HS8.1.5 | Flow, reactive transport and dissolution/precipitation in heterogeneous porous media and fractured rocks: experiments, modeling, field observations and challenges in applications.
Flow, reactive transport and dissolution/precipitation in heterogeneous porous media and fractured rocks: experiments, modeling, field observations and challenges in applications.
Co-sponsored by IAHS
Convener: Alraune Zech | Co-conveners: Piotr Szymczak, Antonio Zarlenga, Linda Luquot, Felipe de Barros, Maria Garcia-Rios
Orals
| Tue, 25 Apr, 08:30–12:30 (CEST)
 
Room 2.31
Posters on site
| Attendance Tue, 25 Apr, 14:00–15:45 (CEST)
 
Hall A
Posters virtual
| Attendance Tue, 25 Apr, 14:00–15:45 (CEST)
 
vHall HS
Orals |
Tue, 08:30
Tue, 14:00
Tue, 14:00
This session combines presentations on recent developments in understanding, measuring, and modeling subsurface flow and transport and reaction. We aim to include processes in the saturated and unsaturated zones, in porous media and fractured rock as well as at different scales.

The correct quantification of transport processes, which occur at different spatial and temporal scales, is challenging. It strongly influences predicted spreading, dilution and mixing rates. However, dispersion, mixing and chemical reactions are local phenomena that strongly depend on the interplay between large-scale system heterogeneity and smaller-scale processes.

Dissolution, precipitation and chemical reactions between infiltrating fluid and rock matrix alter the composition and structure of the rock, either creating or destroying flow paths. Nonlinear couplings between the chemical reactions at mineral surfaces and fluid motion in the pores form intricate patterns: networks of caves and sinkholes in karst area, wormholes or porous channels created during the ascent of magma through peridotite rocks. Dissolution and precipitation processes are also relevant in many industrial applications such as CO2 sequestration, heat extraction from thermal reservoirs, or weathering of building materials. Modern experimental techniques and computational power allow studying these processes by direct visualization as well as simulation at the microscale.

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

Orals: Tue, 25 Apr | Room 2.31

Chairpersons: Antonio Zarlenga, Felipe de Barros
08:30–08:35
Reactive transport and mixing from pore to regional scale
08:35–08:45
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EGU23-4072
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Virtual presentation
Peyman Mostaghimi, Ying da Wang, Traiwit Chung, and Ryan Armstrong

Micro-CT imaging and pore-scale modelling have developed rapidly over the last decade by bridging the disciplines of geology, reservoir engineering, image processing, and computational fluid dynamics. They have provided new pathways for understating complex transport phenomena in heterogeneous geological formations. However, direct simulation of flow in these complex three-dimensional geometries can be difficult and time-consuming. Machine learning and Convolutional Neural Networks (CNN), as a part of the broader field of Artificial Intelligence (AI), can be integrated into the framework of pore-scale modelling. We propose a neural network architecture that considers features of the rock geometry as well as the conservation of mass and predicts the velocity distribution on the images. The method can be applied to two or three-dimensional rock images. The reliability of the flow prediction is studied by comparing the predicted permeability versus ground truth values as a bulk measure. Then, we study the accuracy of solute transport modelling. The results show that velocity fields obtained by CNN can have a considerable degree of error and are not suitable for accurate transport simulations. Finally, challenges and opportunities for the development of machine-learning approaches in porous media applications will be discussed.

How to cite: Mostaghimi, P., Wang, Y. D., Chung, T., and Armstrong, R.: Application of machine learning in predicting flow and transport in porous media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4072, https://doi.org/10.5194/egusphere-egu23-4072, 2023.

08:45–08:55
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EGU23-11598
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ECS
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On-site presentation
Kevin Pierce, Gaute Linga, and Marcel Moura

Solute mixing is efficient in a steady three dimensional porous media flow, since filaments of solute elongate exponentially fast in time. This "chaotic" elongation enables molecular diffusion to rapidly distribute solute concentrations. In two dimensional steady flows, such as through thin fractures in rock, existing knowledge indicates that filaments of solute elongate much more slowly than exponentially, meaning the mixing is far less efficient. Here, we present experimental evidence that when porous media flows are instead unsteady, two dimensional mixing becomes chaotic.  Using 3D printed model porous media with steady longitudinal and oscillating transverse flow components, we measure Lyapunov exponents of filament elongation and quantify solute stretching and folding statistics as a function of the frequency and amplitude of the transverse flow. We find resonances in mixing frequency which are consistent with numerical simulations of the model geometry. These findings improve our understanding of mixing in geological systems and provide insights which may be useful to design efficient geologically-inspired mixing devices in the future.

How to cite: Pierce, K., Linga, G., and Moura, M.: Chaos in flatland: mixing in unsteady two dimensional porous media flow, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11598, https://doi.org/10.5194/egusphere-egu23-11598, 2023.

08:55–09:05
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EGU23-6771
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ECS
|
On-site presentation
Aronne Dell Oca and Marco Dentz
Solute mixing in porous media plays a fundamental role in a variety of applications, e.g., environmental risk assessment, geochemical reactive transport. Mixing dynamics are strongly impacted by the medium heterogeneity, which leads to inhomogeneity of solute concentration within the spreading and the mixing volume. Considering Darcy scale heterogeneous formations, we develop a randomly dispersive lamellae approach in which the variability in the dispersion rates of the lamellae that constitute a solute plume is recognized as a fundamental aspect of the mixing dynamics. The framework allows representing the inhomogeneity of the concentration distribution within the mixing volume before the late time well-mixed condition is reached. Furthermore, in light of the hidden (data scarcity) and heterogeneous nature of environmental porous formations, the degree of mixing of a solute plume is uncertain. The proposed randomly dispersive lamellae framework represents a strategy to quantify the latter. We test our approach for mildly to highly heterogeneous formations.

How to cite: Dell Oca, A. and Dentz, M.: Mechanisms of Solute Mixing in Darcy’s scale Heterogeneous Formations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6771, https://doi.org/10.5194/egusphere-egu23-6771, 2023.

09:05–09:15
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EGU23-10148
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ECS
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On-site presentation
Satoshi Tajima, Tomochika Tokunaga, Jiaqi Liu, and Marco Dentz

The advection-dispersion equation has been a key tool for modelling Darcy-scale solute transport. In the equation, local-scale mixing is expressed by the local dispersion coefficient, which considers mixing by molecular diffusion and pore-scale variability in flow velocity [1]. Mixing is enhanced by velocity variability on the Darcy scale, represented by spatial heterogeneity in hydraulic conductivity (K) [1].

     Observations show that the dispersion coefficient increases with the spatial scale [e.g., 2]. This effect is expressed by the macrodispersion coefficient increasing proportionally to the correlation length of heterogeneity in K [2]. Conventional upscaled advection-dispersion models assume constant macrodispersion coefficients [2], yet they typically overestimate the dispersive effect and can cause problems such as “back dispersion”, an unrealistic spreading of the solute in the direction opposite to the flow when groundwater flows towards a high concentration zone [3]. Explicitly representing local scale medium heterogeneity mitigates the overestimation of dispersion, however, this downscaled approach (hereinafter called the “local dispersion model”) requires the full representation of heterogeneity in K with a high spatial resolution. This comes at a high computational cost in numerical simulation whereas the detailed representation of the full K variability on the field scale is typically not feasible.

     Dentz et al. [4] showed that the effective dispersion coefficient (D) evolves temporally and asymptotically reaches a macrodispersion coefficient. They derived explicit analytical expressions for an idealized setting with an isotropic velocity spectrum in a steady state and constant local dispersion. From this finding, we hypothesise that accounting for the temporal evolution in D can mitigate the overestimation of dispersive processes in the macrodispersion model. Prospecting further applications to complex settings, this study aims to find an empirical formulation of the time-evolving dispersion (TED) coefficient. In this model, D is set to be identical to the molecular diffusion coefficient at the initial stage, and then it increases exponentially over time and asymptotically reaches a value identical to the macrodispersion coefficient after sufficient time has elapsed. We implemented the TED model by modifying the MODFLOW [5] source code and compared the simulation results with those from the macrodispersion and local dispersion models.

     The results from the TED model showed concentration distributions similar to the local dispersion model and less dispersive than those from the macrodispersion model, especially at early times in the simulations. The temporal evolution of D assumed in the TED model well matched that calculated from the spatial variance of the concentration distributions obtained by the local dispersion model. Therefore, the TED model can be an alternative to the conventional models for modelling Darcy-scale solute transport.

