HR: 0800h
AN: H41F-0475    [Abstracts]
TI: Water Sulfate Concentration Variability In Fractured Rock Slopes: An Instantaneous Marker Of Deformation.
AU: * Binet, S
EM: stephane.binet@univ-fcomte.fr
AF: Universite de Franche Comte, 16 route de gray, Besancon, 25000 France
AU: * Binet, S
EM: stephane.binet@univ-fcomte.fr
AF: CNRS UNSA Geosciences Azur, 250 rue Albert Einstein, Valbonne, 06560 France
AU: * Binet, S
EM: stephane.binet@univ-fcomte.fr
AF: Politecnico di Torino, Corso degli Abruzzi, 24, Torino, 10129 Italy
AU: Bertrand, C
EM: catherine.bertrand@univ-fcomte.fr
AF: Universite de Franche Comte, 16 route de gray, Besancon, 25000 France
AU: Mudry, J
EM: jacques.mudry@univ-fcomte.fr
AF: Universite de Franche Comte, 16 route de gray, Besancon, 25000 France
AU: Guglielmi, Y
EM: YGuglielmi@lbl.gov
AF: CNRS UNSA Geosciences Azur, 250 rue Albert Einstein, Valbonne, 06560 France
AU: Scavia, C
EM: claudio.scavia@polito.it
AF: Politecnico di Torino, Corso degli Abruzzi, 24, Torino, 10129 Italy
AU: Troisi, C
H41F-0475 AF: ARPA, Via San Domenico 22/B, Torino, 10129 Italy
AB: An hydrogeochemical study was carried out in two glacial Alpine valleys which are the site of numerous slope rock instabilities in gneissic rocks. Spatial variability of groundwater sulfate concentration in the two valleys, and a seven year long monitoring of groundwater chemistry of springs draining instable areas reveal the possibility to use hydrochemistry (mainly sulfate concentration in water) as a tool to identify current instable area. Hydro-chemistry evolves in time with the reaction kinetics of sulfate dissolution on pyriteous minerals. Significant residence time evolution or deep water mixing at the spring located in the instable area can not explain this evolution. Thus, during low-water periods, the dynamics of dissolution in the moving masses is modified, by water-rock interactions due to hydrological, mechanical and chemical processes. Leaching experiments of gneiss enable to identify the mechanisms of sulfate evolution linked with deformation. Scanning electron microscopy shows thin layers of ferrous oxides on weathered gneiss fractures, where the dissolution has occurred. The observed time evolution of sulfate concentration can be explained by neoformed minerals that limit the kinetics of dissolution. Thus the sulfate content variability in fractured rock slopes is a short term tools to discriminate current instable area.
DE: 1806 Chemistry of fresh water
DE: 1810 Debris flow and landslides
DE: 1826 Geomorphology: hillslope (1625)
DE: 1835 Hydrogeophysics
DE: 1858 Rocks: chemical properties
SC: Hydrology [H]
MN: Fall Meeting 2005