HS8.1.1 | Hydrobiogeochemical processes in heterogeneous multiphase systems across scales
EDI
Hydrobiogeochemical processes in heterogeneous multiphase systems across scales
Co-organized by ERE5/SSS6
Convener: Tomas Aquino | Co-conveners: Efstathios Diamantopoulos, Insa Neuweiler, Christopher Vincent Henri, Gaute LingaECSECS, Giuseppe Brunetti, Jiri Simunek
Orals
| Fri, 19 Apr, 14:00–15:45 (CEST), 16:15–18:00 (CEST)
 
Room 3.16/17
Posters on site
| Attendance Thu, 18 Apr, 16:15–18:00 (CEST) | Display Thu, 18 Apr, 14:00–18:00
 
Hall A
Posters virtual
| Attendance Thu, 18 Apr, 14:00–15:45 (CEST) | Display Thu, 18 Apr, 08:30–18:00
 
vHall A
Orals |
Fri, 14:00
Thu, 16:15
Thu, 14:00
Multiphase flows are central to a broad range of natural and engineered processes, including nutrient cycles and contaminant remediation in soils, geological storage of carbon dioxide and hydrogen in deep reservoirs, and electrochemical applications such as fuel cells. Emerging contaminants (e.g., PFAS, pharmaceuticals, microplastics, natural toxins) and climate change pose new challenges to our already fragile ecosystems. The vadose zone is a dynamically-changing heterogeneous system that plays a key role in regulating exchanges between the atmosphere, vegetation, and groundwater and hosts a large portion of subsurface biochemical reactions. Deeper subsurface systems in turn represent potential reservoirs for underground storage of carbon dioxide and hydrogen. Understanding the interrelation between hydrological, physicochemical, and biological processes in multiphase systems across scales is therefore paramount to developing sustainable management strategies for water resources as well as energy and climate concerns.

The presence of multiple fluid phases enhances heterogeneity at the level of flow, mixing, and reaction in structurally heterogeneous media. This impacts the transport of dissolved substances and fundamentally changes mixing patterns and effective reaction rates, posing major challenges for predictive modeling. Recent theoretical, experimental, and numerical advances provide unprecedented insights into the pore-scale mechanisms governing these processes and open new opportunities to tackle these challenges.

This session aims to bring together researchers working on fundamental and applied aspects of hydrobiogeochemical processes in the vadose zone and other multi-phase systems. In particular, we encourage submissions relating to experimental, numerical, and theoretical contributions pertaining to the following topics:

• Monitoring and modeling of flow, transport, and biochemical reactions from the pore to the field scale.
• Influence of static and dynamical medium properties (e.g., soil structure) on water flow and reactive transport.
• Mixing and reaction of emerging contaminants and other substances in variably-saturated porous media.
• Flow, transport, and reaction in the rhizosphere and plants.
• Model appraisal techniques, including calibration, sensitivity analysis, uncertainty assessment, and surrogate-based modeling for partially-saturated systems.
• Deep geological storage.
• Fuel cells and other electrochemical applications.

Orals: Fri, 19 Apr | Room 3.16/17

Chairpersons: Tomas Aquino, Insa Neuweiler, Efstathios Diamantopoulos
14:00–14:05
Block 1: Fundamental advances in observing, characterizing, and modeling multiphase systems and applications to aquifers and the deep subsurface
14:05–14:25
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EGU24-4162
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solicited
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On-site presentation
Joaquin Jimenez-Martinez, Xueyi Zhang, Ishaan Markale, Dorothee Kurz, Zhi Dou, Maxence Carrel, Veronica Morales, and Markus Holzner

Understanding chemicals mixing and reactions in porous media is critical for many environmental and industrial applications. In the presence of a non-wetting immiscible phase (e.g., gas) within the pore space, it can remain immobile, giving rise to the so-called unsaturated flow, or it can move, resulting in a multiphase flow. In other cases, the immiscible phase can be permeable, as it occurs with biofilms growing within the pore space. We combine experiments and numerical modeling to assess the impact of saturation (fraction of the pore volume occupied by the wetting phase), multiphase flow (stationary two-phase flow), and the presence of permeable biofilm within the pore space on mixing-driven reactions. The product formation is larger for a given flow rate as saturation decreases, while for a given Peclet, it is the opposite. In multiphase flow conditions, for a given flow rate of the wetting phase, the product formation depends on the flow rate of the non-wetting phase. In the presence of biofilms, the product formation is enhanced compared to their absence and is further enhanced with a heterogeneous permeability within the biofilm.

How to cite: Jimenez-Martinez, J., Zhang, X., Markale, I., Kurz, D., Dou, Z., Carrel, M., Morales, V., and Holzner, M.: Impact of an immobile, mobile and permeable phase on mixing-driven reactions in porous media, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4162, https://doi.org/10.5194/egusphere-egu24-4162, 2024.

14:25–14:35
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EGU24-14907
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ECS
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On-site presentation
Oshri Borgman, Francesco Gomez, Tanguy Le Borgne, and Yves Méheust

Mixing-induced reactions are an essential feature of environmental flow and transport processes. They control many reactive transport processes, including mineral precipitation rates and contaminant remediation processes. Natural porous media are characterized by a strong structural heterogeneity, which impacts solute mixing and, therefore, the resulting chemical reaction rates. Establishing a quantitative link between pore-scale heterogeneity and mixing/reaction rates in saturated and unsaturated conditions remains an open question. Here, we study pore-scale solute mixing using high-resolution experimental measurements to quantify the overall reaction rates and product concentrations. Our goals are to study the impact of structural heterogeneity on 1) reaction rates and products during saturated flow and 2) the spatial arrangement of fluid phases during unsaturated flow and its impact on reaction rates and products.

We use two-dimensional porous media consisting of circular posts in a Hele-Shaw-type flow cell. We control heterogeneity by varying the posts’ diameters disorder and correlation length; increasing this length introduces more structure in the porous medium. We utilize an irreversible oxidation reaction to produce fluorescein from its non-fluorescent form. The Damköhler number is sufficiently larger than unity, so the reaction rate is mixing-controlled. We inject a non-fluorescent tracer pulse into the porous medium sample filled with the oxidating reactant under saturated and unsaturated flow conditions. We analyze periodic fluorescence intensity images to track the evolving solute concentration field. The reaction rates and the total reaction product mass are calculated directly from the concentration images.

Solute concentration images show that increasing the spatial correlation length under saturated flow conditions leads to enhanced reaction front stretching and elongation as the solute travels along preferential pathways. Due to this overall stretching, the reaction front is locally more compressed perpendicular to the elongation direction. In a non-correlated, randomly disordered porous medium, overall stretching is reduced, and the front is less compressed locally. Under unsaturated flow conditions, a main preferential flow path characterizes the correlated porous medium. In contrast, the non-correlated medium is characterized by a higher degree of branching and splitting in the velocity field. Solute pulse focusing in the correlated porous medium sample reduces reaction front stretching compared to the non-correlated porous medium, under unsaturated conditions. Under these conditions, the reaction rate increases more than the saturated case due to the unsaturated flow pattern's enhanced reaction front stretching. This effect is more pronounced for the non-correlated sample, where flow path splitting and reaction front stretching are more significant. This work shows that structural heterogeneity has a considerable effect on reactive solute transport and that this effect depends on the system’s saturation.

How to cite: Borgman, O., Gomez, F., Le Borgne, T., and Méheust, Y.: Mixing-induced reactive transport experiments in heterogeneous and variably saturated porous media, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14907, https://doi.org/10.5194/egusphere-egu24-14907, 2024.

14:35–14:45
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EGU24-7889
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ECS
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On-site presentation
Rahul Krishna, Yves Meheust, and Insa Neuweiler

Two-phase flow in geological fractures holds significant relevance in various applications, including subsurface fluid storage and oil and gas exploitation. The pore-scale modelling of such flows is a challenging task influenced by many factors, such as the complex interplay between the viscous, capillary, gravitational and inertial forces, intricate geometries, as well as molecular scale phenomena such as moving contact lines and thin wetting films. Although various modelling approaches have been used to tackle these challenges, the high computational demands required to accurately capture the three-dimensional fluid-fluid interfacial dynamics often render these models impractical for real-world applications. Consequently, from a practical point of view, the simplification of these 3D models may become imperative to facilitate efficient and reasonably accurate predictions of flow quantities.