 

References

[1] Dentz, M., Hidalgo, J. J., & Lester, D. (2022). Transport in Porous Media.

[2] Gelhar, L. W. & Axness, C. L. (1983). Water Resources Research, 19(1), 161–180.

[3] Konikow, L. F. (2011). Ground Water, 49(2), 144-159.

[4] Dentz, M, Kinzelbach, H., Attinger, S., & Kinzelbach, W. (2000). Water Resources Research, 36(12), 3591–3604.

[5] Langevin, C., Hughes, J., Banta, E., Provost, A., Niswonger, R., & Panday, S. (2017). MODFLOW 6.

How to cite: Tajima, S., Tokunaga, T., Liu, J., and Dentz, M.: Time-evolving dispersion (TED) model: towards a more realistic representation of Darcy-scale mixing in porous media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10148, https://doi.org/10.5194/egusphere-egu23-10148, 2023.

09:15–09:25
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EGU23-16362
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On-site presentation
Maria Klepikova, Victor Bense, Olivier Bour, Nicolas Guiheneuf, and Tanguy le Borgne

Being the world’s largest freshwater resource, groundwater is at a continuous risk of overabstraction for human water use. Beside substantial drops in groundwater levels that are the consequence of unsustainable groundwater abstraction, which modify the recharge/discharge relationships between large-scale hydrogeological units, this anthropogenic hydraulic forcing is also responsible for changes in thermal regimes within the critical zone. While the impact of global groundwater pumping on the hydrogeological cycle has long been demonstrated, we still have insufficient knowledge on the influence of human activities on groundwater temperatures and, as a consequence, on stream thermal regimes and groundwater quality.

In this contribution we discuss temperature anomalies that develop in the shallow subsurface as a result of localized groundwater extraction. We study different hydrogeological settings, i.e., porous and fractured aquifers, that we explore via numerical modelling and comparison with field observations. In the field, we use repeated temperature-depth borehole profiles separated by decades, the advantage of which is that differencing the temperature logs for individual boreholes yields real temperature change and eliminates steady-state sources of curvature. Thus, it enables us to detect changes in subsurface thermal regimes, resulting from transient conditions, i.e., climate change and changes in groundwater hydrodynamics.

How to cite: Klepikova, M., Bense, V., Bour, O., Guiheneuf, N., and le Borgne, T.: Impact of groundwater abstraction on subsurface thermal regimes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16362, https://doi.org/10.5194/egusphere-egu23-16362, 2023.

09:25–09:35
|
EGU23-111
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On-site presentation
Charles Werth, Timothy Blount, Kade Kearney, Danielle Tran, and Charles Schaefer

Back diffusion of chlorinated solvents from low permeability media remains a challenge to remediation of contaminated groundwater in heterogeneous subsurface environments. Naturally occurring abiotic dechlorination of trichloroethene (TCE) has shown potential as a viable natural attenuation mechanism, particularly at sites where in-situ remediation technologies have generated reducing conditions favorable for the generation of reduced iron minerals. These abiotic processes may occur under anaerobic conditions or aerobic conditions when oxygen is introduced to reduced sediments. Quantification of aerobic/anaerobic abiotic dechlorination rate constants to date has generally been performed using bench-scale batch experiments with low solids to water ratios and well-mixed conditions, confounding extension of the results to the field where mass transfer limitations dominate.  To address this knowledge gap, bench-scale experiments were conducted to evaluate diffusive transport of TCE and coupled aerobic/anaerobic abiotic dechlorination. The natural clays used in this study were collected from several chlorinated solvent impacted sites and characterized for geochemical parameters including ferrous iron content, electron shuttle mediated oxidation-reduction potential (ORP), and mineralogy via X-ray diffraction (XRD). Clays were packed into gas-tight serum bottles under anaerobic conditions to a saturated bed depth of 4 centimeters, and TCE was injected at the top of the clay beds. For the aerobic experiments, a slug of oxygenated water was introduced at the top of the clay immediately prior to spiking with TCE. Headspace and aqueous samples were periodically collected and monitored for reduced gases and organic acids associated with abiotic transformation of TCE in the presence of ferrous minerals. 14C-radiolabeled TCE was used for select experiments to facilitate detection of dechlorination products at low concentrations indicative of conditions near a dilute solvent plume.   Accumulation of expected TCE dechlorination products under aerobic (organic acids) and anaerobic (primarily acetylene) conditions was observed in the diffusion experiments. Detection of 14C dechlorination products served to clearly distinguish compounds originating from TCE. A one-dimensional coupled reaction and diffusion model was developed to describe diffusive transport of TCE and dechlorination products into and out of the clay bed. First order abiotic dechlorination rate constants were determined by fitting profiles of reduced gas and organic acid generation over time, using literature values for molecular diffusion coefficients and clay tortuosity. Following conclusion of the experiments, depth-discrete ORP measurements of the packed clay beds from the aerobic diffusion experiments will be conducted, providing further insight into the effect of oxidative TCE transformation on local geochemistry near the groundwater table and the relative contribution of aerobic abiotic degradation. The results of this study elucidate the capacity for abiotic natural attenuation to reduce TCE mass flux out of clays in dilute plumes under a variety of geochemical conditions.

How to cite: Werth, C., Blount, T., Kearney, K., Tran, D., and Schaefer, C.: Impact of Abiotic Attenuation Reactions on Chlorinated Solvent Fate in Diffusion-Limited Clay Lenses, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-111, https://doi.org/10.5194/egusphere-egu23-111, 2023.

09:35–09:45
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EGU23-640
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ECS
|
Virtual presentation
Kumar Rishabh Gupta and Pramod Kumar Sharma

The movement of solute or chemical species into the subsurface has been a concern of groundwater quality variation due to its hazardous and severe health-related effects. To understand and reliably predict the migration and fate of contaminants in the subsurface, modeling is necessary. In this study, the experiment is carried out to investigate the contaminant migration through porous media, particularly the solutes emerging through the pesticides. A soil column experiment is setup to trace the particles and their behavior is analyzed, which is validated using the numerical model. This model uses the advection-dispersion equation (ADE), taking the application of effective dispersivity in order to account for the local heterogeneity. The implicit finite difference technique has been incorporated into the numerical model. The implication of macrodispersivity provides a plentiful assay in delineating the transport process and a perspective for large-scale heterogeneities. Results exhibit the concentration profiles of pesticides in the function of depth and time that can be employed to identify the areas with higher contaminant loading in the groundwater, posing a severe threat to groundwater and human health. This necessitates the experimental and numerical model to predict the contaminant migration process and to lay down changes in policy-making, monitoring of harmful chemicals, adoption of good agricultural practices, and execution of water safety regulations which, in turn, can be incorporated in determining the emerging contaminants, PFASs, etc.,  in the groundwater.

How to cite: Gupta, K. R. and Sharma, P. K.: Unraveling the leaching of pesticide transport through porous media with an experimental and numerical study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-640, https://doi.org/10.5194/egusphere-egu23-640, 2023.

09:45–09:55
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EGU23-17347
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On-site presentation
Soonyoung Yu, Han-Suk Kim, Jehyun Shin, and Seong-Taek Yun

A combined analysis was conducted to understand nitrogen loading to a deep (~ 80 m below ground level (bgl)) bedrock aquifer, including hydrochemical, isotopic, microbiological, hydrogeological, and geophysical investigation. The studied site, located in a suburban area, had been used to grow fodder crops for cattle and fertilized with cattle manure. The geology consists of Gyeonggi gneiss complex, fine-grained granite, and alluvium, while the surface is covered by loess deposits. Four boreholes (BH-1~4) were installed in 2018-2019, and geological, hydrogeological and geophysical surveys were conducted. Then hydrochemical, isotopic and microbiological properties were quarterly studied for 4 years at both shallow (~ 30 m bgl) and deep (~ 80m bgl) groundwater in each borehole as well as a pre-existing well. Groundwater levels were automatically monitored using levelogger. The initial depth to groundwater was 20.4 – 24 m bgl. As a result, high concentrations of nitrate were consistently observed in deep groundwater (35.3±16.0 mg/L; n=59) as well as shallow groundwater (50.9±16.8 mg/L; n=60) and a pre-existing well (44.3±6.8 mg/L; n=16). Based on N isotopes of nitrate (8.9-19.0‰; n=27), nitrogen mainly came from manure or sewer. The enrichment of 15N along with decreasing dissolved oxygen and nitrate in deep groundwater indicated denitrification in deep subsurface. Meanwhile ammonium and nitrite were exceptionally high in two deep groundwaters (BH-1d; BH-4d) where fecal coliforms were also occasionally detected. δ15N of ammonium were 9.2 and 14.0‰ in BH-1d and BH-4d, respectively. The hydrochemical, isotopic and microbiological results indicate that the vertical transport of contaminants from surface to deep groundwater is significant in the study area, probably through permeable fractures, given that the integrated interpretation of seismic data and electricity resistivity with geological data suggested fractures in deep weathered soil zones (down to 48 m bgl) and soft rocks. In addition, the borehole logging identified permeable fractures in hard rocks at high dips particularly in BH-1 and BH-4 in the west (up to 72. 9 degree). The natural gamma ray and P-wave velocity were higher in the west, indicating the different geology from the east (BH-2 and BH-3). Besides, the groundwater levels were fluctuated at BH-1d and BH-4d, due to groundwater extraction nearby. This combined examination of hydrochemical, isotopic, microbiological, hydrological, and geophysical characteristics suggests a scenario of contaminant transport from surface to deep subsurface through permeable fractures, which is enhanced by groundwater pumping. The integrated analysis is expected to be useful for subsurface characterization in crystalline bedrocks. <Acknowledgement> This study was supported by the basic research project of Korea Institute of Geoscience and Mineral resources (KIGAM) funded by the Ministry of Science and ICT of Korea (No. 23–3411) and by the Korea Environment Industry & Technology Institute (KEITI) through the Subsurface Environment Management Research Project (No. 2021002440003).

