Subscription Only: Radioactive ‘black soil’ patches: A scourge or a solution?
Asahi Shimbun AJW
By SHOJI NOMURA/ ASAHI SHIMBUN WEEKLY AERA
June 14, 2012
Koichi Oyama noticed something strange when he was measuring radiation levels in Minami-Soma, Fukushima Prefecture. In many places where the readings jumped, the municipal assembly member found patches of dried dark soil.
One reason for the wide prevalence of the black soil is that it contains a micro-organism known as cyanobacteria that is common around Japan.
The bacteria is of a blue-green color, but it turns black upon drying.
There are two major theories on why the cyanobacteria in the black soil has such high levels of radiation, but nothing has been confirmed.
One theory posits that the radiation becomes concentrated in the cyanobacteria. There is scientific evidence that cyanobacteria absorbs cesium, but confirmation has yet to be made on whether such radiation concentration has occurred in the cyanobacteria found in the black soil samples.
Hayakawa’s theory is that the high radiation levels are due to radioactive cesium from the Fukushima nuclear accident that was pushed by rain and wind and accumulated along roads. He believes that the phenomenon occurs even in regular soil containing no cyanobacteria.
According to Hayakawa’s theory, all dirt along roads is capable of recording high radiation levels, regardless of the color of the soil.
Published: June 14th, 2012 at 4:06 pm ET