The Unsaturated Zone (UZ), the portion between the soil surface and the groundwater table, has a significant impact on subsurface water resources. This zone controls water movement from the soil surface to the aquifer and acts as a natural filter, purifying groundwater by removing or transforming solutes as water moves from the surface towards the water table. A thorough understanding of the processes occurring within the UZ is essential for sustainable land and water resource management, especially in the context of climate change and increasing agricultural demands. This study is conducted on a representative scale of the Beauce aquifer and is leverage extensive data from the Observatory of transfers in the Vadose Zone (O-ZNS) in Villamblain, France. The observatory’s unique setup, which includes a 20-meter deep well with a diameter of 4 meters, multiple boreholes, and innovative environmental sensors, provides high-resolution 3D measurements of fluid flow and heat/mass transfer processes.
The complex and coupled processes governing mass and heat transfer in the UZ determine the fate of pollutants and impact groundwater quality. In this study, a coupled model of water, heat, and nitrate transfer in the UZ of the Beauce aquifer is developed to assess the impact of climatic variations and agricultural practices on groundwater responses. Hydraulic properties, meteorological data, water table levels, and agricultural data—including crop types, fertilizer application rates, and pesticide usage reported by local farmers—are used as model inputs for the period from 2021 to 2025.
Numerical simulations are validated against volumetric water content measurements at the well level and against observed water content and temperature profiles in a 2-meterdeep soil pit. The model predictions showed in general good agreement with experimental observations, confirming its reliability. Various scenarios are explored by altering meteorological inputs and nitrogen fertilization rates to evaluate their impacts on groundwater responses. The results demonstrated diverse behaviors of the UZ, highlighting the sensitivity of groundwater quality to agricultural practices and climatic conditions.
The outcomes of this research provide valuable insights into the mechanisms governing the heat and mass transfer through the UZ of carbonate aquifers, contributing to more accurate predictions of groundwater responses to intensive agriculture, ecological and climatic changes.
How to cite: Boujoudar, M., Abbar, B., Azaroual, M., Fahs, M., and Abbani, G.: Modeling Water, Heat, and Nitrate Dynamics in the VadoseZone: A Case Study of the Beauce Aquifer (Orleans, France), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21922, https://doi.org/10.5194/egusphere-egu25-21922, 2025.
Redox (reduction-oxidation) reactions play a crucial role in determining groundwater quality, as they strongly influence the behavior of Contaminants of Emerging Concern (CECs). The extent of mixing between electron donors and acceptors largely governs the occurrence of these reactions. Additionally, increased spatial and temporal variability in redox potential (Eh) has been shown to enhance the likelihood of CEC removal. Numerical modeling studies suggest that injection and extraction engineering can improve mixing, leading to greater Eh variability and, in turn, a higher potential for CEC removal. However, these studies often neglect the critical role of biofilm, as most subsurface redox reactions occur primarily within the relatively immobile biofilm where microbial activity dominates.
In this study, we explored the effects of enhanced mixing in the subsurface, achieved through the use of extraction and injection dipoles in a pilot-scale Managed Aquifer Recharge system, on redox potential distribution and the behavior of CECs and ARGs. Redox potential was continuously monitored using a network of over 30 probes, while CECs and ARGs removal and their associated toxicity (evaluated with zebrafish embryos) were assessed before and after the implementation of EIE. The application of three dipoles in a system with stratified geochemistry caused significant alterations in Eh, initiating new geochemical processes such as iron precipitation. Surprisingly, concentrations of both CECs and ARGs, along with associated toxicity, increased following EIE. This rise was attributed to biofilm detachment, which likely released sorbed CECs and ARGs into the aqueous phase, thereby amplifying their ecotoxicological effects.
How to cite: Rodríguez-Escales, P., Jou-Claus, S., Martínez-Landa, L., Fernàndez-Garcia, D., Trabucchi, M., Quintana, G., Diaz-Cruz, M. S., Navarro-Martin, L., Sanz, C., Piña, B., and Carrera, J.: Does Enhanced Mixing Improve Groundwater Quality? Evaluating the Impact of Injection-Extraction Engineering on Redox Conditions, Contaminants of Emerging Concern, and Antibiotic Resistance Genes , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12273, https://doi.org/10.5194/egusphere-egu25-12273, 2025.
We investigate the impact of porous media heterogeneity on the dynamics of reactive convective density-driven dissolution. We study the convective dissolution of species A in a fluid containing a species B in presence of a binary reaction A + B → C. Fluid density is a function of the Rayleigh number of the species so that, depending on the nature of the species, convection can be enhanced or decreased (Loodts et al., 2014). It has been shown that in homogeneous systems chemical reaction can increase the dissolution fluxes. The impact of the porous media heterogeneity is, however, largely unknown.
