Modeling Cl^? Concentration and ¦Ä³⁷Cl Profiles in Porewater Across a 250m-thick Indurated Argillite at the Tournemire URL (France)

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• 作者：Le Gal La Salle Corinne^a ; ^b ; ^{Corinne.legallasalle@unimes.fr} ; Matray Jean-Michel^c ; Bensenouci Fethi^c ; ^d ; Michelot Jean-Luc^d ; Dauzè ; res Alexandre^c ; Wittebroodt Charles^c ; Frape Shaun^e ; Shouakar-Stashe Orphan^e ; Rebeix Romain^a ; ^b ; Lancelot Joë ; l^a ; ^b
• 关键词：Argillite ; Fracture groundwater ; Porewater ; Chloride ; Chlorine isotopes ; Diffusion ; Transport modelling ; Tournemire URL
• 刊名：Procedia Earth and Planetary Science
• 出版年：2013
• 出版时间：2013
• 年：2013
• 卷：7
• 期：Complete
• 页码：471-474
• 全文大小：381 K

文摘

Dissolved chloride in argillite porewater has been studied as a natural analogue for radionuclides potentially released from radioactive waste disposal. The Tournemire URL intersects impervious and compacted argillite. A previously obtained chloride concentration profile of intact rock is symmetric with a maximum concentration of 0.6¡À0.1 g/L, compared to 19 g/L for the original connate seawater. Dissolved chloride shows high ¦Ä³⁷Cl values, ranging between +6 and +8¡ë vs. SMOC. The modeled profile considers diffusive exchange between connate seawater and meteoric freshwater. Transport parameters were obtained by radial diffusion experiments. Numerical modeling was performed with the coupled reactive-transport code Hytec. Simulations suggest a diffusive-exchange time of 85¡À10 Ma for Cl, which correlates with a major erosional period. Simulated ¦Ä³⁷Cl values between 1.002 and agree with observed porewater ¦Ä³⁷Cl. This study strongly suggests that the dissolved chloride profile in the argillites results from diffusive exchange and indicates that unfractured argillites can provide good confinement.