The workshop aims at gathering high-level scientists, to share their points of view, methodologies, certainties and open questions, within a pluridisciplinary and transversal approach to tackle complex problems. The exchanges are organized around the mechanistic understanding and the spatialized phenomenology of the multiphasic reactive transport within unsaturated hydrosystems impacted by global changes and man activities, as are the critical zone, the depleted aquifers, the deep underground targeted for nuclear wastes, energy and CO2 storages, and associated environmental issues.
The understanding of the behavior of the Critical Zone (CZ) in response to the global changes requires the integration of geological, geochemical and biological cycles and their couplings at different and relevant time-space scales. The OZNS platform (Observatory of the Vadoze Zone (VZ) of the Beauce carbonate aquifer) is a part of the PIVOTS regional program (Innovation Platforms for the valorisation and optimization of environmental technologies: https://plateformes-pivots.eu/ ) with a main objective directed to the understanding of mass and heat transfer mechanisms and the fate of pollutants in the CZ compartments. The OZNS observatory consists of a well prospecting the entire thickness of the VZ up to the water table, with a finite diameter of ~ 4 m and a depth of ~ 20 m. The site is located in the Beauce region, in a heterogeneous carbonaceous formation, with a typical sequence (from top to bottom): ground/cryoturbated limestone / limestone marl / fractured micritic limestone. The well will be equipped with environmental monitoring, soil, and subsoil imaging tools in order to understand reactive transport phenomena and exchanges of mass and heat between phases (water - rock – gas) throughout the continuum «Soil - Unsaturated Zone - Capillary Fringe - Aquifer.
The field acquisitions of long-term environmental data target are crucial to identify the fingerprints of complex and coupled physical, physicochemical and microbiological processes as well as their role in fixation, degradation and / or transfer of pollutants in the VZ. This obviously requires multidisciplinary skills, complementary methods and result joint interpretations as well as renewed theoretical approaches. The development of OZNS platform aims to build a large and sustainable partnerships (academic, industrial, state agencies, etc.), at national and international scales, in a collaborative way that guarantees the continuity between the academic research, industrial needs and the academic training of young engineers and researchers.
Beyond the equipment itself, OZNS aims also at becoming a place to discuss the scientific issues related to unsaturated geological media. This can be either naturally developed within the CZ compartments, or created by industrial purposes at various depths in the underground for CO2 and energy vectors storage and extraction of non-wetting energy substances where the active interfaces between phases play a key role in mass and energy exchanges inducing important petrophysical evolutions of targeted reservoirs and geological structures.