How to cite: Yu, S., Kim, H.-S., Shin, J., and Yun, S.-T.: A combined analysis of hydrochemical, isotopic, microbiological and geophysical characteristics for assessment of nitrogen loading to a deep crystalline bedrock aquifer, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17347, https://doi.org/10.5194/egusphere-egu23-17347, 2023.

09:55–10:05
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EGU23-8503
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ECS
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Virtual presentation
Backward particle tracking analysis for probabilistic contaminant source assessment
(withdrawn)
Paolo Tufoni, Luís Costa, Vânia S. Sousa, José Paulo Monteiro, and Luís M. Nunes
10:05–10:15
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EGU23-1013
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ECS
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On-site presentation
Irene Pomarico, Aldo Fiori, Antonio Zarlenga, Vittorio Catani, and Guido Leone

The aim of the present work is to extend the existing overlay and index method for aquifer vulnerability assessment to groundwater transport. This novel procedure falls into the category of “hybrid” methods since it combines the overlay and index methods, that considers only vertical transport through the vadose zone, with the horizontal transport through groundwater. Based on a simple probabilistic analysis, we can use any overlay and index method for the assessment of the probability that the contaminant reaches the groundwater then such probability is propagated within the aquifer using the piezometric surface as proxy of the groundwater flow. For this purpose, geomorphological methods, usually available in Geographic Information Systems (GIS) software, were used. This study leads to the definition of a new index called combined vulnerability index υ which considers the transport of the contaminant from soil surface that takes care of both transport in the vadose zone and the aquifer. The procedure is applied to a groundwater catchment area in the Campania region (Southern Italy) with the use of QGIS software. The method is independent from the index and overlay method used and the hydraulic characteristics of the aquifer. Furthermore, this procedure is simple as it requires a few data and it can be used to analyze large areas, demonstrating its effectiveness in assessing the intrinsic vulnerability of groundwater.

How to cite: Pomarico, I., Fiori, A., Zarlenga, A., Catani, V., and Leone, G.: The combined vulnerability: a novel hybrid index for the aquifer vulnerability assessment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1013, https://doi.org/10.5194/egusphere-egu23-1013, 2023.

Coffee break
Chairpersons: Piotr Szymczak, Linda Luquot
10:45–10:50
10:50–11:10
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EGU23-17468
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solicited
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On-site presentation
Delphine Roubinet

Simulating hydrodynamic reactive transport processes in heterogeneous systems is required
in various research fields and applications including environmental remediation, geological
storage, and energy production. Developing reliable numerical tools for these environmental
issues requires to consider both the structural heterogeneities encountered in the natural
environment, and the complexity of the (bio)geochemical reactions associated with each
application. The former is very often modeled at the expense of the latter, in particular when
studying large-scale heterogeneous systems such as fractured rocks for which most of the
modeling effort focuses on the multi-scale structural heterogeneities. These features are
responsible for anomalous transport behavior that is well reproduced by particle-based (PB)
methods with optimized computational cost. After introducing PB methods that are usually
used for modeling reactive transport in fractured rocks, I will present a new random walk
approach that is designed for complex (bio)geochemical reactions and upscaling purpose.

How to cite: Roubinet, D.: Reactive transport models in heterogeneous systems from pore to reservoir scale, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17468, https://doi.org/10.5194/egusphere-egu23-17468, 2023.

11:10–11:20
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EGU23-14696
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ECS
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On-site presentation
Radoslav Hurtiš, Peter Guba, and Juraj Kyselica

Convection and chemical dissolution in porous media are observed in many hydrogeological processes such as seawater intrusion in coastal aquifers, CO2 sequestration in saline aquifers and heat transport in geothermal reservoirs. When a porous medium is infiltrated by a fluid contaminated with a reactive solute, convection is accompanied by dissolution of the porous matrix through chemical reactions between the solute and minerals contained in the porous solid, generating reaction products. Here we study how density-driven convection and reactive infiltration affect the transport of the solute and products in the porous medium. Convection and dissolution are modelled by coupled equations describing flow, transport of the solute and products, and mineral dissolution in a two-dimensional rectangular domain with a solute source located along half of the upper boundary. We quantify the average solute flux from the source in unsteady flows and analyze its development towards a steady-state value computed in [1]. Numerical experiments on the temporal development of convective flow and concentration fields are reported (see [2] for more details). The full numerical solutions are augmented with asymptotic analysis in a weakly convective and reactive regime performed in the limit of small Rayleigh and Damköhler numbers.

Acknowledgement:

This work was supported by the Slovak Research and Development Agency under the contract no. APVV-18-0308, and the VEGA project no. 1/0339/21 and the GUK project no. UK/355/2023.

References:

[1] van Reeuwijk, M., Mathias, S. A., Simmons, C. T., and Ward, J. D.: Insights from a pseudospectral approach to the Elder problem, Water Resources Research, 45, W04416, https://doi.org/10.1029/2008WR007421, 2009.

[2] Hurtiš, R., Guba, P., and Kyselica, J.: Simulation of reactive groundwater flow and salinization in carbonate-rock aquifers, 2022 International Conference on Electrical, Computer and Energy Technologies (ICECET), Prague, Czech Republic, 20–22 July 2022, pp. 1–4, https://doi.org/10.1109/ICECET55527.2022.9872944, 2022.

How to cite: Hurtiš, R., Guba, P., and Kyselica, J.: Density-driven convection and chemical infiltration in saturated porous media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14696, https://doi.org/10.5194/egusphere-egu23-14696, 2023.

11:20–11:30
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EGU23-17007
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ECS
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On-site presentation
Yanni Chen, François Guillard, and Itai Einav

Geomaterials are multi-phase materials composed of solid skeletons and pore fluids. Along the solid-fluid interfaces, chemical dissolutions might occur which tends to weaken the strength of geomaterials and can potentially cause catastrophic failures. As the ionic species in the pore fluid evolve during dissolution, we introduce the mass fractions of all the ionic species as independent state variables into the hydrodynamic procedure and develop a mathematically rigorous and thermodynamically consistent modeling framework to address the impact of solid dissolutions on the constitutive properties of poroelastic geomaterials. The development is foundational in that it focuses only on saturated poroelastic systems without accounting for particle crushing, localized plasticity, and surface tensions. However, the theory can be further expanded to deal with such inelastic features under various saturation regimes. For simplicity, the density-dependent linear elasticity is adopted whereby the stiffness degrades as the solid skeleton dissolves and pore fluid pressure is governed by both osmolarity and compressibility. The developed model can naturally recover fluid-related dynamics of Darcy's law, Fick's law, and the law of chemical kinetics. Finally, experimental observations of debonding tests of calcarenite under both oedometric and unconfined conditions are used to validate the model performance.

How to cite: Chen, Y., Guillard, F., and Einav, I.: A hydrodynamic model for chemical dissolution of poroelastic materials, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17007, https://doi.org/10.5194/egusphere-egu23-17007, 2023.