Depth-integrated two-dimensional modelling is one such approach which enables saving computational time and effort at the expense of not resolving the third dimension. Here, the governing equations are solved in two dimensions, the influence of the third dimension being incorporated through appropriate additional terms. While such models have been used previously, they have so far been restricted to either permanent single-phase flow in rough fractures or two-phase flow in 2D porous media of homogeneous depth. In a rough fracture, the fluid-fluid interface possesses not only an in-plane curvature but also an out-of-plane curvature, which must be accommodated in the 2D depth-integrated model. Therefore, to address the immiscible flows in rough fractures it is essential to reformulate the 2-D depth-integrated approach from the first principles.

To perform the depth integration, we proceed from the traditional direct numerical simulation (DNS) approach, where the Navier-Stokes equations, coupled with an interface capturing technique, which in our case is the Volume of Fluid (VOF), are solved numerically. We integrate the governing flow equations in the vertical direction while expressing the flow fields in terms of 2D depth-averaged flow quantities. To account for the out-of-plane curvature and the wall shear stress arising from the no-slip conditions on the fracture walls, we assume locally a plane Poiseuille configuration (Hele-Shaw). 

The derived 2D depth-integrated model is implemented in the open-source CFD code OpenFOAM. We validate our model using the Saffman-Taylor instability case, comparing predictions with experiments and full 3D model results. We then extend our study to two numerically generated rough fractures with (a) smoothly and periodically varying aperture and (b) a more realistic aperture field with a larger roughness. We investigate drainage (i.e., the displacement of the wetting fluid by the non-wetting fluid) over a range of Capillary numbers spanning more than three orders of magnitude. We compare our 2D model predictions of both, pore-scale and macroscopic flow variables, with those obtained using 3D simulations. Our 2D model accurately estimates key statistical indicators with a tenfold reduction in computation time, offering an excellent compromise between solution accuracy and computational efficiency. We also discuss the limitations of the depth-averaged model depending on flow ranges.

How to cite: Krishna, R., Meheust, Y., and Neuweiler, I.: Depth-integrated Two-dimensional Model for Immiscible Two-phase Flow in Open Rough-walled Fractures with Smoothly Varying Aperture, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7889, https://doi.org/10.5194/egusphere-egu24-7889, 2024.

14:45–14:55
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EGU24-9503
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ECS
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On-site presentation
Huhao Gao, Alexandru Tatomir, Hiwa Abdullah, and Martin Sauter

The kinetic interface-sensitive (KIS) tracer test is a newly developed tracer approach to measure the fluid-fluid interfacial area (IFA) during dynamic two-phase flow in porous media. This new tracer approach can be applied for multiple geological applications, where dynamic two-phase flow is involved, e.g. monitoring the plume during geological storage of carbon dioxide. The obtained concentration breakthrough curves by measuring reacted tracer concentration in water samples are interpreted with a specialized Darcy-scale numerical model to determine the IFA. The previous design of the drainage experiments has one major limitation that the volume of the usable water sample after breakthrough for the measurement is often insufficient. An alternative is to employ KIS tracers in a “push-pull” experimental set-up, i.e. primary drainage is followed by a consequent main imbibition process, with the flow direction being reversed. This study applies both the pore-scale numerical simulation and the core-scale column experiments to study the KIS tracer reactive transport during push-pull processes. The pore-scale numerical simulation is done with a phase-field method-based continuous species transport model. The reactive transport of the tracer and the characteristics of the concentration breakthrough curves are analyzed. The Darcy-scale reactive transport model is validated by comparing it to the pore-scale results. Finally, the new method is applied in the column experiment, where the determined specific interfacial area is found to be close to the literature data.

How to cite: Gao, H., Tatomir, A., Abdullah, H., and Sauter, M.: Reservoir characterization by push-pull tests employing Kinetic Interface Sensitive tracers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9503, https://doi.org/10.5194/egusphere-egu24-9503, 2024.

14:55–15:05
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EGU24-4243
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ECS
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On-site presentation
Akanksha Srivastava, Renu Valsala, and Sheeja Jagadevan

Contamination with mono-aromatic hydrocarbons, specifically benzene, toluene, and xylenes (BTX), is one of the major concern to groundwater aquifers. BTX have high environmental stability and are harmful to human health and aquifer ecosystem. Thorough assessment and monitoring of the risk posed by BTX in aquifers are essential for the sustainable use of groundwater resources. The biodegradation of BTX in aquifer rely primarily on anaerobic processes. Nitrate-sulfate-reducing assemblages is considered for BTX bioremediation in such anoxic condition. These assemblages act as a terminal electron acceptor for bacterial respiration. The degree of the interaction between combinations of nitrate-sulfate reduction and BTX elimination determines the efficacy of BTX biological degradation. The interactions, however, received limited attention in the existing literature. Hence, the current analysis focuses co-existence of nitrate-sulfate assemblages affecting BTX bioremediation. A multi-component numerical simulation is performed to investigate the potential of nitrate-sulfate-assemblages for bioremediation of BTX in anoxic conditions. A fully implicit finite-difference novel approach is adopted here to solve the proposed numerical model, which is capable of obtaining spatial variation in BTX concentrations. The results suggest that bioremediation is efficient in removing toxic BTX from aquifers under the coexistence of nitrate-sulfate assemblages. This approach, in addition, can be used in deciding the optimum rate of electron acceptor injection and the time required to bring BTX to standard limits. Furthermore, it can help us to plan sustainable bioremediation strategies for mono-aromatic hydrocarbon contaminated aquifers where such reduction assemblages co-exist. This hydrogeobiochemical modelling study also emphasizes the importance of multidisciplinary methods in dealing with challenging environmental issues in the contaminated aquifers.

Keywords: Hydrogeobiochemical modelling; Bioremediation; BTX; Nitrate-sulfate assemblages; Aquifers.

How to cite: Srivastava, A., Valsala, R., and Jagadevan, S.: Hydrogeobiochemical Modelling for Bioremediation of Mono-Aromatic Hydrocarbons Using Nitrate-Sulfate-Reducing Assemblages in Aquifers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4243, https://doi.org/10.5194/egusphere-egu24-4243, 2024.

15:05–15:15
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EGU24-18863
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ECS
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On-site presentation
Electromagnetohydrodynamic (EMHD) two-phase fluid flow through a porous medium
(withdrawn after no-show)
Promasree Majumdar and Debabrata Dasgupta
15:15–15:25
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EGU24-18085
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ECS
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On-site presentation
Konstantinos Feroukas, Marco Dentz, Juan Hidalgo, and Daniel Lester

Mixing is the process that homogenizes initially segregated miscible constituents, increases the volume occupied by a solute, and decreases concentration peaks. It is important for the assessment of contamination levels and biogeochemical reactions in groundwater and soils. Mixing processes are governed by the interplay of fluid advection, molecular diffusion and local-scale dispersion at Darcy scale. Here we study the mechanisms of mixing in three-dimensional Darcy scale porous media with different heterogeneity structure. We analyze the role of medium and flow topology on the mixing and dispersion behavior. To this end, we perform Darcy-scale numerical simulations of incompressible flow and transport in heterogeneous three-dimensional porous media. Hydraulic conductivity is represented as a multi-Gaussian random field with lognormal marginal distribution. We consider isotropic and anisotropic correlation structures and scalar and tensorial conductivity. Flow is solved using a finite volume two-point method and transport using a Lagrangian approach. The flow topology is quantified by the helicity of the velocity field. We consider a planar injection of particles. Dispersion is quantified by the longitudinal and transverse dispersion coefficient, which are determined by the evolution along time of the position’s variance in the respective direction divide by two. It is also quantified by the breakthrough curves, which measure the distribution of arrival times at a given position from the initial one. Mixing is quantified by the ability of the flow to stretch and elongate a fluid strip which enhances diffusion through the creation and sustaining of concentration gradients. Results show that for a helical flow, a finite transverse dispersion coefficient is observed at long times and that the elongation of elemental strips follow an exponential stretching  (for large logK variances). On the contrary, on non-helical flows, transverse dispersion tends asymptotically to zero and the stretching rate is algebraic. The longitudinal dispersion coefficient seems unaffected by the helicity of the flow. These results shed light on the relation between medium structure and flow topology on mixing, making an important step towards the control, upscaling and large scale representation of mixing in porous media

.

 

How to cite: Feroukas, K., Dentz, M., Hidalgo, J., and Lester, D.: Impact of helicity on mixing in heterogeneous porous media, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18085, https://doi.org/10.5194/egusphere-egu24-18085, 2024.

