HS8.1.3

The sound understanding and quantification of the transport and dispersion
mechanisms of bacteria in porous media is of central concern in applications
such as bioremediation and biomineralization. Recent experimental and numerical
studies indicate that motility plays a key role for the fate of bacteria.
Data from microfluidic experiments in model porous media consisting of randomly
placed pillars show that non-motile bacteria have compact displacement
distributions, while the distribution of motile bacteria are characterized by
strong peak retention and forward tailing. Detailed analysis of bacteria
trajectories reveals two key attributes: 1. The emergence of a motility-induced
trapping and retention process due to active motion from the stream toward the
solid grain. 2. Increase or decrease of dispersion due to the transfer between
pore channels and grains, depending on the flow rate. We develop a physical model
based ona continuous time random walk (CTRW) approach. Bacteria dispersion due to
hydrodynamic flow fluctuations is quantified by a Markov model for the equidistantly
sampled particle speeds. The impact of motility is modeled by a two-rate trapping
process that accounts for the motion toward and active trapping at the grains.
The theoretical model captures the displacement distributions of both non-motile
and motile bacteria. It provides explicit analytical expressions for the motility-induced
hydrodynamic dispersion coefficients in terms of the trapping and release rates,
which characterize the bacteria motility. The experimental data shows that these
motility parameters are flow-rate dependent, which manifest in a reduction of
dispersion compared to the non-motile bacteria at low flow rates, and an increase
at high flow rates. The model reproduces the experimental observations and allows to
predict bacteria dispersion at the continuum scale.  

How to cite: Dentz, M., Creppy, A., Douarche, C., Clément, E., and Auradou, H.: Dispersion of motile bacteria in a porous medium: Experimental data and theory, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7580, https://doi.org/10.5194/egusphere-egu22-7580, 2022.

Natural porous systems, such as soil, membranes, and biological tissues comprise disordered structures characterized by dead-end pores connected to a network of percolating channels. The release and dispersion of particles, solutes, and microorganisms from such features is key for a broad range of environmental and medical applications including soil remediation, drug delivery and filtration. Yet, the role of microscopic structure and flow for the dispersion of particles and solutes in such disordered systems has been only poorly understood, in part due to the stagnant and opaque nature of these microscopic systems. Here, we use a microfluidic model system that features a pore structure characterized by dead-ends to determine how particles are transported, retained and dispersed.  We observe strong tailing of arrival time distributions at the outlet of the medium characterized by power-law decay with an exponent of 2/3. Using numerical simulations and an analytical model, we link this behavior to particles initially located within dead-end pores, and explain the tailing exponent with a hopping and rolling mechanism along the streamlines inside vortices within dead-end pores. These dynamics are quantified by a stochastic model that predicts the full evolution of arrival times. Our results demonstrate how microscopic flow structures can impact macroscopic particle transport.

How to cite: de Anna, P., Bordoloi, A., Scheidweiler, D., Dentz, M., Bouabdellaoui, M., and Abbarchi, M.: Structure induced vortices control anomalous dispersion in porous media, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4562, https://doi.org/10.5194/egusphere-egu22-4562, 2022.

The ability of a colloidal particle to migrate along a local salt concentration gradient, referred to as diffusiophoresis [1, 2], has recently been explored for a variety of technological applications [3-5]. Flows containing dissolved salts and suspended particles in a porous medium can occur in a variety of natural and engineered scenarios including groundwater contamination and remediation, water infiltration in soil, geological carbon sequestration, enhanced oil recovery, to name a few. In all these scenarios, local salt gradients can induce diffusiophoretic motion of transported particles and contribute to the complexity of the overall transport problem. Aiming to unravel the coupling of the underlying physical mechanisms, we conduct pore-scale simulations to investigate the fluid, solute and particle transport in a micromodel. On one hand, we measure the time-lapsed effluent concentration of the colloidal particles close to the outlet and compute the so-called breakthrough curves to understand the influence of diffusiophoresis on the particle macroscopic transport through the whole host medium. On the other hand, we compute Lagrangian statistics from particle tracking at the microscale. Our results hint towards the fact that the microscopic interplay between salt transport, diffusiophoretic particle motion and host medium disorder can impact the macroscale particle dynamics. Lastly, while both, the flow and transport through a porous medium and the diffusiophoretic motion of colloids in a variety of microfluidic devices, are active areas of research, the novelty of our work lies in the intersection of the two.  

