Session HS8.1.5

[Programme]

HS8.1.5 | Contaminant transport in groundwater and remediation: concepts, modelling, observations and challenges in application

Contaminant transport in groundwater and remediation: concepts, modelling, observations and challenges in application

Convener: Antonio Zarlenga | Co-conveners: Alraune Zech, Aldo Fiori, Marco Dentz, Felipe de Barros

Orals

| Mon, 15 Apr, 14:00–15:40 (CEST)

Room 2.15

Posters on site

| Attendance Tue, 16 Apr, 10:45–12:30 (CEST) | Display Tue, 16 Apr, 08:30–12:30

Hall A

This session combines contribution on recent developments in subsurface hydrology; theoretical approaches and experimental works will be discussed to gain reliable insight for groundwater protection and site remediation techniques.

Much effort has been placed in the last years in the understanding of transport processes since they are of practical relevance to identify the fate of contaminants in surface and subsurface water that can affect human health and the environment. The correct quantification of transport processes is challenging and reflect the complexity of flow path in the aquifers. It strongly influences predicted contaminant spreading and plume properties and it is fundamental in the assessment of the efficiency of remediation strategies. An additional effort is now required in the application of these new concepts in practical studies for contamination prevention and vulnerability and risk assessment. The aim of this session is to discuss how the uncertainty related to the groundwater transport can be adopted in practical tools commonly used in groundwater studies and government policies.

Our contributions deal with the questions:

What are the recent improvements appropriate methods to characterize the relevant aquifer properties for a comprehensive modelling of the contamination?

What are the recent improvements in transport measurement technologies?

Which are the more suitable approaches for the application of the theoretical advancements in groundwater transport modelling in practical applications?

Large scale models can be adopted for the Simple models for government agencies?

What is the best way to physically and chemically characterize sites contaminated by anthropogenic chemicals?

How can we assess the most suitable remediation strategy and predict its efficiency?

Studies concerning specific cases and multidisciplinary approaches will be appreciated.

The session is co-sponsored by the Groundwater Commission of IAHS.

Orals: Mon, 15 Apr | Room 2.15

Chairpersons: Antonio Zarlenga, Marco Dentz, Felipe de Barros

14:00–14:10

EGU24-15451

ECS

On-site presentation

Ten years of ground and surface water monitoring in the abandoned Hg-mine of Abbadia San Salvatore (central Italy): geochemical investigations before reclamation

Federica Meloni, Barbara Nisi, Jacopo Cabasso, Giordano Montegrossi, Francesco Bianchi, Daniele Rappuoli, and Orlando Vaselli

Since February 2013, 21 periodical samples (mostly carried out seasonally) of ground and surface waters within and outside the former Hg-mine of Abbadia San Salvatore (Tuscany, central Italy) have been analyzed for the main composition, Hg, As, Sb, and, in most cases, selected trace elements. The groundwater samples refer to a phreatic aquifer at depths between 5 and 10 m, characterized by low transmissivity and whose waters are interacting with terrains containing tailings derived from the production of liquid mercury by roasting cinnabar. The temperatures are thus strongly affected by seasonal variation, while the pH values are mostly circumneutral. The results evidenced the presence of relatively high concentrations of Hg and, to a minor extent, As and Sb, forcing the local authorities to intervene to test specific strategies to remove mercury. Strikingly high seasonal variations of the geochemical facies were observed and were apparently not related to meteoric precipitations. The variability of the main composition, i.e. Ca(Mg)-SO₄, Ca(Mg)-HCO₃and, subordinately, Na-HCO₃, is intimately associated with the large differences recorded in terms of Hg, and, to a lesser extent, As and Sb. This is likely related to the water-rock interaction processes governed by the dissolution of carbonates and gypsum/anhydride (typical minerals recognized in the waste materials used to fill a paleo-valley in the SW margin of the mining area). The highest recorded Hg concentration was 407 µg/L during the wet period, decreasing down to 81.4 µg/L in the dry period, when the groundwater level decreases in most boreholes by up to 2 m. This also results in an increasing electrical conductivity. The low transmissibility of this shallow aquifer is clearly evidenced when the piezometers are purged before sampling, as they tend to be rapidly emptied. The groundwaters upstream and downstream of the mine are found to have a concentration of Hg < 1 ppb. This suggests that there is no interference between the mining area aquifer and the volcanic one. Apparently, no significant correlations were found between Hg and other metals, probably suggesting that the presence of liquid Hg often recovered in the piezometer cores is perhaps the main source of mercury. The speciation of Hg, As, and Sb of selected ground and superficial waters was computed by PHREEQC modelling. In addition, to simulate how Hg is vehiculated through the aquifer, a chemical transport model was developed. Presently, the installation of a hydraulic barrier is the most suitable solution to minimize the water-rock interaction processes, responsible for the recorded Hg variability, possibly coupled with additional operations, e.g. extractant agents or filters, to remove mercury before discharging the pumped waters into a surface stream.

How to cite: Meloni, F., Nisi, B., Cabasso, J., Montegrossi, G., Bianchi, F., Rappuoli, D., and Vaselli, O.: Ten years of ground and surface water monitoring in the abandoned Hg-mine of Abbadia San Salvatore (central Italy): geochemical investigations before reclamation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15451, https://doi.org/10.5194/egusphere-egu24-15451, 2024.

14:10–14:20

EGU24-20058

ECS

On-site presentation

Combining Markov-Chain Monte Carlo Sampling and Geostatistics to Quantify Contaminant Mass Discharge and Uncertainty

Anton Bøllingtoft, Mads Troldborg, Poul L. Bjerg, and Nina Tuxen

Contaminated legacy sites pose a risk to the environment and human health worldwide. The accurate characterization and monitoring of subsurface contamination is crucial for effective risk assessment, management and prioritization of contaminated sites and ultimately ensures a more efficient and sustainable use of the allocated resources.

Contaminant mass discharge (CMD) integrates two important features of contaminant risk: concentration and mobility. CMD is increasingly being incorporated into risk assessments of contaminated sites as an alternative to point-value concentration-based risk assessment. The CMD is estimated by interpolating and integrating multilevel point measurements of concentration and flow across a control plane of interest. However, the geological settings at contaminated sites are typically subject to large heterogeneities resulting in complex hydrogeological conditions and significant spatial variability in the CMD, which combined with limited data availability renders it impossible to determine exact or error-free estimates.

We present a geostatistical method for quantification of CMD uncertainties in a multilevel control plane downstream a contaminated site aimed at practical implementation, with focus on the interpolation and associated uncertainty related to the concentration measurements.