15:25–15:35
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EGU24-4880
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ECS
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On-site presentation
Jiyoung Baek, Byeong-Hak Park, Gabriel Rau, and Kang-Kun Lee

As heat tracing gains versatility in hydrogeological applications, precise thermal dispersion modeling becomes essential. However, limited experimental data for thermal dispersion, influenced by several factors such as particle size or shape, poses a challenge to the understanding of the relationship between flow velocity and thermal dispersion coefficient. To fill these gaps, the solute and heat tracer experiments were conducted using two different sizes of sand. Thermal and solute dispersion were analyzed by applying analytical models. We also systematically collected and revisited literature data to comprehensively interpret the influences of particle size, shape, and pore-scale heterogeneity on dispersion. The results exhibited that the solute and thermal dispersivity were comparable when the dispersion linearly increased to the velocity. However, within the transition regime (Pe < 5), a departure from linearity was observed (R2 < 0.9). The deviation was more pronounced in smaller particle size due to pore-scale heterogeneity arising from the complexity of pore network. Consequently, our findings emphasize the potential necessity for caution when modeling thermal dispersion based on solute dispersion within natural porous materials.

Keywords: Particle size; Thermal dispersion; Pore-scale heterogeneity; Transition regime; Sandbox experiment

 

Acknowledgements

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2022R1A2C1006696). This work was also supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government(MSIT) (No. 2022R1A5A1085103). This work was also supported by the Nuclear Research and Development Program of the National Research Foundation of Korea (NRF-2021M2E1A1085200).

 

How to cite: Baek, J., Park, B.-H., Rau, G., and Lee, K.-K.: Experimental Investigation on Dispersion Within Porous Media Influenced by Particle sizes and Pore-Scale Heterogeneity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4880, https://doi.org/10.5194/egusphere-egu24-4880, 2024.

15:35–15:45
Coffee break
Chairpersons: Tomas Aquino, Insa Neuweiler, Efstathios Diamantopoulos
16:15–16:20
Block 2: Hydrobiogeochemical processes in soils and the vadose zone
16:20–16:30
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EGU24-7503
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On-site presentation
Katharina Lehmann, Dinusha Eshvara Arachchige, Robert Lehmann, and Kai Uwe Totsche

The aeration zone (AZ) below the soils sensu stricto is still neglected compartment regarding its structure, diversity of life and habitats, and role for the provision of ecosystem services. Especially in thick AZ of topographic recharge areas, fluid flow dynamics and the exchange of the total mobile inventory (Lehmann et al. 2021) and their roles for the quality-evolution of groundwater are largely unknown. In the low-mountain topographic recharge area of the Hainich Critical Zone Exploratory (central Germany), we study spatiotemporal dynamics of the fluid fluxes and mobile inventory within the shallow (upper) AZ (regolith) and compare their signature with soil seepage and perched groundwater (deeper AZ). Percolates from 20 drainage collectors (DC) covering a diversity of Triassic mixed carbonate-siliciclastic (sedimentary) bedrock, soil types, and installation depths were sampled for more than 3 years on regular (monthly) and event-based basis and analyzed by various physico-/hydrochemical and spectro-microscopic techniques.

On average, the DC captured ~13% of the percolate from the forest topsoil seepage and 2.4% of precipitation. Seepage volume was mainly influenced by the factors soil thickness and sampling month, followed by scarp slope gradient and seasonal differences. In the upper AZ, the mobile inventory exhibited strong seasonality (e.g. EC, pH, nitrate, sulphate, K, Si, Mn, Al, Fe, particle concentration) and were more dependend on seasonal weather conditions and single (extreme) events (e.g., snow melt, rain events) than on lithology, followed by site-specific structural factors (location, slope), or pedological settings (e.g. overburden soil type, soil thickness). Generally, our results show fluid-rock interactions within the upper AZ with a more similar hydrochemical water signature to perched groundwater. Contrastingly, particulate mobile inventory showed a strong connection to soil seepage signature, comprising a diverse spectrum of mineral particles (mainly clay minerals) and mineral- and mineral-organic associations up to 160 µm, including aggregates and microorganisms. The different flow regimes that prevail during different seasons and weather conditions mainly influenced the amount and spectrum of percolate mobile inventory. During summer, dry periods in conjunction with extreme precipitation events favored translocation of small-sized particles. In winter, fast-flow regimes during normal precipitation as well as during snowmelts contributed strongly to the translocation of organic/inorganic carbon and mineral particle through the AZ and to groundwater. We conclude that the AZ is a complex biogeochemical reactor, that severely alters the percolate composition and properties, already preshaping the biogeochemical groundwater quality as well as due to its functions and services (e.g. water-purification and storage). As such, the aeration zone hast to be considered as a crucial compartment for groundwater quality evolution, especially in topographic recharge areas.

 

Lehmann, K., Lehmann, R., Totsche, K. U. (2021) Event-driven dynamics of the total mobile inventory in undisturbed soil account for significant fluxes of particulate organic carbon. Sci. Total Environ. 756, 143774, doi: https://doi.org/10.1016/j.scitotenv.2020.143774

How to cite: Lehmann, K., Eshvara Arachchige, D., Lehmann, R., and Totsche, K. U.: Dynamics of aeration zone mobile inventory preshape groundwater quality evolution - results from multi-year sampling of regolith seepage , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7503, https://doi.org/10.5194/egusphere-egu24-7503, 2024.

16:30–16:40
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EGU24-5615
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ECS
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On-site presentation
Doron Kalisman, Ishai Dror, and Brian Berkowitz

This study experimentally demonstrates the impact of water and solute influx magnitude, and its resulting local distribution, on transport at timescales longer than the influx duration, through a disparate velocity field of a partially saturated domain. In a sand-filled cell, steady-state flow is maintained with a constant horizontal hydraulic head, while the upper part of the cell is partially saturated. The horizontal velocity varies by orders of magnitude from the surface to the saturated zone. An influx of water with a dissolved tracer is applied at the middle of the upper boundary surface, over several minutes, forming a plume that reaches a depth of a few centimeters. This influx disturbs the flow field locally, but after it is terminated, the return to steady-state flow is of the order of magnitude of the influx timescale. Eventually, the solute flows to the saturated zone and out of the cell through a path on the scale of decimeters, over a time scale of days. Employing ICP-MS as a sensitive measurement tool to detect highly diluted concentrations of solute enables tracking of a small influx volume that does not significantly perturb the flow field. This maintains a separation between the distinct spatial-temporal scales of the short-term local infiltration and the long-term system-scale transport. Applying varying influx magnitudes sets the solute plume across different velocity profiles and thus dictates the downstream plume distribution. A low influx relative to the hydraulic conductivity of the partially saturated sand allows solutes to infiltrate farther down compared to a higher influx, so that the plume reaches higher flow velocities but also spans a wider velocity variability. A higher influx relative to the hydraulic conductivity leads to a local increase in saturation, but a shallower depth of infiltration compared to the lower influx, and the system accordingly exhibits a more uniform plume located at a lower velocity region. In downstream solute concentration measurements, these influx variations result in a faster but more smeared breakthrough for the lower influx compared to a slower and more uniform breakthrough for the higher influx, corresponding to their initial distribution after infiltration.

How to cite: Kalisman, D., Dror, I., and Berkowitz, B.: From infiltration to steady-state flow in partially saturated media – bridging solute transport between millimeter-decimeter and minute-day scales, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5615, https://doi.org/10.5194/egusphere-egu24-5615, 2024.

16:40–16:50
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EGU24-19678
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On-site presentation
Maarten Braakhekke, Pavan Cornelissen, Louise Wipfler, Aaldrik Tiktak, Anton Poot, Bernhard Jene, Gerco Hoogeweg, Abdul Ghafoor, Judith Klein, Michael Stemmer, Amy Ritter, Robin Sur, Gregor Spickermann, Gerard Heuvelink, Gregory Hughes, Stephan Marahrens, Stefan Reichenberger, Nicoleta Suciu, and Michelle Morris

Assessment of the leaching potential of pesticides and their metabolites is an important part of the authorization procedure for pesticides in Europe. To protect groundwater quality, it must be demonstrated that concentrations of active substances in the upper groundwater do not exceed 0.1 μg/L before a pesticide can be approved for use. For the purpose of exposure assessment, this concentration limit is imposed on the water leaching downward at 1 m depth in the soil profile. For a given substance and application pattern, this leaching concentration can vary in space by several orders of magnitude, due to variation in site conditions, most importantly soil properties and climate. Spatially distributed leaching modelling (SDLM) is a methodology for exposure assessment over large spatial extents, dealing with this spatial variability in a comprehensive way. It involves performing simulations for many parametrizations representative for a spatial region and can be used to generate maps or calculate spatio-temporal percentiles of leaching concentrations. While such tools are already used in exposure assessment at national level in several EU member states, no generally accepted SDLM tool is available at the European level. In 2020, a working group of Society of Environmental Toxicology and Chemistry (SETAC) was formed with the purpose to develop a harmonized framework for SDLM across Europe (EU27 + UK).

