原発事故由来の放射性物質の陸域環境における動態(談話室)

抄録

The radioactive cesium released by a nuclear plant accident was dissolved in rainwater and deposited on the land surface. The nuclide was adsorbed strongly by clay fraction as soon as it contacted with the soil and remained in the soil outer layer. Plants absorb various kinds of substances with water from their root, but the cesium in the clay is hardly absorbed.On the other hand, the nuclide moves more easily in sandy soil, peat soil and organic matter layers that accumulated on the forest floor. When cesium is deposited on organic matter, it can be absorbed by plants. The translocation pattern in plants is similar with that of potassium ; transferring and accumulating in the growing part. In the river water, the radioactivity is detected when the soil sediment is contained. It is important to take means not to move a surface soil from the contaminated sites. In forest environments, cesium moves in the ecosystem. The survey of the nuclide deposition at one and a half years after the accident revealed that the radioactivity in the coniferous leaf or bark is approximately reduced to half and that in the soil outer layer increased by degradation of organic matters followed by downward movement by precipitation. The nuclide adsorbed by the soil is hard to move outside the system without artificial disturbance. However, the outflow of the soil by the muddy water is concerned in a steep slope. The preventive measures with an artificial pond, a ditch or the wall will restrain re-pollution.