After radioactive substances discharged from the Fukushima Daiichi Nuclear Power Plant accident and deposited on the land, they entered into dynamic processes that continually move the radionuclides by physical (e.g., wind, rain) and biological methods (e.g., uptake by plants). To reduce the risk of radiation, it is necessary to understand the movement processes and be able to predict where the radiation will be in the future.
For example, cesium-137 attaches to soil particles and is transported with the soil by erosion when it rains, flowing into the sea through rivers. In addition, the soil-bound cesium accumulates as sediments in closed water basins like lakes and marshes. The detachment of cesium away from soils is a slow process that is governed by chemical changes. This knowledge was formed from research on radioactive substances in the past.
However, because Fukushima has more rainfall and its geographical features are much steeper, the conditions that govern the movement of radioactive substances are different from those that have been previously studied. On the basis of these differences, and making good use of past knowledge, our research seeks to clarify the original condition of radioactive substances on the land in Fukushima Prefecture so that we can predict where it will reside in the future.