Much effort has been put into understanding transport processes in recent years because of their practical relevance in determining the fate of contaminants in surface and subsurface waters that may affect human health and the environment. Correct quantification of transport processes is challenging and reflects the complexity of flow paths and physical processes in aquifers, as well as the heterogeneity of . It strongly influences predicted contaminant dispersion and plume properties and is fundamental for assessing the effectiveness of remediation strategies. Further efforts are now needed to apply these new concepts in practice for contamination prevention, vulnerability assessment and risk management.
The aim of this session is to discuss the latest theoretical and practical developments in transport theories and how they can be applied to the problems of aquifer characterisation, transport dynamics and remediation techniques.
Our contributions will address the following questions
- What are the recent improvements in appropriate methods to characterise the relevant aquifer properties for comprehensive modelling of contamination?
- What are the recent improvements in transport measurement techniques?
- What are the most appropriate approaches for the practical application of theoretical advances in groundwater transport modelling?
- How can we assess the most appropriate remediation strategy and predict its effectiveness?
Case studies and multidisciplinary approaches are encouraged.
The session is co-sponsored by the Groundwater Commission of the IAHS.
Orals: Fri, 8 May, 10:45–15:45 | Room 2.44
Managed Aquifer Recharge (MAR) is increasingly recognized as a key strategy to mitigate water scarcity, enhance groundwater quality, and ensure long-term aquifer sustainability. Among the various MAR techniques, infiltration basins are widely implemented due to their operational simplicity and effectiveness in promoting recharge through surface infiltration.
However, the design and operation of infiltration basins involve significant scientific and technical challenges. These challenges stem from the multidisciplinary nature of the system, which integrates diverse hydrological processes such as rainfall variability, surface runoff concentration, reservoir management, and the complex dynamics of flow and solute transport through the vadose zone and into the aquifer. Each of these components introduces uncertainties that complicate predictive modeling and practical implementation.
Critical design aspects include determining appropriate basin dimensions, understanding infiltration dynamics and consequent solute transport, and addressing operational features such as emptying time and clogging. Clogging, in particular, not only reduces infiltration capacity but also influences solute transport behavior in the subsurface, adding complexity to performance assessment. Furthermore, temporal variability in recharge rates requires adaptive management strategies to maintain efficiency over time.
Selected challenges associated with the design and operation of infiltration basins are discussed, emphasizing the interplay between hydrological processes and engineering decisions. It is highlighted the need for simple and integrated approaches to optimize basin performance and ensure sustainability.
How to cite: Fiori, A.: Challenges in Designing Infiltration Basins for Managed Aquifer Recharge, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3512, https://doi.org/10.5194/egusphere-egu26-3512, 2026.
Flow and solute transport in groundwater are primarily controlled by the hydraulic conductivity (K) field. Variations in the K field greatly influence subsurface flow rates and solute migration and dispersion. Due to the importance of aquifer heterogeneity, several approaches have been proposed in the literature for modelling K field spatial distribution based on borehole data. In this work, we evaluate two methods to generate spatial realisations of the K field of a heterogeneous aquifer. Results are analysed in terms of the connectivity of high-K cells, and solute transport results are compared and discussed.
The methodology consists of three main steps. First, borehole PSD data are used to characterise hydrofacies and generate 3D stochastic realisations of those hydrofacies using the Markov-Chain/Transition Probability approach (MC/TP). Resultant realisations are used to fill a 3D grid. Then, two methods are used to generate hydraulic conductivity fields by assigning a K value to each cell on those grids: (1) using the geometric mean of each hydrofacies (GMEAN) and (2) using a value sampled from the KDE probability functions of each hydrofacies (KDE). Two different porosity scenarios are considered (high porosity, HP; and low porosity, LP). Finally, solute transport estimates were computed using MODFLOW and MT3DMS.
Connectivity analysis of the stochastic realisations shows a higher degree of connectivity of high-K cells on the GMEAN mode than in the KDE. The latter leads to overall higher average K values, but also to slower flow regions with lower K values than the GMEAN.
Solute transport runs result in slower travel times and lower peak concentrations on the KDE realisations than in the GMEAN case. Breakthrough curves at different observation points show that, when concentrations fall after peaking (for a time-limited input pulse), both GMEAN and KDE curves tend to converge. The field-scale longitudinal dispersivity implied from the ensemble probability plumes is similar between the two K field realisation approaches modelled, but the vertical dispersivity is higher in the KDE realisations. The high porosity scenario shows higher dispersivities and considerably longer travel times.
Results show that, for the same porosity scenario, contaminant plumes behave similarly for the KDE and GMEAN approaches at longer times and distances from the source. This suggests that, on the studied site, the small-scale heterogeneity has a reduced effect on the on the long term, field scale macrodispersivity and solute transport behaviour.
How to cite: Gallardo Ceron, F., West, L. J., Graham, J., Colombera, L., and Burke, I. T.: Stochastic modelling of aquifer heterogeneity and hydraulic conductivity field distribution: implications for solute transport modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10433, https://doi.org/10.5194/egusphere-egu26-10433, 2026.
In the subsurface, many biogeochemical reactions are characterized by inefficient mixing. Therefore, it is essential to investigate mechanisms that can enhance mixing processes. One example is the case of transient flow conditions. Specifically, Engineered Injection and Extraction (EIE) protocols can generate chaotic advection and are well known in the literature to enhance solute mixing and contaminant degradation. The objective of this work is to provide experimental evidence of the interplay between local dispersion, density-driven flow, and chaotic advection on solute transport and mixing. Density-contrasts are indeed particularly relevant in the context of groundwater remediation and saltwater intrusion. We conducted a series of experiments in a quasi-two-dimensional chamber representing a vertical cross-section of a homogeneous unconfined aquifer. The setup is equipped with four wells which operate sequentially following a prescribed pumping schedule. In our set of experiments, two different grain sizes are used to investigate the role of local dispersion, while different injected solute concentrations are used to study the impact of density contrasts. The effect of chaotic flow generated by the operation of the EIE system is compared to experiments run under no-flow conditions in the surroundings to isolate the contribution of purely density-driven flows to solute mixing. The conservative tracer is injected in the middle of the area delimited by the four wells, and a non-invasive optical method is applied to track the evolution of the solute at a high temporal resolution. Mixing is quantified by computing the plume area. Our results show that local dispersion plays a significant role in density-driven flow as experiments performed in coarse porous media display higher mixing enhancement in comparison to those conducted in the fine porous media. At early times in the experiments, density effects are more pronounced in the experiments performed in the coarse porous material, but they decrease over time when the plume is more diluted and the density-contrasts are less pronounced. Finally, chaotic advection has a major effect on mixing enhancement. However, its impact decreases as the plume area increases, and at later times local dispersion is the dominant process contributing to the enhancement.
How to cite: Ziliotto, F., Basilio Hazas, M., Kotynek-Winter, M., Rolle, M., and Chiogna, G.: Coupled effects of local dispersion, density and chaotic advection on mixing enhancement, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8092, https://doi.org/10.5194/egusphere-egu26-8092, 2026.
