Friday, September 28, 2012

北米に見られる福島放射能放出の痕跡 Trace of Fukushima Radiation in North America

Fukushima radiation found in California kelp

Marla Cone

San Francisco Chronicle April 8, 2012 04:00 AM

Copyright San Francisco Chronicle.

Sunday, April 8, 2012

Kelp off California was contaminated with short-lived radioisotopes a month after Japan's Fukushima Dai-ichi nuclear plant accident, a sign that the spilled radiation reached the state's coastline, according to a new scientific study.

Scientists from CSU Long Beach tested giant kelp collected off Orange County, Santa Cruz and other locations after the March 2011 accident and detected radioactive iodine, which was released from the damaged nuclear reactor.


The largest concentration was about 250 times higher than levels found in kelp before the accident.

"Basically, we saw it in all the California kelp blades we sampled," said Steven Manley, a CSU Long Beach biology professor who specializes in kelp.
「基本的に、汚染は採取したサンプルの全てに見られました。」と、カリフォルニア州ロングビーチ大学、ケルプ専門の生物学教授、Steven Manley氏は言いました。

The radioactivity had no known effects on the giant kelp, or on fish and other marine life, and it was undetectable a month later.

Iodine 131 "has an eight-day half-life, so it's pretty much all gone," Manley said. "But this shows what happens half a world away does effect what happens here. I don't think these levels are harmful, but it's better if we don't have it at all."

Spread in large, dense, brown forests across the ocean off California, giant kelp is the largest of all algae and grows faster than virtually any other life on Earth. It accumulates iodine, making it a useful way to check how far radioactive material spreads.
太平洋を通して、カリフォルニア沖の広大な、密集した、茶色い海中林で、巨大ケルプは、事実上地球上の他のどんな生物よりも早く成長する、最大の藻類菜のです。 それはヨウ素を蓄積し、放射性物質がどこまで拡散したのかを確認する、有益な手段として使えるのです。

Image from Newport Beach Patch

"Kelp forests are some of the most productive ecosystems on Earth," he said. "One thing about (kelp) is it has a large surface canopy," which means it is continually exposed to the air and whatever contaminants are in it.

In addition, giant kelp concentrates radioactive iodine - for every 1 molecule in the water, there would be 10,000 in its tissues.

Kelp was collected at three sites off Orange County, as well as Palos Verdes Peninsula in Los Angeles County, Santa Barbara, Pacific Grove and Santa Cruz. The highest concentration of iodine 131 was found in the kelp off Corona del Mar, a town near Newport Beach that receives runoff from a large portion of Orange County. Its kelp was collected on April 15 of last year and tested five days later.
ケルプは、オレンジ郡と、ロサンジェルスのPalos verdes半島、サンタバーバラ、パシフィックグローブ、サンタクルーズ 沖の3つの場所で集められました。ヨウ素131の最も高い濃縮は、広大なオレンジ郡からの流出を受けているニューポート・ビーチ近くの町、Corna del Mar沖のケルプから見つかりました。そのケルプは去年の4月15日に採取され、5日後に検査されました。

The level of radioactive iodine found there - 2.5 becquerel per gram of dry weight - was "well above" levels sampled in kelps prior to the Fukushima release, according to the paper, published online in the journal Environmental Science & Technology.

Probably not healthful

Santa Cruz had the next highest level, with 2 becquerel per gram. The concentrations in Santa Barbara and Pacific Grove were significantly lower, under 1 becquerel.

CODEX 100ベクレル
アメリカ 170ベクレル
カナダ 飲み水、ミルクは100ベクレル。一般食品は1000ベクレル。
日本 (2012年4月以前) 飲み水、ミルクは300ベクレル。食品は2000ベクレル。
When kelp from the same California sites was resampled a month later, in May 2011, it contained no detectable amounts of radioactive iodine.


Some radioactive material probably accumulated in fish that eat the kelp, including opaleye, halfmoon and senorita.

"If they were feeding on it, they definitely got dosed. We just don't know if it was harmful. It's probably not good for them. But no one knows," Manley said. "In the marine environment, it was significant, but probably not harmful at the levels we detected it, except it may have affected certain fish's thyroid systems."

There is no published research on what iodine 131 might do to fish at the levels found in the kelp.

"That is a good question and one we don't really know the answer to as yet," said Christopher Lowe, a biology professor and director of CSU Long Beach's Sharklab, which studies sharks and game fish. Lowe was co-author of the kelp study.
「それは意味のある疑問ですが、私たちには、本当にまだその答えが分からないのです。」とカリフォルニア州ロングビーチ大学のさめ類・釣り魚研究室長、生物学教授のChristopher Lowe氏は述べました。Lowe氏は、ケルプ研究の共同著者でもあります。

Although radioactive iodine would move up the food web, it would decay at the same time that it is being concentrated, so it would be gone from the fish within days.