A first version of an SDLM—referred to as GeoPEARL-EU—was built around the pesticide leaching model PEARL, a field-scale model of pesticide fate in the soil-plant system. PEARL mechanistically simulates pesticide behaviour in a 1D soil column based on explicit descriptions of transport in the liquid and gas phases, sorption to the solid phase, degradation, volatilisation, and plant-uptake. Soil moisture content and fluxes are provided by the SWAP hydrological model. PEARL is used in regulatory exposure assessment for groundwater and soil. Furthermore, a spatially distributed tool based on PEARL (GeoPEARL) is used for exposure assessment in the Netherlands.

To apply PEARL to Europe, pan-European gridded datasets were collected for several variables, including soil texture, pH, soil organic carbon, weather, irrigation patterns and crop area. These datasets were used to develop a set of parametrizations covering the variability of climate and soil conditions in Europe. To this end, all 1x1 km grid cells for the EU27 + UK were partitioned into approximately 10,000 clusters using k-means clustering, based on several soil- and climate-related variables relevant for leaching vulnerability. Subsequently, a representative grid cell was selected for each cluster, which was used to obtain the data required to parameterize PEARL from the spatial data sets. Pedotransfer functions were used to derive soil hydraulic parameters.

We will present results from GeoPEARL-EU for several test cases with specific attention to the effect of the spatial aggregation approach on the model predictions. Moreover, we discuss how the tool could be used in the tiered approach of the regulatory exposure assessment for groundwater in the EU.

How to cite: Braakhekke, M., Cornelissen, P., Wipfler, L., Tiktak, A., Poot, A., Jene, B., Hoogeweg, G., Ghafoor, A., Klein, J., Stemmer, M., Ritter, A., Sur, R., Spickermann, G., Heuvelink, G., Hughes, G., Marahrens, S., Reichenberger, S., Suciu, N., and Morris, M.: A Spatially Distributed Leaching Model to assess pesticide leaching for exposure assessment at the European level, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19678, https://doi.org/10.5194/egusphere-egu24-19678, 2024.

16:50–17:00
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EGU24-9159
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ECS
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On-site presentation
Giovanna Piazzon, Matteo Longo, Sebastiano Rocco, Francesco Morari, and Nicola Dal Ferro

The movement dynamics of glyphosate (GLY) in soil can be highly complex and challenging to predict, because its high water solubility and strong propensity to soil particle adsorption can interact with agricultural management practices, e.g. tillage operations and water table management. This can make GLY i) sensitive to nonuniform leaching via preferential flow paths into the groundwater before it can degrade, ii) difficult to model according to uniform flows. The aim of this study was to understand GLY dynamics in different agricultural systems of the low-lying Venetian plain, by calibrating a dual permeability model embedded in HYDRUS-1D using a series of GLY experimental data that were collected in the field, and compare it with a dual porosity mobile-immobile approach. Experimental data came from eight drainable lysimeters, where two shallow water table depths (60 cm and 120 cm deep) were compared in conventional (CV) and conservation agriculture (CA) systems as representative of the low-lying Venetian plain conditions (NE Italy). On May 2019, GLY and a tracer (KBr) were applied on bare soil (in CV) and rye that was used as a cover crop, in CA. After the distribution, soil (0-5, 5-15 cm deep) and soil-pore water (15, 30, 60 cm deep) samples were collected for 48 days to follow solutes dynamics. At the same depths, soil moisture and matric potential were monitored using TDR probes and electronic tensiometers. An automated system modulated the suction through matric potential readings combined with an electronic vacuum regulator. The HYDRUS 1-D software package was employed for inverse modelling of soil properties, first through parameterization and matric potential results, while solute movement parameters were calibrated based on GLY and KBr results from soil and water samples. Experimental results showed that GLY was found at different depths, especially soon after its distribution as dependent on intense rainfall events. The MIM model failed to predict any GLY movement, due to its high adsorption coefficient that hindered any GLY exchange between the immobile and mobile phases. In fact, experimental observations revealed that a preferential flow occurred down to the deepest layers (60 cm deep), even in the presence of poorly structured soil and irrespective of both the groundwater level and the cultivation system. In contrast, the dual permeability model provided a more accurate description of GLY dynamics in soil, successfully predicting the observed bypass flow timing experiment. Therefore, dual permeability model seems crucial for describing GLY dynamics in agroecosystems, enabling more accurate predictions of its potential pathways. 

How to cite: Piazzon, G., Longo, M., Rocco, S., Morari, F., and Dal Ferro, N.: Assessing glyphosate movement through different agricultural systems with a shallow water table: insights from an inverse dual permeability model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9159, https://doi.org/10.5194/egusphere-egu24-9159, 2024.

17:00–17:10
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EGU24-2753
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Virtual presentation
Jiaxu Jin, Pengfei Wu, Hongzhi Cui, and Xinlei Zhang

The lead-zinc tailings pond contains a significant concentration of heavy metal pollutants, such as lead, zinc, copper, chromium, cadmium, mercury, and arsenic. These pollutants exist in the form of ions within the tailings. External environmental factors can facilitate the release and transportation of these heavy metal elements from the tailings, resulting in pollution. The factors influencing pollutant release and variations in heavy metal tailings transport across different media were investigated by employing statistical analysis, leaching tests, and heavy metal soil column experiments based on the results of a case study on the Qingshan lead-zinc mining area. The multi-component solute release transport model for tailings to examine the interplay between concentration and seepage fields was constructed by considering hydrodynamics, mass transfer, and chemical reactions. The COMSOL software was performed to develop a customized model for the transport of heavy metal pollutants, wherein specific boundary conditions were set to enable quantitative analysis and interpretation of the release and migration of heavy metal solutes in tailings. The present study establishes a foundation for comprehending the migration patterns, pollution pathways, and mechanisms of heavy metal pollutants in tailings ponds. Furthermore, it provides indispensable technical support for addressing heavy metal contamination in lead-zinc mining regions and developing impermeable systems for tailings ponds.

How to cite: Jin, J., Wu, P., Cui, H., and Zhang, X.: Release and Transport Characteristics of Heavy Metal Pollutants in Tailings Pond, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2753, https://doi.org/10.5194/egusphere-egu24-2753, 2024.

17:10–17:20
|
EGU24-14615
|
ECS
|
On-site presentation
Thomas Ritschel

Water flow in the vadose zone is strongly non-linear due to the feedback of water flow, saturation, and the associated hydraulic conductivity. Therefore, the simulation of unsaturated flow at the continuum scale is notoriously complicated. Yet, not only the solution of the non-linear partial differential equation itself is difficult, also the appropriate parameterization of the unsaturated hydraulic conductivity function poses a challenge. Frequently, hydraulic conductivity is estimated from the water retention curve using capillary bundle models such as the well-established Mualem model or from pedotransfer functions that hardly include information on the actual pore space morphology. Here, a novel approach is presented to estimate the full unsaturated hydraulic conductivity function from a morphological analysis of Xray-CT images in the following way. First, the local pore space morphology is evaluated to obtain pore radius, Euclidean distances to the pore wall, and connectivity measures. Then, a local hydraulic conductivity and capillary forces are calculated for individual voxels of the images. This already permits to estimate the water retention curve and the water distribution inside the pore space at different levels of saturation. These configurations are then used to calculate an associated continuum scale hydraulic conductivity from dry to fully saturated conditions. This approach can be implemented in image analysis software, e.g. ImageJ, in a straight-forward way and may provide much better and specific estimates of the unsaturated hydraulic conductivity that sensitively affects the simulation of fluid flow in soils and the vadose zone provided satisfactory pore space acquisition with Xray-CT is possible.

How to cite: Ritschel, T.: Estimation of unsaturated hydraulic conductivity from morphological analysis of Xray-CT images, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14615, https://doi.org/10.5194/egusphere-egu24-14615, 2024.

