Desorption of cesium from river sediments and aggregation of sediment particles in the brackish water region of river systems

Fujiwara, Kenso ; Iijima, Kazuki  ; Terashima, Motoki  ; Tachi, Yukio  

Due to the accident of the Fukushima Dai-ichi Nuclear Power Plant, radioactive cesium (Cs) was released in a wide range of areas in and around the Fukushima prefecture. Thus, the chemical condition and mechanism governing transport behavior of Cs should be investigated to predict the behavior of Cs in the natural system. In the brackish water region near the river mouth where a cognate ion (Na, K) concentration increases due to the mixture of seawater, two dynamic evolutions influencing Cs behavior are expected. Firstly, the soil has an ion exchange sites, Cs adsorbed onto ion exchange sites of soil particles is likely to be desorbed. Secondly, decreasing of electrostatic repulsion among clay particles causes aggregation of particles leading to deposition with Cs. In this report, Cs desorption and aggregation of particles such as clays was examined using the seawater of the estuary in the coast and the sediments of the riverbed.