Understanding and predicting contaminant migration in heterogeneous aquifers remains a central challenge for groundwater protection and remediation. Accurately predicting the fate and transport of reactive contaminants is hindered by subsurface heterogeneity, scale-dependent dispersion, and complex reaction chains, all of which control plume architecture and thus remediation performance. This study advances current transport theory by introducing a novel sigmoid dispersivity model that provides a bounded, physically meaningful transition from local-scale pore mixing to field-scale macrodispersion. Focusing on a five-species chlorinated solvent (CS) decay chain, the approach is implemented using a two-dimensional advection-dispersion equation solved by an implicit finite difference scheme. The proposed model uniquely introduces an effective dispersivity function that dynamically represents concentration distributions, apprehending non-linear retardation, first-order decay, and pre-asymptotic spreading patterns more accurately than conventional analytical solutions. A comparative evaluation against four widely used dispersivity models demonstrates that the sigmoid model more accurately captures plume skewness, early-time breakthrough behaviour, and long-distance tailing, verified through spatial-moment analysis. Crucially, the results uncover a significant coupled effect where the dispersion of a parent plume exerts a strong control on the mobility and risk footprint of daughter products, a theoretical insight with profound implications for field applications. By improving the upscaling transport parameters across scales, this model provides a robust tool for improved aquifer characterisation, improved vulnerability assessment, and a strong basis for optimised remediation schemes for persistent groundwater contaminants. Moreover, it directly contributes to bridging theoretical developments in transport modelling with practical field applications, offering a promising tool for risk management and long-term groundwater sustainability.
How to cite: Gupta, K. R. and Sharma, P. K.: From Local Mixing to Macrodispersion: A Sigmoid Approach to Modelling Scale-Dependent Contaminant Transport, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1124, https://doi.org/10.5194/egusphere-egu26-1124, 2026.
Reliable modelling of contaminant spreading remains a formidable challenge in hydrogeology. The MADE (macro-dispersion) natural-gradient tracer field experiments and related data provide an excellent opportunity to test methods for solute transport and related uncertainty.
Most published MADE- models have been based on a single conceptualisation and on spatial hydraulic conductivity structures derived from large volumes of published data. At best, this approach allows parametric uncertainty to be determined, but it provides no assessment of the impact of conceptual uncertainty.
Herweijer et al. (2026) conducted a ‘back to basics’ review of the original MADE reports and concluded that there are significant unexplored conceptual issues that influenced the migration of the tracer plume and or biased observations. These issues include geology (sedimentological heterogeneity at three scale levels), unreliable measurement of hydraulic conductivity, biased tracer concentrations, and a non-stationary flow field. As a result, we developed a framework of knowns and unknowns, with the latter category being very important for further uncertainty analysis.
We demonstrate that, with limited drilling and hydraulic conductivity data, but using sedimentological inferences, a 3D spatial hydrogeological architecture can be established for MADE. Using this architecture and lithological information a heterogenous hydraulic conductivity field can be established. The latter involves some alternate conceptual models reflecting sedimentological uncertainty, which can be further constrained using affordable and reliable piezometric data. Additional conceptual models are proposed to test uncertainty in boundary conditions and data validity.
The known-and-unknown framework yields an ensemble of numerical and analytical models that can be built to address the underdetermined nature of modelling results arising from multiple concepts and imperfect data. It is concluded that the ensemble result would provide a more holistic assessment of transport uncertainty
Herweijer J.C., S. C Young, P. Hayes, and O. Batelaan, 2026, A multi-conceptual model approach to untangling the MADE experiment, Accepted for Publication in Groundwater.
How to cite: Herweijer, J., Young, S., Hayes, P., and Batelaan, O.: Uncertainty assessment with multi-conceptual models and sedimentology in a key role – The MADE case , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16265, https://doi.org/10.5194/egusphere-egu26-16265, 2026.
Contaminated sites with non-aqueous phase liquid (NAPL) source zones are persistent due to the slow release of the dissolved phase in the generated plume. The groundwater quality criteria for many NAPL chemical compounds are very low, making complete remediation difficult. Most of the ‘easy’ sites with shallow and accessible source zones were remediated using excavation and off site treatment or landfill, leaving the deep, complex and buried source zones under infrastructure to be treated, which requires in situ remediation technologies. The development of innovative solution involves a multi-scale experimental approach. This involves progressing from batch tests to evaluate compatibility and performance, to 1D column experiments to determine cleaning efficiency and NAPL recovery mechanisms, and finally to 2D and 3D sand tank models to visualize solute propagation and performance, prior to a field pilot test and the full implementation of the technology. This paper presents and discusses some examples of thermal (e.g. electrical resistivity heating and thermal conduction heating), chemical (e.g. surfactant, chemical oxidation and foam) and biological (e.g. enzyme) treatments, showing their limitations and the challenges to be overcome.
How to cite: Martel, R. and Abolhosseini, P.: Innovative in situ treatments of NAPL source zones, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17099, https://doi.org/10.5194/egusphere-egu26-17099, 2026.
Urban contamination of soil and groundwater by BTEX (benzene, toluene, ethylbenzene, xylene) compounds remains a widespread environmental concern that requires effective remediation strategies. Among available technologies, biological methods have gained significant attention for being both cost‑effective and environmentally sustainable. However, in‑situ bioremediation of BTEX is often limited by low subsurface temperatures (10–15 °C), which suppress microbial activity. Raising subsurface temperatures can stimulate microbial growth and accelerate contaminant degradation, but conventional heating methods can be costly. Geothermal heating offers a sustainable alternative by using shallow subsurface systems to extract heat in winter and inject excess heat in summer through ground‑source heat pumps. This excess thermal energy can serve as a heat source to enhance bioremediation processes.
This study investigates the effects of cyclic temperature fluctuations (5–40 °C) on BTEX biodegradation in contaminated soils at a small scale. Experiments using native microbial consortia across three soil types showed that cyclic heating significantly enhanced microbial metabolism and BTEX degradation compared with constant subsurface temperatures. Among the tested soils, silty loam exhibited the highest biodegradation under cyclic heating, outperforming sandy soil.
Overall, this research highlights the potential for leveraging geothermal heating systems to support more sustainable and efficient in‑situ remediation of BTEX‑contaminated subsurface environments.
How to cite: Krol, M., Kaur, G., and Brar, S.: Geothermal heating impacts on BTEX biodegradation in various soils under cyclic fluctuating temperatures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13073, https://doi.org/10.5194/egusphere-egu26-13073, 2026.
