INFLOW assembles an interdisciplinary team at the interface between chemistry, fluid mechanics and Earth sciences to explore how multiphase flows of water and air control the chemical reactivity at mineral surfaces in unsaturated porous media. These dynamics play a central role in the transport and degradation of contaminants in soils, which constitute highly heterogeneous and dynamic reactors. While reactive transport properties are generally characterized in saturated conditions, it is unknown how different levels of water saturations alter reaction kinetics. To address these scientific challenges, INFLOW will combine comprehensive experimental investigations of molecular mechanisms at mineral/water interfaces (WP1) with pore-scale imaging of transport and reaction rates using emerging microfluidic techniques (WP2). These experimental data will feed the development of a new modelling framework for upscaling reactive transport dynamics in unsaturated porous media (WP3), integrating reaction rates and thermodynamic parameters, as well as transport dynamics in multiphase flows. A key challenge is to bridge the gap between the molecular scale chemical processes and physical processes (e.g. multiphase flow and dispersion/diffusion in porous media). The coupling of modern in situ interfacial chemistry measurements and emerging microfluidics techniques offer a unique opportunity to unlock this major scientific question. INFLOW will tackle this issue by focusing on the case of antibiotic agents widely used in human and veterinary medicine. Recently, quinolones and other antibacterial agents have emerged as aqueous micropollutants in surface waters, groundwater and soils. Their transport and mobility in the environment are strongly related to the nature and relative abundance of the mineral phases, e.g. Fe-oxyhydroxides, commonly found in the Earth’s near-surface environment. Although redox transformation of these compounds is key to their environmental and engineered degradation, the underlying reaction mechanisms remain elusive. In particular, the surface speciation of antibiotics and their molecular transformation on mineral surfaces is unclear. In addition, much of knowledge that currently exists concerns the reactivity of environmental mineral surfaces in suspension or slurry systems, and under equilibrium conditions. Therefore, it is unknown how unsaturated flow dynamics influence these interfacial processes and likely drive non-equilibrium reactions. Our research hypotheses are: (i) multiphase flow of water and air in porous media induces strong macroscopic heterogeneities in water content and flow velocities, thus controlling solute residence times and exposure to reactive surfaces; (ii) at the pore-scale, the induced enhanced concentration gradients lead to breakdown of the complete pore-scale mixing assumption of conventional reactive transport models; (iii) unsaturated flow dynamics likely have a major impact on the fate of organic compounds bound to mineral surfaces. To test these hypotheses, INFLOW will combine novel experimental investigations (WP1 and WP2) with advanced numerical and theoretical modeling (WP3). This multidisciplinary approach will provide a unique dataset from the molecular scale to the porous media scale. INFLOW is the first project to develop a multi-scale and interdisciplinary methodology linking molecular mechanisms of chemical reactions with multiphase flow dynamics in porous media, hence opening a broad range of environmental applications.

The project H2MNO4 will develop numerical models for reactive transport in heterogeneous media. It defines six mathematical and computational challenges and three applications for environmental problems with societal impact. This basic research project matches perfectly well with the first topic of the ANR program and concerns also the fifth topic. The project relies on a consortium of six partners, involving four public research laboratories (INRIA, Geosciences Rennes, ICJ, Pprime), one public institution (ANDRA) and one SME (ITASCA). The consortium has strong interactions with the H+ observatory and two international research laboratories. Numerical models and simulations are essential for studying the fate of contaminants in aquifers. The three applications concern freshwater supply, remediation of mine drainage, waste geological disposal. Chemical reactions must be coupled with advection and dispersion when modeling the contamination of aquifers. The objective is to design both Eulerian and Lagrangian models to deal with challenging modeling issues. Indeed: • the two scales of chemistry and transport must be coupled; • chemical reactivity is conditioned by physical processes, among which diffusion, hydrodynamic dispersion and mixing; • chemical reactions involve many species, interacting with each other and with the aquifer; thresholds govern the precipitation or dissolution of minerals; • dispersion coefficients can vary from one species to another; • waste storage means an evolution of the repository during thousands of years; • reactions are highly nonlinear and lead to dynamic sharp fronts. These complex models give rise to numerical difficulties that require adaptive discrete schemes and advanced computational tools. An original Lagrangian model, dealing with interacting particles and heterogeneity, will be designed by the project and will rely on a sound mathematical study. Chemistry will include kinetic and equilibrium reactions, with mobile and fixed species produced by sorption or precipitation. The coupled model is then a set of nonlinear Partial Differential Algebraic Equations. So far, simulations using Lagrangian methods do not take into account such complex systems thus a breakthrough of the project will be to overcome this limit. If Eulerian methods are able to deal with complex chemistry, the transport process, the nonlinearities and the size of the problems require advanced computational tools. Numerical artifacts such as artificial diffusion or oscillations can appear, mainly when advection dominates. Global methods are more robust than sequential ones, at the price of solving large sparse linear systems (the size is the number of cells times the number of primary species). The target is to run 3D models with 10 millions of cells and 30 species. In such models, memory and CPU requirements are large, because of the spatial and temporal scales. The project aims at using high performance computing and scalable solvers in order to provide efficient methods. Target computers are composed of up to 500 cores in clusters of Grid’5000 and up to 2000 cores of multiprocessors at Genci (Idris and Cines). Software development and simulations on multicore architectures is a major task in the project. Emphasis will be put on adaptive discrete schemes and on optimized parallel algorithms. Another strong point of the project is related to benchmarking. Test cases will help in validating the numerical models and software. They will contribute to choosing the best method for the problem at hand and to solving industrial problems that arise in water resources management, mine drainage and waste disposal.