11:30–11:40
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EGU23-9735
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ECS
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On-site presentation
Flore Rembert, Marie Leger, Damien Jougnot, and Linda Luquot

This study attempts to give some answers on how the electrical signal is impacted by conduit formation in limestone due to calcite dissolution, and how the electrical properties can be related to evolving structural parameters. Ensuring sustainable strategies to manage water resources in karst reservoirs requires a better understanding of the mechanisms responsible for dissolution features in the rock mass. The dissolution of carbonate core samples caused by CO2 or acid solution injection has already been well studied in the laboratory to understand the formation of conduits and their intricate coupling with transport properties such as permeability and porosity. However, these experiments generally rely on image analysis, an accurate technique that cannot be used in the field. Additionally, in a subsurface context, chemical analysis of the pore water can be quite intrusive, providing only restricted and spatially limited information. Thus, studying large-scale heterogeneities such as karst environments can benefit from the use of non-invasive tools such as the ones proposed in hydrogeophysics. In particular, geoelectrical methods are good candidates to detect the emergence of karstification related to the heterogeneous dissolution of large volumes since they present a high sensitivity to the physical and chemical properties of both porous matrix and interstitial fluids. We monitored the electrical conductivity, porosity, and permeability of two limestone core samples during controlled dissolution experiments driven by acid injection at atmospheric conditions under different flow rates creating preferential conduits. These two samples were also characterized before and after the acid percolation with laboratory methods and CT scan imaging. First, we confront the electrical conductivity variations to the evolution of permeability with time. We show that monitoring electrical properties allows us to sense the impact of dissolution in the porous medium long before the sample is percolated. This result is a key finding to highlight the great interest that electrical properties can represent in monitoring reactive percolation in karst systems. Then, we interpret the monitored electrical conductivity of the acid percolation with a physics-based model. This model describes the porous medium as a fractal cumulative distribution of tortuous capillaries with a sinusoidal variation of their radius. According to the model description, the sample electrical conductivity is interpreted in terms of effective structural parameters which are tortuosity and constrictivity. Confronting the model with the experimental results shows that the electrical signature of calcite dissolution is more impacted by the evolution of constrictivity than by tortuosity, while most of the literature focuses on the tortuosity and even neglects constrictivity when describing the pore space complexity with electrical conductivity measurements. Finally, based on our experimental results and data sets from the literature, we show that the characteristic Johnson length is a valuable structural witness of calcite dissolution impact linking electrical and hydrological properties. This small-scale approach to heterogeneous dissolution is an analog of the natural processes involved in forming conduits by dissolution leading to karstification. The results of this study are transferable to large-scale applications such as the survey of karst formation, CO2 geological storage, and geothermal energy recovery.

How to cite: Rembert, F., Leger, M., Jougnot, D., and Luquot, L.: Assessing karst formation at the laboratory scale by confronting geoelectrical and hydro-chemical monitoring, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9735, https://doi.org/10.5194/egusphere-egu23-9735, 2023.

11:40–11:50
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EGU23-6162
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On-site presentation
Guido Gonzalez-Subiabre, Daniel Fernàndez-Garcia, Michela Trabucchi, and Daniela Reales-Nuñez

Calcium carbonates precipitation plays an important role in several geological, biogeochemical and engineered processes. It has been extensively studied for its application in remediation of contaminated groundwater, enhancing oil and gas recovery, improving geological carbon storage, reducing leakage in tunnel buildings and also to understand dissolution processes in coastal karst aquifers. Most of these works are based on theoretical formulations,  numerical simulations or batch/column experiments and little experimental evidence under transport conditions are reported in the literature. In this work through mixing-induce precipitation experiments we propose the visualization and characterization of the dynamic of precipitation processes focused on the understanding of its influence in solute breakthrough. We performed the experiments in a transparent horizontal cell flow made of plexiglass with 26 x 20 x 1 cm dimensions. The tank was disposed horizontally and filled with glass beads of 2 millimeter. The flow-cell was initially saturated with double-deionized water. In the experimental investigation, two different chemical solutions containing 0,1 M CaCl2 and 0,1 M NaCO3 were injected in two separate inlet ports. Color tracer tests consisted on fluorescein were injected before and after the precipitation experiment with the objective of visualizing and quantifying the impact of precipitation in solute transport. We evaluated the effectiveness of the standard solute transport equation to represent precipitation processes and developed new mechanistic transport models.

How to cite: Gonzalez-Subiabre, G., Fernàndez-Garcia, D., Trabucchi, M., and Reales-Nuñez, D.: Precipitation of CaCO3 through induced mixing and its impact on solute breakthrough, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6162, https://doi.org/10.5194/egusphere-egu23-6162, 2023.

11:50–12:00
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EGU23-739
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ECS
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On-site presentation
Michał Dzikowski, Piotr Szymczak, and Rishabh Sharma

Advent of pre-exascale and exascale computers opens possibility for much higher resolution simulations of porous media flows. During the launch phase of the LUMI supercomputer, a number of simulations of wormhole growth commenced with an aim to use as much spatial information as possible with up to 1e9 DOFs. The goal was to investigate if properties of growing wormholes could be recovered if sufficient resolution is assured. Samples used in this study underwent experimental studies. They were scanned before and after the experiment, as well as during the dissolution. This 4D tomographic data provided necessary input for high-res simulations as well as validation framework.

Fig: Wormhole groth patter with branching and rapid direction change observed in evperiment

As the LUMI computer, as well as most of the newly built HPC machines, is based on GPUs we decided to use the Lattice Boltzmann code as main flow and transport solver. LBM has significant number-crunching performance thanks to its intrinsic parallelization properties which was paramount for this study. Based on an open-source, highly parallel multi-GPU TCLB solver, we design the model capable of handling Darcy - scale simulations with the initial porosity fields constructed based on X-ray microtomography images. In particular, we analyze the reactive-infiltration instabilities, which lead to the  formation of dissolution fingers (wormholes), in which both the flow and reactant transport become spontaneously localized.

 

Since dissolution fingers dramatically increase permeability of the rock, wormholing is important both for industrial applications and in hydrogeological studies. The main problem in modeling of wormholing is a multi-scale character of this process, with flow and transport near a wormhole tip strongly coupled to the macroscopic geometry of the emerging structures. The ability to perform large scale parametric and sensitivity studies of wormholing constitutes thus an important addition to experimental studies, hence the need for a high throughput simulator. 

We test our numerical predictions against the data from time-lapse dissolution experiments in an aim of constructing a predictive model capable of recovering time evolution of 3D wormhole shape based on the initial X-ray tomography data. 

 

 

How to cite: Dzikowski, M., Szymczak, P., and Sharma, R.: Empowering pre-exascale computers for Darcy-Brinkman simulation of wormhole growth based on X-CT data - can we recover experiments?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-739, https://doi.org/10.5194/egusphere-egu23-739, 2023.

12:00–12:10
|
EGU23-10829
|
ECS
|
On-site presentation
|
Nimo Kwarkye, Elisabeth Lehmann, Ivo Nischang, Jürgen Vitz, Ulrich Schubert, Thomas Ritschel, and Kai Totsche

Soil releases a significant proportion of organic colloids such as humic substances, proteins, and polysaccharides that are mobile and reactive within subsurface fluids. The mobility of such colloids is governed by colloidal hydrodynamics and frequently features strong interactions at biogeochemical interfaces in porous media. Yet, the compositional and functional diversity of organic colloids makes it difficult to trace the mobility of specific colloidal fractions and identify the alteration of surfaces following local interactions. Additionally, conventional reactive tracers used to study solute transport in the subsurface usually fail to cover hydrodynamics of small-sized organic colloids. Hence, transport principles governing the mobility of organic colloids in the subsurface are not comprehensively explored. In this study, we applied tailor-made poly(ethylene glycol) (PEG) as a reactive tracer in column and batch experiments with naturally occurring calcium carbonate as the substrate. We demonstrate that PEG transport features strong interactions at carbonate biogeochemical interfaces as known for humic substances, proteins, and polysaccharides. Such interaction can be facilitated by electrostatic interactions between PEG and the surfaces of the carbonate substrate. With the tendency to alter mineral surfaces, scanning electron microscopy (SEM) images of substrates after transport experiments showed a characteristic modification of surface morphology. Besides sharing similar reactivity with organic colloids, PEG breakthrough was reconstructed using a continuum scale model with high accuracy. With PEG being available in similar hydrodynamic sizes as small-sized organic colloids, it can be a promising tracer to follow mobility of other organic colloids in the subsurface.

How to cite: Kwarkye, N., Lehmann, E., Nischang, I., Vitz, J., Schubert, U., Ritschel, T., and Totsche, K.: The mobility and interaction of colloidal-sized poly(ethylene glycol) in column experiments with carbonate rock, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10829, https://doi.org/10.5194/egusphere-egu23-10829, 2023.