To address the effect of heterogeneity on reactive convective dissolution we consider heterogeneous scenarios with horizontally stratified, vertically stratified, and log-normally distributed permeability fields. We analyze the resulting fingering pattern, mass of the reaction product, mixing length and reaction front topology. Results show that the reaction front progresses more rapidly in vertically stratified permeability fields than in horizontally stratified ones, where convective fingers spread laterally and struggle to move vertically. In horizontally stratified fields, the fingers appear thicker compared to those in vertically stratified fields. This observation is corroborated by the higher mixing lengths in the vertically stratified scenarios. The mass of the reaction product is also affected by the heterogeneity. Vertically stratified scenarios display the fastest growth of the reaction product while the horizontally stratified have the lowest reaction product. Homogeneous and log-normally distributed cases lay in between the two other scenarios. In log-normally distributed cases the reaction product, as well as the mixing length, are proportional to the anisotropy ratio between the correlation length in the vertical and horizontal directions.
References.
V. Loodts, C. Thomas, L. Rongy, and A. De Wit. Control of convective dissolution by chemical reactions: General classification and application to CO2 dissolution in reactive aqueous solutions. Physical Review Letters, 113:114501, 2014
How to cite: Hidalgo, J. J., Benhammadi, R., and De Wit, A.: Effect of heterogeneity on reactive convective dissolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11475, https://doi.org/10.5194/egusphere-egu25-11475, 2025.
Previous studies on contaminant transport models have primarily focused on boundary sources, limiting their applicability to scenarios with multiple internal pollution sources. This study develops a semi-analytical model for multispecies contaminant transport that incorporates advection, dispersion, rate-limited sorption, and first-order degradation, accommodating arbitrary time-dependent pollutant sources. By addressing rate-limited sorption, the model avoids underestimating degradable pollutant concentrations in non-equilibrium scenarios. The model is derived using the Laplace transform, finite cosine Fourier transform, generalized integral transform, and inverse transformations. Results highlight the sensitivity of contaminant and degradation product concentrations to time-dependent source variations. The model's key contribution lies in its ability to simulate dispersion from multiple internal sources under rate-limited sorption conditions, providing more accurate predictions of pollution plume dynamics and offering a robust alternative to boundary-source models for preliminary pollution management.
How to cite: Nguyen, T.-U. and Chen, J.-S.: Semi-Analytical Modeling of Contaminant Migration and Degradation from Multiple Pollution Sources under Rate-Limited Sorption, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5469, https://doi.org/10.5194/egusphere-egu25-5469, 2025.
Biofilms in porous media host microbial communities that play a central role in the degradation of nutrients and Contaminants of Emerging Concern, significantly enhancing water quality through contaminant removal. Current research focuses on strategies to prevent bio-clogging in natural and engineered systems while promoting controlled and widespread biofilm growth. This dual approach aims to maintain permeability while leveraging biofilm activity for bioremediation purposes. Biofilm growth dynamics and spatial distribution are shaped by factors such as the mixing of nutrients (electron donors and acceptors), flow and transport processes, and the inherent heterogeneity of the porous medium, although these processes are not yet fully understood. In this context, we seek to understand how mixing affects biofilm growth and vice versa, as well as whether it is possible to maximize the bio-reactive zone while minimizing clogging.
To achieve this, we conducted a flow-through experiment in a 60 cm homogeneous sand-packed column. By injecting multiple sequences of electron donor and electron acceptor solutions, we created periodic reactive mixing zones with complementary reactants to stimulate microbial activity. This setup mimics a fluctuating geochemical environment, resulting in multiple mixing areas that evolve in both space and time. The interplay between limited nutrient supply and biofilm development turned biofilm growth into a process driven by mixing and transport dynamics. The monitoring system enabled us to indirectly assess integrated microbial activity alongside overall flow and transport behavior. We recorded the temporal evolution of (i) downstream redox potential, (ii) differential pressure, and (iii) tracer breakthrough curves. Data suggest an early onset of microbial activity, inferred from a rapid decrease in redox potential, as well as a gradual decline in hydraulic conductivity and an increase in BTC tailing, indicating enhanced immobile porosity due to biofilm growth. Moreover, the spatial and temporal evolution of microbial activity inside the column—directly linked to the evolution of mixing dynamics—was characterized through semi-continuous measurements of pH and CO2 at ten non-invasive sensor spots. Results indicate an expansion of the bio-reactive zone (i.e., the mixing zone) over time, likely driven by increased dispersion, and a spatial shift of the area with the highest activity over time.
How to cite: Trabucchi, M., Rodriguez-Escales, P., Guardia, M., Dawi, M., Fernàndez Garcia, D., Carrera, J., and Sanchez Vila, X.: Exploring Positive Feedback Between Biofilm Growth and Mixing in porous media: Insights from Darcy-Scale Flow-Through Column Experiment , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18211, https://doi.org/10.5194/egusphere-egu25-18211, 2025.