The method uses geostatistical conditional simulation and applies an analytical solution of a macro-dispersive transport equation to simulate the spatially varying global mean. A Box-cox transformation is employed to ensure non-negative concentration values and account for skewness. The method is a development of that presented by Troldborg et al. (2012). We have refined the parameter identification by applying a Markov-Chain Monte Carlo (MCMC) algorithm for parameter sampling and furthermore constrained the prior sampling distributions to ensure the posterior is linked to conceptual site-specific knowledge. This links the CMD estimation to the conceptual site model and allows for source-zone data and geologic knowledge to be incorporated into the CMD estimate, which increases credibility, especially for low sampling density transects. The MCMC algorithm efficiently explores the high-dimensional parameter space, generating a statistically representative sample of geostatistical, transformation and transport-model parameters, thereby characterizing the uncertainty associated with model parameter identification in heterogeneous geologic settings. The result of the conditional simulations is an ensemble of concentration realizations that all honor the measured concentration data and capture the spatial variability of the contaminant plume.

The method has successfully been applied to determine the CMD uncertainty at multiple contaminated sites. It is firstly demonstrated at a site with substantial data and prior knowledge, and secondly at two sites to assess the challenges related to prior knowledge, sampling density and different hydrogeological conditions.

The proposed method represents a practical solution for quantifying CMD uncertainty at contaminated sites. By combining MCMC sampling and geostatistics, it overcomes the limitations of traditional deterministic methods and provides involved stakeholders with probabilistic estimates for better informed remediation and risk assessment practice when managing contaminated soil- and groundwater.

References
Troldborg, M., Nowak, W., Lange, I. V., Pompeia Ramos dos Santos, M. C., Binning, P. J., and Bjerg, P.L. (2012). Application of bayesian geostatistics for evaluation of mass discharge uncertainty at contaminated sites. Water Resources Research, 48(9):W09535. DOI: 10.1029/2011WR011785

How to cite: Bøllingtoft, A., Troldborg, M., L. Bjerg, P., and Tuxen, N.: Combining Markov-Chain Monte Carlo Sampling and Geostatistics to Quantify Contaminant Mass Discharge and Uncertainty, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20058, https://doi.org/10.5194/egusphere-egu24-20058, 2024.

14:20–14:30

EGU24-10433

ECS

On-site presentation

Applying multivariate statistics to analyse data variability in groundwater quality monitoring of contaminated sites

Davide Sartirana, Alice Palazzi, Chiara Zanotti, Letizia Fumagalli, Andrea Franzetti, Ilaria Pietrini, Tullia Bonomi, and Marco Rotiroti

Groundwater quality monitoring of contaminated sites represents a fundamental step for implementing effective remediation strategies. Groundwater in hydrocarbon contaminated sites is often monitored using fully screened piezometers, obtaining concentration time-series that can be affected by a strong variability. This variability can complicate data interpretation and lead to prolonged site closures. One possible solution to compensate for this data variability is to increase the monitoring frequency to better detect contamination trends. Nonetheless, this solution can be less economically sustainable. Thus, understanding and quantifying variability of monitoring data is pivotal to support remediation strategies. According with McHugh et al. (2011), the variability of monitoring data could be due to: a) long-term trend in the contaminant source; b) time-independent factors related to both well (e.g., screen length and depth) and aquifer characteristics (e.g., hydraulic conductivity, unsaturated zone thickness); c) non-standardized sampling procedures (e.g., purging and sampling flow rates, vertical position of the sampling pump); d) frequent changes in the laboratory.

This study presents the analysis and quantification of data variability of contaminant (total hydrocarbons and benzene) concentrations in a former oil refinery located in Northern Italy. Data variability was firstly quantified calculating the coefficient of variation (CV). Subsequently, different statistical analyses were conducted to identify and quantify the main factors affecting the data variability: Mann-Kendall test and Sen’s slope estimator, correlation analysis, factor analysis and multiple linear regression models. The working dataset refers to total hydrocarbons, benzene, redox-sensitive species (oxygen, nitrate, manganese, iron, sulfate and methane) and field parameters monitored in 41 fully screened piezometers from 2011 to 2021. Results pointed out that 11 years’ time-series of concentration do not show significant temporal trends, thus evidencing a relative stability of the contaminant plume. The CV of total hydrocarbons and benzene resulted lower in the plume core, characterized by methanogenesis and iron reduction, and higher in the plume fringe, characterized by sulfate, nitrate and/or oxygen reduction. The greater variability found in the fringe area is consistent with the vertical heterogeneity of biodegradation activities and redox states featuring the plume fringe (Meckenstock et al. 2015). Accordingly, factor analysis pointed out a positive correlation between CV and sulfate and a negative correlation between CV and methane. A multiple linear regression model of total hydrocarbons with sulfate and methane as independent variables (p-value of 0.031) obtained a r² value of 0.439. This result can indicate that vertical heterogeneity is able to explain the 43.9% of total variability in total hydrocarbons concentrations. The remaining percentage of data variability is due to unidentified factors, including the adoption of non-standardized sampling procedures, the change in analytical procedures and labs, etc. In conclusion, this works confirmed the ineffectiveness of monitoring groundwater quality through fully screened piezometers in hydrocarbon contaminated sites. The adoption of multi-depth monitoring system could reduce data variability in the studied site of, at least, the ~44%.

References:

McHugh et al. (2011) Gr Water Monit Remediat 31:92–101. https://doi.org/10.1111/j.1745-6592.2011.01337.x

Meckenstock et al. (2015) Environ Sci Technol 49:7073–7081. https://doi.org/10.1021/acs.est.5b00715

How to cite: Sartirana, D., Palazzi, A., Zanotti, C., Fumagalli, L., Franzetti, A., Pietrini, I., Bonomi, T., and Rotiroti, M.: Applying multivariate statistics to analyse data variability in groundwater quality monitoring of contaminated sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10433, https://doi.org/10.5194/egusphere-egu24-10433, 2024.

14:30–14:40

EGU24-14943

On-site presentation

Use of Active-DTS (heat tracer experiment) and FVPDM (tracer experiment) for field quantification of groundwater fluxes

Serge Brouyère, Laura Balzani, Pierre Jamin, Luca Varisano, and Nataline Simon

Understanding of transport processes is essential to identify the fate of contaminants in surface and subsurface water. Quantification of such transport processes requires a sound understanding and quantification of groundwater flow fields. Over the past decades, efforts have been made to develop and propose field methods that provide direct estimates of groundwater fluxes. The challenge is to propose field methods able to reflect the complexity of groundwater flow pathes in aquifer systems. In this context, we investigated the potential of two field methods to estimate groundwater fluxes in consolidated aquifers. Both FVPDM (Finite Volume Point Dilution Method) and Active-DTS (Distributed Temperature Sensing) measurements were conducted in a single piezometer in a fractured chalk aquifer. On the one hand, the FVPDM, a single-well tracer experiment, provided a measurement of the groundwater flow rate across the tested piezometer. On the other hand, the Active-DTS method was performed by deploying a Fiber-Optic (FO) cable outside the piezometer within the gravel filter. This method provided high-resolution and local groundwater flux estimates along the heated section. We relied on numerical simulations to assess the distortion of the groundwater flow field induced by the presence of the well. The groundwater flux is maximum within the well screen, where the FVPDM test was conducted. In the vicinity of the well, where the heated FO cable was installed, the groundwater flow is lower, and the flow pattern consists of converging and diverging flow lines. Thus, the position of the heated FO cable related to the flow direction is critical and can have a significant impact on the estimation of the groundwater flux. Regardless, we demonstrate that deploying the FO cable within the gravel pack is a novel and efficient approach, which opens up interesting perspectives for the use of Active-DTS measurements in consolidated aquifers to estimate vertical heterogeneities.