12:10–12:20
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EGU23-6329
|
ECS
|
On-site presentation
Annette Dietmaier and Thomas Baumann

The Northern Alpine Foreland Basin (NAFB) in southwest Germany is home to more deep geothermal plants than any other region in the country. The upper Jurassic, its main aquifer, consists of permeable carbonates which bear waters with temperatures of up to 150 °C on the southern border, and total dissolved salts values of up to 2 g/L. Geothermal applications in the NAFB include medical spas, geothermal district heating and power generation.

In the case of heating and power generation, cooled-off waters are reinjected underground where rock-fluid interactions can lead to changes in the rock matrix and flow pathways. These interactions are thus an important factor to consider in the maintenance of geothermal plants. In carbonate systems, a decrease of temperature after heat extraction leads to an undersaturation of the previously equilibrated waters with regard to the host formation. The injected water dissolves the rock matrix along the borehole and the flow paths into the reservoir. This can increase the risk of a thermal breakthrough between injection and production well and possibly affect the borehole integrity. While the overall amount of dissolution has been monitored and modelled previously, the microscopic changes to the flow paths are still under investigation.

We used rock samples coated with a 2-component paint and produced one microfracture in the coating to overcome experimental restrictions due to a limited fluid volume of the autoclave. The experiments were run at typical injection temperatures between 40°C and 75°C. The CO2 partial pressure wasadjusted to the measured values in the injection borehole. Microscopic and Raman images were taken before and after the exposition of the rock to the undersaturated waters and complemented by hydrochemical analyses.

The dissolution of the limestones picked up microstructures and led to a heterogeneous development of the flow path. In an early stage of the injection, an underprediction of the increase of the hydraulic conductivity is thus expected.

These assessments allow insights into the kinetics taking place at the artificial disturbance, which will make it possible to characterize and quantify the 3-dimensional pattern of calcite dissolution at a localized scale which is important for the development of the hydraulic properties, and affects further dissolution.

How to cite: Dietmaier, A. and Baumann, T.: Local effects of the injection of undersaturated waters in geothermal applications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6329, https://doi.org/10.5194/egusphere-egu23-6329, 2023.

12:20–12:30
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EGU23-14256
|
Virtual presentation
Alba Zappone and Stefan Wiemer and the DemoUpStorage Team

Mineral carbonation (MC) has long been suggested as a potential way to permanently store CO2 captured from smaller/medium emitters, as alternative to conventional geological sequestration in depleted oil and gas fields. MC consist in CO2 reacting with calcium-, magnesium- and iron-rich minerals to form carbonates.  MC is a promising option in terms of available resources and security of permanent storage. Nevertheless, this technology, tested in laboratories and small projects, has not yet taken off on a large scale. In situ large scale projects can contribute in reducing the knowledge gaps on MC fundamentals and allowing cost analyses and optimization. Since almost a decade CO2 is injected in Icelandic basalts, providing a field scale laboratory for testing MC. 

The DemoUpStorage, together with its partner project DemoUpCARMA, is a pilot project by ETH Zurich (http://www.demoupcarma.ethz.ch), EAWAG, EPFL and University of Geneva that aims to demonstrate the implementation and scale—up of CO2 geological storage using MC. The project investigates the fate of CO2 transported from an emitter in Switzerland to Helguvik (Iceland), where it is then mixed with oceanic water and injected in basalts at a depth of c.a. 400m.  The monitoring involves a combination of technologies that independently but synchronously observe changes in underground. In particular time-lapse acquisitions of different physical parameters (electrical resistivity, seismic P- and S-wave velocity, attenuation factor Q) will be conducted in parallel with fluid geochemistry monitoring and dissolved gas sampling in boreholes. Repeated cross-hole Vertical Seismic Profiling (VSP) will be performed across an array of three boreholes, of which one is the injection and two are monitoring boreholes. Fiber optic technology will be used in parallel to conventional hydrophones. Additionally, a dense, regular grid of seismic sensors will be deployed at the surface during VSP acquisitions with the goal to provide a high-resolution 3D imaging of the subsurface at the reservoir scale. Downhole Electrical Resistivity Tomography logs in one of the two monitoring wells will be repeatedly performed to constrain the build-up of CO2-related resistivity signatures in conjunction with CO2 saturation levels monitored by regular fluid sampling. A portable mass spectrometer connected to a borehole will provide continuous gas analysis to determine the temporal evolution of the local fluid dynamics, to validate permanent storage and to monitor for potential leakage.  Risk mitigation actions comprise monitor the background seismicity before, during and after the whole injection operations. Laboratory observations on rock samples from the Helguvik area complete the set of observation and offer the possibility to model at small scale porosity changes due to MC.  Predictive numerical simulations at reservoir scale are performed and will be continuously updated with the acquisition of the data. The start of the injection is foreseen in Spring 2023. 

How to cite: Zappone, A. and Wiemer, S. and the DemoUpStorage Team: The DemoUpStorage Project: monitoring mineral carbonation in Icelandic basalts, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14256, https://doi.org/10.5194/egusphere-egu23-14256, 2023.

Posters on site: Tue, 25 Apr, 14:00–15:45 | Hall A

Chairperson: Maria Garcia-Rios
A.153
|
EGU23-1703
Sookyun Wang, Minhee Lee, and Seon-Ok Kim

Geological CO2 sequestration (GCS) is one of the most promising technologies for mitigating greenhouse-gas emission into the atmosphere. In GCS operations, residual trapping is the most favorable form of trapping mechanism because of its storage security and capacity. This novel storage option for CO2 involves injecting supercritical CO2 (scCO2) into porous formations saturated with pore fluid such as brine and initiate CO2 flooding with immiscible displacement. Despite of significant effects on macroscopic migration and distribution of injected CO2, however, only a limited information is available on the effects of immiscible two-phase flow on dynamic phenomena in microscopic scCO2-brine-glass pore systems. In this study, the effects of hydrodynamic characteristics of two immiscible fluids - carbon dioxide in supercritical phase and porewater - and their interfaces on their migration and distribution patterns in heterogeneous pore networks are investigated. For the purpose, a series of injection experiments were performed using 2D transparent micromodels. The immiscible two-phase flow with displacement and residual phenomena during drainage processes in heterogeneous pore networks were visually observed using a high-resolution microscope and a camera, and the temporal and spatial changes in distribution and saturation of the two immiscible fluids were quantitatively estimated at the pore-scale using image processing. To compare with experimental results and to analyze the phenomena quantitatively, a series of numerical simulations are also carried out. A 2D phase field model is established in the COMSOL Multiphysics platform and is applied to simulate the two-phase flow and immiscible displacement phenomena during drainage processes in pore networks with varying major model parameters such as injection mass flow rates, contact angles, viscosity ratios etc. The experimental observations are used to validate the accuracy of the numerical model. The results from experimental observations and numerical simulations are in good agreement in migration and distribution patterns and can provide important fundamental information on hydrodynamic characteristics of immiscible two-phase flow at pore-scale in porous networks for geological CO2 sequestration.

How to cite: Wang, S., Lee, M., and Kim, S.-O.: The effects of fluid characteristics in immiscible two-phase flow on migration and residual phenomena in heterogeneous pore networks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1703, https://doi.org/10.5194/egusphere-egu23-1703, 2023.

A.154
|
EGU23-15561
|
ECS
Araceli Martín Candilejo

Natural soils are home to an enormous variety of microorganisms. Microbial transport is important for a wide range of natural and artificial processes. However, the transport and distribution of bacteria in water flow at porous scale is still to be fully understood.

The Biofilm is a collective structure of microorganisms and it is covered by a protective layer secreted by the microorganisms themselves. The objective of this study is to identify and characterize the Elemental Biofilm Architectures that develop in a porous medium crossed by a laminar flow. This is a process that frequently occurs in nature, when there is water flow through the soil.

In the case of this study, different flow velocities and the percentage of nutrients (% LB Broth diluted in water) were tested, as well as oxygen control. A non-flagellated fluorescent mutant bacterium of P.Putida was used to analyze bacterial and biofilm growth through a homogeneous porous medium. Also, two different methodologies were carried out during the experiments: Methodology A and B. With methodology A the bacteria were initially grown in the porous media, and then and bacterial free flow was injected at a constant flow rate. In methodology B, the porous media was initially free of bacteria, and a bacterial solution was injected at a constant flow rate during the experiment.

