52 % Fe<sup>2+</sup>, and ∼11 % Zn<sup>2+</sup> from the primary column. In the secondary hybrid column, 99.53 % Cd<sup>2+</sup>, 100 % Cu<sup>2+</sup>, 55.20 % Mn<sup>2+</sup>, 100 % Fe<sup>2+</sup>, and 74.03 % Zn<sup>2+</sup> were removed. Cu<sup>2+</sup> > Fe<sup>2+</sup> > Cd<sup>2+</sup>> Zn<sup>2+</sup>> Mn<sup>2+</sup> was the column mode metal removal order. The columns' pH profiles changed significantly during metal sorption, suggesting buffering processes and acidic metal ion elimination. Column modeling using Thomas and Yoon–Nelson equations confirmed high adsorption capacities and extended breakthrough times, particularly in the hybrid system. Mechanistic analysis via SEM–EDS revealed surface deposition and co-precipitation of Cd<sup>2+</sup>, Cu<sup>2+</sup>, and Fe<sup>2+</sup> on RO and OB, while FTIR spectra and XRD patterns confirmed the roles of carbonate, hydroxyl, phosphate, and amine groups in metal binding. LB's porous structure and functional groups enhanced Mn<sup>2+</sup> and Zn<sup>2+</sup> removal through complexation and diffusion-driven sorption. The findings support the potential of oyster shell-based composites as sustainable biosorbents for the remediation of metal-contaminated, acid mine water, and highlight future opportunities for optimization through surface functionalization and hybrid treatment designs.</div></div>","PeriodicalId":37879,"journal":{"name":"Groundwater for Sustainable Development","volume":"31 ","pages":"Article 101506"},"PeriodicalIF":4.9,"publicationDate":"2025-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Integration of hydrogeophysical and remote sensing data for enhanced groundwater potential mapping in fractured limestone aquifers: A case study in southeast Beni Suef, Egypt","authors":"Hakeem Musaed , Khaled Gemail , Sayed Bedair , Mohamed El Alfy","doi":"10.1016/j.gsd.2025.101507","DOIUrl":"10.1016/j.gsd.2025.101507","url":null,"abstract":"<div><div>Identifying groundwater potential zones in arid regions is crucial in mitigating depletion and enhancing the sustainability of water resources and food security. To develop an effective groundwater management framework for fractured aquifers in these regions, a thorough understanding of the site's conceptual flow model is crucial for ensuring irrigation water sustainability. It is essential to discern the groundwater potential zones (GWPZs) that have a high likelihood of accessing groundwater resources. This study aims to establish an integrated framework for mapping GWPZs in fractured limestone aquifers by capitalizing on remote sensing (RS) and surficial Direct Current (DC) resistivity data within a Geographic Information System (GIS) environment. By harmonizing surface (precipitation rates, lineament density, watershed, drainage system, land use) and hydrogeophysical data (layer thicknesses, aquifer resistivity, overburden infiltration capacity, and buried geologic structures), this holistic approach aspires to enhance the understanding of hydrogeological frameworks in limestone aquifers, encompassing geological features, hydrological pathways, and hydraulic properties. Focused on the southeastern Beni Suef area, the current findings pinpoint groundwater zones and provide insights into groundwater movement and recharge mechanisms. The area highly suitable for artificial recharge spans 53.71 km<sup>2</sup> (41 %), whereas the good and low-suitability zones cover 29.98 km<sup>2</sup> (23 %) and 43.30 km<sup>2</sup> (33 %), respectively. The resulting framework exhibits potential for broader applications in analogous arid regions, streamlining groundwater exploration, fostering artificial recharge strategies, and promoting sustainable water resource management practices on a global scale. Ultimately, this research not only aids local decision-makers in optimizing groundwater use but also contributes to international efforts to achieve sustainable development goals related to water security and environmental resilience.</div></div>","PeriodicalId":37879,"journal":{"name":"Groundwater for Sustainable Development","volume":"31 ","pages":"Article 101507"},"PeriodicalIF":4.9,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144895954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nini Li , Jiangtao He , Baonan He , Yanjia Chu , Zhen Chen
{"title":"Comparative study of hydrochemical and machine learning methods for Fe anomaly identification and NBLs estimation in shallow groundwater of representative hydrogeological units in the North China plain","authors":"Nini Li , Jiangtao He , Baonan He , Yanjia Chu , Zhen Chen","doi":"10.1016/j.gsd.2025.101505","DOIUrl":"10.1016/j.gsd.2025.101505","url":null,"abstract":"<div><div>Iron (Fe) in groundwater results from both natural sedimentation and human activities, impacting biogeochemical cycles and the migration of various components. Increased human activities have disrupted Fe concentrations, causing deviations from the natural state. Thus, identifying Fe anomalies and determining its natural background levels (NBLs) are crucial. In this study, based on subdivided NBLs units, four typical units were selected for anomaly identification using Iterative 2-Sigma method, modified hydrochemical method (MI-OPT), and Isolation Forest model. The results showed that the MI-OPT method showed stable performance and also identified anomalies related to hydrochemical indicators. The Isolation Forest model efficiently detected Fe anomalies through a machine learning-based partitioning approach. In contrast, the Iterative 2-Sigma method exhibited instability due to its dependence on data distribution. Based on the distribution characteristics of the remaining data, the anomaly identification results from the MI-OPT method were selected as the final reference for determining the NBLs of Fe in the four units, with the upper limits being 0.45 mg/L, 2.80 mg/L, 2.58 mg/L, and 1.59 mg/L, progressively transitioning from the recharge area to the runoff and discharge areas. Additionally, an integrated analysis incorporating information entropy, PPI values, and environmental pollution source data explained most of the detected anomalies, validating the reliability of the anomaly identification results. The methods and results presented in this study offer a new perspective on Fe anomaly identification in groundwater.</div></div>","PeriodicalId":37879,"journal":{"name":"Groundwater for Sustainable Development","volume":"31 ","pages":"Article 101505"},"PeriodicalIF":4.9,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144864074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}