How to cite: Brouyère, S., Balzani, L., Jamin, P., Varisano, L., and Simon, N.: Use of Active-DTS (heat tracer experiment) and FVPDM (tracer experiment) for field quantification of groundwater fluxes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14943, https://doi.org/10.5194/egusphere-egu24-14943, 2024.

14:40–14:50

EGU24-4252

On-site presentation

Measurement and analysis of anomalous diffusion in porous rock

Brian Berkowitz, Ashish Rajyaguru, Ralf Metzler, Ishai Dror, and Daniel Grolimund

Molecular diffusion, or more specifically, diffusion-controlled transport, of tracers, contaminants, and chemical species --- in soil and rock formations, and in river, lake, and marine sediments --- plays a critical role in many dynamic processes that affect water chemistry and properties of the host domain. The spreading of dissolved ionic species via Brownian motion is generally described by a Gaussian law for the probability density function, with diffusion (embodying Fick’s second law) then being described by the classical diffusion equation. Solution of this equation shows that the spreading pattern of chemical species is characterized by a mean squared displacement that scales linearly with time. However, in other porous domains like biological tissues and cells, dense liquids, and gels, diffusion behavior often deviates from Fickian, instead exhibiting anomalous (or non-Fickian) diffusion. More specifically, tracer movements in these “crowded environments” exhibit a spreading pattern wherein the mean squared displacement scales as a power law. Somewhat surprisingly, in studies involving water-saturated porous rock, diffusion of chemical species is generally assumed to follow Fick’s second law, ignoring the possible occurrence of anomalous diffusion. To test this assumption, we measure molecular diffusion in five chalk and dolomite rock samples using a specially designed diffusion cell. The set-up enables high-resolution measurement of extended, long-time tailing at the measurement plane, which is required to distinguish between Fickian and anomalous diffusion behavior. In all of the rock samples, the diffusion behavior is demonstrated to be significantly different than Fickian, with extreme long-time tailing of tracer advance relative to conventional Fickian diffusion. The measured breakthrough curves are then analyzed using a continuous time random walk framework that describes anomalous diffusion in heterogeneous porous materials. The analysis (i) provides a framework to distinguish between Fickian and anomalous diffusion, and (ii) demonstrates that anomalous diffusion in geological formations is likely ubiquitous and implies that diffusion-controlled transport processes should be analyzed using tools that account for such behavior.

How to cite: Berkowitz, B., Rajyaguru, A., Metzler, R., Dror, I., and Grolimund, D.: Measurement and analysis of anomalous diffusion in porous rock, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4252, https://doi.org/10.5194/egusphere-egu24-4252, 2024.

14:50–15:00

EGU24-6127

ECS

On-site presentation

Effect of Local Dispersion on Mixing Enhancement when Applying an Engineered Injection and Extraction System: Laboratory and Model-based Evidence

Francesca Ziliotto, Mónica Basilio Hazas, Markus Muhr, Massimo Rolle, and Gabriele Chiogna

Engineered Injection and Extraction (EIE) systems represent a promising groundwater remediation technique. This technology generates transient groundwater flow fields by periodically operating a system of pumping wells, with the goal of enhancing contaminant degradation through mixing with a treatment solution. The objective of this work is to provide experimental evidence of the effect of an EIE system on plume mixing and to investigate the effect of local dispersion on mixing enhancement. We perform laboratory experiments in a quasi-two-dimensional setup representing a vertical cross-section of an unconfined homogeneous aquifer. The setup is equipped with four wells, connected to a peristaltic pump, which are activated one at a time following an injection-extraction sequence. The wells operation establishes transient flows within the setup and introduces fluctuations in the groundwater table. A conservative tracer is injected in the middle of the area delimited by the wells, and a high-resolution image analysis technique is applied to track the evolution of the tracer concentration. We perform the experiments considering two different grain sizes and investigate the effect of the application of the EIE system on the plume mixing and spreading in contrast to two benchmark experiments where the wells are not operating and, therefore, only diffusion affects the tracer plume. Additionally, for one porous material, we permute the injection-extraction sequence to study the effect of different transient flow conditions and groundwater table fluctuations on plume deformation and mixing. We also provide a model-based interpretation of the experimental results using Richards equation and the conservative advection-dispersion equation to describe flow and transport processes, respectively. Plume spreading is quantified by computing the second central spatial moments, while the degree of mixing is estimated by calculating the plume area. We use the Okubo-Weiss metric computed over the plume area to link the mixing enhancement to the change in the flow topology. Our results show that EIE effectively enhances mixing and spreading at the laboratory scale, especially when the flow field leads to high values of the Okubo-Weiss metric. Moreover, local dispersion is shown to be a key factor for mixing enhancement in engineered injection and extraction systems.

How to cite: Ziliotto, F., Basilio Hazas, M., Muhr, M., Rolle, M., and Chiogna, G.: Effect of Local Dispersion on Mixing Enhancement when Applying an Engineered Injection and Extraction System: Laboratory and Model-based Evidence, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6127, https://doi.org/10.5194/egusphere-egu24-6127, 2024.

15:00–15:10

EGU24-16467

On-site presentation

Contaminant Source Identification via Transfer Learning on Multifidelity-Data.

Alessia Chiofalo, Valentina Ciriello, and Daniel M. Tartakovsky

Reconstruction of contaminant release history is crucial for subsurface remediation actions. This task amounts to a high-dimensional inverse problem, whose solution requires multiple forward solves of contaminant transport equations. It also must cope with both sparse observations of solute concentration and subsurface heterogeneity. The computational burden of solving this inverse problem can be reduced by deploying a surrogate model, e.g., neural networks (NNs), which provides a low-cost approximation of its expensive physics-based counterpart. However, to construct such NNs, a large amount of high-fidelity forward runs may be required to provide training data, and these computations might be as cost-prohibitive as the solution of the inverse problem. To address this issue, we generate multi-fidelity data by running simulations of the forward transport model on fine and coarse meshes. The resulting high- and low-fidelity temporal snapshots of solute concentration are subsequently used, with a Transfer Learning technique, to train a Convolutional NN to identify the initial contaminant source location. The training is divided into three phases. In the initial phase, the training exclusively employs low-fidelity data. In the subsequent two steps, the learning phase for the network is finalized with only a relatively small number of high-fidelity data. The obtained results demonstrate that the transfer-learning-based surrogate model is a promising tool to reduce the computational cost as well as to obtain accurate solutions of high dimensional inverse problems.

How to cite: Chiofalo, A., Ciriello, V., and Tartakovsky, D. M.: Contaminant Source Identification via Transfer Learning on Multifidelity-Data., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16467, https://doi.org/10.5194/egusphere-egu24-16467, 2024.

