The Yomiuri Shimbun
Authorities trying to decontaminate radioactive soil in the aftermath of the accident at the Fukushima No. 1 nuclear power plant have found that sunflowers, despite their reputation for absorbing radioactive cesium, have little effect, an experiment has shown.
The experiment was conducted by the Agriculture, Forestry and Fisheries Ministry. Following the outbreak of the nuclear crisis, a large amount of radioactive substances were released, contaminating the areas around the plant.
Although the experiment found that scraping away the surface of the contaminated soil is effective to reduce the density of radioactive cesium, this method leaves the problem of how to dispose of a large quantity of contaminated soil.
The experiment on removing radioactive cesium started in May in farmland totaling 7,000 square meters in Iitatemura and other locations in Fukushima Prefecture.
In the experiment, the effects of the following four methods were examined: scraping away surface soil; washing contaminated soil with water and removing the water; burying topsoil and replacing it with subsoil; and using sunflowers and other plants to absorb radioactive cesium in soil.
The results showed the least effective of the four methods was the use of plants.
Sunflowers, which were planted in May and bloomed in August, absorbed only 520 becquerels, or about 0.05 percent, of about 1.07 million becquerels of radioactive cesium per square meter of contaminated soil.
When four centimeters of topsoil was scraped away, the density of radioactive cesium was reduced by up to 75 percent. When three centimeters was scraped away from pastures with green grass, the density was reduced by up to 97 percent.
While switching topsoil and subsoil reduced the density of cesium on the surface, the amount of radioactive cesium remained unchanged.
The central government restricts rice growing in paddy fields with soil containing more than 5,000 becquerels of radioactive cesium per kilogram.
In Fukushima Prefecture alone, there are about 8,300 hectares of rice and vegetable fields in which radiation levels were found to exceed the government-set limit. If the topsoil of all the fields is scraped away, about 3 million to 4 million tons of contaminated soil is expected to be removed.
Based on the experiment's results, the ministry intends to finance the removal of cesium-contaminated soil in the prefecture with reserve funds and the third supplementary budget for this fiscal year.
As it is an enormous task to scrape away such a large amount of soil, the ministry is expected to coordinate with local governments on decontamination efforts.
(Sep. 16, 2011)
Showing posts with label sunflowers. Show all posts
Showing posts with label sunflowers. Show all posts
Friday, September 16, 2011
Saturday, April 23, 2011
23/04 Sunflowers to clean up radioactive soil
The Yomiuri Shimbun
Japanese researchers who study space agriculture believe growing sunflowers will remove radioactive cesium from contaminated soil around the Fukushima No.1 nuclear power plant, and are planning a project to plant as many of the yellow flowers as possible this year.
They have invited people to sow sunflower seeds near the Fukushima Prefecture power station, hoping the sunflower will become a symbol of recovery in the areas affected by the nuclear crisis.
After the sunflowers are harvested, they will be decomposed with bacteria, according to a plan by a Japan Aerospace Exploration Agency group led by Prof. Masamichi Yamashita.
After the 1986 Chernobyl nuclear disaster, sunflowers and rape blossoms were used to decontaminate soil in Ukraine. Radioactive cesium is similar to kalium, a commonly used fertilizer. If kalium is not present, sunflowers will absorb cesium instead.
If the harvested sunflowers are disposed of by burning them, radioactive cesium could be dispersed through smoke, which is why the researchers are considering using hyperthermophilic aerobic bacteria--used to produce compost--to decompose the plants. The decomposing process will reduce the sunflowers to about 1 percent of their previous volume, which will slash the amount of radioactive waste that needs to be dealt with.
The group has gathered about 300 kilograms of sunflower seeds and has also asked Thailand, a major producer of sunflower seeds, for cooperation in the project.
They also plan to ask high schools in and near the 30-kilometer zone around the Fukushima plant to grow sunflowers on their school grounds. Kanagawa prefectural Hiratsuka Agricultural High School has agreed to produce seedlings.
"We're still in the process of planning for the decomposition facility and some other things. Looking toward the autumn harvest, we'd like as many people as possible to join the project," Yamashita said.
For details about the project, see http://surc.isas.jaxa.jp/space_agriculture/ (in Japanese).
(Apr. 23, 2011)
Japanese researchers who study space agriculture believe growing sunflowers will remove radioactive cesium from contaminated soil around the Fukushima No.1 nuclear power plant, and are planning a project to plant as many of the yellow flowers as possible this year.
They have invited people to sow sunflower seeds near the Fukushima Prefecture power station, hoping the sunflower will become a symbol of recovery in the areas affected by the nuclear crisis.
After the sunflowers are harvested, they will be decomposed with bacteria, according to a plan by a Japan Aerospace Exploration Agency group led by Prof. Masamichi Yamashita.
After the 1986 Chernobyl nuclear disaster, sunflowers and rape blossoms were used to decontaminate soil in Ukraine. Radioactive cesium is similar to kalium, a commonly used fertilizer. If kalium is not present, sunflowers will absorb cesium instead.
If the harvested sunflowers are disposed of by burning them, radioactive cesium could be dispersed through smoke, which is why the researchers are considering using hyperthermophilic aerobic bacteria--used to produce compost--to decompose the plants. The decomposing process will reduce the sunflowers to about 1 percent of their previous volume, which will slash the amount of radioactive waste that needs to be dealt with.
The group has gathered about 300 kilograms of sunflower seeds and has also asked Thailand, a major producer of sunflower seeds, for cooperation in the project.
They also plan to ask high schools in and near the 30-kilometer zone around the Fukushima plant to grow sunflowers on their school grounds. Kanagawa prefectural Hiratsuka Agricultural High School has agreed to produce seedlings.
"We're still in the process of planning for the decomposition facility and some other things. Looking toward the autumn harvest, we'd like as many people as possible to join the project," Yamashita said.
For details about the project, see http://surc.isas.jaxa.jp/space_agriculture/ (in Japanese).
(Apr. 23, 2011)
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