Groundwater pollution from decades-old NO3 inputs is still a problem throughout Germany and the rest of the EU, with concentrations in many aquifers exceeding the 50 mg/l threshold mandated by the EU groundwater and drinking water directives. This situation has remained largely unchanged since the early 2000’s and quality targets for groundwater set by the European Environment Agency until 2030 are projected to not be met (EEA, 2025). In the light of these nitrate pollution legacies in situ remediation schemes have some appeal. In the NitratLURCH project funded by the German Federal Ministry of Research, Technology and Space (BMFTR, FONA-LURCH) as part of a funding scheme on sustainable groundwater management, we investigate the in situ remediation of nitrate pollution in groundwater via stimulated denitrification using CH₄/H₂ gas injections. In a pilot study at a former drinking water well contaminated with nitrate, nested numerical groundwater flow and transport models, in conjunction with intensive geologic site characterization, are used to support the setup of a gas injection system and to evaluate its ability to reduce nitrate concentrations in the groundwater flowing to the well. Regional geologic and hydrogeologic data were compiled to build a MODFLOW subcatchment scale groundwater model surrounding the drinking water well. The local aquifer system consists of about 150m thick glacio-fluvial Quaternary and Tertiary deposits with high transmissivity shallow sands and gravel beds significantly affecting groundwater flux dynamics in uppermost 10 – 20 m. A complex hydrofacies architecture, revealed during site characterization, was implemented into evolving versions of the flow model and further refined for a local, inset reactive transport model (codes Min3P and PHT3D) for a 1600 m2 area and 20 m deep section of the local aquifer. Conservative and reactive transport simulations and dozens of scenarios were realized to plan and operate an in situ CH4/H2 gas injection system, controlling and mitigating explosivity risks, optimizing reactant quantities and budgets, and evaluating reactions and turnover (e.g. incomplete denitrification leading to NO2 generation, unreacted CH4 etc.) in order to ensure legal compliance with the local water agency. Modeled optimal system performance under the local physical constraints and the assumption of maximum denitrification rates predicted a 30% reduction in nitrate concentrations in the pumped water (from about 50 to 35 mg/l) considering dilution from untreated water from parts of the complex groundwater flow system. Overall our modeling results suggest the viability of the tested remediation concept at the site.
EEA (2025). Nitrate in groundwater in Europe. Published 10 Nov 2025.
How to cite: Falchi Bernardo, V., Fleckenstein, J., Wunderlich, A., Seeholzer, A., Einsiedl, F., and Alte, M.: Modeling nitrate remediation in groundwater using CH₄/H₂ gas injections, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13066, https://doi.org/10.5194/egusphere-egu26-13066, 2026.
Recent development of the Analytic Element Method (AEM) (Köhler et al., 2026) enables simulation of steady-state reactive transport in two-dimensional aquifers considering several types of contamination scenarios, which otherwise would only be feasible with numerical models.
But even in numerical models, source geometries and architectures are often overly simplified as, e.g., simple line or patch sources. Such simplifications may significantly impair the reliability of model results. The AEM approach facilitates the representation of more complex source shapes also including discontinuities and multiple sources by superposition of elements. In the developed 2D model, the contaminant sources are considered as a combination of line and circle elements of constant concentration.
The effect of source discontinuities on steady-state plumes is qualitatively evaluated for both horizontally and vertically oriented domains. Further, an empiric relation between both number and width of source discontinuities, and the maximum plume length, in both domain orientations is derived. Evaluation of plume lengths from synthetic cases provide a linear and quadratic dependency of the number and width of discontinuities, respectively. This leads to an empirical formulation of a simplified effective source extent based on these two parameters.
The results highlight the advantages of the AEM model for simulating practical cases, particularly, in the early assessment stages, but also show that the method is appropriate for gaining insight in complex problem settings at a conceptual modelling stage. Computationally efficient methods such as the AEM may also help in future developments as part of hybrid modelling approaches to improve early site assessment.
Köhler, A. V., Craig, J. R., Yadav, P. K.,&Liedl, R. (2026). An Analytic Element Method solution for simulating multiple steady-state groundwater contamination scenarios. Journal of Contaminant Hydrology, 276, 104733. https://doi.org/10.1016/j.jconhyd.2025.104733
How to cite: Köhler, A. V., Yadav, P. K., Tripathi, M., Craig, J. R., Liedl, R., Grathwohl, P., and Dietrich, P.: The effect of source discontinuities on steady-state plume extents, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19419, https://doi.org/10.5194/egusphere-egu26-19419, 2026.
Groundwater is the most dependent source of irrigation and public water supply in most countries; hence, it requires the best quality management practices to safeguard against contamination. Groundwater quality management requires the best models to assess the extent of migration and spatiotemporal variation. The extent of contamination is often studied through the application of mesh-based methods, such as the finite difference method (FDM) and the finite element method (FEM). Moreover, in recent decades, various groundwater meshless studies have provided better alternatives to mesh-based methods for solving complex groundwater contamination problems. The meshless methods eliminate the need for generating a computational mesh; they operate on a set of scattered nodes distributed across the aquifer domain, which can be easily added or removed as needed, depending on the field scenario and its complexity. Recent studies have demonstrated the development of various meshless methods for modeling groundwater contaminant transport, enabling the assessment of transport behavior. In this study, a groundwater contaminant transport model is developed using the generalized finite difference method (GFDM), which employs the Taylor series and the moving least squares (MLS) method to determine the spatial and temporal variations of contaminant in the aquifer domain. The application of the developed GFCT model is demonstrated for various heterogeneous porous media, and the results are compared with those from the MT3DMS model.
How to cite: Singh, K. G. and Pathania, T.: Two-dimensional meshless simulation of contaminant transport in porous media using the generalized finite difference method (GFDM), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10814, https://doi.org/10.5194/egusphere-egu26-10814, 2026.
Groundwater contamination has become an increasingly critical environmental concern worldwide. In-situ chemical oxidation (ISCO) is considered a promising technology for groundwater remediation, but its performance in heterogeneous aquifers is often constrained by mass-transfer limitations in low-permeability zones, leading to suboptimal treatment efficiency. Theoretically, ultrasound can enhance permeability in low-permeability regions, accelerate oxidant transport, and activate oxidants to strengthen their degradation capacity; however, the remediation performance and underlying mechanisms of ultrasound-ISCO coupling have not yet been systematically validated through experiments. To address this gap, this study conducted degradation experiments under three ultrasonic modes (no ultrasound, ultrasonic pre-treatment, and continuous ultrasound) and employed nuclear magnetic resonance (NMR) to quantitatively characterize contaminant distribution and degradation behavior within the pore space. The results show that ultrasonic pre-treatment reconstructs the pore structure of the porous medium via cavitation and mechanical vibration, thereby enhancing permeability and oxidant mass transfer and consequently accelerating contaminant removal. When ultrasound is continuously applied during ISCO, it not only maintains permeability enhancement but also activates the oxidant, modulates the transformation pathways of key intermediates, and promotes deeper oxidation and mineralization, ultimately yielding the highest degradation efficiency due to the synergistic action of permeability enhancement and oxidant activation. This study demonstrates the effectiveness of ultrasound-ISCO coupled technology for remediation of contaminated heterogeneous aquifers and systematically elucidates the synergistic mechanisms between ultrasonic permeability enhancement and intensified oxidation, providing theoretical support for its engineering application under complex hydrogeological conditions.
How to cite: Zhao, Y.: Mechanisms of Enhanced In-situ Chemical Oxidation for Groundwater Remediation via Ultrasonic Permeability Improvement, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5126, https://doi.org/10.5194/egusphere-egu26-5126, 2026.