15:10–15:20

EGU24-8335

ECS

On-site presentation

Graphene oxide as a component of a Permeable Reactive Barrier for aquifer pollution remediation

Chuchao Liang, Paula Rodriguez Escales, and Xavier Sanchez Vila

Groundwater contamination sources are ubiquitous, with the heavy metal ion lead being released to the aquifer systems as a common anthropogenic contaminant. Lead can cause serious damage to both human and ecosystem health. In this sense, its remediation through sorption technologies, such as Permeable Reactive Barriers (PRBs), is basic to minimize its impact. Quartz as the most common and economically heavy metal adsorbent has been widely studied. However, the new generation of potential adsorbents, here including graphene oxide (GO), has not been fully researched. Particularly, there is little research on how to set surface adsorption models of GO, with most studies limited to batch and transport experiments.

This study aimed to investigate the performance of quartz and graphene oxide (GO) as adsorbents in PPRBs. We evaluated the adsorption capacity of quartz sand and GO under different conditions through batch experiments, examining factors including pollutant concentration, pH, and competing ions. The experimental results were validated using a coupled surface complexation and precipitation model developed with the Phreeqc code, and the findings from the batch experiments will also be used as calibration data for the Phreeqc model, and the code (PEST) was used for parameter estimation.

Keywords: Graphene oxide, Heavy metal, Permeable Reactive Barriers, Surface complexation, Phreeqc.

How to cite: Liang, C., Rodriguez Escales, P., and Sanchez Vila, X.: Graphene oxide as a component of a Permeable Reactive Barrier for aquifer pollution remediation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8335, https://doi.org/10.5194/egusphere-egu24-8335, 2024.

15:20–15:30

EGU24-16396

ECS

Virtual presentation

Assessment of Fate and Transport of Heavy Metals (Cr, Cd) in Hardrock Aquifers

Aishwarya Bhattacharya, Brijesh Kumar Yadav, and Nitin Khandelwal

This study delves into chromium (Cr) and cadmium (Cd) behavior in varied hard-rock aquifer lithologies, exploring their sorption capacities and transport characteristics. The research aims to understand how these heavy metals affect groundwater quality in lithologically diverse settings. Hard rocks, known for their low porosity and heterogeneity, significantly influence the movement of contaminants through fractures and surfaces. Cadmium, a toxic metal primarily from human activities like mining and industrial discharge, poses significant risks to ecosystems. Chromium, particularly its hexavalent form, Cr (VI), originating from industrial and agricultural sources, is also a concern due to its carcinogenicity. WHO guidelines recommend limits of 0.003 mg/L for Cd²⁺ and 0.05 mg/L for Cr (VI) in groundwater, often exceeded in many regions, indicating environmental hazards and health risks. The study involved characterizing hard rock materials and conducting batch-sorption and column transport experiments to gauge contaminant-rock interactions. Results indicated varying sorption capacities across lithologies showing minimum value by granite (499.15 ± 99.41 mg/kg) and maximum value by limestone (872.37 ± 2.37 mg/kg) for 7ppm concentration. In case of studied aquifer systems, basaltic aquifers are demonstrating superior chromium retention compared to granitic ones. Ionic competition minimally affected sorption, prompting the use of NaCl solutions in subsequent experiments. These findings offer insights into the complex interplay between lithological compositions and contaminant sorption, crucial for groundwater management and environmental protection strategies.

Key words: Rocks and minerals, contaminant interaction, batch sorption, column transport.

How to cite: Bhattacharya, A., Yadav, B. K., and Khandelwal, N.: Assessment of Fate and Transport of Heavy Metals (Cr, Cd) in Hardrock Aquifers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16396, https://doi.org/10.5194/egusphere-egu24-16396, 2024.

15:30–15:40

EGU24-329

ECS

On-site presentation

Adsorption Kinetics and Contaminant Removal Efficiency of Nitrate and Phosphate Using Various Adsorbents.

Roohmoney Roohmoney, Sumedha Chakma, and Ravinder Kaur

Nitrate and phosphate play critical functions in plant development, yet their extensive usage in agriculture and industry pollutes water. This not only leads to diseases like cancer but also promotes the environmentally harmful process of eutrophication. Despite significant studies on phosphate and nitrate ion removal from water, the problem is in developing highly selective adsorbents to improve removal efficiency. This study provides a thorough evaluation of the effectiveness of nitrate and phosphate removal from synthetic solutions using three different adsorbents: Powdered activated carbon (PAC), modified activated carbon (MAC), and Activated Alumina (AA). Batch adsorption experiments were carried out across a variety of time periods and doses to investigate the dynamic interactions between the adsorbents and pollutants. The results showed that MAC treated with FeCl₃ had the best nitrate removal effectiveness of 97%, outperforming PAC and AA. Conversely, AA demonstrated superior phosphate removal efficiency, outperforming MAC and PAC. The pseudo-second-order kinetic model was shown to be the best fit for modeling the adsorption kinetics, offering useful insights into the time-dependent adsorption processes for both nitrate and phosphate. This study's findings not only help in the optimization of water treatment operations but also highlight the significance of selecting the suitable adsorbent for certain pollutants. The findings of this study benefit environmental science and water treatment technologies by offering practical insights into the comparative performance of commonly utilized adsorbents. The discovery of MAC as a powerful nitrate removal agent and AA as a phosphate removal agent has implications for the development of efficient, customized water treatment applications.

How to cite: Roohmoney, R., Chakma, S., and Kaur, R.: Adsorption Kinetics and Contaminant Removal Efficiency of Nitrate and Phosphate Using Various Adsorbents., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-329, https://doi.org/10.5194/egusphere-egu24-329, 2024.

Posters on site: Tue, 16 Apr, 10:45–12:30 | Hall A

Display time: Tue, 16 Apr, 08:30–Tue, 16 Apr, 12:30

Chairpersons: Antonio Zarlenga, Marco Dentz, Felipe de Barros

A.95

EGU24-247

ECS

Exploring the deposition mechanism in saturated porous media for polydisperse composites of XG and nZVI@rGO

Liming Ren, Bing Qin, and Fengyi Cao

Engineered nanomaterials (ENMs) have shown promise for remediation of groundwater contaminants and the potential application relies on the delivery of aqueous solutions of ENMs to a targeted subsurface location or region. Thus, the ability to accurately predict nanoparticle transport and retention in saturated porous media is one of the most technical challenges faced by the design and assessment of potential field-scale environmental applications. Here, a prior prediction model was presented by coupling the effect of Derjaguine-Landaue-Verweye-Overbeek (DLVO) interaction, Brownian diffusion, hydrodynamics and interception. Characteristics used in the model were medium size, porosity, injection velocity, size distribution of particles, attachment efficiency, single-collector contact efficiency. The direct comparison of parameterized prior model predictions to experimental measurements was proposed to thoroughly understand deposition mechanism of polydisperse ENM. The model predicted deposition rate coefficient quantitatively very close to measured rates. When the particle diameter (d_p) of ENM excessed 1.2080 mm, it was retained in the porous medium by interception; When d_p < 0.1737 mm, ENM would deposite in the porous medium if the kinetic energy (E_k) it possessed is less than the depth of the secondary energy minimum; When 0.1737 mm < d_p < 1.2080 mm, deposition occurred where adhesive torques (T_A) was in excess of hydrodynamic drag torgues (T_H) particles subject to. Further, deposition rate was positive correlated with injection concentrations among the range of 0.34 g/L~1.70 g/L. Besides, low deposition rates were observed with injection velocities around 0.69 cm/min.