"It's definitely not harmful to humans," Manley said.

Not naturally occurring

Iodine 131, found in nuclear fission products, is not naturally occurring and is not naturally found in oceans. The ocean and everything in it, however, contain many other naturally radioactive materials.

U.S. Environmental Protection Agency officials in San Francisco and Washington, D.C., declined to comment on the report or whether they will consider monitoring kelp. The EPA measured air and milk on the West Coast after Fukushima and concluded that "radiation levels remained well below any level of public health concern."

The kelp study can be found at


この事象について、Scientivic Americanは、以下のようにも報告しています。



“The reality is there are far more natural radionuclides in marine life than manmade ones,” Fisher said. “There are naturally occurring radioisotopes that have been in the ocean for billions of years, before man ever showed up and they occur at pretty high concentrations in organisms, much more than the artificial radioactivity introduced by Fukushima, or even Chernobyl, which was worse. Even at its peak, it was probably very low compared to the natural radionuclides."


Manley said that natural radiation in the ocean water is around 15 becquerel per liter. And if they calculated the levels in the water squeezed out of the kelp, "it would be 400 Bq per liter, which is well above the ocean average for natural radiation,” he said. In the kelp itself, the amounts of Fukushima radioactivity were about the same as natural radioactive potassium found in other research.



What was reported from Canada?

Amount of radiation in rainwater decreasing

Tracy Sherlock, Postmedia News

Published: Wednesday, April 06, 2011

Radiation in B.C. rainwater is decreasing, a trend that could mean either the end of radiation emissions in Japan or a change in the weather, a nuclear scientist said Tuesday.


"I looked into the sample for yesterday and I see very little iodine-131," Krzysktof Starosta, a nuclear chemist and physicist at Simon Fraser University, said in an e-mail. "I am not sure if this is the end of the releases or a change in the weather pattern, the time will show."
「昨日のサンプルを調べ、ほんの少しのヨウ素131しか見られませんでした。」とサイモンフレーザー大学、原子力化学、物理学者のKrzysktof Starosta氏はEmailで述べました。「これが放出の終わりなのか、天候のパターンの変化なのかは定かではありませんが、時間と共に分かるでしょう。」

A chart provided by Starosta shows that iodine-131 in rainwater in Vancouver peaked on March 20 at 12 becquerel per litre. Levels were at zero becquerel per litre up to March 18, 2011, and as of March 29, 2011 had fallen to just above three becquerel per litre. A becquerel is an international measurement of radioactivity related to radioactive decay per second.

Meanwhile, seaweed samples were still showing increasing iodine-131 as of March 28, according to data provided by Starosta. In samples of dehydrated seaweed taken near the North Vancouver SeaBus terminal, the count was zero on March 15, 310 becquerel per kilogram on March 22 and 380 Bq/kg on March 28.

© Alberni Valley Times 2011

The radiation was reported from New Hampshire, too.


これに関する記事は こちら(以下抜粋)

The paper reports that testing in New Hampshire's Mink Brook watershed during March through May 2011 showed the amount of radioactive iodine deposition in the soil was minimal, with calculations revealing the total amount to be on the order of 6,000 atoms per square meter. Landis comments that "at these levels, it is unlikely that this is going to cause measurable health consequences."


However, sampling of Mink Brook stream sediments showed a doubling of iodine concentrations relative to what was found in soils. But even in these concentrations, stream and river transport are expected to result in significant dilution.
しかしながら、Mink Brook川の堆積物は、ヨウ素の濃縮が土壌で発見されたものの倍になっていました。が、それらの濃縮でさえ、川の水が運び、相当に薄められると考えられています。

This is not the case with another isotope, iodine-129, released concurrently with iodine-131. It is not as radioactive, which makes it much harder to measure, but it is much longer lasting and, as it concentrates in certain areas over time, it may become more hazardous. "Due to its long half-life and continued release from ongoing nuclear energy production, [iodine-129] is perpetually accumulating in the environment and poses a growing radiological risk," the authors point out.

The production rate of these two isotopes in a nuclear reactor occurs at a fixed ratio of 3 parts iodine-131 to one part iodine-129. The two substances travel together, so the presence of the easily detectable isotope also signals the presence of the longer-lived one.

"If you have a recent event like Fukushima, you are going to have both present. The iodine-131 is going to decay away pretty quickly over the course of weeks, but the iodine-129 is there forever, essentially," Landis says. However, he explains, "Once the iodine-131 decays, you lose your ability to track the migration of either isotope."

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