Globally rising numbers of contaminated sites, in millions that are yet to undergo an initial assessment, highlight the limitations of currently available models, as well as signify the need for the development of more practical application models, such as Hybrid models. These hybrid models can be a combination of available models, e.g., combining solutions provided by currently available numerical and analytical models. Effectively this can use the complexity of numerical models and the simplicity of analytical models and yet efficiently provide the required practical solution. However, the hybrid combination may not be limited to available numerical and analytical models, but they could also include Machine Learning (ML)-based surrogate models or much simpler ones based on the Analytic Element Method, which can provide more flexibility with respect to, for example, source and domain complexities. The literature already provides several attempts showcasing the importance of combining different (numerical and analytical) modelling methods, but these efforts have been rather limited and not appropriately defined for example as Hybrid Models. This work attempts to more appropriately define hybrid models and the associated terminologies, and demonstrate with examples that such (hybrid) models can and should be developed.
How to cite: Yadav, P. K., Köhler, A., Tripathi, M., Grathwohl, P., Dietrich, P., and Liedl, R.: Should and can hybrid models for contaminant transport be developed?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12078, https://doi.org/10.5194/egusphere-egu25-12078, 2025.
Transport processes in porous media are ubiquitous, and their manifestation depends on the scale of observation. The effect of pore scale processes is typically upscaled by considering full mixing and assuming full mixing within pores and Fickian transport fully defined by a mean pore velocity and a constant Darcy’s scale dispersivity. Theoretical development, supported by experimental results, evidenced the emergence of incomplete mixing accompanied by non-Fickian transport, which impacts the reactions upon mixing. We performed laboratory scale experiments in a porous media created by hydrogel spheres with a refraction index matching that of the water. Rhodamine B was injected at the inlet of a 9 cm x 9 cm x 17 cm sample, and its spreading was monitored by using Planar Laser-Induced Fluorescence (PLIF), which provided the distribution of the concentration within a control plane normal to the mean flow direction at a high resolution. The images were obtained at constant time intervals of two seconds.
The PLIF images were processed by calibrating pixel intensity values against Rhodamine B concentrations using standard PLIF calibration procedure. This calibration enabled the determination of spatial concentration distributions within the imaging plane. Breakthrough curves (BTCs) were obtained from these image data, and variance was computed at each time step. The breakthrough curve (BTC) provides a macroscopic representation of solute transport, capturing the temporal evolution of solute concentrations at a downstream control plane. In a Lagrangian framework, the BTC is determined by displacement moments, which describe the key characteristics of the transport process.
Three models for displacement moments were analyzed. The classical Fickian model considers dispersivity values in the longitudinal and transverse directions. The stochastic macrodispersion model (Dagan, 1989) uses medium variance and its integral scale. The extended Saffman model incorporates sphere diameters and interstitial flow speed as its parameters.The Fickian model provided dispersivity values consistent with those reported by Eames and Bush (1999) for a medium composed of impermeable spheres. However, it struggled to capture the early and late parts of the BTC, indicating that incomplete mixing and pre-Fickian transport behavior can occur even at the laboratory scale.In contrast, the stochastic macrodispersion model and the extended Saffman model yielded more accurate results. Both models successfully reproduced BTCs across the entire observation period, including early arrivals and tails. Additionally, the Saffman model effectively represented physical properties of the medium, such as interstitial velocity and pore size, which aligned with the measured values.
References
1. G. Dagan. Flow and transport in porous formations. Springer-Verlag, New York, 1989
2. Eames, I. and Bush, J.W.M., 1999. Longitudinal dispersion by bodies fixed in a potential flow. Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences, 455(1990), pp.3665-3686.
3. P. G. Saffman. A theory of dispersion in a porous medium. Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, 251(1264):313–328, 1959.
How to cite: Ekanayake, P., Di Dato, M., Tonina, D., and Bellin, A.: Mathematical Modeling of Laboratory-Scale Solute Transport in Porous Media, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19427, https://doi.org/10.5194/egusphere-egu25-19427, 2025.
In the central Venetian plain (Northeastern Italy), drinking water demand is mainly met by groundwater abstraction from the complex underlying aquifer system. From the foothills of the Prealps towards the coast, this system consists of a thick unconfined aquifer made up of coarse sediments – mainly of fluvial or fluvioglacial origin – transitioning into a multi-layered aquifer system with progressively thicker clay layers. The deep confined aquifers in the latter region are heavily exploited, as they represent a valuable source of high-quality drinking water. In this context, proper delineation of well capture zones and wellhead protection areas (WHPAs) is critical to ensure drinking water quality. However, for wells exploiting the deep confined aquifers, especially in such a complex geological context, relying on the simple geometric or analytical criteria seems inadequate. Moreover, due to the high level of uncertainty involved, a deterministic definition of the spatial continuity, extent, and connectivity of structures with different permeabilities could lead to misleading results. In this work, we adopted a stochastic approach that allows for geological realism and for uncertainty quantification. Using an extensive dataset of borehole stratigraphic information, we set up a geostatistical model for the hierarchical simulation of lithofacies and validated it by means of K-fold cross-validation. Through subsequent groundwater flow modeling of multiple equiprobable realizations, we assessed the impact of structural uncertainty on the groundwater dynamics. Then, through the application of backward particle tracking techniques we analyzed the uncertainty in the preliminary delineation of WHPAs for deep wells. Furthermore, this study presents one of the first real-world applications of particle tracking that integrates the displacement of particles along surface watercourses. This latter method allows us to account for the high dependence of the groundwater system under investigation on the dynamics of the Piave River, and sheds light on the relevance of surface water–groundwater interactions in the problem of capture zones identification.