How to cite: Ren, L., Qin, B., and Cao, F.: Exploring the deposition mechanism in saturated porous media for polydisperse composites of XG and nZVI@rGO, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-247, https://doi.org/10.5194/egusphere-egu24-247, 2024.

A.96

EGU24-828

ECS

Establishing Relation Between Variance of Permeability and Tortuosity for Composite Liner Material

(withdrawn after no-show)

Ekta Chaudhary and Deepak Swami

A.97

EGU24-2369

Recursive analytical solution for nonequilibrium multispecies transport of decaying contaminants simultaneously coupled in both the dissolved and sorbed phases

Jui-Sheng Chen, Yu-Chieh Ho, Ching-Ping Liang, Heejun Suk, Thu-Uyen Nguyen, and Chen-Wuing Liu

Few analytical or semi-analytical models simulating the transport of sequentially decaying reaction products affected by nonequilibrium sorption in the groundwater have been presented considering decay or degradation reaction occurring exclusively in the dissolved phase in the literature. However, the process of decay in the sorbed phase, which is important for the transport of decaying contaminants, has been neglected in previously developed analytical models. This study is thus designed to develop a novel semi-analytical model for simulating the multispecies transport of decaying contaminants subject to a nonequilibrium sorption process simultaneously coupled in both the dissolved and sorbed phases. For this purpose, a set of first-order reversible kinetic sorption reaction equations that respectively represent the nonequilibrium sorption processes between the dissolved and sorbed phases, are coupled to a set of advection-dispersion equations, to illustrate the decay process which occurs in both the dissolved and the sorbed phases. By including the decay in the sorbed phase both the parent sorbed concentration and daughter sorbed concentration coexist in a set of first-order reversible kinetic sorption reaction equations, which absolutely complicate the theoretical derivation of the analytical solution.
Recursive analytical solutions are derived to account for the concentration distribution of arbitrary transformation products with the aid of the Laplace transform and generalized integral transform. The correctness of the solutions is confirmed through a comparison of our newly derived recursive analytical solution with an existing model which considers an equilibrium sorption process. The newly developed recursive analytical solution is then applied to investigate how the decay in the sorbed phase affects the nonequilibrium transport of a four-member radionuclide decay chain. The result clearly predicts a lower radioactivity concentration of the first nuclide (238Pu), with decay in the sorbed phase, than the simulated results obtained using a model without decay in the sorbed phase. For other daughter elements (234 U, 230 Th, 226 Ra) of the radionuclide decay chain, neglect of decay in the sorbed phase leads to overestimation of the radioactivity concentrations. The result of large differences found in dissolved radioactivity concentration between the decay and no decay in sorbed phase may alter the decision of health risk assessment in the performance of radioactive waste disposal site. The implication is that the decay reactions of contaminants in the sorbed phase are important mechanisms that should be taken into accounts for accurately simulating and assessing the nonequilibrium multispecies transport of decaying contaminants.

How to cite: Chen, J.-S., Ho, Y.-C., Liang, C.-P., Suk, H., Nguyen, T.-U., and Liu, C.-W.: Recursive analytical solution for nonequilibrium multispecies transport of decaying contaminants simultaneously coupled in both the dissolved and sorbed phases, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2369, https://doi.org/10.5194/egusphere-egu24-2369, 2024.

A.98

EGU24-2373

Assessing Non-Carcinogenic and Carcinogenic Health Risk for Chlorinated Solvent Contaminated Groundwater Using MUSt Software Palckage: Case Study

Ching-Ping Liang, Jui-Sheng Chen, and Zhong-Yi Laio

A.99

EGU24-4470

ECS

Solute transport in heterogeneous compressible aquifers under transient forcing

Satoshi Tajima and Marco Dentz

Transient forcing, such as tidal fluctuations, enhances mixing within aquifers [1, 2]. This study focuses on two pivotal characteristics of typical aquifers—heterogeneity in hydraulic conductivity (K) and compressible properties, represented by the log-hydraulic conductivity variance (σ_f²) and specific storage (S_s), respectively. Previous research has individually addressed the influence of these parameters on solute dynamics [3, 4, 5], yet their combined effects remain inadequately understood. Here, we explore how heterogeneity and compressibility (finite storage) in combination governs solute transport in aquifers under transient forcing. To this end, this study employs Monte Carlo particle tracking simulations, providing a comprehensive representation of K heterogeneity. The simulations yield temporal evolutions of the centre of mass and spatial concentration variance. These results are compared with those derived from analytical solutions applicable to homogeneous compressive porous media (σ_f² = 0, S_s ≠ 0) [5]. Our findings reveal that increasing values of σ_f² and S_s result in a delayed temporal evolution of the centre of mass compared to the predictions of the homogeneous analytical solution. In addition, the homogeneous analytical solution with zero local dispersion predicts a consistently zero concentration variance, whereas our heterogeneous simulations demonstrate an increasing concentration variance over time. The simulations also show that the higher σ_f² and S_s, the faster the temporal evolution of the concentration variance. These insights offer a deeper understanding of transport dynamics under transient forcing conditions, providing valuable information for accurate assessments of tidal impacts on salinity distributions in coastal aquifers.

References

[1] Oberdorfer, J. A., Hogan, P. J., and Buddemeier, R. W. (1990). Atoll island hydrogeology: flow and freshwater occurrence in a tidally dominated system. Journal of Hydrology 120, 327-340.

[2] Inouchi, K., Kishi, Y., and Kakinuma, T. (1990). The motion of coastal groundwater in response to the tide. Journal of Hydrology 115, 165-191.

[3] Dagan, G., Bellin, A., and Rubin, Y. (1996). Lagrangian analysis of transport in heterogeneous formations under transient flow conditions. Water Resources Research 32, 891-899.

[4] Dentz, M., and Carrera, J. (2003). Effective dispersion in temporally fluctuating flow through a heterogeneous medium. Physical Review E 68, 036310.

[5] Pool, M., Dentz, M., and Post, V. E. A. (2016). Transient forcing effects on mixing of two fluids for a stable stratification. Water Resources Research 52, 7178-7197.

How to cite: Tajima, S. and Dentz, M.: Solute transport in heterogeneous compressible aquifers under transient forcing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4470, https://doi.org/10.5194/egusphere-egu24-4470, 2024.

