ChemicalWalks · Reactive Transport and Mixing in Heterogeneous Media: Chemical Random Walks under Local Non-equilibrium
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2019-06-17 → 2021-06-16
- EU contribution
- €184,708
- Participants
- 1
- Scheme
- MSCA-IF-EF-ST
Lines connect the coordinator with its partners.
Results in brief
Reactive Transport and Mixing in Heterogeneous Media: Chemical Random Walks under Local Non-equilibrium
Geological media are heterogeneous at a multitude of scales. At the large scale, aquifers are composed of different materials, arranged in different structures; and below the millimeter scale, rocks are porous materials. Heterogeneity in continuum (Darcy)-scale velocity magnitudes in heterogeneous subsurface media (figure left panel) represents an average over pore-scale structural heterogeneity. Dissolved substances, such as contaminants or nutrients, move through these complex porous media in the subsurface, resulting in spatially-variable subscale solute concentrations (figure middle panel). The solid phase at the pore scale is also composed of different minerals and highly heterogeneous from a chemical perspective (figure right panel). The heterogeneity affects the way water flows, which in turn affects the spatial distribution of these dissolved substances and the way in which they interact amongst themselves and with other resident components such as mineral formations. Understanding these processes is key to central societal issues such as water quality control and resources management. Predicting the amount of dissolved substances present in groundwater and their spatial distribution in geological structures requires modeling transport and reactions in these complex media. Most current models assume that, although the concentration plume of, for example, a contaminant may be complex at the aquifer scale, it is homogeneous at the small scales corresponding to the pore spaces in geological materials. This leads to predictions of reaction rates that are often much larger than those found in real aquifers. The ChemicalWalks project proposed a new way to account for this incomplete mixing at the pore scale, by describing its impact in terms of a reaction slowdown due to the time it takes for different substances to come together and react. The project has led to novel theoretical and numerical frameworks that significantly advance the state-of-the-art understanding of chemical reactions under transport limitations and incomplete mixing.
Data: CORDIS, © European Union
Project objective
Understanding and modelling reactive transport in porous media is fundamental to predicting field-scale biogeochemical reactions, which play a key role in current environmental issues such as water resources management and carbon dioxide sequestration. A major scientific challenge is to capture the dynamics of coupled solute mixing and reaction processes in the context of multiscale heterogeneity, which characterise most natural porous media. In particular, the impact of pore-scale mixing on large- (Darcy-)scale reactive transport is a critical scientific question. ChemicalWalks addresses this question by coupling for the first time the lamella theory of mixing, developed by the host supervisor, and the chemical CTRW model for reaction kinetics under incomplete mixing, recently developed by the ER. While the lamella theory has successfully quantified mixing processes and fluid-fluid reactions at pore scale, its application to fluid-solid reactions, which are ubiquitous in natural systems, remains to be explored. The key idea of ChemicalWalks is to use the lamella theory to determine how pore-scale concentration distributions control the distribution of fluid-solid reaction rates, and formalize a predictive theory for upscaled reaction kinetics through the chemical CTRW framework (WP1). The complementary expertise of the researcher and the host will ensure a particularly efficient two-way transfer of knowledge to achieve this goal. This will open the door to the development of a hybrid computational method, quantifying the effect of pore-scale mixing on Darcy-scale reactive transport phenomena at a scale relevant to environmental applications (WP2). ChemicalWalks will be firmly rooted on a career development plan and supported by scientific training in state-of-the-art mixing theories and data processing and interpretation techniques, placing the fellow at the forefront of reactive transport modelling.
Original text from CORDIS.
Participants
- UNIVERSITE DE RENNES I · RENNES CEDEXCoordinatorFrance
Links
Data: CORDIS, © European Union