Cadmium (Cd) is a priority groundwater contaminant of significant environmental concern, as its presence in subsurface water systems poses serious risks to both human and ecosystem health. A better understanding of cadmium transport under heterogeneous subsurface conditions representative of real aquifers is essential for accurately predicting its fate and for designing effective remediation strategies. This study investigates cadmium transport in saturated heterogeneous subsurface using a two-dimensional laboratory tank packed with an undisturbed soil core to generate high-quality experimental data under realistic flow regimes. Initially, a conservative tracer test using sodium chloride (NaCl) was conducted to assess flow dynamics, hydraulic connectivity, and preferential flow pathways within the heterogeneous medium system. The tracer results confirmed non-uniform flow behaviour and significantly reduced pore-water velocities due to the low permeability and structural heterogeneity of the undisturbed soil. After achieving steady-state flow conditions, a cadmium transport experiment was performed by introducing a 1000 ppb Cd solution under constant hydraulic conditions. Water samples were collected at selected time intervals and analysed using inductively coupled plasma mass spectrometry (ICP-MS) to quantify cadmium concentrations. The experimental results reveal delayed cadmium breakthrough and pronounced tailing behaviour, highlighting the dominant influence of heterogeneity, reduced hydraulic conductivity, and enhanced sorption processes on cadmium transport dynamics in natural subsurface systems. The dataset generated provides a robust foundation for calibrating and validating reactive transport modelling under heterogeneous conditions. This experimental framework supports science-based groundwater quality management and informed decision-making in contaminated aquifers.
How to cite: Gayari, S. B., Chakma, S., and Gupta, P. K.: Experimental Insights into Cadmium Transport in a Heterogeneous Saturated Subsurface Using a Two-Dimensional Tank, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4219, https://doi.org/10.5194/egusphere-egu26-4219, 2026.
Light non-aqueous phase liquids (LNAPLs) are common industrial contaminants, posing significant environmental risks. Understanding the distribution of LNAPL in the vadose zone is crucial for developing effective remediation strategies. This study combined capillary modeling with sandbox experiments across dry sand to capillary zones to analyze the spatial and temporal distribution of LNAPL using modified light transmission techniques. The research examined the effects of particle size, viscosity, and the slope of phreatic surface on the spatiotemporal distribution behavior of LNAPL. Key findings reveal that capillary pressure transitions from gas-LNAPL driving to LNAPL-water resistance, which significantly influences the vertical infiltration of LNAPL in dry sand and horizontal migration in the capillary zone. This transition leads to the formation of a "levitational" lens above the groundwater table. Moreover, finer particles elevate LNAPL-water capillary resistance, forming a new "double shark-fin" vertical saturation profile. Higher viscosity narrows "shark-fin" profiles by impeding vertical migration. Enhanced hydraulic gradients expand distribution vertically/horizontally, elevating saturation peaks by 50%. Notably, optical transmission imaging detects sub-residual LNAPL in "shark-fin" saturation overlooked by conventional models. Underestimation of this critical zone directly compromises contamination severity assessment. Our study corrects residual saturation benchmarks for accurate risk management, informing more effective LNAPL remediation strategies.
How to cite: Cui, Y.: Insights into LNAPL saturation distribution in capillary zone based on light transmission and mechanical analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10367, https://doi.org/10.5194/egusphere-egu26-10367, 2026.
Groundwater sampling is a critical component of hydrogeological investigations and is essential for accurate hydrogeochemical analyses. Fully representative samples can be obtained after effective purging of non-representative stagnant water from monitoring wells. However, the procedure and threshold for sufficient well purge remain unresolved. In practice, wells are often purged from 5 to 60 minutes according to the stabilization of chemical-physical parameters or 3–5 well volumes without a rigorous scientific basis, after which samples are collected under the assumption that they represent formation conditions. This introduces substantial uncertainty and potential errors into sampling data.
To address this issue, we develop a well storage-mixing model to characterize the combined effects of two key processes during purging: well storage depletion and wellbore mixing. By modeling the dimensionless completion variables of these two processes, ηq [-] and ηc [-], we demonstrate that sufficient well purge is controlled by the process with the longer characteristic timescale. In high-yield aquifers or large, deep wells, wellbore mixing limits the time required to achieve sufficient purging; conversely, in low-yield aquifers or shallow, small wells, storage depletion is the limiting process. Field data from recent sampling campaigns in Rome, Italy, and Inner Mongolia, China, exhibit mixing-limited and storage-limited purge modes, respectively, indicating that different well geometries and hydrogeological settings lead to distinct purge times and volumes. Accordingly, purge criteria should be dynamic to avoid over-purging (unnecessary capital costs) or insufficient purging (non-representative samples). Dynamic purging informed by the storage-mixing model significantly improves data accuracy while reducing capital costs and should be widely adopted, particularly for monitoring well networks with highly variable well geometries and aquifer conditions.
How to cite: He, Y., De Filippi, F. M., Qu, S., and Luo, J.: Dynamic Purging for Groundwater Sampling Informed by a Storage–Mixing Model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6183, https://doi.org/10.5194/egusphere-egu26-6183, 2026.
Freshwater security in Mediterranean islands is under threat due to the decoupling of water demand from natural recharge rates, which is being pushed by climate instability and tourism-induced urbanization. This study assesses the hydro-geochemical mechanisms that influence groundwater quality on Bozcaada Island, Türkiye, to determine its appropriateness for drinking and irrigation. A total of 21 groundwater samples were collected during the dry season (June 2025), coinciding with a demographic surge from approximately 1,200 to over 40000 inhabitants to evaluate the groundwater salinity and water quality parameters (EC, TDS, pH, HCO3−, NO3−, SO42−, Cl−, Na+, Ca2+, K+, Mg2+, As, Fe, Mn). The methodological framework combined multivariate statistical analyses, notably Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA), with geochemical modeling, water quality index (WQI) analysis, and GIS-based spatial distribution mapping. Hydro-geochemical analysis shows that the groundwater chemistry in the permeable Fıçıtepe and Kirazlı formations is primarily influenced by lateral seawater intrusion and water-rock interactions. The Principal Component Analysis (PCA) successfully distinguished between geogenic weathering processes and anthropogenic salinity inputs, indicating that seasonal over-abstraction reverses hydraulic gradients in sensitive coastal zones. As a result, hydrochemical facies change from Na-HCO3 in interior recharge areas to Na-Cl in coastal over-abstraction areas. Increased electrical conductivity (EC) and chloride concentrations were spatially linked with saltwater intrusion and high-populated tourism areas, depicting an important fraction of coastal groundwater unsuitable for drinking usage and irrigation due to elevated sodium adsorption ratio (SAR), residual sodium carbonate (RSC), and magnesium hazard exceeding the limits set by the World Health Organization (WHO) and Turkish drinking water standards. The groundwater is of type Na-HCO3, Na-CL, and Ca-Mg-HCO3. The Water Quality Index (WQI) assessment shows that groundwater quality for domestic use is frequently contaminated due to excessive EC, Cl-, Na+, SO42-, F-, As, Mn, and Fe content, requiring treatment before consumption. As of current, the island depends on submarine pipelines water supply to address its water deficit, the research highlights how important this dependence is during moments of peak demand. The findings' conclusion summarizes that sustainable water security needs the integration of Nature-Based Solutions, especially Managed Aquifer Recharge, to restore hydrodynamic equilibrium and mitigate the continuity of salinization fronts in the coastal aquifer.
How to cite: Zulal, K., Baba, A., and Gündüz, O.: Evaluation of Hydro-Geochemical Processes Affecting Groundwater Quality in Bozcaada Island Using Water Quality Index, Multivariate Statistical Analyses, and Spatial Distribution Mapping, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16624, https://doi.org/10.5194/egusphere-egu26-16624, 2026.