A.100

EGU24-5135

ECS

Mechanistic Insights into the Selectivity of Sulfidated Zero-Valent Iron Materials in Chlorinated Ethenes Removal: A DFT Study

Miroslav Brumovsky and Daniel Tunega

Chlorinated ethenes (CEs), such as perchloroethene (PCE) and trichloroethene (TCE), are pervasive groundwater contaminants. Owing to their toxic properties, there is a considerable effort for their remediation. In this context, in situ CE chemical reduction using zero-valent iron (ZVI) materials represents a promising strategy. However, the intrinsic low electron selectivity of pristine ZVI often results in its rapid surface corrosion and passivation in subsurface environments. In the last years, sulfidation has emerged as an effective means to enhance the reactive lifetime of ZVI. Despite the efficiency of sulfidated ZVI (S-ZVI) in dechlorinating TCE and trans-1,2-dichloroethene (trans-DCE), a notably lower reactivity has been typically observed for PCE and cis-1,2-dichloroethene (cis-DCE). The mechanisms governing the variable reactivity of S-ZVI with different CEs remain poorly understood.

To shed more light on the mechanisms controlling S-ZVI selectivity, we calculated the dechlorination barriers of various CEs at multiple S-ZVI surface models using density functional theory (DFT). Specifically, we focused on the electron transfer-controlled β-elimination reactions, identified as the predominant pathway for CE dechlorination with S-ZVI. Reactions of PCE, TCE, and both cis- and trans-DCE isomers were investigated at different S-ZVI surface sites, including surfaces with varying sulfur coverage.

Our calculations revealed that CE dechlorination reactions are both kinetically and thermodynamically more favorable at Fe sites compared to S sites. This finding indicates that the overall promoting effect of ZVI sulfidation on CE degradation is indirect, primarily involving the protection of the ZVI surface from corrosion in water. Sulfur coverage was identified to significantly influence the S-ZVI selectivity for individual CEs. Under low S coverage, the reactivity of Fe sites followed the order trans-DCE ≈ TCE > cis-DCE > PCE, with PCE degradation hindered by steric effects from nearby S atoms. Conversely, at high S coverage, Fe sites were sterically hindered for all CEs, and reactivity was controlled by S sites. In this scenario, energy barriers correlated with the energy of the lowest unoccupied molecular orbital (E_LUMO) of CEs in the order PCE < TCE < DCE isomers. These findings demonstrate that the experimentally observed trends in S-ZVI selectivity for individual CEs can be explained by the interplay between the affinity of CEs for electron transfer and steric effects of S atoms at the ZVI surface.

Acknowledgments

This work was funded by the Austrian Science Fund (FWF), project M 2892-N. The Vienna Scientific Cluster (project no. 70544) is gratefully acknowledged for providing computational resources.

How to cite: Brumovsky, M. and Tunega, D.: Mechanistic Insights into the Selectivity of Sulfidated Zero-Valent Iron Materials in Chlorinated Ethenes Removal: A DFT Study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5135, https://doi.org/10.5194/egusphere-egu24-5135, 2024.

A.101

EGU24-5154

ECS

Impact of Chaotic Advection on Solute Transport in Porous Media

Carla Feistner, Mónica Basilio Hazas, Barbara Wohlmuth, and Gabriele Chiogna

Chaotic advection can enhance mixing processes in porous media by increasing the solution-solvent interface available for diffusion. While the pore structure can generate chaotic advection at the pore scale, transient flow fields can lead to chaotic advection at the Darcy scale. This concept can be applied to groundwater remediation, as the flow field can be engineered using injection-extraction systems. This study investigates two injection-extraction systems known to exhibit chaotic structures: a source-sink dipole and a rotated potential mixing. Using Lagrangian particle tracking combined with random walk we solve the stochastic differential equation to simulate solute transport. The pulsed source-sink system is parametrized by the pumping rate, while for the rotated potential mixing system, we use the rotation angle and the rotation frequency to change the flow properties. Using a grid search over the parameter spaces of both systems, we test different configurations. We quantify the temporal increase in dilution and the mixing enhancement with the dilution index by using a novel approach of selecting the optimal grid size with minimal approximation error for each particle density estimation. Furthermore, we analyze the corresponding flow structure to identify Kolmogorov-Arnol'd-Moser (KAM) islands, non-mixing regions that arise around elliptic points of the flow. We find that the parameters of the system control the occurrence and size of KAM islands, which consequently affect the increase in dilution by limiting the chaotic area in the domain. Overall, our results show that not all chaotic systems lead to the same maximum mixing enhancement. Therefore, it is important to properly assess the uncertainty in the design parameters of injection-extraction systems to effectively engineer chaotic advection.

How to cite: Feistner, C., Basilio Hazas, M., Wohlmuth, B., and Chiogna, G.: Impact of Chaotic Advection on Solute Transport in Porous Media, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5154, https://doi.org/10.5194/egusphere-egu24-5154, 2024.

A.102

EGU24-6503

Laboratory tests and modeling of a reactive multibarrier for the remediation of a contaminated aquifer system

Rajandrea Sethi, Leonardo Magherini, and Carlo Bianco

This study presents the treatability tests and modeling aimed at dimensioning of an in-situ reactive multibarrier, designed to purify an aquifer contaminated with a range of chlorinated organic compounds and arsenic, with 1,2-dichloroethane (1,2-DCA) presenting a significant resistance to conventional treatments.
The remediation strategy involves the implementation of a reactive multibarrier system comprising two series-connected reactive filters: the first filled with millimetric zerovalent iron (ZVI) to remove arsenic and most of the chlorinated hydrocarbons through abiotic reductive dehalogenation, and the second with granular activated carbon (GAC) to adsorb 1,2-DCA and other residual organic contaminants.
To optimize the site-specific design and sizing of the reactive filters, groundwater treatability tests were conducted in the laboratory. Initial batch tests compared various ZVI and GAC types to select the most effective materials. Subsequent column tests assessed the treatment chain's efficacy under flow conditions and determined the longevity of the reactive materials.
The results demonstrated the multibarrier's high effectiveness, with the ZVI filter removing 99.9% of several chlorinated solvents and all arsenic, and GAC achieving complete removal of the remaining contaminants to meet water quality standards. Mathematical models were employed to interpret the experimental findings and provide quantitative parameters essential for designing a large-scale multibarrier, such as kinetic constants for contaminant removal, reactive material longevity, and reagent volumes. A multicomponent adsorption model specifically aided in designing the GAC filtration step. he preliminary results of the pilot test, which is still ongoing, confirmed the potentiality of the reactive multibarrier to effectively remediate groundwater in site-specific conditions.

How to cite: Sethi, R., Magherini, L., and Bianco, C.: Laboratory tests and modeling of a reactive multibarrier for the remediation of a contaminated aquifer system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6503, https://doi.org/10.5194/egusphere-egu24-6503, 2024.