In the experiments, the results show different architectural formations such as streamers, chains, ripples and fine lines. With both methodologies, bacteria develop similar biofilm architectures, such as streamers and ripples; but distributed differently throughout the porous media. The biggest difference relies on the deposit profile: in Methodology A most of the biomass accumulates towards the outlet of the porous media, while for Methodology B towards the inlet.

How to cite: Martín Candilejo, A.: Biofilm growth at pore scale in laminar flow, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15561, https://doi.org/10.5194/egusphere-egu23-15561, 2023.

A.155
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EGU23-5683
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ECS
Tomas Aquino, Tanguy Le Borgne, and Joris Heyman

Biogeochemical reactions at the interface between fluid and solid phases are of central importance to a broad range of natural and engineered processes in porous media. As dissolved reactants are transported through a porous medium, advection and diffusion act to homogenize their concentrations, in competition with reactive depletion at the solid interface. Transport limitations can limit reactant availability, leading to reduced reaction efficiency when compared to well-mixed conditions. Chaotic advection has been recently established to occur spontaneously in steady, three-dimensional flows through porous media. In this work, we explore and quantify its role in mitigating transport limitations and correspondingly increasing reaction efficiency. We employ the continuous time random walk framework to connect reaction delays due to transport limitations to the statistics of solute excursion times to the interface. Chaotic advection is associated with a rapid loss of memory of initial conditions and efficient exploration of the bulk of the pore space. We model the corresponding effect on excursion times through a stochastic restart process, such that reactant positions are randomly restarted homogeneously across the domain over a characteristic time scale that depends on flow and geometry. Processes that restart under some condition have received much attention in the context of search strategies, where it is known that they can increase the efficiency of the underlying process. Here, we find a corresponding effect on excursion times, and a consequent increase of reaction efficiency with Péclet number. As chaotic advection leads to efficient bulk exploration, low velocities near the interface due to no-slip boundary conditions become the limiting factor on mixing and thus control the restart rate. This has the surprising consequence that, while chaotic advection sets the stage for enhanced reaction efficiency, the increase is insensitive to the "strength" of chaos as quantified by the Lyapunov exponent, and is instead controlled by flow shear at the interface. The theoretical predictions are in excellent agreement with numerical simulations of reactive decay at solid surfaces in a crystalline porous medium, over a broad range of Péclet and Damköhler numbers.

How to cite: Aquino, T., Le Borgne, T., and Heyman, J.: Chaos, Mixing, and Restart - Fluid-solid reaction enhancement under pore-scale chaotic advection, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5683, https://doi.org/10.5194/egusphere-egu23-5683, 2023.

A.156
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EGU23-13254
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ECS
Christopher Vincent Henri and Efstathios Diamantopoulos

Soils are characterized by structural components on multiple spatial scales, originating from soil formation processes, soil-plant interactions, microbial activity and management operations. This leads to local heterogeneities for almost all measurements of physical, chemical and biological state variables. This includes the diffusion process, which is known to be affected by the tortuosity, and therefore the water content. Also, biochemical reactions in soils appear to be highly variable in space and time. Yet, the identification of the main controlling factors of the dynamic of reaction rates in unsaturated porous media remain partial.

Studying biochemical reaction in real-world soil-plant-atmosphere systems is highly challenging since the true underlying structures can never be absolutely known. For this, it is appealing to employ synthetic experiments. In this study, we consider a simple A+B à C reaction and investigate the potential impact of small-scale heterogeneity, infiltration fluxes and diffusion on apparent reaction rates in a series of synthetic soils geostatistically described by the Miller-Miller theory. Reactive transport is solved using the random-walk particle-tracking approach to properly account for dispersion and mixing conditions.

Results indicates a synergetic control of the intensity of soil heterogeneity, the Peclet number and the spatial variability of the (tortuosity-dependent) diffusion coefficient on mixing conditions, which has a great impact on effective reaction rates and on the formation of hot-spots and hot-moments. The initial location of the reactants appears to also condition the mixing state of the system and, therefore, the dynamic of reactions. We illustrate then 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: Vincent Henri, C. and Diamantopoulos, E.: On the control of small-scale heterogeneity and (spatially variable) diffusion on mixing-limited reactions in unsaturated soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13254, https://doi.org/10.5194/egusphere-egu23-13254, 2023.

A.157
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EGU23-416
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ECS
Snigdha Pandey and Pramod Kumar Sharma

Accurate prediction of flow and solute migration through the subsurface porous media is essential for the reclamation of the polluted aquifer and future contamination control. This study focuses on the dispersion process under non-Darcian flow conditions in the laboratory using a synthetic single fracture. A sand-packed single fracture of 1000 cm length and 0.3 cm fracture aperture was fabricated in the laboratory for conducting flow and contaminant transport experiments. Non-Darcian flow conditions prevailed in the filled-single fracture and were best simulated by the Forchheimer equation. Sodium Flouride (NaF) was used as a reactive contaminant in the experiments and was injected using Pulse-type boundary conditions. The resulting Breakthrough Curves (BTCs) were found to be non-Fickian with long tailings and early arrival. Solutions of the Convective-Dispersive equation (CDE) and Mobile Immobile (MIM) transport equations (for constant, linear, and exponential distance-dependent dispersion) were obtained through the Implicit finite difference technique. For different flow velocities, the MIM model was better at simulating the long tailings and early arrival of BTCs. Further, it is observed that constant (MIMC) and exponential distance-dependent (MIME) dispersion models are better at simulating observed BTCs compared to the linear-distance dependent (MIML) dispersion model. Through the statistical analysis and goodness of fit, the suitability of MIME and MIMC in describing contaminant transport through fracture was further confirmed.

Keywords:  non-Fickian; Filled-single fracture; non-Darcian; Breakthrough curves; Forchheimer equation; MIM model.

How to cite: Pandey, S. and Sharma, P. K.: Experimental and numerical simulation of the reactive contaminant migration for non-Darcian flow in a filled-single fracture, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-416, https://doi.org/10.5194/egusphere-egu23-416, 2023.

A.158
|
EGU23-2665
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ECS
Mohamad Omidi and Thomas Baumann

Scaling summarizes precipitation of solids on the surface of pipes, heat exchangers, and other equipment in various industrial processes, including geothermal systems. Scalings in carbonate systems, which make up one of the most important geothermal reservoirs, are caused by a disruption of the lime-carbonic acid-equilibrium. Increasing temperatures (e.g. at the motor of a pump) lead to oversaturation. Decreasing pressure itself also leads to oversaturation but also to the formation of gas bubbles and stripping of CO2. The latter causes a shift to higher pH-values and massive oversaturation and affects most facilities in the North-Alpine Foreland Basin. The omnipresent scalings reduce the efficiency and may cause significant downtimes. It is therefore important to predict the amount of scalings along the geothermal cycle.

While current hydrogeochemical models are capable to predict the risk and position of scalings, they are falling short with regard to the temporal development. They generally over-predict the amount of scalings which indicates that limiting processes, e.g. diffusion limited crystal growth, partial volume effects, and local equilibria have to be considered. This requires a combination of a fluid dynamics model and a hydrogeochemical model. Since the geothermal fluids are quite heterogeneous in their hydrochemical composition (from fresh water to brine) and both, equilibrium constants and kinetic rate constants, depend on the hydrochemical composition, coupling to an established hydrogeochemical model is favored to shorthand implementations of individual reactions.

Benchmark data for such improved models can be obtained from bubble columns. Here, a gas is injected at the bottom of a usually transparent pipe filled with a fluid of known chemical composition and the effects of stripping (or gas augmentation) can be monitored with high temporal and spatial resolution. The fluid flow is accessible through tracking of particles and gas bubbles. Bubble columns are also used in different industrial processes, providing additional applications for the developed model.

In this contribution we show the coupling of OpenFOAM, a very versatile computational fluid dynamics model, with PhreeqC, a widely used hydrogeochemical model, to simulate the effects of stripping on the formation of carbonate precipitates on the pipe walls and in dispersion. The model is compared to experimental data and a hybrid hydrogeochemical model which used an effective mass transfer rate for the gas-water exchange reaction as fitting parameter to cover the rate limiting processes.

How to cite: Omidi, M. and Baumann, T.: Numerical analysis of scaling formation in geothermal systems: application in bubble columns, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2665, https://doi.org/10.5194/egusphere-egu23-2665, 2023.

A.159
|
EGU23-7438
|
ECS
Rima Benhammadi, Juan José Hidalgo, and Marco Dentz

Convective mixing is present in a large assortment of natural and industrial processes, such as in carbon capture and sequestration, where it ensures a safer storage of carbon dioxide, seawater intrusion, high-level radioactive waste disposal sites and geothermal energy production. In this work, we study the effect of the heterogeneity on the behavior of convective mixing since most of the works that have been conducted so far did not take heterogeneity into consideration.