17:20–17:30
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EGU24-3853
|
On-site presentation
Claus Florian Stange

The power mean is the generalization of the common averaging methods, such as harmonic, geometric and arithmetic mean, but also minimum and maximum. However, it also allows an infinite number of other means between these common means and can therefore be adapted very flexibly to the specific task of upscaling. This will be demonstrated in the contribution by calculating the effective thermal conductivity as the mean of the partial conductivities of soil components (typically of the solid, liquid, and gaseous phase). Soil thermal conductivity is a key factor for the soil heat balance and is widely used in many fields of science. However, it is elaborate to measure thermal conductivity of soils that have different porosities and degrees of saturation. Effective thermal conductivity of soil strongly depends on the arrangement of particles (soil structure) and on the interaction of added water to the solid phase (e.g., menisci).  To improve the prediction of soil thermal conductivity, specific information of soil structure needs to be taken into account. The relationship between the power mean exponents p and the degree of saturation is an indicator of the existing soil structure.

How to cite: Stange, C. F.: On the possibilities of the power mean as an upscaling method using the example of thermal conductivity in soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3853, https://doi.org/10.5194/egusphere-egu24-3853, 2024.

17:30–17:40
|
EGU24-20806
|
On-site presentation
Jafar Qajar, Alejandra Reyes Amezaga, Selen Ezgi Celik Selen Ezgi Celik, Sebastiaan Godts, Laurenz Schröer, Amir Raoof Amir Raoof, and Veerle Cnudde

Drying of building materials filled with salt-containing moisture is a common example of salt weathering [1]. Fluid flow, such as capillary uptake of water, and local climate changes stand out as key factors in salt weathering, substantially impacting the Earth's landscape and building infrastructure [2]. While microbial organisms are known to alter rock surfaces, some exhibit physiological capabilities that beneficially impact rock properties by producing biofilms, biocement and biogas [3]. Environmental factors such as temperature, relative humidity, and ionic strength of the medium influence microbial-induced products [4]. The impact of salt type, concentration, and ionic strength on microbially mediated reactions inside porous media is a largely unexplored phenomenon at the pore scale. Effective addressing of the respective challenges requires understanding the synergistic and counter effects of bacterial interactions and salt crystallization within the internal pore structure of rocks, influencing related pore-scale processes. In this study, we explored the response to the drying process in a range of porous materials, from PDMS transparent micromodels to sedimentary porous rocks containing brine solutions of various compositions in the presence and without bacterial solutions. We used Paracoccus denitrificans bacteria in our experiments. We specifically consider the case where air with different levels of humidity and at a constant temperature is exposed to one side of the porous media, forming a drying front—a defined interface separating liquid-saturated and partially gas-filled domains. High-resolution optical and confocal microscopy, Raman spectroscopy, and X-ray micro-computed tomography (µ-CT) were used to visualize and characterize bacteria-salt aggregates interactions in the porous media. Systematic investigations were carried out to understand how the interactions between salt crystallization and bacterial reactions depend on pore space morphology, type, and ionic strength of salt solutions. The findings highlight the potential of advanced 2D and 3D imaging techniques for enhanced understanding of the transport-crystallization coupling with bacterial activity through in-situ experiments and, hence, for constructing more accurate prediction models and conservation strategies.

Keywords: Salt weathering; Bacteria; Ionic strength; Relative humidity; Evaporation; Imaging techniques.

Acknowledgement: This project has received funding from the Dutch Research Council (NWO) through the BugControl project (project number VI.C.202.074) of the NWO Talent program and from the EU INFRAIA project (H2020) the EXCITE Network.

References

[1]       Sghaier, N., S. Geoffroy, M. Prat, H. Eloukabi, and S. Ben Nasrallah, Evaporation-driven growth of large crystallized salt structures in a porous medium. Physical Review E, 2014. 90(4): p. 042402.

[2]       Grossi, C.M., P. Brimblecombe, B. Menéndez, D. Benavente, I. Harris, and M. Déqué, Climatology of salt transitions and implications for stone weathering. Science of The Total Environment, 2011. 409(13): p. 2577-2585.

[3]       Llop, E., I. Alvaro, A. Gómez-Bolea, M. Hernández Mariné, and S. Sammut, Biological crusts contribute to the protection of NeolithicHeritage in the Mediterranean region, in Science and Technology for the Conservation of Cultural Heritage. 2013. p. 33-36.

[4]       Ferrer, M.R., J. Quevedo-Sarmiento, M.A. Rivadeneyra, V. Bejar, R. Delgado, and A. Ramos-Cormenzana, Calcium carbonate precipitation by two groups of moderately halophilic microorganisms at different temperatures and salt concentrations. Current Microbiology, 1988. 17(4): p. 221-227.

How to cite: Qajar, J., Reyes Amezaga, A., Selen Ezgi Celik, S. E. C., Godts, S., Schröer, L., Amir Raoof, A. R., and Cnudde, V.: Pore-scale investigations of interactions between microorganisms and ionic strength: Implications for salt crystallization damage in porous media, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20806, https://doi.org/10.5194/egusphere-egu24-20806, 2024.

17:40–17:50
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EGU24-20741
|
On-site presentation
Quantifying the influence of matrix diffusion on transit time distributions (TTDs) in mountain catchments
(withdrawn after no-show)
Harihar Rajaram
17:50–18:00

Posters on site: Thu, 18 Apr, 16:15–18:00 | Hall A

Display time: Thu, 18 Apr 14:00–Thu, 18 Apr 18:00
Chairpersons: Tomas Aquino, Christopher Vincent Henri
A.67
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EGU24-3458
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ECS
Anirban Chakraborty and Ziv Moreno

Simulations of two-phase flow in heterogeneous porous media are crucial for several applications, such as CO2 sequestration, efficient oil and gas recovery, and groundwater pollution remediation. Modeling of two-phase flow systems becomes very challenging when capillary heterogeneity and hydraulic discontinuities are considered. Traditional models use numerical techniques such as finite difference, finite element, and finite volume for solving the partial differential equations of the system. Although numerical methods have been shown to produce reliable solutions for complex flow problems, they can become computationally expensive. This emphasizes the high computational demand for solving the inverse problem. The use of DNNs (deep neural networks) has become more common in predicting subsurface flow behavior. DNNs is a data-driven approach that enables the learning of a system by linking input and output parameters and provides fast predictions of dynamic, complex systems. Nevertheless, when data is extremely scarce, particularly in subsurface systems, standard DNNs are unable to yield robust results. Recent advancements enable the integration of physical constraints as partial differential equations (PDEs) into the DNNs scheme. Such a class of deep learning techniques is generally referred to as physics-informed neural networks (PINNs). PINNs are also capable to provide forward solutions for PDEs.  In this work, we examined PINNs' capabilities to provide forward solutions of a 1D steady-state two-phase flow with capillary heterogeneity at the sub-core scale. Here, we trained a PINNs system that incorporates high variability in the hydraulic properties and boundary conditions implemented as input parameters. We compared the PINNs results with numerical solutions to test the efficiency of the developed PINNs system. Results have shown that the trained PINNs system could reproduce both capillary pressure and phase saturation profiles for altering fractional flows, injection rates, hydraulic properties, and domain lengths with high accuracy and within a single training. Training the extended PINNs system was obtained in a few hours, and the post-trained system provided unlimited solutions for variable structures and boundary conditions within a few seconds. 

How to cite: Chakraborty, A. and Moreno, Z.: Simulating two-phase flow using Physics-informed neural networks with capillary heterogeneity and hydraulic discontinuities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3458, https://doi.org/10.5194/egusphere-egu24-3458, 2024.

A.68
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EGU24-4230
Xiaoying Zhang

Plutonium (Pu) in the subsurface environment can transport in different oxidation states as an aqueous solute or as colloidal particles. The transport behavior of Pu is affected by the relative abundances of these species and can be difficult to predict when they simultaneously exist. This study investigates the concurrent transport of Pu intrinsic colloids, Pu(IV)(aq) and Pu(V-VI)(aq) through a combination of controlled experiments and semi-analytical dual-porosity transport modeling. Pu transport experiments were conducted in a fractured granite to elucidate sorption processes and their scaling behavior. In the experiments, Pu(IV)(aq) was the least mobile of the Pu species, Pu(V-VI)(aq) had intermediate mobility, and the colloidal Pu, which consisted mainly of precipitated and/or hydrolyzed Pu(IV), was the most mobile. The semi-analytical modeling revealed that the sorption of each Pu species was rate-limited, as the sorption could not be described by assuming local equilibrium in the experiments. The model was able to describe the sorption of the different Pu species that occurring either on fracture surfaces, in the pores of the rock matrix, or simultaneously in both locations. While equally good fits to the data could be achieved using any of these assumptions, a fracture-dominated process was considered to be the most plausible because it provided the most reasonable estimates of sorption rate constants. Importantly, a key result of this work is that the sorption rate constant of all Pu species tends to decrease with increasing time scales, which implies that Pu will tend to be more mobile at longer time scales than observations at shorter time scales suggest. 

