This paper illustrates the behavior of radioactive cesium (radiocesium) in agricultural environment mostly based on the new findings obtained during the last 5 years after the Tokyo Electric Power Company (TEPCO)- Fukushima Daiichi Nuclear Power Plant (FDNPP) acci-dent in 2011, in comparison with the knowledge in Europe after the Chernobyl Nuclear Power Plant (CNPP) accident in 1986. The highlight topics are on the potassium (K) application as the most effective measure to reduce trans-fer factor (TF) of radiocesium from soil to crop; discovery and characterization of a few micrometer-size particulate radiocesium deposits; formulation of effective solid-liquid
distribution coefficient (Kd) to elucidate in-situ Kd varia-tion; unexpectedly rapid migration rate of radiocesium in
soil in Europe as well as in Japan; importance of long-term monitoring of radiocesium inventory in soil, etc. Fur-ther research needs to ensure the long-term safety on the crop production in the contaminated/decontaminated agri-cultural soils would be proposed as follows: developing Kd database and Kd formula; proposing appropriate K ap-plication scenario by using short- to long-term TF predic-tion model; reconstructing water-soluble/particulate radio-cesium deposition map in 2011; and understanding the bio-geochemical cycle of radiocesium in relation with that of stable cesium in agricultural environment.
We are on the way to remediate radioactive pol-lutants emitted from Fukushima daiichi nuclear power sta-tion after the great east Japan earthquake. Migration and redistribution of radioactive cesium was expected to be very slow. It was thought Cs must remain near the sur-face soil for years. However, rapid migration of radioac-tive cesium into deeper layer was observed in some area in Fukushima. In this article, factors affecting and caus-ing rapid migration of radioactive cesium in soils are dis-cussed. Frayed edge sites (FES) at the edge of illite and vermiculite clays are thought to retain Cs quite strongly. However, it might take time for cesium to reach the FESs. Unexpected migration of Cs may take place if a sort of transport phenomena such as percolation or infiltration of liquid water occurs during an approaching of Cs to the strongly bound sites. Besides, dissolved organic matter in soil would obstruct approach of cesium to FESs. This might be another factor to cause rapid migration of ra-dioactive Cs into deeper layer.