How to cite: Furlanetto, D., Pérez-Illanes, R., Fernàndez-Garcia, D., and Camporese, M.: Structural uncertainty and surface water–groundwater interactions in the probabilistic delineation of well capture zones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5826, https://doi.org/10.5194/egusphere-egu25-5826, 2025.
This study examined the ability of subsurface dams to protect freshwater abstraction against seawater intrusion in both homogeneous and layered heterogeneous aquifers. Laboratory experiments were conducted in a synthetic aquifer where a subsurface dam was simulated in a homogeneous scenario (case H), and in another scenario where a top low permeability layer was placed in the upper part of the aquifer (case LH). We then conducted numerical simulations using the SEAWAT model to validate the experimental results and examine other numerical cases where a low K layer existed at the middle (case HLH) and the bottom of the aquifer (case HL). Case LH needed 52% more pumping than case H for the wedge to spill over the dam into the landside. The existence of a low permeability layer has generally delayed the upconing, and it took longer for the SWI to contaminate the abstraction well. The clean-up time varied substantially from one case to another, with the case HL taking longer than the other cases for SWI removal. The cleanup time was reduced by 23% in the presence of a top low-K layer compared to the homogeneous aquifer. The study demonstrates that the presence of the low-K layer on the top of the aquifer contributed positively to improving the ability of the subsurface dams to obstruct SWI, limit saltwater upconing and, therefore, allow more optimal freshwater abstraction. A feature of this study was it examined the ability of dams to prevent seawater intrusion in the existence of freshwater pumping, which has not been discussed in previous studies, at least in laboratory experiments.
How to cite: Abdoulhalik, A., Ahmed, A., and Abd-Elaty, I.: The Impact of Layered Heterogeneity on the Ability of Subsurface Dams to Protect Groundwater Pumping in Coastal Aquifers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9593, https://doi.org/10.5194/egusphere-egu25-9593, 2025.
Submarine groundwater discharge (SGD) is a key pathway for transporting terrestrially derived nutrients, including elevated nitrate levels, from coastal groundwater to coastal waters, thereby impacting coastal water quality and ecosystem health. Tidally driven saltwater-freshwater mixing zones in coastal aquifers can promote denitrification, which attenuates terrestrially derived nitrate in groundwater before its discharge into coastal waters. However, the effect of rainfall recharge, which can significantly alter flow and mixing regimes in intertidal zones, on this mixing-dependent denitrification remains poorly understood. In this study, we employ a numerical variable-density groundwater flow and reactive transport model to evaluate how rainfall recharge interacts with spring-neap tides to shape denitrification spatially and temporally. We conduct a sensitivity analysis across various rainfall recharge patterns (uniform, random, extreme, and seasonal), recharge intensities, dissolved organic carbon (DOC) reactivity, and recharge-derived solutes. Our results show that rainfall recharge and spring-neap tides jointly regulate denitrification patterns. However, as DOC reactivity increases, the dominant driver shifts from rainfall recharge to tidal forcing. While different rainfall recharge patterns result in similar annual nitrate removal, they lead to substantial variability in daily removal rates. Increasing recharge intensity generally reduces overall nitrate removal unless additional nitrate is introduced via recharge. Additionally, in all scenarios, the percentage of nitrate removed relative to terrestrial inputs declines with increasing recharge intensity. These results underscore the interconnected hydrological and biogeochemical controls on denitrification in intertidal zones, offering important implications for estimating coastal nutrient fluxes and managing coastal water quality.
How to cite: Wu, H., Yan, M., Lu, C., and Prommer, H.: Spatiotemporal Variability of Denitrification in Intertidal Mixing Zones: The Roles of Rainfall Recharge and Spring-Neap Tides, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4947, https://doi.org/10.5194/egusphere-egu25-4947, 2025.
Posters on site: Wed, 30 Apr, 08:30–10:15 | Hall A
The remediation of groundwater contaminants, such as chlorinated aliphatic hydrocarbons (CAHs) and nitrate, often requires the injection of electron donors. Vegetable oil, commonly used as a cost-effective electron donor, is typically emulsified with surfactants before injection. However, some surfactants pose ecological risks to aquatic ecosystems during prolonged exposure. To overcome this challenge, a humic acid-based emulsified oil was developed, leveraging humic acid's non-toxic, naturally occurring, and affordable properties. This study investigates the fermentation process of the emulsified oil by analyzing degradation byproducts and its long-term electron supply potential. It also evaluates its performance in degrading organic and inorganic contaminants through laboratory- and pilot-scale experiments.
Batch reactors were used to conduct lab-scale fermentation test (LFT) and lab-scale degradation test (LDT) for assessing fermentation and contaminant degradation characteristics. The emulsified oil was added to reactors filled with groundwater at concentrations between 0.1% and 1.0% (v/v) during the LFT, and the reactors were monitored for 200 days. Target contaminants—trichloroethylene (TCE) and nitrate—were tested in the LDT using 0.1% and 0.5% (v/v) emulsified oil concentrations, and results were compared with control reactors. In a pilot-scale degradation test (PDT) conducted in an aquifer contaminated with TCE and PCE in Iksan, South Korea, the effectiveness of emulsified oil was further assessed using push-pull and drift tests.
