After having spent much of sunday in a fruitless search for a storage box for my garden tools, I get the chance to write to my beloved readers another blog entry. Now all along I had been making the prediction that the cesium would stick like glue to the soil and stay in the top layer. Some workers have examined soil samples and in a paper (Takeshi Fujiwara, Takumi Saito, Yusa Muroya, Hiroyuki Sawahata, Yuji Yamashita, Shinya Nagasaki, Koji Okamoto, Hiroyuki Takahashi, Mitsuru Uesaka, Yosuke Katsumura and Satoru Tanaka, Journal of Environmental Radioactivity, 2012, 113, 37-44) an examination of soil samples from the Fukushima area has been reported. In this paper it has been shown that the cesium is concentrated in the top layer of the soil.
Circa 70 % of the cesium is in the top 2 cm in the soil, while the iodine was more mobile. The good news is that the cesium will not enter ground water, further good news is that plants with deep root systems are unlikely to absorb much cesium. The bad news is that the cesium will be in the right part of the soil to enter grass via its shallow roots and the fact that the cesium is in the upper layers of the soil will increase the external threat due to gamma photons.
It is interesting to note that the Japanese may not worked out a sensible way to store the contaminated soil which is removed during the clean up of land. It has been reported that people are being required to store contaminated soil from cleaning up their own gardens on their own land. I think it would be better if industrial estates were used as places to store the contaminated soil while the government find a place to store the soil for the next 300 years.
I have spoken to my legal advisor about human rights, and my advisor told me that the right to have a safe environment could override the right to object to a waste store in a given town. I hold the view that if the waste stores are sited well away from homes and other places where the general public spend a lot of time, then it is OK to raise the dose rate in the waste store. The waste store should be designed to avoid releasing cesium into the environment and the construction of the waste store should be done in such a way that it does not increase the dose rate at the edge of the site. I think that the reference dose rate for the latter point should be the dose rate at the edge of the site before the clean up is done.
If the dose rate at the edge of the site is 2 microSv per hour, then this will give a person a dose per year of 17.5 mSv which is a big dose for the general public. But if the dose rate at the same spot was 2 microSv per hour before the clean up which generated the waste which will go into the store is conducted then the clean up will have a neutral effect at the edge of the waste store but will have a good effect on the majority of the land.
I may do some calculations on the subject if I get time in the near future.