Posters on site: Fri, 8 May, 16:15–18:00 | Hall A
In Kanpur Dehat, India, the Rania–Khan Chandpur villages have multiple Chromite Ore Processing Residue (COPR) dumps that have been open for decades. This procedure has allowed leachate from rain to infiltrate into the soil-groundwater systems and elevated the levels of Chromium (Cr) in groundwater up to 39 mg L⁻¹ in 2023 and 27 mg L⁻¹ in 2024. Despite ongoing contamination, there is limited quantitative understanding of local soil’s retention or release capacity for Cr, making it difficult to predict plume migration or design effective remediation. Therefore, the present study specifically focuses on Rania–Khan Chandpur to generate site-relevant sorption and transport parameters essential for assessing long-term groundwater monitoring. To understand the specific characteristics of Cr in the soil–groundwater system, a batch experiment was performed and fitted with isotherm models. The distribution coefficient (Kd) values for Rania soil ranged from 0.088 to 0.047 L kg⁻¹, indicating substantial Cr adsorption capacity. The KL values were 0.043 at pH 4, 0.015 at pH 7, and 0.007 at pH 11. Freundlich parameters (Kf and 1/n) further confirmed favorable and heterogeneous surface-controlled adsorption behavior across all pH levels. A rainfall-driven column experiment was conducted to evaluate Cr leaching and transport from a 2 cm COPR layer through 15 cm of soil collected from Rania-Khan Chandpur, simulating natural seasonal recharge conditions at the site. Breakthrough curves (C/C₀ vs Pore Volume (PV)) showed Cr breakthrough at approximately 0.3 PV, reaching a peak near 0.8–0.9 PV, followed by long tailing extending up to around 7 PV, indicating strong initial adsorption and subsequent slow desorption and release over time. This finding suggests that while soil can temporarily restrict Cr movement, it gradually releases retained Cr, acting as a long-term source, which helps explain the persistent groundwater contamination. These findings highlight that although soil temporarily retains Cr, long-term release sustains plume persistence, emphasizing the need for site-specific remediation and improved predictive modelling for soil-groundwater systems.
How to cite: Deoli, V. and Malik, A.: Isotherm-Driven Sorption Dynamics and Breakthrough Behaviour of Chromium in COPR-Impacted Soils: A Field-scale Study from Rania–Khan Chandpur, India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-925, https://doi.org/10.5194/egusphere-egu26-925, 2026.
The migration of groundwater pollutants is concealed, and accurately and efficiently tracing the source of groundwater pollution is the difficulty in the remediation and control of groundwater pollution. To ensure the accuracy and efficiency of source tracing, this paper takes a contaminated site along the lower reaches of the Ganjiang River as an example and constructs a groundwater pollution source tracing framework based on Bayesian optimization. The Kepler optimization algorithm was adopted to optimize the parameters of the basic water flow model. A dynamic model was established by coupling the water level of the Ganjiang River, and the migration law of pollutants in the dynamic groundwater flow field was studied. Qualitative identification of site pollution sources is carried out through self-organizing mapping neural networks to determine the homology of pollution indicators. By using the IFM interface provided by FEFLOW and combining the Bayesian optimization algorithm with the solute transport model through the Python language, the parameters of pollution sources are inverted. The main achievements are as follows:
(1) Through the statistical analysis of groundwater quality data, it can be known that the typical pollutants in groundwater are manganese, ammonia nitrogen, iron and fluoride. There is an abnormal enrichment phenomenon caused by multi-source input and local pollution release in the field area.
(2) The pollution sources were qualitatively identified based on the self-organizing mapping neural network method. The results showed that they originated from agricultural production, livestock activities, and industrial production activities in the original factory area.
(3) Based on the site investigation data, a basic groundwater flow model was established. The model parameters were optimized through the Kepler optimization algorithm. The absolute error between the simulated water head and the actual water head at 39 water level observation points decreased from 2.62 to 0.36.
(4) By coupling the water level of the Ganjiang River to establish a dynamic water flow model, it was calculated that the influence radius of the Ganjiang River water level is approximately 350 meters. The contaminated site is precisely located at the edge of the influence radius. Through comparative experiments, it was found that the solute transport results within the site are less affected by the water level of the Ganjiang River.
(5) For the nonlinear high-dimensional optimization problem of groundwater pollution source parameter inversion, a physical constraint inversion framework based on Bayesian optimization is proposed. The Bayesian optimization algorithm can quickly identify the location with the highest possibility of pollution sources and simulate the matching parameter groups of pollution sources within a finite number of iterations. The entire process only takes 20 minutes. Subsequently, by means of combined source inversion, the locations of potential pollution sources are identified, and the causes and mechanisms of their formation are analyzed based on the integration of multi-source data.
How to cite: Xu, M., Zhang, C., and Guo, J.: Research on Groundwater Pollution Source Tracing of Abandoned Industrial Sites along the River Based on Bayesian Optimization, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3344, https://doi.org/10.5194/egusphere-egu26-3344, 2026.
Aquifers are typically heterogeneous in both structure, which appears as variations in hydraulic conductivity (K), and chemistry, which is governed by the spatial distribution of electron accepting and donating capacity (EAC and EDC). Arsenic (As), a highly toxic and strongly mobile groundwater pollutant, requires a comprehensive understanding of its transport and transformation behaviour—especially during early remediation stages. Studying the dynamics of As is challenging in highly heterogeneous aquifers, where both flow paths (controlled by structure) and reaction rates (influenced by chemistry) play complex roles. For the first time, the redox capacity is used to characterize biogeochemical reaction processes. Static batch experiments confirmed that the redox capacity-mediated reaction kinetics framework effectively captured electron transfer from various active components. Furthermore, the validated reaction kinetics was applied to a two-dimensional radial model to examine how As transports and transforms in the aquifer matrix and lens structures. The study also quantified the relationship between physicochemical heterogeneity and the breakthrough curves (BTCs) of As. The research offered a new framework for understanding arsenic dynamics from an electron-transfer-based perspective.
How to cite: Gong, K.: Arsenic dynamics in physicochemically heterogeneous aerobic aquifers mediated by redox capacity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4265, https://doi.org/10.5194/egusphere-egu26-4265, 2026.
Climate change has increased the frequency and intensity of wildfires, resulting in enhanced accumulation of incompletely combusted organic materials such as black carbon (BC) in soil and subsurface environments. The presence of wildfire-derived BC modifies the physicochemical characteristics of groundwater–soil systems and can alter the retention behavior of various contaminants. Among these, radiocesium (Cs), which may be released into the environment following nuclear power plant accidents, is of particular concern due to its high mobility and long-term persistence. Understanding how BC formation conditions influence Cs retention is therefore essential for predicting radionuclide behavior in wildfire-affected subsurface environments.