A.103

EGU24-6985

Assessing source zone distribution and persistence at a trichloroethylene contaminated site

Chiu-Shia Fen and Yu-Yang Zhuang

Chlorinated solvents are prevalent and persistent contaminants, classified as dense nonaqueous phase liquids (DNAPLs) in both soil and groundwater systems. They have been identified at numerous sites globally, significantly impacting our environment. The subsurface distribution of DNAPLs creates a source zone with complex geometry, strongly influenced by the specific characteristics of soil textures and stratification. Accurately defining the location and extent of DNAPL source zones at contaminated sites poses a considerable challenge due to these complexities.

The aim of this study is to delineate the spatial distribution and persistence of trichloroethylene (TCE) in the subsurface for a long-term period of TCE leakage. The studied area is situated at a factory in Taiwan. Employing the T2VOC module within PetraSim 2019 software, we analyzed TCE movement and distribution in the subsurface over a 42-year timeframe which encompasses a 22-year period of TCE leakage and an additional 20-year period preceding remedial activities. Field data from site investigation and remediation reports were incorporated into the analysis, encompassing information on groundwater table contours, soil layers, lithologies, permeabilities and the historical usage of TCE. Relevant parameters, such as relative permeability, liquid residual saturation, capillary pressure and fluid saturation relationships, were determined based on literature sources.

Results show that TCE infiltrates to a depth of 13 m, reaching a low permeability zone below the ground surface. However, the site investigation only extended to a depth of 10 m (the lower bound of a high-permeability zone). Significant TCE residuals persist in both the upper and lower layers of the high-permeability zone after the 42-year simulation period. The dissolved phase of TCE follows the groundwater flow, extending up to 80 m downstream with notable concentration levels. However, if considering volatilization of TCE (resulting in an 80% reduction in leakage) and an 80% reduction in the leakage area, it becomes improbable for TCE to infiltrate to the lower low-permeability layer. This suggests a potential underestimation of the current assessment of TCE usage. Moreover, the study underscores the influence of groundwater velocity and TCE residual saturation on the retention and persistence of TCE in the soil layers. This emphasizes the importance of investigating hydrogeological environment and assessing TCE residuals in various soil textures at such contaminated sites.

How to cite: Fen, C.-S. and Zhuang, Y.-Y.: Assessing source zone distribution and persistence at a trichloroethylene contaminated site, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6985, https://doi.org/10.5194/egusphere-egu24-6985, 2024.

A.104

EGU24-7282

ECS

High Iron and Manganese in Groundwater of Brahmaputra River Plains: concerns for drinking water quality and remediation

David Anand Aind and Abhijit Mukherjee

Apart from the health risks associated with the consumption of contaminated water, the suitability of water, based on its visual appeal, taste, and odor, is a matter of paramount importance. Elevated levels of Iron (Fe) and Manganese (Mn) lead to the discoloration of sanitary wares and laundry, besides resulting in deposits within distribution systems and contributing to an undesirable taste in drinking water. The mobilization of Fe and Mn in groundwater is predominantly governed by redox processes. In this study, we conducted an analysis of shallow groundwater (n=145) in the Brahmaputra River Plains (BRP), India, which shows that 85 percent (n=123) and 80 percent (n=116) of the groundwater exceed the WHO acceptable limit of Fe (0.3 mg/L) and Mn (0.1 mg/L), respectively. The highest concentration of Iron (II) is 7 mg/L with a median value of 3 mg/L (n=35). However, they are heterogeneously distributed among the Piedmont deposits, Older Alluviums, and Younger Alluviums. Spearman’s correlation shows that total Fe has a strong correlation (0.89) with Fe (II), and a comparison between them reveals that Fe (II) is the dominant species. The reducing nature of the groundwater with low dissolved oxygen and a high dissolved organic carbon suggests reductive dissolution of Fe and Mn oxyhydroxides as a possible mechanism of Fe and Mn release in the groundwater. Therefore, there is a need to mitigate the high Fe and Mn levels in the groundwater-sourced drinking water to avoid health and suitability concerns. Treatment facilities, including the use of iron-removal sand filters and aeration, have been installed across the region to mitigate the problem. Investigation of Fe (II) concentrations in the treated household-supplied water shows a considerable decrease in the Fe (II). Implementing effective mitigation measures, such as the use of iron-removal filters, is crucial to ensure the provision of safe drinking water.

How to cite: Aind, D. A. and Mukherjee, A.: High Iron and Manganese in Groundwater of Brahmaputra River Plains: concerns for drinking water quality and remediation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7282, https://doi.org/10.5194/egusphere-egu24-7282, 2024.

A.105

EGU24-9021

Delineating Hydraulic Heterogeneity Using Fiber Bragg Grating Multi-Level Well and Hydraulic Tomography – A Case Study in Taiwan

Jui-Pin Tsai, Tian-Chyi Yeh, Bo-Tsen Wang, Chia‐Hao Chang, and Che-Wei Liang

Hydraulic tomography (HT) is an innovative method for characterizing the heterogeneous properties of aquifers. This technique involves sequential pumping/injection tests using a network of wells, with simultaneous measurement of groundwater pressure variations. The resulting pressure data is then transformed into hydraulic heterogeneity using a geostatistical approach. Traditional HT tests utilize wells with screens at a single target depth, limiting pressure data collection to specific depth ranges. In contrast, a multilevel well-monitoring system (MLMS) employs multiple open screens at different depths, separated by packers, to prevent vertical flow connections. This configuration significantly increases the amount of pressure data compared to traditional wells. In this study, we implemented a novel multilevel well system based on fiber Bragg grating (FBG) technology for conducting HT at a contaminated site in Taiwan. A comparative analysis of hydraulic conductivity profiles obtained from HT with FBG MLMS and electrical resistivity was undertaken to validate the effectiveness of the FBG MLMS in HT applications. The results demonstrate the reliability and practicality of using an FBG multilevel well system for hydraulic tomography, highlighting its potential for enhanced data collection in heterogeneous aquifer characterization.

How to cite: Tsai, J.-P., Yeh, T.-C., Wang, B.-T., Chang, C., and Liang, C.-W.: Delineating Hydraulic Heterogeneity Using Fiber Bragg Grating Multi-Level Well and Hydraulic Tomography – A Case Study in Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9021, https://doi.org/10.5194/egusphere-egu24-9021, 2024.

A.106

EGU24-11221

ECS

Empirical and computational study on conservative tracer migration through a single fracture

Snigdha Pandey and Pramod Kumar Sharma

The escalation of industrialization and population growth in recent decades has increased the prominence of groundwater pollution in environmental concerns. However, accurate prediction of the contaminant migration through the fractured aquifer is still an arduous task. The current research is dedicated to evaluating the predictive accuracy of three models: the Advection Dispersion Equation (ADE), Advection Dispersion Equation with Retardation (ADE-R), and Single Rate Mobile-Immobile (MIM) model. Constant dispersivity is assumed for all the models. These models were employed to predict the migration of the solute, particularly NaCl, within a single fracture characterized by a 0.3 cm aperture and 1000 cm length and filled with fine sand. The study maintained non-Darcian flow conditions throughout the experimental runs. The simulated BTCs exhibited a non-Fickian trend and were subsequently subjected to fitting using the ADE, ADE-R, and MIM models. Notably, the MIM model proved the most adept at fitting the simulated BTCs, effectively capturing both early arrival and long tails. Conversely, the ADE-R model excelled in predicting the early arrival but fell short in fitting the long tails of the BTCs.