The LFT revealed sustained lipase activity and byproducts, including fatty acids (e.g., stearic acid), organic acids (e.g., propionic acid), carbon dioxide, and methane, indicating that a 0.1% (v/v) oil concentration supported optimal fermentation. For nitrate in the LDT, degradation rates of approximately –30 mg N/L/d were observed across both tested concentrations, whereas TCE exhibited higher degradation rates under 0.1% (v/v) conditions (–0.51 mg/L/d), about twice as effective as 0.5% (v/v). The PDT demonstrated significant CAH degradation, with TCE's first-order degradation rate constant increasing 17-fold and enhanced production of dechlorination byproducts, such as vinyl chloride (VC) and ethene (ETH). These findings highlight the humic acid-based emulsified oil as an effective electron donor for promoting the biological degradation of both organic and inorganic contaminants, offering a promising solution for groundwater remediation.
How to cite: Yeum, Y., Kim, Y., Kwon, S., and Han, K.: Fermentation and Degradation Characteristics of Humic Acid-Based Emulsified Oil for Organic and Inorganic Contaminants in Groundwater, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2875, https://doi.org/10.5194/egusphere-egu25-2875, 2025.
Due to the steep terrain and seasonal precipitation, retaining water on the surface in Taiwan is challenging. As a result, groundwater resources play a significant role in most types of water usage. However, historical data suggest that groundwater in the shallow layers near the coastal region of the South Jhuoshuei River Alluvial Fan has become widely salinized. This study collected multiple batches of water samples to analyze their characteristics and seasonal variations. The results indicate that the degree of salinization in the shallow layer is higher than in the deep layer. However, the data from the water samples only suggest that salinity is contributed to by saline water, without clarifying whether the source is lateral intrusion or surface contamination. To better understand salinity in this region, this study used Chelex-100 chromatography to reduce salinity and concentrate trace metals in the samples. The concentration of trace elements differs significantly between seawater, which has low levels, and fish farms, which exhibit higher levels. This distinction helps identify the source of the saline water. Initial tests showed that wells near Taixi had higher concentrations of trace elements, particularly Pb. In contrast, wells near Yiwu and Qiongpu displayed lower concentrations of trace elements. These findings suggest that salinization in the Taixi region is likely caused by anthropogenic sources, while salinization near Yiwu and Qiongpu results from lateral intrusion.
How to cite: Kuo, C.-C., Liou, S. Y. H., Tai, T.-L., and Yang, W.-T.: Applying the Chelex-100 to Measure Trace Metals in High Salinity Samples in Southern Jhuoshuei River Alluvial Fan in Central Taiwan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2968, https://doi.org/10.5194/egusphere-egu25-2968, 2025.
In this study, groundwater contamination in the Plana Sur Aquifer of Valencia was analyzed using the PRZM (Pesticide Root Zone Model). The analysis included modeling the concentrations of two pesticides, terbuthylazine and desethyl-terbuthylazine, based on observed concentrations in six monitoring wells belonging to the groundwater quality control network of the Júcar River Basin. These wells were specifically chosen as they contain data on the pesticides in question.
The modeling was based on data recorded from the quality network wells of the Júcar River Basin Authority. In the Plana Sur of Valencia, six wells were analyzed, with five of them showing desethyl-terbuthylazine concentrations exceeding permissible limits (with a maximum value of 0.3 µg/L recorded on April 14, 2015). In contrast, the detected concentrations of terbuthylazine were consistently below the legal threshold. For the region's piezometry, results from a previously developed flow model using MODFLOW were utilized. Climatic variables such as precipitation and evapotranspiration were derived from databases associated with the closest climatological monitoring stations to each well.
Crop typologies were determined based on land-use information from the SIOSE database. Application doses were inferred from interviews with farmers, supplemented by data from the Ministry of Agriculture’s "Annual Statistics on Pesticide Use" and "Five-Year Statistics on Pesticide Use in Agriculture." However, the information provided in these documents was insufficient to precisely determine the applied doses. Therefore, calibration was performed using proposed scenarios, with terbuthylazine application rates set at 0.5, 0.6, and 0.8 kg/ha.
A sensitivity analysis of parameters allowed for the formulation of 54 simulation scenarios for each of the six analyzed wells, varying the year pesticide application ceased, the applied dose, and the characteristics of the soil column. Results indicate that desethyl-terbuthylazine concentrations are typically higher than those of terbuthylazine, as it is a metabolite of the latter. In some simulated wells and specific scenarios, these concentrations exceeded the reference value of 0.1 µg/L established by current legislation.
This study underscores the need for detailed scenario-based analysis and calibration to accurately assess the contamination risks and inform effective water quality management.
