Impact of the electron donor on in situ microbial nitrate reduction in Opalinus Clay: results from the Mont Terri rock laboratory (Switzerland)

Mont Terri rock laboratory, located in the Swiss Jurassic Mountains, was established with the focus on the investigation and analysys of the properties of argillaceous formations. The scope of Opalinus Clay as a safe, potential option for nuclear waste disposal was broaden, as the behaviour of claystone is of high interest also in the context of caprocks, and hence, for many dynamical processes in the subsurfaces. Extensive research has been performed already for more than 20 years by the partners of the Mont Terri Consortium. These close cooperations cover a broad range of scientific aspects using numerical modelling, laboratory studies, and last not least in-situ experiments. Here, included in the long-term monitoring programme, new investigations apply tiltmeters. Since April 2019, platform tiltmeters have been installed at various locations within the galleries and niches of Mont Terri. The biaxial instruments have resolutions of 1 nrad and 0.1 &#181;rad, respectively (Applied Geomechanics and Lippmann Geophysikalische Messger&#228;te). The tilt measurements are embedded within various experiments contributing to specific, multiparametrical studies. However, the growing tilt network as a whole will also provide novel information of the rock laboratory. The different time-scales of interest include long-term observations of yearly and decadal variability. So far tilt signals were identified due to excavations during the recent enlargement of the laboratory, earthquake activity (Albania), and local effects. First results of these quasi-continuous recordings will be presented.

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In situ measurements at the Mont Terri rock laboratory to study argillaceous rocks

10.5194/egusphere-egu21-8552 ◽

2021 ◽

Author(s):

Dorothee Rebscher ◽

Thies Beilecke ◽

Stephan Costabel ◽

Markus Furche ◽

Jürgen Hesser ◽

...

Keyword(s):

Saturation Pressure ◽

Opalinus Clay ◽

Knowledge Gain ◽

Rock Laboratory ◽

Federal Institute ◽

Argillaceous Rocks ◽

Fruitful Cooperation ◽

Mont Terri ◽

Mont Terri Rock Laboratory

Safe as well as sensible economic uses of the subsurface demand both the comprehensive knowledge of the present state of a system and the understanding of the relevant dynamical processes. In order to facilitate these requirements, adequate characterisation, sufficient monitoring, and conclusive experiments have to be performed. Following this directive, the German Federal Institute for Geosciences and Natural Resources (BGR) has developed, adapted, and successfully employed methods to prospect Opalinus Clay in the Swiss Mont Terri rock laboratory. These methods encompass geoscientific in situ characterisations as well as investigation techniques as part of long-term monitoring programmes from the complementing fields of e.g. micro-seismics, Electrical Resistivity Tomography, micro-structural petrography, geohydrology, and Nuclear Magnetic Resonance. With this expertise, BGR has contributed numerous experiments, which are embedded and coordinated in the long-standing and fruitful cooperation with the partners of the Mont Terri Consortium.The knowledge gain, based on now almost 25&#160;years of BGR's engagement in the Mont Terri Project, offers comparison and evaluation of different, complementing methods determining present values and their evolution in time of e.g. moisture, saturation, pressure, deformation, the characterisation of parameter variability, and localisation of heterogeneities. It provides information allowing for programme optimisation of in situ measuring methods concerning penetration, resolution, effort, time, or feasibility. Therefore, the research results can be used for decision-making to refine investigation endevours in regards to specific demands of a certain site or a particular scientific problem not only for Opalinus Clay but also other claystone formations, and in some cases even for non-argillaceous rocks.

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