This project aims to provide the very first realistic assessment of the contribution of microorganisms to the weathering rates of silicates in the subsurface, which is considered here as the zone extending from the saprolite to the shallow rocky substrate. The motivation is simple: ~70% of bacteria and archaea live underground, and it has long been suspected that these microorganisms contribute significantly to silicate weathering. Silicate weathering is a fundamental process in the chemical geodynamics of our planet, controlling pedogenesis and the renewal of nutrient stocks in soils, while contributing to the carbon cycle and the Earth's climate over geological time scales. However, the rates and mechanisms of microbial weathering of silicates remain essentially unknown, and the contribution of microbes is therefore not implemented in current weathering models. The subsurface, and in particular that found in basaltic environments, is also considered as a potential host for the early stages of life on Earth, and represents a prime target for massive CO2 injection to combat global warming, the success of which relies heavily on the reactivity of silicates. Thus, the acquisition of in-depth knowledge of the respective biotic and abiotic contributions to the weathering rates of subsurface silicates is both fundamental and urgent. Achieving this goal requires going beyond the conventional approach classically used to study microorganism-induced silicate dissolution, consisting of the use of growth media on the one hand, and freshly ground minerals on the other. Such a protocol favors the stimulation of microbial activity while enhancing the reactivity of the mineral substrate, which results in a dramatic overestimation of the actual contribution of microorganisms to the weathering rates in natural settings. This project offers a solution: An interdisciplinary and unconventional approach to assess the contribution of microbes to silicate weathering rates in complex environmental media, which we have recently implemented to provide the first estimates of the contribution of fungal hyphae to silicate weathering in topsoil horizons. This approach involves replacing conventional measurements of elemental release in solution to quantify dissolution rates with non-invasive nanotopography measurements of reacted substrates in natural solutions. These substrates will be pre-treated to obtain surface properties that simulate different stages of silicate aging. These measurements of weathering rates will be combined with studies of the microbial diversity associated with the substrates to identify the microbial actors of the weathering, as well as innovative nanoscale characterizations of the reacted surfaces coupled with ab initio modeling of the dissolution process to confirm the mechanisms and biosignatures of the weathering of microbial origin. This strategy will provide an unprecedented picture of the functioning and rates of microbial weathering of silicates in the subsurface.

Understanding how the environment reacts to anthropogenic or natural disturbances at short- and long-term time scales is one of the major societal and scientific challenges in the field of natural resource management and conservation. Among the wide field of the environmental challenges, this project aims to evaluate water and soil resources, related to climatic changes (rainfall regime, temperature increase) and anthropogenic actions (forest management) in medium altitude forested watersheds. For that, the project proposes a detailed understanding of the transport processes of water and its related chemical fluxes to elaborate physically based models, which should be applicable and adaptable in other climatic, ecologic and geologic environments. These models will be able to simulate and thus predict future evolution of such a natural ecosystem in response to disturbances like climate change or logging. Thus, the aim of this project are (i) to develop a methodology based on tight coupling of several geophysical, hydrological and geochemical approaches to estimate water and solute fluxes and their associate models at a watershed scale and (ii) to evaluate the methodology on the Strengbach watershed (80 ha granitic catchment in NE of France- 90% vegetation cover- Vosges Massif). Since 1986, the climatic, hydrological and geochemical parameters of this watershed have been recorded, which represents one of oldest monitored sites on granitic basement in the world. The project will be handled within four work-packages (WPs) with very strong interactions between the first three. - WP1: underground imaging and groundwater survey: Subsurface geophysics. This WP consists in combining different geophysical methods in order to build a spatial geometric image of the different depth and superficial lithological structures of the catchment. Groundwater storage will be estimated by gravimetry and RMS; - WP2: Surface/subsurface hydrology and water resources. Geophysical and geochemical approaches with biospheric and hydrologic modeling will be gathered to improve our knowledge of the hydrological functioning at the watershed scale (water storage, water pathways, water balances….); - WP3: Water/rocks/vegetation interactions. Geochemical/isotopic tracers, mineralogical and ecological data, and laboratory experiments will be used to better identify and characterize the water/rock interactions and the biogeochemical signature of soil solution, springs and stream waters. - WP4: Impact of climate change on water resources and soil mineral fertility. Calibrated models obtained through WP2 and WP3 will be used to estimate the evolution of water resources and soil mineral composition until 2100. The link between the 3 first WPs can be summary as: - WP1 will provide statistical information about the underground structure and water volume to WP2 and WP3 - WP2 will provide parameter distribution and water volumes to WP1 to assess petrophysical relationships and geophysical surveys. WP2 will also provide water pathways and travel time to WP3. - WP3 will provide constraints from the water/rock processes and therefore evaluate the reliability of the results given by WP2. The three first WPs will work inside an iterative loop between the WPs until a good match between modeling and observations is reached. Due to an EQUIPEX (CRITEX) most of the equipment required for this project is already installed and operational. The consortium is based on 7 multidisciplinary institutes, 1 foreign researcher, 1 private office, an university department for science popularization and the ONF (French forest national agency). Most of the teams involved in this project have already worked together on the Strengbach watershed but never at this level of interdisciplinarity. This project will provide a better understanding of the long-term variation of water and mineral nutrient availabilities and of forest health in middle altitude mountain areas.

