Geochemical analysis of groundwater chemistry after the drift closure in the granite

Hayashida, Kazuki; Kato, Toshihiro; Kubota, Mitsuru; Iwatsuki, Teruki  

This study aims to understand the hydrogeochemical condition and dominant process after the drift closure. To this aim the drift closure experiment was conducted in the granitic rock of 500 m below ground level of Mizunami Underground Research Laboratory. The groundwater chemistry such as major chemical component, pH and redox condition has been monitored in closed drift for 1 year. Dominant processes on chemical evolution of isolated groundwater in the closed drift were identified as follows; continuous replacement by surround rock water, microbial reduction, water-mineral interactions with evaporite, shotcrete and granite.