Health Effects of Radiation:
5 Themes
Visiting

(v) Behavior of radioactive materials

In various monitoring results, radioactive material detection is decreasing.
Where has the cesium released into the environment gone?

Transfer of Fallen and Deposited Cesium in the Environment

Transfer of Fallen and Deposited Cesium in the Environment

The above figure illustrates the process of fallen and deposited cesium in the forest flowing from upstream to a downstream dam lake. The two enlarged pictures show the forest floor and the sediment at the bottom of the dam lake, both indicating that the cesium is deposited in the surface layer of soil.
Distribution of radioactive cesium released into the environment due to the accident at Tokyo Electric Power Company (TEPCO)'s Fukushima Daiichi NPS has changed significantly over time. Cesium that adhered to tree bark, branches and leaves immediately after the accident transferred onto the forest soil due to leaf fall and precipitation, etc. At present, over 90% is found to be located within a depth of 5 cm from the ground surface.

For more information about transfer of cesium in the environment, see page 178 of Vol. 1, FY2017 edition.