In this study, BC was produced from oak and pine biomass under controlled laboratory conditions, with final pyrolysis temperatures ranging from approximately 300–400 °C to ≥500 °C. Previous batch sorption experiments showed that Cs is preferentially sorbed onto low-temperature BC, whereas high-temperature BC exhibits reduced Cs uptake. To investigate the physical mechanisms underlying this temperature-dependent behavior, synchrotron-based X-ray computed tomography (CT) was conducted at the Pohang Accelerator Laboratory (PAL 6C) using 25 keV X-rays with a voxel resolution of 3.25 μm. CT images reveal that BC produced at lower temperatures preserves an interconnected internal pore structure inherited from the original biomass, whereas BC produced at ≥500 °C exhibits pronounced microstructural degradation, including pore collapse and loss of pore connectivity. These structural trends were consistently observed despite inherent heterogeneity associated with different biomass precursors. The results indicate that Cs sorption onto BC is controlled by a coupled effect of surface chemical functionalities and microstructural integrity, which governs the accessibility of reactive sites. High-temperature thermal alteration induces physical damage to the BC structure, thereby limiting effective Cs retention even as aromaticity increases. These findings highlight the importance of considering wildfire-induced changes in BC properties when assessing radionuclide retention in subsurface environments.
How to cite: Choung, S. and Bae, H.: Wildfire-derived black carbon alters cesium retention in subsurface environments: insights from synchrotron X-ray imaging, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4684, https://doi.org/10.5194/egusphere-egu26-4684, 2026.
Bioremediation is a promising strategy for sustainable management and treatment of field sites with soil and groundwater contamination. Understanding the fate of contaminants is key for identifying optimal conditions and prediction of biodegradation in the subsurface. We develop the open-source Python package mibitrans for hydrogeological reactive transport modelling for simple use of field site modelling, transport prediction and management optimization. Mibitrans is developed in the frame of the EU-funded MiBiRem project.
Mibitrans is based on physics-based (semi-)analytical solutions for multidimensional solute transport in groundwater. Biodegradation can be modelled in various ways, including simple first-order decay and chemical reactions based on electron acceptor concentrations. The mibitrans package is modular, fully tested, well documented and well-structured to allow for easy adaptation and use in various field situations. We will present the use with example field site data from ongoing bioremediation projects.
How to cite: Zech, A., Bakker, J., van Leeuwen, J., Richardson, R., and Camphuijsen, J.: Mibitrans: A python package for modelling subsurface contaminant transport and natural attenuation decision support , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8272, https://doi.org/10.5194/egusphere-egu26-8272, 2026.
Nitrate contamination is one of the dominant groundwater-quality pressures in Mediterranean irrigated plains. In the Plana de Valencia (eastern Spain), intensive agriculture and irrigation return flows coexist with strong groundwater–surface water connectivity and ecologically sensitive receptors such as the Albufera wetland system. We present a regional-scale numerical framework that couples groundwater flow and conservative solute transport to reproduce observed nitrate dynamics and to provide a basis for scenario testing of mitigation measures.
A previously developed transient groundwater-flow model of the Plana de Valencia was implemented in the ModelMuse graphical environment and used as the hydraulic driver for MT3DMS multi-species transport simulations. The hydrogeological conceptualization comprises four model layers representing (i) highly permeable Quaternary detrital deposits, (ii) Tertiary formations of intermediate permeability (limestones/sandstones/conglomerates), (iii) low-permeability Miocene marls, and (iv) permeable Mesozoic carbonates over an impermeable Keuper basement. External stresses include spatially distributed recharge (rainfall infiltration and irrigation returns), exchanges with rivers, channels and wetlands (“ullals”), pumping abstractions, and lateral boundary transfers, consistent with a predominantly inland-to-coast hydraulic gradient.
Agricultural nitrate inputs were spatially allocated using land-use information (CORINE) and fertilization constraints from the regional regulatory framework, translated into gridded source terms (1 km × 1 km) and applied through the sink/source mixing package. Simulations covered 1980–2017 and were evaluated against nitrate time series from the Júcar River Basin Authority monitoring network at multiple observation wells across both the northern and southern sectors of the aquifer. Manual multi-well calibration produced acceptable agreement in most wells; a classification of fit quality indicates good performance for 8 wells and poor performance for 3 wells, with no clear spatial clustering of misfits, suggesting the need for local refinement or parameter regionalization. Model performance improved after reducing the fraction of applied nitrate reaching groundwater from 10% to 7%, and the best correspondence commonly occurred in the second layer (typical monitoring depths ~40–50 m).
Results confirm widespread exceedance of the 50 mg/L threshold in the majority of wells and a generally increasing temporal trend even under regulated application rates, highlighting the risk of persistent degradation and potential downstream impacts on the Albufera system. The proposed model constitutes a transferable decision-support baseline for testing management scenarios (fertilization control, irrigation efficiency, drought sequences, and saltwater intrusion) and for advancing toward automated calibration and uncertainty quantification.
How to cite: Rodrigo-Ilarri, J., Cassiraga, E., Rodrigo-Clavero, M.-E., and Escrivá-Benito, L.: Coupled MODFLOW–MT3DMS simulation of nitrate transport in the Plana de Valencia coastal aquifer (Spain): calibration to monitoring wells and implications for groundwater–wetland interactions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10368, https://doi.org/10.5194/egusphere-egu26-10368, 2026.
Transverse dispersivity 𝛼𝑇[𝐿], both horizontal (𝛼𝑇ℎ [L]) and vertical (𝛼𝑇𝑣 [L]), is frequently cited as a major source of error in groundwater contamination modeling. These dispersivities depend on several subsurface factors (e.g., sediment structure, grainsize); however, their sub-centimeter scale makes accurate estimation for field data highly uncertain. Consequently, only limited highly reliable field transverse dispersivity data can be found in the literature, leading to their insufficient characterization and dependence on quantities’ affecting reactive transport in the groundwater.
This study evaluates over 150 laboratory transverse dispersivity data, obtained from the literature, considering various flow and transport factors (e.g., grainsize, flow-velocity). The evaluation considers the combined data as a global dataset, i.e., independent of a particular experimental setup. The analysis leads to a development of a new transverse dispersivity model: 𝐷𝑇= 𝐷𝑝+ 0.23𝐷𝑎𝑞Pe0.59, (similar to Olsson et al., 2007); 𝐷𝑇, 𝐷𝑝 and 𝐷𝑎𝑞 [L2T−1] denote the transverse dispersion coefficient, pore and aqueous diffusion coefficients, respectively and Pe [-] is the Peclet number.
Field based 𝛼𝑇ℎ and 𝛼𝑇𝑣 are obtained using field site data (over 60 sites, mostly BTEX sites) by inverting an Analytical Element Model (AEM) developed by Köhler et al (2026). The maximum plume length (𝐿max) in the dataset was used as the controlling factor, while source geometry and different combination of reactants (O2, NO3, SO4 etc.), among others, served as the experimental variables in quantifying 𝛼𝑇. The obtained results for both 𝛼𝑇ℎ and 𝛼𝑇𝑣 range from 1mm to 60 mm and generally agree with literature results when the source thickness is much smaller (< 50%) than aquifer thickness and when combination of several reactants are considered. For all other scenarios, the obtained results significantly differ (up to order of magnitude) from the published values. In general, laboratory dispersivities are substantially smaller compared to field data. Furthermore, field 𝛼𝑇ℎ is mostly less than 5 times compared to 𝛼𝑇𝑣. The ongoing work involves analyzing obtained 𝛼𝑇 results with different field properties (e.g., hydraulic conductivity) and applying the findings to contaminated sites.
References:
Köhler, A. V., J. R. Craig, P. K. Yadav, and R. Liedl. 2026. An Analytic Element Method solution for simulating multiple steady-state groundwater contamination scenarios. J. Contam. Hydrol. 276, January: 104733, https://doi.org/10.1016/j.jconhyd.2025.104733.
