Tuesday, May 15, 2012

Radioactive Cesium From Fukushima Flowing Into Tokyo Bay from Rivers

Cesium spikes in Tokyo Bay samples
The Japan Times
May 15, 2012

Cesium spikes in Tokyo Bay samples
Contamination linked to Fukushima plant; no immediate threat to health Sludge samples taken at the mouths of two major rivers emptying into Tokyo Bay showed radioactive cesium contamination linked to the Fukushima No. 1 nuclear plant crisis grew by 1.5 to 13 times since August, a researcher at Kinki University said Monday.
The contamination poses no immediate health risk [...]
“Contamination is flowing into the bay from rivers, including the Edogawa River, where cities with high radiation levels like Kashiwa (in Chiba Prefecture) are located upstream,” Yamazaki told The Japan Times. [...]
[...] the peak contamination concentrations should be within the next couple of years, considering that the half-life of cesium-134 is about two years, Yamazaki said.
“If the contamination were to spread to fish, it is possible that radioactive isotopes could accumulate when bigger fish feed on smaller ones,” he said. [...]

May 10, 2012
Researchers measuring fallout from the Fukushima nuclear disaster say radioactive cesium deposits in Tokyo Bay have increased by up to 70 percent since last summer.


Cesium in Tokyo Bay focus of new study

The Asahi Shimbun  


Hideo Yamazaki, a professor of environmental analysis at Kinki University in Osaka Prefecture, sampled mud at four locations near the mouth of the Arakawa river last August.
At one location, cesium was detected at a depth of more than 20 centimeters.
He measured cesium concentrations of several hundred becquerels per kilogram of mud, roughly the same level as found dozens of kilometers from the Fukushima nuclear plant.
However, almost no cesium has been found in fish in Tokyo Bay.
Cesium binds itself with clay, when mixed in mud, and does not seep into the water. For this reason, it is believed that cesium is not easily absorbed by plants or transferred to creatures that live in the sea.
It is estimated that cesium concentrations of mud flowing into the bay will peak a year or two after the nuclear disaster. ... There are two types of radioactive cesium: one remains for more than 20 years and the other disappears very quickly.
Cesium sampled in Tokyo Bay includes the latter type, which has led scientists to believe that it did not derive from the Chernobyl nuclear disaster in 1986.


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