Concerned residents of Yokohama City tweeted their City Assemblymen about the discovery of radioactive strontium in Yokohama, the news broken by independent journalist Yasumi Iwakami. (Read my posts here and here for more.)
One assemblyman, Yutaro Yokoyama, gave an interesting answer to the strontium question. He said on his tweets:
I knew that [discovery of radioactive strontium in Yokohama] since early September. For our political faction, strontium is a thing of the past. I myself touched on the [subject, I hope, not strontium] on the standing committee on September 13, as strontium is highly water-soluble. However, it's not known whether it fell from the sky or was carried by a volunteer (in person or by car).
Radioactive materials can be easily obtained anywhere in Fukushima. It is possible to carry them by artificial means [as opposed to naturally falling from the sky, I guess]. If radioactive strontium came by artificial means, I don't think it is a job of a City Assemblyman to pursue how it got here, so I won't.
He is insinuating that water-soluble radioactive strontium was carried intentionally by a volunteer or by a car driven by a volunteer and released on top of an apartment building, as any radioactive material is readily available anywhere in Fukushima Prefecture. And it's none of his business as a City Assemblyman to figure out how it got there.
Best of luck, citizens of Yokohama.
In the meantime, one major MSM newspaper carried the story, and more to follow I hear.
Here's from Asahi Shinbun (3:32AM JST 10/12/2011):
195 becquerels/kg of radioactive strontium has been detected from the sediment on the rooftop of an apartment building in Kohoku-ku in Yokohama City. A private laboratory did the testing. It is considered to have been released from Fukushima I Nuclear Power Plant after the accident. On receiving the result, Yokohama City has doing its own testing.
It was strontium-90 (half life of about 30 years) that was detected. The nuclide has been detected within 100 kilometers from Fukushima I Nuke Plant in Fukushima Prefecture and the southern Miyagi Prefecture according to the survey by the Ministry of Education and Science. However, this is the first detection in Yokohama City, about 250 kilometers from the plant.
Strontium-90 was detected on the rooftop of a 5-story apartment building which was built 7 years ago. A resident of the apartment building took the sediment in the drain and had it tested at Isotope Research Institute in Tsurumi-ku in Yokohama City. The result may not be easily comparable to the results in Fukushima, as radioactive materials may be concentrated in locations like this one. Nonetheless, it is higher than 77 becquerels/kg of radioactive strontium detected in Fukushima City in April and May.
From the same sediment, 63,434 becquerels/kg of radioactive cesium has been detected. The city hasn't publicly released the data as the building is a private property, but when the city did its own testing of the same sediment at Yokohama City Institute of Health, 105,600 becquerels/kg of radioactive cesium was detected.