Olsson, A.H., Grathwohl, P. (2007): Transverse Dispersion of Non-reactive Tracers in Porous Media: A new Nonlinear Relationship to Predict Dispersion Coefficients. J. Contam. Hydrol., 92, 3-4, 149 – 161
How to cite: Sreelekshmi, S., Puri, U., Köhler, A., Tripathi, M., Yadav, P. K., Yadav, A., Grathwohl, P., Dietrich, P., and Chahar, B. R.: Evaluating transverse dispersivities obtained from large laboratory and field datasets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12915, https://doi.org/10.5194/egusphere-egu26-12915, 2026.
Elevated Fe/Mn in coastal groundwater threatens water safety and ecosystems, yet their coupled natural-anthropogenic drivers remain poorly quantified in complex multi-aquifer systems. Given the quantitative limitations of conventional hydrochemical and statistical analyses, this study developed a numerical modeling-driven framework integrating PMF-based quantitative source apportionment of Fe/Mn with PHREEQC-constrained reactive transport modeling (via GMS) in Zhanjiang City, China. Dataset from 1970s to present revealed persistent Fe/Mn contamination across this groundwater-dependent region. PMF analysis quantitatively differentiated natural sources (dominantly silicate weathering and Fe/Mn-bearing mineral dissolution) from anthropogenic inputs, constraining reaction pathways. PHREEQC inverse modeling further quantified Fe/Mn-bearing mineral dissolution rates, generating essential reaction parameters for transport simulations. Forward modeling assessed Fe/Mn mobility under saline-water mixing and CO2 equilibrium conditions. Simulations indicated that low seawater mixing best reproduced observed Fe/Mn levels, with Ca2+/Mg2+ exchange as a key control. Discrepancies between modeled and observed ion compositions implied possible contributions from deep brine upcoming or anthropogenic inputs. 3D numerical simulations characterized flow dynamics and reactive transport. Results revealed spatially constrained Fe/Mn dispersion, indicating limited aquifer hydrogeological connectivity regardless of pollution source location. Large-scale pumping neither induced significant downstream dispersion nor facilitated upstream transport, highlighting the dominance of natural hydrogeochemical controls. Redox conditions and hydraulic parameters were key regulators of Fe/Mn mobility. This framework quantifies redox-driven Fe/Mn contamination mechanisms under combined stressors, offering transferable solutions for global coastal groundwater management.
How to cite: Xiao, S. and Wang, Y.: Quantifying Mechanisms of Elevated Iron and Manganese Concentrations in Coastal Multi-Layer Aquifers via Numerical Modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13203, https://doi.org/10.5194/egusphere-egu26-13203, 2026.
This study establishes a systematic framework for investigating seasonal groundwater flow dynamics and contaminant migration at chlorinated-solvent-contaminated sites in Taiwan. Due to strong seasonal rainfall patterns, groundwater levels fluctuate significantly, influencing flow directions and contaminant transport behavior. Continuous groundwater-level monitoring from April to September 2025 shows noticeable seasonal variations, with well K00318 exhibiting the greatest decline, suggesting potential shifts in the local flow field. Rainfall–water level correlations further indicate high vertical hydraulic conductivity in the unsaturated zone. Seven rounds of groundwater sampling reveal exceedances of TCE, DCE, and occasionally VC in several monitoring wells, including K00407, K00381, K00296, K00237, K00284, and K00358, while all remaining wells stayed below monitoring and regulatory limits. The results highlight spatial variability in contamination severity and emphasize the need for continued monitoring to assess plume behavior and support future management decisions.
How to cite: Chen, J.-S., Liang, C.-P., Ho, Y. C., Liao, Z.-Y., Nguyen, T.-T.-H., and Chang, J.-Y.: Investigation and Analysis of seasonal Groundwater Flow dynamics and Contaminant Migration at Chlorinated-Solvent-Contaminated Sites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16462, https://doi.org/10.5194/egusphere-egu26-16462, 2026.
Diffuse nitrate pollution in groundwater from intensive agriculture continues to contribute to a persistent risk to groundwater quality. While natural nitrate degradation processes can mitigate anthropogenic nitrate inputs, the available electron donors in the pore structure of aquifers, primarily pyrite (FeS₂) and organic carbon (Corg), are finite resources. Quantifying these resources is crucial for the long-term management of groundwater resources; however, the quality of this quantification is often limited by a lack of real-world data.
This study presents a comprehensive approach to characterizing denitrification potentials in various aquifers (porous and bedrock) based on solid-phase analysis of drill core samples combined with hydrochemical and isotopic data in the state of Sachsen-Anhalt, Germany. The methodology integrates the geochemical quantification of reducing agents with hydraulic parameters to calculate a specific lifetime of nitrate degradation (denitrification potential) for the historical reference period (1961 – 2020) and for future projections (2020 – 2100) using modeled groundwater recharge rates for the RCP 2.6 and RCP 8.5 climate scenarios.
The results show a clear division between aquifer types. Aquifers in bedrock (e.g., Keuper, bunter sandstone) exhibit high resilience with lifetimes > 10,000 years, primarily due to a high autotrophic denitrification potential. In contrast, porous aquifers, particularly the covered Pleistocene units, were identified as highly vulnerable groundwater systems. Historical analysis shows that these aquifers have significantly lower reducing agent reserves, resulting in lifetimes of less than 1,000 years. Future climate projections indicate a critical depletion of these resources, mainly driven by climate-related changes in groundwater recharge and continuous nitrate inputs. The remaining lifetime of porous aquifers is projected to decrease to less than 40 years in some cases this century under both climate scenarios, potentially leading to a large-scale nitrate breakthrough. The combination of rapidly depleting denitrification buffer and the hydraulic lag of the systems underscores the urgency of implementing strategies in vulnerable catchment areas, as reliance on natural attenuation is no longer a sustainable safeguard.
How to cite: Rößger, J. and Siebert, C.: Historic and future classification of nitrate degradation for porous and fractured aquifers in terms of their denitrification potential using isotopic, hydrochemical and borehole data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21109, https://doi.org/10.5194/egusphere-egu26-21109, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot A
EGU26-6358 | Posters virtual | VPS8
Spatial Variability of Uranium in Shallow Aquifers of Semi-Urban Indian LandscapesTue, 05 May, 14:06–14:09 (CEST) vPoster spot A
Uranium contamination in shallow aquifers is emerging as a concern for groundwater-quality issues across several parts of India. The present study evaluates the spatial distribution, concentration levels in shallow groundwater systems of selected semi-urban regions of India. Secondary data used in this assessment were obtained from the Central Ground Water Board (CGWB), covering semi-urban areas across all Indian states. The results reveal pronounced spatial heterogeneity in uranium concentrations, with numerous locations exceeding the permissible limits prescribed by the World Health Organization (WHO) and the Bureau of Indian Standards (BIS) for drinking water. Analysis of uranium concentration data for the period 2024–2025 indicates that shallow aquifers in parts of Karnataka, Punjab, and Rajasthan exhibit average uranium concentrations of approximately 133 ppb, 48 ppb, and 79 ppb, respectively, while maximum concentrations of 488 ppb, 202 ppb, and 119 ppb respectively, were recorded at select locations. A substantial proportion of groundwater samples were found to exceed WHO guideline values, highlighting widespread contamination concerns. The findings of this study offer critical insights for water-resource managers and policymakers in developing strategies to protect drinking-water security in uranium-affected regions of India.
