Tc interaction with crystalline rock from Äspö (Sweden): Effect of in-situ rock redox capacity

Autor: Horst Geckeis, Rémi Marsac, Dieter Schild, Yury Totskiy, Tonya Vitova, I. Pidchenko, Florian Huber, Thorsten Schäfer, Stepan N. Kalmykov
Přispěvatelé: Karlsruhe Institute of Technology (KIT), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Lomonosov Moscow State University (MSU), 02 E 10800, Federal Ministry of Economics and Technology, 269658, European Union's European Atomic Energy Community's (Euratom), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS)
Jazyk: angličtina
Rok vydání: 2017
Předmět:
Zdroj: Applied geochemistry, 80, 90–101
Applied Geochemistry
Applied Geochemistry, 2017, 80, pp.90-101. ⟨10.1016/j.apgeochem.2017.01.026⟩
Applied Geochemistry, Elsevier, 2017, 80, pp.90-101. ⟨10.1016/j.apgeochem.2017.01.026⟩
ISSN: 0883-2927
1872-9134
Popis: International audience; The interaction of Tc(VII) with crushed crystalline rock (Äspö diorite; 1–2 mm size fraction) from the Äspö Hard Rock Laboratory (HRL) (Sweden) was studied by laboratory batch sorption and desorption experiments under Ar atmosphere using both natural and synthetic groundwater. The Äspö diorite used in the experiments was drilled, transported and handled as far as possible under anoxic conditions to preserve the in-situ rock redox capacity. For comparison, identical experiments using artificially oxidized Äspö diorite have been carried out to examine the effect of in-situ redox capacity on Tc uptake. According to the batch studies, Tc(VII) uptake on the Äspö diorite is strongly dependent on redox capacity. Uptake on un-oxidized rock is approximately 2 times higher compared to oxidized rock samples, most likely due to higher Fe(II) contents of the un-oxidized rock. Tc redox states and speciation both on the mineral surface and in the bulk were studied using X-ray photoelectron spectroscopy (XPS) and Tc K-edge X-ray absorption near edge structure (XANES) spectroscopy. The spectroscopic results verify a Tc(VII) reduction to Tc(IV) at the rock surface. Distribution coefficients (Kd) and surface normalized distribution coefficients (Ka) were determined and compared to available literature data. The formation of a Tc colloidal phase was not observed under the geochemical conditions prevailing in the experimental studies. Desorption of Tc is very low under anoxic conditions, but after artificial oxidation Tc mobility is strongly increased. The results of this work clearly highlight the effect of in-situ rock redox capacity on Tc retention.
Databáze: OpenAIRE
Externí odkaz: