| Volumes and Issues Contents of Issue 4 |
www.hydrol-earth-syst-sci-discuss.net/6/5415/2009/
doi:10.5194/hessd-6-5415-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Variability of the groundwater sulfate concentration in fractured rock slopes: a tool to identify active unstable areas
1Institut des Sciences de la Terre d'Orléans – ISTO, UMR 6113, Université d'Orléans, CNRS/INSU, Université François Rabelais, Tours, Campus Géosciences, 1A, rue de la Férollerie, 45071 Orléans cedex 2, France
2Laboratoire de Géophysique interne et tectonophysique – LGIT, UMR 5559, Université Joseph Fourier, CNRS/INSU, Observatoire de Grenoble – BP 53, 38041 Grenoble, France
3Laboratoire de Chrono-Environnement – LCE, UMR 6249, Université de Franche-Comté, CNRS/INSU, France
4GéoSciences Azur (GA) – UMR6526, CNRS/INSU/IRD, UR082, Observatoire de la Cote d'Azur, Université de Nice Sophia-Antipolis, Université Pierre et Marie Curie, Paris VI, 250 rue A. Einstein, 06560, Valbonne, France
5Dipartemento Ingegneria Strutturale e Geotecnica – DIST, Politecnico di Torino, Corso Duca Abruzzi 24, 10129 Torino, Italia
Abstract. Water chemical analysis of 100 springs from the Orco and the Tinée valleys (Western Italy and Southern France) and a 7 years groundwater chemistry monitoring of the 5 main springs were performed. All these springs drain crystalline rock slopes. Some of these drain currently active gravitational slope deformations.
The pyrite nuclei contained in crystalline rock materials were found in the fractures to be covered superficially by iron oxide coatings. Potentially, the infiltration of oxidigenated waters leads to the dissolution of iron(II) sulfides associated with precipitation of insoluble iron(III) oxides and with a consequent release of sulfate ions to solution, such as observed.
All the waters flowing through unstable slopes show anomalies in the sulfate concentrations compared to stable aquifers. A sulfate concentrations increasing was observed repeatability after five consecutive landslides and suggest that the mechanical deformation is the origin of changes of the water composition and of the superficial mineralogy in the fractures. Moreover, the long-term observation of changes in water chemistry, rock mineral composition and associated calculation shows that sliding acceleration and chemical composition are closely related. Such signatures is produced even from slow (mm/yr) and low magnitude deformations. This result opens interesting perspective for the follow-up of sliding dynamic in landslides or in (a)seismic events and for the eventual prediction of catastrophic ruptures.
Discussion Paper (PDF, 5115 KB) Interactive Discussion (Closed, 4 Comments) Final Revised Paper (HESS)
Citation: Binet, S., Spadini, L., Bertrand, C., Guglielmi, Y., Mudry, J., and Scavia, C.: Variability of the groundwater sulfate concentration in fractured rock slopes: a tool to identify active unstable areas, Hydrol. Earth Syst. Sci. Discuss., 6, 5415-5444, doi:10.5194/hessd-6-5415-2009, 2009. Bibtex EndNote Reference Manager XML
