Sunflower Planting Hardly Did Anything to Reduce Radioactive Cesium in Soil

Well, it sure looked pretty, a field of sunflowers, but if the Ministry of Agriculture, Forestry and Fisheries is to be believed, it did not do much more than looking pretty, and creating radioactive sunflowers that'll have to be somehow safety disposed as nuclear waste.

Sunflower seeds were planted in many, many areas within the 20-kilometer radius exclusion zone. Who is going to dispose these nuclear waste, and how?

From Asahi Shinbun (9/14/2011):

放射性物質によって汚れた農地をどのように除染するのが効果的かを福島県内で検証してきた農林水産省は１４日、これまでの結果を発表した。表土を削り取る方法が有効と確認できた一方、ヒマワリを植えて放射性セシウムを吸い上げる方法には、ほとんど効果がないことがわかった。

The Ministry of Agriculture, Forestry and Fisheries announced the result of its study in Fukushima Prefecture on the effectiveness of various method of decontamination of the farmland that have been contaminated with radioactive materials. While it was confirmed that scraping off the surface soil was effective, planting sunflowers to absorb radioactive cesium proved to be hardly effective at all.

　農水省は５月下旬から、東京電力福島第一原発に近い飯舘村と川俣町の６カ所の田畑を使い、除染方法を実証実験してきた。

The Ministry has been experimenting on the decontamination methods since late May, using 6 locations in Iitate-mura and Kawamata-machi, which are close to Fukushima I Nuclear Power Plant.

　表土を削る方法のうち、最も効果が大きかったのは、根の浅い牧草ごと約３センチはぎ取る方法。セシウムの減少率は９７％と高かった。ふつうに表土を削り取る場合は深さ約４センチで７５％の減少。化学物質の固化剤を使って表土を固めてから削ると８２％減と、より効果が上がった。

Of different methods to scrape off the surface soil, the most effective was scraping about 3 centimeters with the shallow-rooted grass. This method decreased radioactive cesium by 97%. Scraping the soil alone about 4 centimeters achieved 75% reduction. If the surface soil was treated with solidifying agent before being scraped, the reduction was 82%.

　水田に水をはって耕し、排水する方法は３６％の減少率。田畑を３０～６０センチの深さで掘って表土と入れ替えるのも放射線量を半減させる効果があった。

Filling the rice paddies with water, then tilling and stirring the soil and draining the water reduced radioactive cesium by 36%. Digging the field 30 to 60 centimeter deep and burying the surface soil was also effective in reducing the radiation level in half.

　一方、ヒマワリが土壌から吸い上げる量は土のセシウム濃度の２千分の１にとどまった。農水省は「ほかに吸収量の高い植物の候補もない。現実的には除染には使えない」とした。

On the other hand, the amount of cesium that sunflowers absorbed from the soil was only one-2000th of the density of radioactive cesium in the soil. The Ministry concluded that "there is no other candidate that has higher absorption ratio. Practically speaking, sunflowers are not effective in decontamination".

　これらの結果を踏まえたうえで、農水省は土壌の汚染度合いに応じた除染の考え方を示した。

Based on the result, the Ministry disclosed its ideas of decontamination based on the density of radioactive materials in the soil.

　イネの作付け制限がかかる土１キロあたり５千ベクレル以上の福島県内の農地は推計で８３００ヘクタール。実験の結果から、作付け可能な５千ベクレル未満まで下げるには、１万ベクレルを超す田畑では表土を削る方法以外は難しいことがわかった。５千～１万ベクレルの範囲でもほかの手法を使える場所は限られるという。

The farmland whose radioactive materials in the soil would exceed 5,000 becquerels/kg (limit above which the planting of rice is prohibited) is estimated to be 8,300 hectares [about 20,500 acres]. From the result of the experiments, in case of the farmland whose radioactive material density exceeds 10,000 becquerels/kg, it may be difficult to reduce the level down below 5,000 becquerels/kg unless the surface soil is removed. Between 5,000 and 10,000 becquerels/kg, there may not be other choices but removing the surface soil.

　仮に８３００ヘクタールすべてを削った場合に発生する土は３００万トンを超す。同省は「土からセシウムだけを除去する技術開発に取り組み、土をできるだけ戻せるようにしたい」と話している。（井上恵一朗）

If the surface soil is removed in 8,300 hectares, the amount of contaminated soil generated would exceed 3 million tonnes. The Ministry says it hopes to develop a technology to remove cesium from the soil so that the soil can be put back in the field. (reported by Keiichiro Inoue)

What about plutonium and strontium? Cobalt-60?

Isn't removing the surface soil what Russia/Ukraine/Beralus have done and to very little effect? The fresh supply of radioactive cesium and other nuclides come down from the mountains. What about decontaminating the mountains?

Impossible.

I wouldn't call Iitate-mura and Kawamata-machi "close to Fukushima I Nuclear Power Plant". They are more than 35 kilometers away. The reporter should have said "close enough for the government researchers to go anywhere near the plant".

By the way, as one refugee from Iitate-mura strongly hints in his tweets, Iitate-mura's political leaders seem in excellent terms with the national government and government-connected contractors keen on getting "decon" jobs. After all, 200 billion yen (US$2.6 billion) is to be spent on this village of 6,000 people alone so that the villagers can come home in 2 years.

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