How to cite: Kumar, D., Khare, S., and Kurre, S.: Spatial Variability of Uranium in Shallow Aquifers of Semi-Urban Indian Landscapes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6358, https://doi.org/10.5194/egusphere-egu26-6358, 2026.
EGU26-12747 | ECS | Posters virtual | VPS8
Hydrogeochemical Forensics of Pyrite Oxidation in Unsaturated Mine Overburden: A Numerical Simulation Framework for Groundwater Contaminant Migration.Tue, 05 May, 14:09–14:12 (CEST) vPoster spot A
Groundwater contamination arising from mining activities represents a persistent and complex environmental challenge, particularly in coal-bearing regions where sulfide-rich mine overburden is extensively exposed to atmospheric conditions. Upon interaction with oxygen and moisture, pyrite oxidation generates acidic by-products and mobilizes dissolved constituents, such as ferrous, ferric iron, sulfate, and hydrogen ions. Understanding and predicting the spatiotemporal evolution of contaminant plumes in such systems remains challenging due to the coupled nature of variably saturated flow, multicomponent geochemical reactions, and microbially mediated processes. This study develops a comprehensive numerical modeling framework for simulating contaminant transport and remediation processes associated with oxidation reactions in unsaturated mine overburden systems. Variably saturated flow is represented through discretization of the governing flow equation in the vertical domain using hydraulic head-based parameters, and the resulting tridiagonal system of linear equations is efficiently solved using the Thomas algorithm. The model couples variably saturated groundwater flow, represented by Richards’ equation, with multicomponent reactive transport equations describing the generation and migration of key oxidation products (Fe²⁺, Fe³⁺, SO₄²⁻, and H⁺). In addition, sulfate reduction mediated by sulfate-reducing bacteria (SRB) is incorporated to capture biologically driven attenuation mechanisms relevant to natural and engineered remediation scenarios. Simulations are performed for a total of 22 years (8030 days). A time step of 0.1 day and a grid size of 0.2 m are identified as the optimal choices for the simulations. The simulation results indicate that the concentrations of oxidation-derived species decrease significantly from 200 to 40 mol/m³ in clay, 300 to 95 mol/m³ in loam, and 1 to 0.2 mol/m³ in sand. Sensitivity analysis shows that peak sulphate sensitivity in clay with a sensitivity index (SI) of 0.65 and in loam with an SI of 0.5 under high saturation condition (water content, wc = 0.9), while ferrous ions exhibit maximum sensitivity in loam under low saturation condition (wc = 0.2) with an SI of 750. The findings support the development of predictive frameworks that can inform sustainable groundwater management, optimize remediation strategies, and address key challenges in the practical application of contaminant transport models.
How to cite: Roy, G. and Sivakumar, B.: Hydrogeochemical Forensics of Pyrite Oxidation in Unsaturated Mine Overburden: A Numerical Simulation Framework for Groundwater Contaminant Migration., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12747, https://doi.org/10.5194/egusphere-egu26-12747, 2026.
EGU26-15319 | ECS | Posters virtual | VPS8
Groundwater quality assessment in semi-arid Morocco: spatial analysis and monitoringTue, 05 May, 14:12–14:15 (CEST) vPoster spot A
Groundwater is a critical water resource in Morocco, particularly in semi-arid regions where agricultural demand and local uses place increasing pressure on aquifers. In this setting, a clear and spatially explicit assessment of groundwater quality is essential to support monitoring strategies and contribute to more sustainable water management.
This study presents an approach for characterizing groundwater quality in a semi-arid area of Morocco based on physico-chemical analyses of groundwater samples collected from wells and springs. Water quality is identified through the computation of a groundwater quality index derived from multiple measured parameters, providing a synthetic and comparable metric across sampling points. The results are then integrated within a Geographic Information System (GIS) framework to explore spatial patterns and support interpretation at the territorial scale. Spatial interpolation is used to map the distribution of both the individual parameters and the quality index, highlighting local contrasts and potential hotspots within the study area.
Overall, the findings indicate generally satisfactory groundwater quality, while also revealing localized variations that justify targeted follow-up and site-specific attention. The proposed workflow is transferable and can be adapted to other semi-arid settings in Morocco to support diagnosis, prioritization of actions, and long-term, sustainable groundwater resource management.
Keywords : Groundwater quality; Morocco; semi-arid environment; physico-chemical parameters; water quality index; GIS; spatial interpolation; mapping; sustainable water management
How to cite: Mouncif, A., Nait-Taleb, O., Karroum, M., Krimissa, S., Namous, M., and Elaloui, A.: Groundwater quality assessment in semi-arid Morocco: spatial analysis and monitoring, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15319, https://doi.org/10.5194/egusphere-egu26-15319, 2026.
EGU26-1227 | ECS | Posters virtual | VPS8
Integrated EWQI–Monte Carlo framework for assessing groundwater quality and health risk in the Khetri mining region of Jhunjhunu district, Rajasthan, IndiaTue, 05 May, 14:51–14:54 (CEST) vPoster spot A
In various parts of arid and semi-arid region of India such as Rajasthan people are mainly depended on groundwater for fulfil their daily demands like drinking and watering their crops. However, in the Khetri mining region of Jhunjhunu district, extensive mining and smelting of copper and associated sulfide minerals have led to heavy metal contamination and a deterioration in groundwater quality. Therefore, this study evaluates the overall groundwater quality and the related human health risks in the region severely affected by copper mining and metallurgical activities. We have collected total 59 groundwater samples from both pre- and post-monsoon periods and were examined for physicochemical parameters, cations, anions, and heavy metals (Pb, Cd, Cr, Cu, Fe). Multivariate analysis, including PCA and correlation, revealed that geogenic processes, such as carbonate and silicate weathering, dominate natural groundwater chemistry. Whereas anthropogenic inputs from mining, ore processing, agriculture, and industrial waste significantly elevate toxic metal concentrations. The elevated level of Pb, Cd and Cr were detected across many locations, often exceeding permissible limits. Non-carcinogenic risks (HI) for Cr, Pb and Cd surpassed the safe thresholds in many locations, and carcinogenic risks (CR) for Cr, Cd, and Pb exceeds the permitted limit of 1 × 10⁻⁴ at multiple sites, indicating significant long-term health threats. The integrated EWQI–Monte Carlo framework thus combines the objectivity of entropy-based weighting with the statistical power of probabilistic simulation, enabling a more realistic and comprehensive evaluation of both groundwater quality and the related human health risks. In addition of this, the risk assessment for human health (HRA) revealed that children are at more danger than adults due to their greater exposure per body weight. These findings clearly indicate an urgent need for groundwater quality management through the adoption of remediation actions and the exploration of alternative sources to protect community health from contaminated groundwater.
How to cite: Kumar, M., Pathania, T., and Gaurav, K.: Integrated EWQI–Monte Carlo framework for assessing groundwater quality and health risk in the Khetri mining region of Jhunjhunu district, Rajasthan, India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1227, https://doi.org/10.5194/egusphere-egu26-1227, 2026.