References:

[1] Derjaguin et al. (1947), “Kinetic phenomenon in boundary films of liquids”, Colloid J. USSR, 9, 335-347.

[2] Anderson (1989), “Colloid transport by interfacial forces”, Annu. Rev. Fluid Mech., 21 (1), 61-99.

[3] Kar et al. (2015), “Enhanced Transport into and out of dead-end pores”, ACS Nano, 9(1), 746-753.

[4] Shin et al. (2017), “Membraneless water filtration using CO₂”, Nat. Commun., 8(1), 15181.

[5] Rasmussen et al. (2020), “Size and surface charge characterization of nanoparticles with a salt gradient”, Nat. Commun., 11(1), 2337.

How to cite: Jotkar, M., de Ana, P., and Cueto-Felgueroso, L.: Diffusiophoretic transport of colloids in a porous medium, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5735, https://doi.org/10.5194/egusphere-egu22-5735, 2022.

Abstract

The process of a fluid replacing a separate miscible fluid in a porous medium is present in many industrial and natural systems, such as enhanced oil recovery, CO2 sequestration and salt-fresh water interfaces in the ground. While the replacement can be approximated with the Darcy law, the mechanisms of the miscible phases mixing to the displacement remain unclear, specifically as the heterogeneity of the domain increases. As this mixing influences the reaction pattern between the fluids, it is important to estimate it using indirect measurements that are available, such as pressure and flux measurements. We propose a set of experiments that allow us to observe and measure the displacement and mixing process in high resolution and with the use of image analysis we can distinguish between the mechanisms. We can clearly see how the heterogeneous rate of the pore structure influences the mixing pattern, rate, and duration. Surprisingly, we found a clear and typical “mark” of the mechanisms on the flow rate, under constant pressure, which allows us to relate the heterogeneity level of the structure to the ratio of displacement to mixing.

How to cite: Eliyahu-Yakir, Y., Ballas, T., Abezgauz, L., and Edery, Y.: Investigating the pore scale mechanism of miscible phases mixing in porous medium 2D, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9229, https://doi.org/10.5194/egusphere-egu22-9229, 2022.

The Anthropocene, a new geological period when human actions are altering the habitability of the Earth for all forms of life, raises new challenges in terms of knowledge integration that fragmented approaches cannot overtake. Due to complex interactions within geo-eco-socio-systems (GESS), a “whole system” approach is required to answer societal concerns around soil capital, water resources, chemical pressure and biodiversity.

To address these challenges, the TERRA FORMA project will design and test in-situ observation plateform coupling sensor viewpoints on human, biotic and abiotic dynamics. This project builds on pioneering and mature technological advances (optical sensors, 3D printing, IoT, AI) to design and probe a scalable network of smart sensors. We will develop a new generation of smart, connected, low-cost, low-impact and socially appropriated environmental sensors, adapted to field conditions, dedicated to capture the behavior, metabolism and trajectory of GESS emerging from states and fluxes of liquid, gas and solid matter and biota. These new technologies will contribute to shed light on “essential variables” for GESS and evaluate the descriptive and predictive potential of models over a wide range of contexts. TERRA FORMA gathers scientists, in an interdisciplinary effort at the crossroad of Earth, environmental, technological, computer and social sciences.

In this presentation, we will show how instrumental developments (spectroscopy, lab on a chip, …) and methodological developments (biogeophysics, …) contributes to the construction of the observation plateform.

