STUDY ON REMOVAL OF CONTAMINATED SOIL ON FOREST SLOPE FOCUSING ON DIFFERENCE IN DENSITY OF SUBSURFACE GROUND

Abstract

A large amount of radioactive cesium was released from the Fukushima Daiichi nuclear power
station. Decontamination in living area has been almost completed for seven years. However, decontamination
has not progressed much in forests where people do not enter. The decontamination of soil on forest slope
cannot be done using heavy machinery unlike that on flatland. The effective decontamination method for the
forest slope is desired. Therefore, in this study, the collecting method of slope surface soil through flushing
water and the soil separation method focusing on the difference in the density of minerals were proposed and
examined. In the proposed method, it is expected to reduce the volume of contaminated soil through the
separation of the contaminated part and non-contaminated one. In this study, the laboratory test is conducted
to evaluate the usefulness of the proposed method. In the test, a device of simulating the slope and a device to
flush the soil by flowing water is produced. When an actual soil is utilized for the experiment, it is difficult to
ensure the experimental repeatability due to soil variability. Therefore, simulated soil consists of Toyoura
standard sand and vermiculite. To simulate soil contaminated with cesium, cesium standard solution is added
into the simulated soil. The soil is set on the slope, and the test is conducted to flush and collect the soil by
running water from upside to downside. As a result, it is clarified that only soil containing cesium can be
removed by separating the soil after flushing.