Fluid flow in porous media plays a central role in a large spectrum of geological, biological and industrial systems. Recent advances have shown that microscale chemical gradients are sustained by pore-scale chaotic flow dynamics. This fundamentally challenges the current macrodispersion paradigm that assumes that porous transport processes occurs under well-mixed microscale conditions. Using novel experimental, numerical and theoretical approaches, CHORUS will explore the origin, diversity and consequences of chaotic mixing in porous and fractured media. For this, the team will develop a new generation of imaging techniques coupling laser induced fluorescence, refractive index matching and additive manufacturing of complex and realistic porous and fractured architectures (WP1 and WP2). The CHORUS team will use these insights to develop new modelling concepts for describing scalar mixing and dispersion in microscale (WP3) and multiscale (WP4) systems. Building on these experimental, numerical and theoretical breakthroughs, CHORUS will design “smart” porous flows with porous architectures that selectively optimize mixing, dispersive or reactive properties (WP5). CHORUS will thus develop a new paradigm for transport dynamics in porous and fractured media, with far-reaching applications for the understanding, modelling and control of a range of natural and industrial processes, including contaminant transport and biogeochemical reactions in the subsurface, CO2 sequestration, membrane-less flow batteries, flow chemistry, chromatography or catalysis.

How and when the Tibetan plateau developed has long been a puzzling question with implications for the current understanding of the behavior of the continental lithosphere in convergent zones. The Central Tibetan plateau provides the ideal existing laboratory to understand the evolution of a large scale collisional orogen. Its evolution is now well constrained by an increasing amount of high quality surface and subsurface data. The integration of these data has led to the proposition of the achetypical models of orogenic evolution. Some models focus on the importance of the underthrusting of the rigid Indian and Asian plates beneath Tibet, others argue that the crust and lithosphere are weak and the thickening of the Asian lithosphere is distributed. In this project, we target Central Tibet. Although it remains the least studied part of the collision zone, it constitutes a key element for reconstructions and models involving processes such as continental subduction, underplating or extrusion to be evidenced there. We will provide detailed quantitative data on rates and mechanisms of thickening processes in central Tibet based on an integrate petrologic study of volcanic rocks and associated mantle and lower crustal xenoliths, paleomagnetic data acquired on volcanic rocks, reappraisal of available geophysical data (tomography, heat flow, Bouguer anomaly, refraction and reflection seismicity) and numerical modeling. The comparison with the geometry, lithology and evolution of the Bohemian massif will offer an overarching vision of the evolution of large scale orogens through time. These different approaches, although highly complementary, are rarely integrated within a single project to study a particular mountain belt. We propose to develop an integrated study of deep and surface processes evolution in the core of the orogen. Our aim is to focus on the Central part of the Tibet, Qiangtang Terrane and to compare it with the Moldanubian zone in the Bohemian massif as these zones correspond to the core of the orogen far away from the preserved continental subductions zones that rejunavated the initial orogenic recordings. The interest to compare the Bohemian massif with the Qiangtang Terrane is that the former offers the opportunity to observe directly in the field the root of the orogen while the second is a still active unroofed orogenic zone.