How to cite: Longuevergne, L., Elger, A., and Girard, V.: TERRA FORMA: Developing the observation platform of the Anthropocene, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13559, https://doi.org/10.5194/egusphere-egu22-13559, 2022.

Hydrological predictions for ungauged basins at catchment and regional scales still faces the challenge of lack of available data. To meet this challenge, we propose a new method relying on the structure of the stream network. Under the assumption that the perennial stream network is mostly fed by groundwaters, its structure derives from the underlying aquifer properties. It is especially the case for shallow crystalline aquifers under temperate climates where the surface and subsurface hydrological systems are directly connected. The groundwater table remains close to the topography and the spatial extent of the stream network is then controlled by the magnitude of the subsurface hydraulic conductivity (K) with respect to the actual recharge rates (R).

Using a parsimonious 3D groundwater flow model, we propose a novel performance criterion to assess the similarity between the modelled seepage areas and the observed stream network. We investigate the sensitivity of our methodology to different digital elevation models (DEM) and stream network products from different databases that may impact the estimates through their different spatial resolutions. We use this method to determine the equivalent hydraulic conductivity for 25 crystalline catchments in western France.

The results show that our methodology allows predicting the spatial patterns of the stream network with a high sensitivity to the hydraulic conductivity. We found that estimated hydraulic conductivities vary over two orders of magnitude [10^-5 to 10^-4 m/s] across the 25 investigated catchments and are well correlated to the lithology. While the DEM resolution has no major effect on the results, we found that the proportion of described low-order streams significantly controls the estimations.

The proposed approach constitutes a paradigm shift in current methodologies designed to assess catchment-scale hydraulic properties with great perspectives regarding the emergence of remote sensing techniques for the mapping of wetlands and soil moisture. Our method might bring up new opportunities to provide predictions for ungauged basins such as the hydrographic network dynamics in a changing climate.

How to cite: Abhervé, R., Gauvain, A., Roques, C., Longuevergne, L., Aquilina, L., and de Dreuzy, J.-R.: Assessment of hydraulic conductivity from the hydrographic network in shallow crystalline aquifers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13555, https://doi.org/10.5194/egusphere-egu22-13555, 2022.

Climate change is one of the most important and probable aspects influencing the stability of human societies. Anaerobic carbon oxidation by methane producing bacteria (MPB) in natural and human-made freshwater ecosystems influence the global greenhouse gas (GHG) emissions and its dynamics.  Moreover, these ecosystems are highly sensitive to climate change. However, GHG emissions assessment methodologies are complex and cannot be applied continuously. Thus, better tools to characterize methane emissions and its dynamics in these ecosystems are of capital importance to deal with climate change. Bioelectrochemical systems (BES) are devices that transform the chemical energy of organic and inorganic substrates into electric current thanks to the metabolic activity of the electroactive bacteria (EAB’s). EAB and MPB oxidate the same carbon source (acetate) and, therefore, current produced by EAB can be used as a proxy for methane formation. BES-based biosensors are an interesting type of biosensors since they do not need a transducer, can be manufactured using cost-effective materials and can be applied for real-time and remote location monitoring. The work presented aim to assess the potential use of the electric signal produced by a low-cost, membrane-less BES-based biosensor as an indicator of methane emissions. To this purpose, 3.8L PVC vessels representing a core of a shallow flooded ecosystem were constructed and a BES cell was placed in the centre for the biosensing assessment. Methane emissions were assessed through the close chamber method and analysed by gas chromatography coupled to a flame ionisation detector while the bio-electric signal was continuously recorded. Results show that the methane and the electric production follow a similar pattern, but are displaced in time, being the electric production faster than the methane one. Results indicate that the electric current of a BES-based biosensor has the potential to be used as an indirect measure of methane emissions.

How to cite: Fernandez-Gatell, M., Sanchez-Vila, X., and Puigagut, J.: BES-based biosensors for methane emissions assessment in freshwater ecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7629, https://doi.org/10.5194/egusphere-egu22-7629, 2022.