To do so, we consider the Horton-Rogers-Lapwood problem where convection is triggered by a Rayleigh-Bénard instability. Heterogeneity is represented by 2-D multi-Gaussian log-Normally distributed anisotropic permeability fields. We perform a parametric study in which we explore the effect of the variation of the Rayleigh number (Ra), the variance and the correlation length of the permeability field on the fingering patterns, mixing and dissolution fluxes. Mixing is characterized by the scalar dissipation rate and the boundary fluxes. The mixing state is evaluated through the probability density function (pdf) of the concentration and the intensity of segregation. We show the difference in behavior between the dissolution fluxes and the mixing state both for the case of homogeneous and heterogeneous porous media. We observe that convective mixing is enhanced in the case of heterogeneous porous media compared to the homogeneous counterparts.
An increase of Ra and of the variance of the permeability field causes a more rapid homogenization of the system and also a decrease in the interface width, the variance of the concentration pdf and the intensity of segregation. For permeability fields with a small correlation length, the effect of the heterogeneity is substantial only for a variance higher than 2. However, for a larger correlation length, this effect is more pronounced and the fingering patterns are no longer smooth but dispersive.

Based on these observations, an upscaling of the model based on the effective longitudinal and transverse permeability and the dispersion coefficient is performed.

Key words: convective mixing, Rayleigh-Bénard instability, heterogeneity, scalar dissipation rate, dissolution fluxes.

How to cite: Benhammadi, R., Hidalgo, J. J., and Dentz, M.: Rayleigh-Bénard instability in heterogeneous porous media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7438, https://doi.org/10.5194/egusphere-egu23-7438, 2023.

A.160
|
EGU23-2015
Antonio Zarlenga and Maria Rita Maggi

Heterogeneous aquifer characterization is a key step in both quantitative and qualitative groundwater studies. The high cost required in the flow field characterization and the small budget usually available make accurate and effective models for data analysis and information acquisition necessary.

We present here a methodology for the interpretation of the tracer test data widely used in the aquifer characterization; in particular we focus on the push and pull test, the latter is commonly adopted for the investigation of the hydrogeological and chemical parameters of aquifers.

Our stochastic methodology through the direct simulation of transport within a heterogeneous formation, allows to characterize the main geostatistical properties of the flow field and the main transport parameters. The model conceptualization is a stratified formation with isotropic log-hydraulic conductivity normally distributed; the integral scale in the vertical direction is IY,V while the horizontal integral scale is unbounded IY,H=∞ The flow field is assumed to be steady state and driven by the pumping rate. Transport is simulated by a Lagrangian procedure considering advection dispersion and equilibrium adsorption reaction. The results show that adopting different test setup many aquifer parameters can be obtained. The promising methodology was tested with field data from literature, showing encouraging results.

How to cite: Zarlenga, A. and Maggi, M. R.: Interpretation of the push and pull tracer test data in heterogeneous aquifers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2015, https://doi.org/10.5194/egusphere-egu23-2015, 2023.

A.161
|
EGU23-4264
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ECS
|
Sascha Rudolph, Sven Philipp, Michael Pirrung, Karl-Heinz Köppen, and Thorsten Schäfer

The lake Laacher See (East Eifel, Germany) is affected by eutrophication due to high phosphorous concentration for stagnant waters averaging 34 µg/l (range of 25–40 µg/l P since the year 2000). These elevated concentrations have been monitored since the 1950s and an oligotrophic status could not be achieved despite various measures [2]. A linear correlation was determined between dissolved phosphate (211 – 643 μg/l) and vanadium (6.7 – 28.4 μg/l) in groundwaters of the Ringseitert volcanic complex (West Eifel) with implications for drinking water use [4]. These issues are the motivation to investigate the geogenic input of phosphorous into Laacher See and of vanadium into groundwaters by fluid-rock-interaction.

Laacher See is the water-filled crater area of the Plinian-erupted Laacher-See-volcano, which belongs to the East Eifel Volcanic Field with an active volcanism for 0.46 Ma [6]. The catchment of this lake includes rocks of siliciclastic Lower Devonian basement, scoria cones and lava flows of basanitic and tephritic compositions, and phonolithic to foiditic tephra from the Rieden volcanic complex. The youngest volcanic unit is the phonolithic, strong geochemically zoned tephra from the Laacher-See-volcano, which ejected 6 km³ magma in form of pumice and ash 12.9 ka ago [3,6].

The dissolution of apatite (primary) and vivianite (secondary phosphate phase) is assumed to be the reason of geogenic input of phosphorous and vanadium by groundwater flow. A particularity of the Laacher See area is the occurrence of mofettes that lead to elevated concentrations of CO2, decreased pH and enhanced apatite dissolution [5]. The hydrochemical modelling program PHREEQC is used to investigate the equilibrium state of phosphate and vanadium in groundwaters at specific Eh/pH-conditions, p(CO2)-values and compositions. In addition, residence times calculated by hydraulic conductivities and dissolution rates from batch experiments are used to distinguish between rate-limited or equilibrium process in phosphate dissolution. Data on phosphorous concentrations and pH of soils in the vicinity of the Laacher See and their equilibrium solutions are evaluated to their geological, geochemical and anthropogenic background and provide clues to phosphorous sources [1].

In future studies, bulk rock concentrations will be measured using XRF and total digestion, and detailed dissolution rates will be measured using extended batch experiments to combine these findings into a conceptual hydrogeological model of geogenic phosphate and vanadium input to lake Laacher See.

References:

[1] Armbruster, M. & Wiesler, F. 2012. Ermittlung der P-Gehalte entlang von 10 Transekten am Laacher See. LUFA Speyer, Speyer. P.24 (unpublished)

[2] Block, U. et al. 2015. Übersicht über die Phosphatthematik am Laacher See. Fachhochschule Bingen. P.41

[3] Bogaard, P.v.d. & Schmincke, H.U. 1984. The eruptive center of the late quaternary Laacher see tephra. Geologische Rundschau, 73, 933-980, http://doi.org/10.1007/BF01820883.

[4] Härter, L.M. et al. 2020. Vorkommen von Vanadium im Grundwasser der Vulkaneifel. Grundwasser, 25, 127-136, http://doi.org/10.1007/s00767-020-00447-x.

[5] Pan, H.B. & Darvell, B.W. 2009. Calcium Phosphate Solubility: The Need for Re-Evaluation. Crystal Growth & Design, 9, 639-645, http://doi.org/10.1021/cg801118v.

[6] Schmincke, H.-U. 2007. The Quaternary Volcanic Fields of the East and West Eifel (Germany). In: Ritter, J.R.R. & Christensen, U.R. (eds) Mantle Plumes: A Multidisciplinary Approach. Springer Berlin Heidelberg, Berlin, Heidelberg, 241-322, http://doi.org/10.1007/978-3-540-68046-8_8

How to cite: Rudolph, S., Philipp, S., Pirrung, M., Köppen, K.-H., and Schäfer, T.: The Input of Phosphate & Vanadium into the Lake Laacher See by Dissolution of Volcanic Rocks (East Eifel, Germany), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4264, https://doi.org/10.5194/egusphere-egu23-4264, 2023.

A.162
|
EGU23-12548
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ECS
Sharad Patel and Kumar Gaurav

We develop a global collocation based meshfree method for simulation of solute transport in the saturated aquifer formations. We prove that the projected model is free from the limitations of mesh or grid which are used in finite element method (FEM) and finite difference method (FDM). We apply this model on different one and two-dimensional synthetic aquifer problems with advection-dispersion phenomenon. The results of these problems demonstrate that the proposed model is free from the limitations of unstable convergence and has a fixed range (i.e., 2-3) of shape parameter hence it requires less number of simulations to calibrate the model. More importantly, the proposed model is simple to code and shows a higher degree of unanimity with the analytical solution, making it a viable alternative to grid-based traditional methods. 

 

How to cite: Patel, S. and Gaurav, K.: Groundwater solute transport simulation using global collocation radial basis function based meshfree method, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12548, https://doi.org/10.5194/egusphere-egu23-12548, 2023.