How to cite: Rodrigo-Ilarri, J., Rodrigo-Clavero, M. E., and Cassiraga, E.: Analysis of Groundwater Contamination by Terbuthylazine and Desethyl-terbuthylazine in the Plana Sur Aquifer of Valencia (Spain), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4202, https://doi.org/10.5194/egusphere-egu25-4202, 2025.
Chlorinated solvents are common groundwater contaminants, their behavior as Dense Non-Aqueous Phase Liquids (DNAPLs) complicates remediation efforts, and their carcinogenic properties pose significant risks to human health. These highlight the urgent need for advanced tools to support site management and health risk assessment. This study enhances existing software MUSt by integrating advanced functionalities for managing and geographically visualizing the site-specific data, including the range of the contaminated site, geological and hydrological conditions, and contaminant distribution. Additionally, the human health risk assessment module has been expanded to consider multiple exposure pathways, further strengthening the software's ability to provide a comprehensive framework for site evaluation and decision-making. These advancements improve the efficiency of site management while enhancing risk communication, enabling more informed decisions and fostering better stakeholder engagement.
How to cite: Liao, H.-Y., Chen, J.-S., and Liang, C.-P.: A software integrating sophisticated transport analytical model, GIS, and human health risk assessment for comprehensive site evaluation of groundwater contaminated with chlorinated solvents, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5589, https://doi.org/10.5194/egusphere-egu25-5589, 2025.
Pharmaceuticals and anthropogenic organic compounds are crucial to healthcare and agriculture but are also increasingly recognized as environmental contaminants with significant environmental and public health impacts. These substances enter groundwater through different pathways such as wastewater discharge, agricultural runoff and landfill leachate, posing challenges for groundwater quality and ecosystem integrity. This study investigates the presence, distribution and temporal trends of pharmaceutical contaminants in groundwater resources, using Slovenia as an example?. Between 2014 and 2024, groundwater samples were collected at over 100 sites across urban, industrial and agricultural regions, in karst and intergranular aquifers in the scope of state monitoring programs, following strict protocols to ensure reliability. Compounds such as caffeine, carbamazepine and sulfamethoxazole exhibited consistently high detection frequencies, highlighting their persistence and environmental significance. Conversely, other compounds were often present at concentrations below the limit of detection (LOD). The findings underscore the influence of aquifer type and land use on contamination pathways and emphasize the need for comprehensive monitoring frameworks and targeted mitigation strategies to safeguard groundwater resources and public health.
How to cite: Perović, I. and Koroša, A.: A national-scale assessment of pharmaceutical and other organic compounds (CECs) in groundwater (Slovenia), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6119, https://doi.org/10.5194/egusphere-egu25-6119, 2025.
Mountain systems are an important source of high-quality freshwater. Mountain aquifers, found at higher altitudes, are typically composed of fractured rocks and karst systems, while alluvial aquifers, located in valleys, are more permeable and often connected to mountain aquifers. This connection transfers large water volumes downstream, supporting urban water needs. Additionally, groundwater serves as a natural water storage, sustaining river flows during dry periods and helping mitigate extreme droughts.
Despite the pivotal importance of groundwater in mountain systems, monitoring efforts in such environments remain limited, which hinders the efficiency of groundwater models. Data on hydraulic properties and piezometric heads are typically scarce. As a consequence, groundwater modeling suffers intrinsically from equifinality and high parameter uncertainty.
We analyzed the uncertainty associated with the flow and transport model of the lower Chiese valley in the Italian Alps. The valley hosts an aquifer exploited to provide the water needed for the local fishery industry. The fisheries are exposed to the risk of contamination from the upstream industrial activities. We developed the flow and transport model of the aquifer, depending on the following parameters: the homogeneous hydraulic conductivity of the aquifer, the Chiese riverbed conductivity, and the mountain block recharge from the east and the west hillslopes. Datasets available include groundwater level measurements in 41 wells and piezometers, the chemical signature in 3 piezometers, and PFOS concentration in 7 wells, representing sensitive points. We computed the posterior parameters pdfs by means of Markov Chain Monte Carlo with three levels of information. At the first level, we used only piezometric data, then at the second level, we added chemical signatures at the observation wells and springs, and finally, at the third level, we added PFOS concentrations at 7 observation wells.
Simulations showed that groundwater levels alone allow a small reduction of uncertainty, i.e., the posterior pdfs of the parameters differ slightly from the prior ones. By incorporating chemical and contaminant concentrations into the model calibration, we observe a considerable reduction of model uncertainty, with posterior pdfs significantly different from the prior ones. In particular, the posterior pdf of the hydraulic conductivity is very narrow, with the most probable value of 10-1 m/s, which is compatible with the prevalence of sandy/gravel material through the entire formation, as shown by the available well logs. On the other hand, the posterior pdfs of the mountain block recharge and riverbed conductivity are narrower than the a priori ones, but the reduction in the amplitude is smaller for that of the hydraulic conductivity. This indicates that the primary source of model uncertainty lies in the exchange fluxes among the aquifer, the mountain block, and the river, with the chemical composition of the water and pollutant concentrations being the most effective data for reducing this uncertainty. Piezometric heads alone introduce little constraints to these fluxes. The proposed procedure can be applied to other Alpine valleys of mountain regions, where important water resources are threatened by overexploitation and contamination due to anthropic activities.
