The observatory (O-ZNS platform), a part of the family of PIVOTS program (Environmental Technology Innovation, Development and Optimization Platforms) aims to understand the fluids-rock-biosphere interactions and the mass (water and contaminants) and heat transfers in the vadose zone (VZ). This will allow to characterize the dynamics and transfers within and throughout the unsaturated zone in order to understand the behavior of the Critical Zone (CZ) captured through an agricultural plot of 2,400 m2. The site is located in the Beauce region (France), in a heterogeneous carbonaceous formation, with a typical geological sequence (from top to bottom): ground/cryoturbated limestone / limestone marl / fractured micritic limestone. The concept of O-ZNS is based on carrying out 13 to 15 boreholes of 20 to 25 m of depth and a central well with exceptional dimensions (depth – 20 m & diameter – 4m) with 2 lysimetric boxes, offering a unique opportunity to finely decipher coupled processes in the environmental geoscience.
The field work to set up the observatory has started the 25th of February. The completion of the first borehole with 25 m deep and 6.5 cm in diameter was realized. The piezometric level (nappe de Beauce) is currently at 18.80 m and it oscillates annually between 16 and 20 m.
Progress of work :
- The boreholes drilling installation work will continue until the end of April
- The digging of the large central well will start around next mid-May
- The installation of the entire O-ZNS observatory system will last until the end of 2020
Do not hesitate to express your needs and wishes for obtaining rock samples or do measurements before, during and after digging the big well !
O-ZNS platform, what for ?
The platform allows the development/adaptation of innovative geophysical and physico-chemical sensors to quantify water transfers in the VZ relative to reactive chemicals, redox barriers, capillary fringe, etc. in a porous/fissured carbonated structure. The research field aspire to identify the level of coupling between the interfacial properties of phases, and the electrical, electrokinetic, electrochemical properties associated with moving fluids and biogeochemical reactions. The deployment of physical chemical sensors to monitor temperature, pressure, water content, gas, pH, Eh, micro-displacement, etc. in different parts of the O-ZNS platform should make it possible to detect the impact of variations of atmospheric temperature, rainfall, agricultural practices, etc. Indeed, these parameter impacts the heat and mass transfers from the surface to the aquifer and from the aquifer to the atmosphere flowing throughout the continuum “soil – rhizosphere – unsaturated zone – capillary fringe – aquifer”.
With strong support from the O-ZNS observatory data, we will be able to revisit and integrate the reactive transport models into other community models (especially geophysics, hydrogeology, …) facilitating process understanding across disciplines and across different time-space scales with relevant couplings. Geophysical imaging, made from the surface as well as in boreholes, make it possible to obtain information on the lithology as well as on the presence of clay levels, the density, the porosity and the resistivity of the VZ.
The O-ZNS observatory is planned to last several decades during which original and unique massive data on the mass (water, solutes, organic and inorganic contaminants, gases, etc.) and heat (induced by gradients temperature, microbiological reactions, etc.) transfers will be acquired across this continuum of CZ for environmental issues for different georesources needs (agriculture, water, energy, … ).