How to cite: Zhang, X.: Plutonium reactive transport in fractured granite: Multi-species experiments and simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4230, https://doi.org/10.5194/egusphere-egu24-4230, 2024.

A.69
|
EGU24-5866
|
ECS
Pavan Cornelissen, Louise Wipfler, Maarten Braakhekke, and Marius Heinen

Soil properties such as the dry bulk density and soil hydraulic parameters can significantly affect the environmental fate of pesticides. These properties are often assumed to remain constant in time in numerical models. In reality, however, these properties change over time due ploughing and consolidation. In this study, we modeled the time-varying soil properties induced by ploughing and consolidation and assessed its effect on pesticide accumulation in the topsoil and leaching to the groundwater. For this purpose, time-dependent soil properties have been implemented in the hydrological model SWAP and the pesticide fate model PEARL. Ploughing instantaneously decreases the bulk density, after which it gradually increases again to its original value due to consolidation caused by rainfall. The time-dependent soil properties are modelled based on empirical relationships between the dry bulk density and the Mualem-Van Genuchten parameters found in the literature.

Ploughing leads to a short-term deviation of the soil water content and concentration compared to the reference case (i.e., the case with constant soil properties). We included mixing of pesticide over the ploughing layer due to ploughing in both cases. However, under Central European climate conditions, the effect of ploughing vanishes within several months in the entire soil profile. For assessing the impact on the leaching of pesticide to groundwater, we evaluated the pesticide concentration in pore water at 1 meter depth. The effect of time-varying soil properties due to ploughing and consolidation on the leaching concentration was found to be small for both a tracer and an adsorbing solute. Even for an extreme case with three ploughing events per year, the effect on the 90th-percentile of daily leaching concentration was smaller than 0.3%. For assessing the impact on the exposure of soil organisms to pesticides, we considered the pesticide concentration in pore water averaged over the upper 20 centimeters of the soil. For the tracer, ploughing resulted in a 1.2% decrease of the 90th-percentile of daily topsoil concentration data for the extreme case of three ploughing events per year. Interpretation of the results for adsorbing solutes in the topsoil is hampered by the fact that soil mass is not conserved in the current approach. More advanced models must be developed that allow for conservation of soil mass for assessing the impact of time-dependent soil properties on concentrations in the topsoil.

How to cite: Cornelissen, P., Wipfler, L., Braakhekke, M., and Heinen, M.: The Effect of Time-Varying Soil Properties Caused by Ploughing and Consolidation on Pesticide Fate in Soil and Groundwater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5866, https://doi.org/10.5194/egusphere-egu24-5866, 2024.

A.70
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EGU24-8091
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ECS
Frederic Leuther and Efstathios Diamantopoulos

Evaporation of soil water depends not only on climatic conditions, soil texture, and soil hydraulic properties but also on the soils’ macro-structure. Often, evaporation is characterised by water losses over time for a defined soil volume where soils are assumed to be homogeneous in texture and structure. In this study, we investigated the potential and limitations of 3D modelling of evaporation processes on soil cores with structural features ≥ 480 µm determined by X-ray computed tomography (X-ray µCT). The method was tested for two contrasting soil structures (ploughed vs. non-ploughed grassland) which experienced structural changes due 19 cycles of freezing and thawing. For all real soil samples, we simulated three different conditions of atmospheric demand with Hydrus 3D. It was hypothesised that the different distribution of air-filled macro-pores, the macro-connectivity of soil matrix and the surface area will affect bare soil evaporation and more specific the transition from stage 1 to stage 2 evaporation. To evaluate the effect of soil macro-structure on the column scale, we investigated the spatial distribution of water content and water fluxes. The combination of X-ray µCT and HYDRUS 3D was able to capture the effect of ploughing and freezing-thawing on soil macro-structure and to quantify the effect on the water dynamics inside the samples for various atmospheric demands and thus the feedback with evaporation.

How to cite: Leuther, F. and Diamantopoulos, E.: The effect of soil macro-structure on bare soil evaporation – using HYDRUS 3D simulation on X-ray µCT determined soil structures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8091, https://doi.org/10.5194/egusphere-egu24-8091, 2024.

A.71
|
EGU24-8793
Salvatore Straface, Guglielmo Federico Antonio Brunetti, and Andrea Scozzari

Innovative monitoring techniques today facilitate advanced and reliable measurements in the vadose zone. This, coupled with the predictive capabilities of machine learning, has an ever-growing impact on the management of agricultural and irrigation practices. The vadose zone, particularly the root zone, plays a pivotal role in hydrological processes by regulating water and energy fluxes across the soil surface. Additionally, it influences nutrient transport, groundwater recharge, groundwater pollution, microbial activity, and plant physiology, as it links the atmosphere, soil, and groundwater. Among various monitoring techniques, Cosmic-Ray Neutron Sensing (CRNS) stands out as a ground-based remote sensing technique capable of measuring soil moisture within the root zone at relevant scales (up to 240 m) with a high level of reliability. It is based on nuclear interactions between incoming cosmic rays and elements in the Earth’s atmosphere, such as hydrogen. By employing the Hydrus-1D Cosmic module, effective soil moisture values can be derived based on the neutron intensity detected by Cosmic-Ray Neutron Probes (CRNPs). On the other hand, machine learning methods and neural networks (NN) hold enormous potential despite inherent limitations, notably the requirement for extensive datasets and their lack of a physical foundation in reproducing soil processes. In this study, we propose a synergistic approach to overcome these limitations. The physically-based Hydrus-1D model was utilized to train a single-layer NN for the direct prediction of soil moisture and irrigation water demand, relying exclusively on atmospheric forcings (temperature and precipitation) as input. In a proof-of-concept aimed at assessing the validity and robustness of our approach, a time series of synthetic data replicating soil characteristics, atmospheric forcings, and field measurements conducted through CRNPs was generated. These data were employed in the Hydrus-1D Cosmic module to calibrate a physically-based model, facilitating the generation of a continuous and extensive spatiotemporal soil moisture output dataset for the simulated synthetic field. The single-layer NN, trained with this synthetic soil moisture and atmospheric forcing data, demonstrated the potential to accurately predict soil moisture and irrigation needs of the terrain straightforwardly, using only atmospheric variables as input. The proposed synergistic approach has exhibited significant potential, and future developments in this research will involve the incorporation of real data.

How to cite: Straface, S., Brunetti, G. F. A., and Scozzari, A.: Advancing Irrigation Strategies: Synergistic Modeling of Soil Moisture Using Cosmic-Ray Neutron Sensing, Hydrus-1D, and Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8793, https://doi.org/10.5194/egusphere-egu24-8793, 2024.

A.72
|
EGU24-9957
Christopher Henri and Efstathios Diamantopoulos

Soils are complex systems where different physical, chemical and biological processes occurring simultaneously and interact in a non-linear way. This includes the diffusion process, which is known to be affected by the tortuosity, and therefore the water content. Additionally, the high degree of soil heterogeneity poses significant challenges in studying soil reactivity due to its high impact on mixing. In this study we evaluate the effect of a series of what we could be key controlling factors of effective reaction rates in soils at the plot scale: the degree of heterogeneity, the hydraulic structure, the reaction rate, the initial distribution of reactants, and the heterogeneity in the diffusion coefficient.

We tackle this by explicitly simulating hypothetical biomolecular soil reaction (A+B C) for different degrees of heterogeneity, different hydraulic structures, different reaction rates, different initial distribution of the reactants and different representation of diffusion. Results are evaluated in terms of effective reaction rates at the plot scale.

The simulation results reveal that mixing conditions control reactions in unsaturated soils. Non-ideal reactivity due to mixing-limited conditions is not only a consequence of the simple presence of heterogeneity or even of its intensity. Instead, it results from (at least): the characteristics of heterogeneity, the Pe number, the Da number, the spatial distribution of the reactants. Interestingly, the spatial variability of the (tortuosity-dependent) diffusion coefficient appears to also have a significant effect on mixing conditions.  

By these results, we illustrate the high complexity of reactive systems in unsaturated soils, which makes the use of average macroscopic reaction rates (as in most agriculture, environmental and geoengineering models) at least questionable.