How to cite: Di Dato, M., Betterle, A., and Bellin, A.: Integrating hydrological data and hydrochemical data to reduce uncertainty in mountain aquifer modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8088, https://doi.org/10.5194/egusphere-egu25-8088, 2025.
As surface waters become more polluted, many communities around the world need to turn to groundwater resources for their drinking water needs. Groundwaters on the other hand, carry the risk of having geogenic arsenic (As) that is at hazardous levels for human health. As is legislated by many governments in more recent years to a maximum concentration of 10 ppb in drinking waters as recommended by the World Health Organization since 1991. This has caused a surge in research related to removal of arsenic from drinking waters.
Using adsorptive materials, among other alternatives stand out, for adsorption itself being the major mechanism that determines the fate of dissolved arsenic; and relevant methods being generally easy to operate, cost effective, and having the potential of regeneration. Interest has grown in the 2010’s for graphene-based nanocomposites due to their 2-D single layer structure, large surface area and pore volumes, high mechanical stability, flexibility of surface chemistry and abundant production from natural sources. Magnetite reduced graphene oxide (MRGO) among others have an additional benefit of implementing the adsorptive capacities of iron oxides towards arsenic, and is also studied in batch for its adsorption capacity, kinetic and isotherm models under extremely high initial arsenic concentrations to demonstrate its capabilities at laboratory scale.
This study aims to build on the available literature and contribute further by assessing optimal reactor design and operational conditions for arsenic removal from water by column experiments. A custom-designed adsorption column with three sampling ports is implemented to collect data including pH, dissolved oxygen, iron concentration, and As+3 and As+5 concentrations with time, to evaluate the impact of different conditions such as initial arsenic species (As+3 or As+5), flowrate, and ionic composition on arsenic removal efficiency. Speciation analysis data is expected to yield novel insights about adsorption mechanisms as well. The collected data will be later used to model the column with hydrogeochemical and reactive transport models to make assessments about larger-scaled systems.
Acknowledgement: This study is supported by TUBITAK (The Scientific and Technological Research Council of Turkey) 1001 Project with Grant Number 123Y025 and Research Fund of the Middle East Technical University, Research Universities Support Program (ADEP) with Grant Number ADEP-311-2022-11172
How to cite: Çelebi, S., Elkawefi, O. A. I. M., Şenol, A., Şengör, S. S., Ertaş, G., and Ünlü, K.: Arsenic removal from drinking water with magnetite (Fe3O4) reduced graphene oxide (MRGO) nanocomposite material: Evaluations on process chemistry, system design and engineering applications , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9942, https://doi.org/10.5194/egusphere-egu25-9942, 2025.
A new analytic element approach is presented for steady-state reactive contaminant transport modelling with circular boundaries. Two solute compounds (electron donor and electron acceptor) are assumed to undergo an instantaneous and binary reaction [1] in a uniform flow field, forming a steady plume [2]. Transformations of the advection-dispersion-reaction equation are applied resulting in a reactive contaminant transport system governed by the modified Helmholtz equation. Comprehensive solutions to a single as well as multiple superimposed, interacting circular contaminant (electron donor) source elements are expressed by infinite series expansions of Mathieu functions [3]. The concentration of the electron donor and electron acceptor can be calculated at any point in the domain, while boundary conditions are met approximately, by adjusting the unknown coefficients of the truncated series of Mathieu functions. Accuracy at the boundary interfaces is increased with an increase of number of terms used in the Mathieu functions series expansion. The potential of this novel approach lies in the flexibility of boundary conditions, while maintaining computational efficiency.
The model is implemented using the Python programming language. Model verification was achieved by evaluating the residual of a central difference scheme, evaluation of the error along the boundary interfaces and a comparison with a simple MODFLOW / MT3DMS model setup. Current development includes expansion of the model to line source elements and discontinuous contaminant sources. Further advancements may be achieved by increasing source shape complexity of contaminant sources by superimposing a large number of elements and introducing remediation actions in the form of interacting electron acceptor elements.
[1] O. A. Cirpka, Å. Olsson, Q. Ju, Md. A. Rahman, and P. Grathwohl, ‘Determination of Transverse Dispersion Coefficients from Reactive Plume Lengths’, Groundwater, vol. 44, no. 2, pp. 212–221, 2006, doi: 10.1111/j.1745-6584.2005.00124.x.
[2] R. Liedl, A. J. Valocchi, P. Dietrich, and P. Grathwohl, ‘Finiteness of steady state plumes’, Water Resources Research, vol. 41, Dec. 2005, doi: 10.1029/2005WR004000.
[3] M. Bakker, ‘Modeling groundwater flow to elliptical lakes and through multi-aquifer elliptical inhomogeneities’, Advances in Water Resources, vol. 27, no. 5, pp. 497–506, May 2004, doi: 10.1016/j.advwatres.2004.02.015.
