R4: Mineral sciences of the Earth surface

[R4-01] Remediation mechanisms of uranium mill-tailing site at Ningyo-toge, Japan, under the circumneutral condition

*Keisuke Kawamoto¹, Asumi Ochiai¹, Ayaka Takeda¹, Yuriko Nakano¹, Hiroki Yokoo¹, Takumi Oki¹, Toshihiko Ohnuki², Yoshiyuki Ohara³, Kenjin Fukuyama³, Satoshi Utsunomiya¹ (1. Kyushu University, 2. Tokyo Institute of Technology, 3. Japan Atomic Energy Agency)

Keywords:natural attenuation, ferrihydrite, birnessite, uranium mine, Ningyo-toge

In the Ningyo-toge uranium mine, Okayama, Japan, various toxic elements such as U, As, and Ra are present in the mine wastewaters, of which the concentration except for Ra in the wastewater decrease below the regulatory limit by transport to downstream. In order to understand the fundamental processes of natural attenuation at this site, collected samples were analyzed using a variety of analytical techniques. Consequently, Fe hydroxides nanoparticles and Mn dioxides in Ningyo-toge play a key role on removing U, As and Ra from the wastewater.