How to cite: Henri, C. and Diamantopoulos, E.: What control reactions in unsaturated soils? On the dynamic effect of small-scale heterogeneity and (spatially variable) diffusion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9957, https://doi.org/10.5194/egusphere-egu24-9957, 2024.

A.73
|
EGU24-10423
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ECS
Ludovica Presta, Giuseppe Brunetti, Christine Stumpp, Michele Turco, and Patrizia Piro

Nature Based Solutions (NBS) are known to play a key role in urban water management by increasing the infiltration, retention, and evapotranspiration capacity of urban areas. However, their potential use for contaminant removal has only been partially investigated. To address this issue, this study presents an experimental analysis of the nitrogen turnover in selected typical NBS substrates. Soil column experiments were combined with laboratory methods to characterize the hydrodynamic properties of porous media and elucidate the nitrification process in NBSs. In a first experimental campaign, saturated soil columns were injected with a natural tracer (deuterium) to characterize non-reactive solute transport in different substrates. Breakthrough curves exhibit significant tailing, thus suggesting the existence of a complex interplay between a mobile and an immobile domain. A second experimental campaign was carried out in larger unsaturated soil columns periodically injected with wastewater. Nitrogen species were measured in the effluent to describe the nitrogen turnover in soils. Results are characterized by two distinct phases, in which nitrate is initially not detectable in the outflow but later becomes the dominant species. This behavior indicates the existence of an initial microbial adaptation phase, followed by an efficient nitrification process supported by the oxic conditions in the substrate. Altogether, observations highlight the complex hydraulic and reactive behavior of NBSs substrates, which should be properly combined with modeling to better understand and design NBS systems for pollutant treatment.

How to cite: Presta, L., Brunetti, G., Stumpp, C., Turco, M., and Piro, P.: Disentangling nitrogen turnover in Nature Based Solutions: hydrodynamic properties and reactive behavior , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10423, https://doi.org/10.5194/egusphere-egu24-10423, 2024.

A.74
|
EGU24-12231
|
ECS
|
Yao Xu, Marcel Moura, Hilmar Yngvi Birgisson, and Knut Jørgen Måløy

Density-driven convection of CO2 in water will trigger the spatiotemporal evolution of pH and carbon concentration, impacting the understanding of CO2 dissolution and implementations of geological carbon sequestration. Building upon the conventional methodology which applies a single pH indicator and Schlieren imaging analysis, the enhanced experimental technique, offering a holistic view of CO2 convection within water, resulted in an accurate and visual representation of the CO2 plume propagation and a wider range of pH alteration and carbon concentration during CO2-water interactions. In response to the broad pH variations with continuous CO2 dissolution, this study utilized three pH indicators combined with the novel image analysis method to correlate the solutions’ colors to their pH. Afterwards, the carbon concentration is derived from the pH values by employing the pseudo-equilibrium theories. Leveraging an experimental technique and analytical tools to measure the spatiotemporal pH and carbon concentration, the research aims to deepen the understanding of CO2 convection behaviors, paving the way for enhanced insights into carbon sequestration and related environmental processes.

Keywords: Carbon sequestration, CO2 convection, density-driven, pH, carbon concentration

How to cite: Xu, Y., Moura, M., Birgisson, H. Y., and Måløy, K. J.: An Experimental Technique for Measuring Spatiotemporal pH and Carbon Concentration During Density-Driven Convection of CO2 in Water, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12231, https://doi.org/10.5194/egusphere-egu24-12231, 2024.

A.75
|
EGU24-15195
|
ECS
Jean Maillet, Emilie Thory, Christelle Latrille, and Sébastien Savoye

Mechanisms involved in the radionuclide mobility in water-saturated environments have been extensively studied in order to predict their migration. However, in natural environments, a partially water-saturated zone occurs between the soil surface and the water table. It is well known that a decrease in water content reduces the porosity available for flow. Various studies have reported a increase or reduction of the contaminants residence time in porous media, explained by the flow paths complexity increase, a preferential path by the macroporosity and a reduced accessibility to reactive sites [1]. This study aims to understand the influence of water content on transport parameters such as dispersivity, porosity and chemical reactivity. This study investigates the effect of water content by comparing column transport experiments performed with inert (enriched-HDO water) and reactive (strontium) tracers on water-saturated and partially saturated soil.

Transport experiments were carried out on columns filled with the 300-400 µm fraction extracted by dry sieving from a sedimentary alluvium. This material was then compacted inside a glass column to reach the same density as that measured in the field (1.47 g.cm-3). Transport experiments were performed under water saturated and partially saturated conditions corresponding to 0.43 to 0.19 water content, with a CaCl2 solution equilibrated with calcite at pCO2 atm. At steady flow, tracers were introduced into the system by an injecting loop, passed through the material and was collected in sequenced fractions. Sensors placed at both inlet and outlet of the column [2] allowed pH and electrical conductivity to be continuously controlled. HDO and Sr were measured with a deuterium analyser and an ICP MS respectively. HDO and Sr breakthrough curves were interpreted with HYDRUS-1D coupled with PhreeqC softwares. A multi-site ion exchange model was implemented in PhreeqC [2]. Flowrate and porosity were experimentally measured while dispersivity was determined by inverse modelling. To compare the different experiments, results were expressed in dimensionless units: relative concentration (C/C0) and pore volume passed through the column normalized to the column pore volume (V/Vpore).

Based on experiments carried out in water-saturated media with HDO, the dispersivity in the material was estimated at 0.1 cm-1. The Sr residence time was tenfold more than HDO (from 2.5 to 30 V/Vpore), which confirms that chemical retention drives the cation migration into porous media. Three HDO experiments carried out at various water contents (0.24 to 0.19 cm.cm-1) revealed a regular dispersivity increase with decreasing water content from 0.1 to 0.2 cm-1. For Sr experiments, decreasing water content led to the increase of the breakthrough curve intensities and a tailing effect, meaning that Sr would be less retained and more spread with reduced water content.

These results show that reducing the water content in porous media leads to reduce the porosity accessibility to flow and to increase the dispersivity. This suggests that the water content decrease constrains the water flow path, this is intensified with the desaturation. The Sr transport behaviour change with desaturation may be explained by the reduction in the accessibility to the sorption sites.

 

How to cite: Maillet, J., Thory, E., Latrille, C., and Savoye, S.: Effect of water content on transport of water tracer and strontium in compacted clay-rich soil column, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15195, https://doi.org/10.5194/egusphere-egu24-15195, 2024.

A.76
|
EGU24-18902
Bartosz Balis, Mateusz Pawlowicz, Adam Szymkiewicz, Jirka Simunek, Anna Gumula-Kawecka, and Beata Jaworska-Szulc

Groundwater management relies increasingly on numerical models to assess past, present, and future conditions, optimize strategies, and protect resources from climate and land use changes. Groundwater systems encompass the unsaturated (vadose) and saturated (groundwater) zones, with vadose zone modeling presenting computational challenges due to nonlinear equations and complex parameters. One possible solution to include the vadose zone processes in groundwater models in a flexible manner is to couple computer programs modeling 3D flow in the saturated zone with programs modeling 1D flow in the vadose zone. 

 

In this study, we introduce the HYDRUS-MODFLOW Synergy Engine (HMSE), a novel coupling approach for HYDRUS-1D and MODFLOW-2005, aimed at enhancing groundwater modeling. HMSE employs external coupling via a versatile interface, offering three deployment options: a desktop application, a Docker container, and a Kubernetes cluster. Users interact through a web interface, enabling project setup, model uploads, configuration adjustments, simulations, and result retrieval.

 

The MODFLOW's area is divided into recharge zones, each assigned a HYDRUS-1D model representing soil profiles, land cover, groundwater depth, and weather conditions. HMSE offers two coupling modes. In the simple mode, groundwater table positions are assumed constant, HYDRUS-1D simulations are performed for the entire period, and average recharge rates are calculated for MODFLOW. In the second coupling mode, MODFLOW and HYDRUS-1D interact iteratively to update the water table position in HYDRUS-1D profiles after each stress period in the MODFLOW simulation. This involves splitting the MODFLOW model into segments corresponding to different stress periods, performing HYDRUS-1D simulations, passing recharge data to the RCH file, running a MODFLOW simulation for each stress period, and using MODFLOW results to calculate the average water table depth for each recharge zone, thus updating the corresponding HYDRUS profiles while avoiding oscillations in recharge flux. 

 

HMSE combines the strengths of mature and validated HYDRUS-1D and MODFLOW-2005 programs, offering a more comprehensive understanding of groundwater systems. Our study presents a preliminary validation of HMSE for a shallow aquifer in northern Poland. We also evaluated HMSE performance in the three deployments (desktop, Docker and Kubernetes). 

