Ra geochemistry in the Ningyo-toge mine area

Abstract

In this study, we investigated the geochemical behavior of Ra focusing on its distribution between sediment and water. We collected surface sediment and water samples for Ra-226 analysis in the Ningyo-toge area. XRD and XAFS analyses indicated that surface sediments were composed of ferrihydrite and goethite. Apparent distribution coefficients of Ra between sediment and water were larger than those determined experimentally for ferrihydrite and goethite. Thus, it is possible that a minor component contributed to an increase in the apparent distribution coefficients. Another possibility is upward flow of pore water containing Ra-226 or diffusion of Ra-226 released from lower sediment layers.