Keywords: ADE model; ADE-R model; Breakthrough curves; filled-single fracture; MIM model; non-Darcian flow

How to cite: Pandey, S. and Sharma, P. K.: Empirical and computational study on conservative tracer migration through a single fracture, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11221, https://doi.org/10.5194/egusphere-egu24-11221, 2024.

A.107

EGU24-14458

ECS

Model-based evaluation of efficiency of electrolysis-enhanced in-situ bioremediation for trichloroethylene using tandem circulation well

Shuting Yang, Zhang wen, Qi Zhu, Songhu Yuan, and Yiming Li

Aerobic bioremediation combined with electrolytic enhancement, stimulating the indigenous subsurface microflora to degrade TCE, in the recirculating system of groundwater and solute induced by tandem circulation well (TCW) is a novel in-situ remediation method which has been gradually valued for its great application prospects due its environmental and economic advantages. Previous investigations have been limited to few laboratory experiments, and neither the evaluation of remediation efficiency nor the improvement methods in application were fully understood. This study developed a reactive transport model for in-situ TCE bioremediation, simulating TCW-induced groundwater recirculating system, aerobic biodegradation process of TCE and electrolytic enhanced oxygen supply. A regionalized sensitivity analysis (RSA) was conducted based on the experimental data to quantify the influences of parameters, reduce the number of parameters inverted and provide the value of reactive kinetic parameters for this model. Different simulation cases were conducted to investigate influence of operating parameters and well spacing for remediation efficiency. The results show that increase in both current and pumping rate can improve the degradation efficiency but has a maximum degradation capacity due the limitation of saturated DO concentration in wellbore. Through a quantitative characterization of solute mixing, the model demonstrated an optimal operating parameters index (α_optimal), helping to find the optimal ratio of current and pumping rate. The results of the influence of well spacing indicate that too close an injection/extraction well distance is detrimental to degradation efficiency and the current and pumping rate need to increase in the same proportion with the increasing remediation area to remain the optimal efficiency.

How to cite: Yang, S., wen, Z., Zhu, Q., Yuan, S., and Li, Y.: Model-based evaluation of efficiency of electrolysis-enhanced in-situ bioremediation for trichloroethylene using tandem circulation well, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14458, https://doi.org/10.5194/egusphere-egu24-14458, 2024.

A.108

EGU24-15489

Design of system and method on field-scale solute migration experiment for evaluating radionuclide’s migration properties at a deep borehole

Jiwon Park, Jun-Young Ahn, Jong-Hwa Yi, Jeong-Yong Cheon, Myeong-Jae Yi, and Seong-Chun Jun

Disposal methods for storing high-level radioactive waste deep underground are being researched and implemented worldwide. In constructing a high-level radioactive waste disposal facility, groundwater reaction front moves and geochemical buffering capacity may be changed, affecting the long-term storage stability. Although various studies have been conducted in this regard in Korea, field-scale studies are still in shortage, in cases compared to overseas cases. This study aims to establish a long-term solute migration experiment system and experimental method for deep depths, to identify the migration and retardation characteristics of released nuclides in the deep underground environment.

For field-scale tests, KURT(KAERI Underground Research Tunnel) was constructed in 2006 and in-situ solute migration tests were conducted. However, that was conducted in shallow depth, which has limitations in realizing an actual disposal environments. Therefore, the long-term solute migration experiment to be designed in this study targets underground depths, where reduced-state groundwater exists and disposal site construction is considered, to get empirical data in deep depth. The in-situ solute migration experiment system designed in this study is composed of an injection part and an extraction part. The injection unit was designed to be in charge of injecting simulated nuclides into the injection borehole. The extraction unit was designed to extract groundwater, including the injected tracer, to obtain a sample for analysis and to measure the properties of groundwater flowing through fractured rock in real-time. Both sorbing and non-sorbing tracers are used in long-term solute migration experiments. The non-sorbing tracers are suitable such as Eosin B, fluorescein sodium, and potassium bromide. The sorbent tracers which can simulate the behavior characteristics of radionuclides are suitable such as rubidium, nickel, zirconium, and samarium. Using the solute migration experiment system and experimental method designed in this study, a long-term solute migration experiment will be carred out in the deep depths around KURT, to obtain the results of the radionuclides’ migration and retardation characteristics for the deep depths.

Acknowledgements

This research was supported by the National Research Foundation of Korea(NRF) under the project 'Development of Core Technologies for the Safety of Used Nuclear Fuel Storage and Disposal; NRF-2022M2E1A1052570'.

How to cite: Park, J., Ahn, J.-Y., Yi, J.-H., Cheon, J.-Y., Yi, M.-J., and Jun, S.-C.: Design of system and method on field-scale solute migration experiment for evaluating radionuclide’s migration properties at a deep borehole, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15489, https://doi.org/10.5194/egusphere-egu24-15489, 2024.

A.109

EGU24-7175

The effect of surge inundation on shallow groundwater salinity in the coastal low-lying poldered area of southwest Bangladesh-a 3D model investigation

Chi San Tsai, Hoque Mo, and Adrian P Butler

Pervasive salinity in soil, surface water and groundwater is a significant challenge in many coastal poldered areas of Bangladesh. These areas are characterized by their vulnerability to cyclone-induced surge inundation due to the low-lying flat topography and their concave coastal profile. The surge water leads to the areas being inundated, which may result in elevated salinity levels in surface water and groundwater. High salinity can affect the availability of potable water and have a serious impact on agriculture, ecosystems, and the health of coastal communities. To effectively address the issue of groundwater salinity in these coastal areas, a comprehensive understanding of the contributing causes is required. A 3D model, HydroGeoSphere, was developed to examine the effect of surge inundations on surface and groundwater salinities. This model coupled surface and subsurface domains, using surge levels data from Chittagong station and a digital elevation model from USGS Earth Explorer. Evaporation and monsoon data were collected at the pond of the DAB site (Dacope, Khulna, Southwest coastal Bangladesh). The results show that even one year after the storm surges, salinity levels in the surface and near-surface areas remained elevated. The high salinity levels near the surface area may be primarily due to the surge water being trapped in depressions, as well as the effects of evaporation reducing the water content of the soil, leaving concentrated salt behind. Also, low-permeable sediments in the area may contribute to the persistent high salinity levels. The modelled groundwater salinity distributions showed good agreement with the measured groundwater salinity distributions derived from electrical conductivities obtained in 14 tube wells at various depths and locations along a cross-section.

How to cite: Tsai, C. S., Mo, H., and Butler, A. P.: The effect of surge inundation on shallow groundwater salinity in the coastal low-lying poldered area of southwest Bangladesh-a 3D model investigation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7175, https://doi.org/10.5194/egusphere-egu24-7175, 2024.