How to cite: Balis, B., Pawlowicz, M., Szymkiewicz, A., Simunek, J., Gumula-Kawecka, A., and Jaworska-Szulc, B.: Development of a new computer tool for coupling HYDRUS-1D and MODFLOW, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18902, https://doi.org/10.5194/egusphere-egu24-18902, 2024.

A.77
|
EGU24-20448
Modeling Immiscible Fluid Flow: Insights into Air Displacement of Water in Microscale Porous Media
(withdrawn after no-show)
Sookyun Wang, Minhee Lee, and Seon-Ok Kim
A.78
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EGU24-20962
|
ECS
Stefanie Kiemle, Theresa Schollenberger, Katharina Heck, Rainer Helmig, Carina Bringedal, and Hans van Duijn

Soil salinization causes severe problems in agriculture, especially in arid and semi-arid regions, as it leads to soil degradation and reduces plant growth. During evaporation from a saline-water-saturated soil, salt accumulates near the top of the soil. Depending on the conditions, the increasing salt concentration will either lead to precipitation once the solubility limit is reached or due to the increase in the liquid density a gravitationally unstable situation is given, where instabilities in the form of fingers will develop. Hence, salt can be transported downwards. The development of these instabilities and the potential salt precipitation have been analyzed using numerical simulations on the REV-scale. The simulations were performed by using the numerical simulator DuMuX.  

We analyzed the relevant processes to identify the influence of different parameters like soil-hydraulic properties, evaporation rate, or salt properties on precipitation. In Bringedal et. al., 2022, the appearance of instabilities during evaporation from a one-phase system was investigated using a linear stability analysis and numerical simulations on the REV-scale. The linear stability set criteria for the onset of instabilities for a large range of parameters, whereas the numerical simulations provide information about the development of the instabilities after onset. By combining both methods, we can predict the occurrence of instabilities and their effect on the salt concentration near the top boundary. This analysis has been extended to two-phase systems to analyze the impact of phase saturation on the development of salt instabilities. 

In future work,  we plan to improve the REV-scale models with the help of the pore-network model. This will be done by identifying relevant parameters for salinization processes on the pore scale and using suitable upscaling methods for the use on the REV-scale.

How to cite: Kiemle, S., Schollenberger, T., Heck, K., Helmig, R., Bringedal, C., and van Duijn, H.: Preventing Salt Precipitation in Soils through Density-Driven Salt Instabilities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20962, https://doi.org/10.5194/egusphere-egu24-20962, 2024.

A.79
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EGU24-21133
Jiri Simunek, Efstathios Diamantopoulos, and Tobias K. D. Weber

The modular framework for modelling unsaturated soil hydraulic properties over the full moisture range of Weber et al. (2019) and Streck and Weber (2020) was implemented in the Hydrus Suite. Users can now additionally choose between four different variants of the Brunswick model: i) van Genuchten-Mualem (van Genuchten, 1980; Mualem, 1976), ii) Brooks-Corey (Brooks and Corey, 1964), iii) Kosugi (Kosugi, 1996), and iv) modified van Genuchten (Vogel and Cislerova, 1988). For demonstration purposes, simulation results of bare soil evaporation and root water uptake with Hydrus are presented, along with a comparison of the original van Genuchten-Mualem model and its Brunswick variant. Results show that the original van Genuchten-Mualem model underestimates the simulated cumulative evaporation and cumulative transpiration due to the inconsistent representation of the soil hydraulic properties in the dry moisture range. We also implemented a two-step hydro-ptf into the Hydrus Suite that converts the parameters of the original van Genuchten-Mualem model to the Brunswick variant (Weber et al., 2020). In that way, physically comprehensive simulations are ensured in case no data on soil hydraulic properties are directly available, but information on physical soil properties (e.q., texture, bulk density) exists.

How to cite: Simunek, J., Diamantopoulos, E., and K. D. Weber, T.: Implementation of the Brunswick model system into the Hydrus software suite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21133, https://doi.org/10.5194/egusphere-egu24-21133, 2024.

A.80
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EGU24-21207
Giuseppe Brunetti, Radka Kodešová, Miroslav Fér, Antonín Nikodem, Aleš Klement, and Jiří Šimůnek

The combined effect of anthropogenic and climatic stressors deeply influences the hydrological behavior of agricultural areas, especially on hillslopes. Tillage induces an abrupt change in the soil's hydraulic functioning, which can be dynamically recovered in time due to natural consolidation, alternation of wetting and drying cycles, and other biophysical factors. Heavy rainfall can accelerate the recovery process, but also induce erosion events in tilled soils, further exacerbating the spatial variability of the topsoil hydraulic properties. To better understand the mechanisms driving the spatio-temporal variability of soil hydraulic properties in agricultural areas, we combine the modified hydrological model HYDRUS with transient soil moisture observations from two hillslopes in the Czech Republic exposed to tillage and erosion. In particular, the Bayesian inference is used to calibrate two alternative HYDRUS implementations at five different locations along the hillslopes. The first model assumes static soil hydraulic properties, while the second simulates their dynamic change induced by tillage and natural consolidation (due to rainfall). The Watanabe-Akaike Information Criterion (WAIC) is used to compare the two models by considering not only the fitting accuracy, but also the predictive uncertainty. The results show that both models can reproduce soil moisture observations satisfactorily at different depths and locations. While the dynamic model exhibits slightly better fitting, this is compensated by larger predictive uncertainty compared to the static model. This is confirmed by the WAIC values, which are similar for the two models. An in-depth analysis indicates that the dynamic recovery of soil hydraulic properties happens during the first few rainfall events (confirming what was observed in other studies) and suggests that higher resolution measurements are needed to better estimate recovery factors. Finally, the spatial variability of the estimated soil hydraulic parameters hints at a possible role of overland flow fluxes along the hillslope as a heterogeneity-generating factor. 

How to cite: Brunetti, G., Kodešová, R., Fér, M., Nikodem, A., Klement, A., and Šimůnek, J.:  Dissecting the spatio-temporal variability of soil hydraulic properties in an agricultural eroded area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21207, https://doi.org/10.5194/egusphere-egu24-21207, 2024.

Posters virtual: Thu, 18 Apr, 14:00–15:45 | vHall A

Display time: Thu, 18 Apr 08:30–Thu, 18 Apr 18:00
Chairpersons: Tomas Aquino, Christopher Vincent Henri
vA.24
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EGU24-19360
Takashi Fujii, Masashige Shiga, Yasuki Oikawa, and Xinglin Lei

In the course of CO2 injection into a storage reservoir, understanding of a volumetric change (e.g., swelling), induced by interacting among CO2, water and rock into pores of rocks should be a critical step for modeling of hydro-mechanical response relevant to CO2 capture and storage (CCS) technology. For the majority of ongoing and planning CCS sites in the globe, hard sedimentary rocks, which is main component of quartz and feldspars with less clay minerals (e.g., smectite, illite), is a representative reservoir rock. It is well-known that caprocks (i.e., mudstone and shale) occur the swelling behavior of a rock matrix in the presence of water and/or CO2 due to intercalation and exchange reactions between layers of clay minerals. However, such volumetric change effect for quartz-rich rocks is not yet being investigated enough. In this study, we investigate geomechanical behavior of quartz-rich sandstone (Berea sandstone) in supercritical CO2 (scCO2)-water system under effective pressure of 10 MPa for up to approximately 1 week, the condition of which assumes that CO2 is injected into a storage reservoir at 1 km depth. Our results demonstrated that quartz-rich sandstone had a significant potential for changes in geomechanical properties (i.e., axial stress, displacement, volumetric strain) in scCO2-water system, like that do clay-rich caprocks, although little the change being observed for only water-saturation under the same effective stresses, and its maximum value was approximately 0.3 % for scCO2/water system. Also, increasing axial stress induced by the change in volumetric strain of the rock sample tested were more than 1 MPa for all experimental runs. A comparison results suggested that the obtained volumetric strains for this system could not be explained fully by change in bulk modulus before and after introducing scCO2 into the rock sample. The findings of our study might provide a significant contribution for the coupled hydro-mechanical behavior in storing CO2 into hard sedimentary rocks.

How to cite: Fujii, T., Shiga, M., Oikawa, Y., and Lei, X.: Effect of supercritical CO2/water interactions on geomechanical behavior of quartz-rich sandstone for CO2 geological storage, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19360, https://doi.org/10.5194/egusphere-egu24-19360, 2024.