DECISIVE - Tracking degradation of soil pollutants with multi-elemental compound-specific isotope analysis Agricultural and urban soils were exposed to many organic pollutants (pesticides, industrial pollutants) which are leached to groundwater. Transition to eco-phyto practice and clean production will stop most new contamination, but old contamination still needs to be managed, because pollutants and some degradation products leach to groundwater and drinking water, or run to surface water where they contaminate fish and the food chain. The project DECiSIvE proposes a new tool to monitor the natural degradation of organic chemicals: Multi-Element Compound-Specific Stable Isotope Analysis (ME-CSIA). With the help of this technique, the processes acting on remaining pollutants (e.g. physical processes, abiotic degradation or biodegradation) can be identified and the advancement of removal can be quantified. This technique will be used in agricultural and urban soils for the target pollutants hydrocarbons, substituted phenyl-ureas (e.g. isoproturon), s-triazines (e.g. atrazine, simazine), chloroacetanilides (e.g. S-metolachlor) and chlordecone, including stable isotopes of carbon, hydrogen, nitrogen and chlorine. The project is structured in 6 work packages: WP1) Coordination; WP 2) Database of stable isotope values for commercial formulation; WP3) Development of specific extraction/purification methods for pesticide CSIA in soils; WP4) Abiotic transformation of soil persistent pollutants; WP5) Biotic degradation of soil persistent pollutants by ME-CSIA; and WP6) : Dissemination of results. The project partners are the Laboratory of Environmental Chemistry of Aix-Marseille University, the Laboratoire d’Hydrologie et de Géochimie of Strasbourg University and the unit Agroecology of the INRA at Dijon. The fallout of this project is a validated tool and a guideline allowing the application of ME-CSIA and the decision between natural attenuation and enhanced remediation, and guiding the management practice of land in transition to sustainable eco-functioning.

Calcium (Ca) is an essential nutrient in biology, and key element in natural, biogeochemical carbon sequestration. Despite advances in Ca isotope biogeochemistry, Ca dynamics in the Critical Zone are not well understood. The FILi-CaBeSo project will represent a breakthrough in our understanding of the isotope fractionation mechanisms of dissolved species at equilibrium, with application to the behavior of calcium (Ca) in the soil system. We will develop a (numerically affordable) methodological scheme to predict the isotopic fractionation properties of dissolved species, from an atomistic approach, 1) not requiring the harmonic approximation, so as to overcome the challenges posed by the dynamic behavior of solutions, and 2) based on a first-principles, or ab initio, modeling of atomic bonding (i.e. not based on empirical energy potentials), so as to ensure an application to virtually any aqueous species. To this aim, the present project relies on the interplay of several innovative numerical approaches. In particular, atomic interactions will be described by empirical potentials or by an ab initio approach, and various molecular dynamics schemes will be used. Our working hypotheses are that: • the structure, in particular the coordination, of Ca species in solution (the Ca2+(H2O)n (aq) aqua complex or other complexes in aqueous solution) is suitably described by molecular dynamics (MD). • for a species in solution, isotope fractionation should be computed based on a path integral molecular dynamics (PIMD), as developed in a PhD thesis supervised by the PI1. Static molecular cluster approaches, used by many, are inaccurate approximations. • Implementing advanced PIMD methodological schemes (path integral Langevin dynamics, ring polymer contraction), imported from the community of fundamental chemists, will significantly reduce the numerical cost, thus permitting an application to other species.

The need for the implementation of innovative governance of water resources in general and coastal aquifers in particular taking into account the technological development as well as socio-economic factors has become a worldwide necessity. In compliance with the challenges and scope of the PRIMA call topic 1.1.2 entitled “Sustainable, integrated water management”, Sustain-COAST main goal is to implement a new innovative governance approach of coastal aquifers between multiple water users and beneficiaries under severe changing climate conditions in 4 countries located in the both sides of the Mediterranean Sea (Greece, Tunisia, Italy and Turkey). For this aim, this project intends to establish an adapted multi-criteria decision supporting system (DSS) and Geographical Information System (GIS) platform with an online access for water stakeholders and policy makers. This DSS and platform will be based on: i) an active and continuous social participation and learning, ii) the use of advanced technologies and tools, such as optical sensors and remote sensing capacities, iii) the use of various available numerical models (Feflow and Modflow) for the prediction of these coastal aquifers quantity and quality progress in time and iv) the use of smart, adapted and visualized web applications. On the other hand, this project will permit the preservation of the studied coastal aquifers against anthropogenic pollution through the promotion of the local water management concept which is based on the 4R principles (Reduce; Recycle; Reuse and Recover). The main outcomes of this project will be communicated and disseminated by using the best practices and means for the highest profit of all the concerned actors. Thanks to this project, Mediterranean coastal groundwater will be managed in harmony and enthusiasm under the responsibility of all the concerned actors taking into account the local socio-economic context and the meteo-climatic trends.