How to cite: Köhler, A., Craig, J., Yadav, P. K., and Liedl, R.: An Analytic Element Method solution for multispecies reactive contaminant transport, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10360, https://doi.org/10.5194/egusphere-egu25-10360, 2025.
Mixing in porous media is the process from which the homogenization of an initially segregated system is done. It is a key process for a vast type of applications, from ground remediation methods to numerous engineering applications where the facilitation of chemical reactions is needed. This process is the result of the interaction of spatial velocity fluctuations and diffusion or local-scale dispersion. The velocity fluctuations are induced by spatial medium heterogeneities at the pore, Darcy or regional scales which will enhance mixing by stretching the fluid elements of the groundwater. Stretching of fluid elements augments the ratio of surface to volume of the solute, making thus place for diffusion to destroy the concentration gradients on pore-scale. The main objective of this work is to unravel and quantify the mechanisms and laws that explain the impact of structure on stretching and dispersion dynamics in heterogeneous porous media, constituting two fundamental mechanisms for the understanding of mixing. The objectives are thus to quantify and understand the impact structure and media on stretching and dispersion on 2D Darcy scale heterogeneous porous media. Upscaling models for the previous mechanisms are also derived to predict large scale transport behaviors and understand the key parameters governing these mechanisms.
The methodology consists of numerical and theoretical derivations. The heterogeneity of the media is modeled by a stochastic model to systematically study the impact of spatial variability. Transport is analyzed through a Lagrangian framework by particle tracking. Deterministic and stochastic models for breakthrough curves, dispersion coefficients and stretching rates are proposed, demonstrating strong agreement.
How to cite: Feroukas, K., J. Hidalgo, J., Lester, D., and Dentz, M.: Stretching, Dispersion and Mixing in 2D Darcy scale heterogeneous porous media, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15671, https://doi.org/10.5194/egusphere-egu25-15671, 2025.
This study delves into resolving the knowledge gaps concerning the dynamic correlation between the bulk partition of nonionic surfactants and the solubilization of residual non-aqueous phase liquids (NAPLs) for the technology of surfactant-enhanced aquifer remediation (SEAR) through a delicate investigation on the elution of dodecane by low-concentration Triton X-100 (TX-100) in saturated porous media. First an interesting phenomenon, the presence of local concentration of TX-100 higher than injected (i.e., C/C0>1), was observed and then the mechanism was disclosed through a series of demonstration experiments to be the interplay between the kinetics of bulk partition of the surfactant and solubilization of residual dodecane. The rate-limited micelle-based solubilization of residual dodecane by TX-100, which induced the release of TX-100 from the residual dodecane phase as the source established by quick bulk partition of TX-100, resulted in the emergence of C/C0>1 under flow-interruption condition. Interface partition of the ionic surfactant of SDBS and bulk partition of the miscible solvent of n-propanol could not cause such a phenomenon, demonstrating the importance of the occurrence of both bulk partition and micelle-based solubilization processes. The knowledge obtained in this study supplement to the current cognition of the dynamics of surfactant partition and NAPL solubilization, which can be helpful to optimize the application of surfactants in in-situ groundwater remediation techniques.
How to cite: Huo, L., Liu, G., and Zhong, H.: Presence of local concentration higher than injected for non-ionic surfactant to solubilize NAPL in porous media: a result of interplay between partition and solubilization kinetics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10117, https://doi.org/10.5194/egusphere-egu25-10117, 2025.
Posters virtual: Mon, 28 Apr, 14:00–15:45 | vPoster spot A
EGU25-20494 | ECS | Posters virtual | VPS8
Spatiotemporal Assessment of Arsenic, Fluoride, and PFOS Co-Contamination in Yorkshire's Water ResourcesMon, 28 Apr, 14:00–15:45 (CEST) | vPA.8
Contaminant co-occurrence in water resources poses significant threats to public health and ecosystem stability, necessitating comprehensive monitoring and analysis. This study investigates the spatiotemporal distribution of arsenic, fluoride, and perfluorooctane sulfonate (PFOS) contamination in groundwater and surface water across Yorkshire from 2000 to 2023. Data for this assessment were obtained from the Environment Agency, ensuring reliable and standardised measurements across the study period. The results reveal a concerning trend of increasing arsenic and fluoride concentrations, particularly in the eastern and southern regions, with arsenic levels exceeding 10 µg/L and fluoride concentrations surpassing 1.5 mg/L in several areas by 2023. The PFOS contamination, assessed in both groundwater and surface water for 2023, highlights significant contamination in the southern regions, with concentrations exceeding 0.001 µg/L in some hotspots. The co-contamination maps indicate overlapping regions of high contaminant concentrations, suggesting potential sources of industrial pollution and agricultural runoff. This study emphasises the need for targeted mitigation strategies and continuous monitoring to protect public health and ensure water quality standards across the region.
How to cite: Agarwal, V., Kumar, M., and Saxena, A.: Spatiotemporal Assessment of Arsenic, Fluoride, and PFOS Co-Contamination in Yorkshire's Water Resources, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20494, https://doi.org/10.5194/egusphere-egu25-20494, 2025.