A.163
|
EGU23-13866
yams: Yet another modeling software (Julia) for the simulation of coupled reactive transport processes (THC) in geothermal systems.
(withdrawn)
Manfred W. Wuttke
A.164
|
EGU23-1804
|
ECS
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Abhay Guleria and Sumedha Chakma

Simulation of fate and transport mechanisms in the porous systems from contaminant transport models are affected by uncertainty associated with input model parameters. Sensitivity analysis (SA) provides tools to quantify the sources of uncertainty to the variations in the model output metrics. To quantify the uncertainty associated with physical non-equilibrium contaminant transport model, global SA was conducted for the problem mimicking reactive transport in the saturated soil column conditions. Five global SA methods, namely Morris, RSA (Regionalized Sensitivity Analysis), Sobol, FAST (Fourier Amplitude Sensitivity Test), and PAWN, were tested based on the temporal moments of contaminant concentrations for two output metrics: zeroth temporal moment (ZTM) and mean residence time (MRT). The ranking order of ten input model parameters from global SA methods for two output metrics was compared. Morris SA implied that the ZTM at outlet of the soil column is highly sensitive to sorption distribution coefficient in the mobile and immobile regions and less sensitive to dispersion coefficient and degradation rate constant in the immobile region. The mass-transfer coefficient showed highest non-linear interactions with other flow and transport parameters based on the highest value of standard deviation of elementary effects (EEs) for ZTM output metric. The sorption distribution coefficient in the mobile region and mass-transfer coefficient showed highest sensitivity and non-linear effect toward MRT based on the Morris method. The comparison of global SA methods revealed that the top two sensitive parameters affecting ZTM and MRT were the same from all the considered methods. However, large difference in the ranking order of bottom three sensitive parameters was observed. The sorption distribution coefficient of mobile region and mass-transfer coefficient were observed as the most sensitive parameters affecting ZTM and MRT based on the comparison of all five global SA methods. Overall results suggest that the non-linear contaminant transport model should be examined based on multiple sensitivity output metrics via a multi-model approach. The multi-model global SA approach implemented in this study highlighted its significance in quantifying the interplay of non-linear model parameters.

How to cite: Guleria, A. and Chakma, S.: Global sensitivity analysis of physical non-equilibrium contaminant transport model for reactive transport in a saturated porous system, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1804, https://doi.org/10.5194/egusphere-egu23-1804, 2023.

Posters virtual: Tue, 25 Apr, 14:00–15:45 | vHall HS

vHS.30
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EGU23-12742
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ECS
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Xinying Min, Naaran Brindt, Sunghwan Jung, and Tammo Steenhuis

Both preferential flow and colloid-sized particles facilitate groundwater pollution in the vadose zone. Preferential flow in sandy soils that overlays most aquifers is through unstable finger-like features. Studying colloid movement in these preferential flow paths is a crucial step toward better strategies for dealing with this pollution. In this study, we aimed to examine how the wetting front of fingers affects colloid mobilization and movement in dry sands. We postulate that the discontinuous pressure at the finger front results in the wetting front to move one pore at a time, causing high pore velocities with increased interfacial contact angles according to the Hoffman-Jiang equation. In a series of flow cell infiltration experiments, we used a high-speed camera (500 fps) to capture the colloid movement at the wetting front as water infiltrated acid-washed sands (2 mm in diameter). Four hundred and fifty milligrams of the sand particles were packed in a 0.6 x 0.2 x 2 cm channel and flushed with red-colored deionized water at 10 μl/min. Colloids were introduced by applying to the sand hydrophilic blue carboxylated microspheres (10.3 μm) or water-repellent polystyrene microspheres (10.2 μm) at a concentration of spheres/gram of sand before cell packing. Frame-by-frame image analysis was used to determine the position and velocity of the colloid movements, wetting front, and the advancing front contact angle. The results of the different experiments showed that the water velocity in the pore behind the front, based on the colloid velocity, is often quite different from the wetting front velocity and lacks a direct connection to it. In some cases, the wetting front advancement speed was 20 mm/s, four times faster than colloids. In others, the velocity of colloids could achieve around 10 mm/s while the wetting front’s velocity was 2 to 3 times less. The results also show that the changes in contact angle between the wetting front and particle surface are consistent with the Hoffman theory and are close to the value derived from the Hoffman Jiang equation. It confirmed that the change in contact angle during infiltration should be considered when studying water and colloid transport in sands.

 
 

How to cite: Min, X., Brindt, N., Jung, S., and Steenhuis, T.: Colloids movement at the wetting front during infiltration to sand, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12742, https://doi.org/10.5194/egusphere-egu23-12742, 2023.

vHS.31
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EGU23-3793
Qingmin Dong and Shiyue Chen

The second member of the Kongdian Formation (Ek2) in the Cangdong Sag has become an important field of shale oil exploration in the Bohai Bay Basin. To investigate the occurrence characteristics and discuss the controlling factors of shale oil mobility in the Ek2, the research presented in this study is based on core and thin section observations, XRD analysis, total organic carbon (TOC), Rock-Eval pyrolysis, multiple isothermal stages (MIS) pyrolysis, low-temperature nitrogen physisorption (LNP), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). The results show that the Ek2 shales can be classified into five types of lithofacies, including laminated felsic shales, laminated mixed shales, massive mixed shales, laminated carbonate shales, and massive carbonate shales. The shales were characterized by high organic matter abundance and moderate thermal evolution with good to excellent hydrocarbon generation potential and contained a high abundance of Type I and II1 kerogens. Laminated felsic shales and laminated mixed shales had obvious advantages in the thermally extractable hydrocarbon content (S1) value, oil saturation index (OSI) value, free oil, and movable oil content with other lithofacies. Analysis of LNP, MIP, and MIS pyrolysis show that the residual shale oil mainly occurred in the pores with diameters smaller than 200 nm, and the occurrence pore diameters of residual oil in some laminated shale samples could reach 50 μm. The lower limits of the occurrence pore diameter of free oil and movable oil were 7 nm and 30 nm, respectively. The mobility of shale oil is controlled by the shale oil component, thermal maturity, TOC content, and pore volume.

How to cite: Dong, Q. and Chen, S.: Occurrence characteristics of lacustrine shale oil in the second member of the Kongdian Formation in the Cangdong Sag, Bohai Bay Basin, China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3793, https://doi.org/10.5194/egusphere-egu23-3793, 2023.

vHS.32
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EGU23-12599
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ECS
Xin Huang, Tianshuo Pan, Mingda Cao, Jie Zhang, and Zhixin Zhang

To investigate the rock weathering processes in silicate-dominated subtropical basin in east China, we analyzed major ion compositions of rivers and precipitation samples in the Qingyi River basin in the lower reaches of the Yangtze River. In this study, the characteristics of weathering processes in the Qingyi River basin were identified, and the rock weathering rates and consumption rates of atmospheric CO2 were estimated based on water chemistry and the forward model. The results showed that the anthropogenic influences on rock weathering was not significant, which means the rock weathering in the study area was mainly induced by carbonic acid while the influence of sulfuric acid and nitric acid could be neglected. The cations of rivers were mainly contributed by weathering of carbonates (59.2%), followed by weathering of silicates (17.9%). Atmospheric precipitation and evaporites contributed 9.6% and 5.6%, respectively. Spatially, the carbonate weathering rates and silicate weathering rates decreased as order of tributary Huishui river in the upstream mountainous areas (32.04 t·km-2·a-1 and 20.97 t·km-2·a-1) > main stream of Qingyi river (24.12 t·km-2·a-1 and 8.91 t·km-2·a-1) > tributary Zhanghe river in the downstream areas (13.68 t·km-2·a-1 and 2.85 t·km-2·a-1). Similarly, the CO2 consumption rates from carbonates weathering and silicate weathering followed the order of tributary Huishui river (5.86×105·mol·km-2 a-1 and 3.29×105·mol·km-2 a-1) > main stream of Qingyi river (2.45×105·mol·km-2 a-1 and 2.43×105·mol·km-2 a-1) > tributary Zhanghe river (0.77×105·mol·km-2 a-1 and1.39×105·mol·km-2 a-1). In conclusion, carbonate weathering induced by carbonic acid was dominant in the Qingyi River basin, with chemical weathering rates slightly lower than similar silicate-dominated subtropical basins in east China. The rock weathering rates in the study area differed spatially. In particular, silicate weathering in upstream mountainous areas accounted for more carbon sink of the whole Qingyi River basin, which is of great importance for the regional carbon cycle.

Key words: subtropical; Qingyi River basin; rock weathering; atmospheric CO2 consumption; carbon sink

How to cite: Huang, X., Pan, T., Cao, M., Zhang, J., and Zhang, Z.: Riverine water chemistry and rock weathering processes of Qingyi River basin, a subtropical basin in east China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12599, https://doi.org/10.5194/egusphere-egu23-12599, 2023.