Radioactive cesium did not penetrate the soil in forests in Iitate, Fukushima Prefecture, in the two months after the crisis started at the Fukushima No. 1 nuclear power plant, according to a study.
Radioactive cesium did not penetrate the soil in forests in Iitate, Fukushima Prefecture, in the two months after the crisis started at the Fukushima No. 1 nuclear power plant, according to a study.
The study, headed by Toshihiko Ohnuki, a researcher at the Japan Atomic Energy Agency, could lead to a reduction in the amount of soil needed to be removed for decontamination work.
The cesium spewed from the plant remained on tree trunks and leaf surfaces, Ohnuki said.
"Temperatures were around zero around the time when rain containing cesium fell in March, and rain turned into snow or ice," Ohnuki said. "Radioactive materials apparently did not flow onto the land surface and remained on leaves and other parts."
The agriculture ministry had earlier said its studies showed that removing fallen leaves and grass would be effective in reducing radioactive materials in forests.
But the study by Ohnuki and other researchers showed that the volume of soil needed to be removed can be reduced by cleaning up only areas where cesium is concentrated.
The results of the study will be carried in a journal of the Atomic Energy Society of Japan in January.
The researchers examined cesium on cedar, plum, "kaya" and other trees, as well as ferns and pastures, on May 14, about two months after the March 11 Great East Japan Earthquake and tsunami crippled the Fukushima No. 1 plant.
The trees did not absorb radioactive materials, as cesium was concentrated on trunk surfaces or leaves on high branches, according to the study. Only small amounts of cesium were detected on young leaves that grew after the accident started.
Cesium was not detected on ferns. On pastures, cesium was found only on the grass, but not the roots, Ohnuki said.