"Black Dust" in Soma City Is Also Highly #Radioactive, at 56.3 Microsievert/Hr

There's a newspaper published by a citizen group in Soma City, Fukushima, urging the former residents, particularly mothers with children, to return to the city. Soma City is located just north of Minami Soma City where the "black dust" was first reported by Assemblyman Ooyama.

It turns out (no real surprise, but...) that Soma City also has "black dust" with very high radiation. The newspaper that urges mothers to come back has this article in its May 2012 issue:

It says:

Please be careful!

On the roads and near the side drains by the side walks in Minami Soma City and Soma City, we've started to see the black substance that looks like dirt. There has been some media report on this substance, and it is said to be a certain kind of bacteria that has dried out. It has been known to have very high radiation levels, and there is a possibility that it affects human bodies. Please do not go near it. We placed the survey meter on the substance in the photo. The survey meter shows 56.3 microsieverts/hour. Young children in particular should pay attention.

Again, the group wants mothers with children who evacuated from the city to come back. The reason why the group is publishing the newspaper is, according to the website:

子どもたちを守りたい。
未来に希望を残したい。

そのためにわたしたちは生き方を「変える」。
まちをゲンキに「変える」。

We want to protect our children.
We want to keep hope for the future.

TO do that, we will "change" our way of life.
We will "change" the city into a healthy city.

How are they going to achieve that? By measuring radiation, as far as I could tell from their newspaper.

Sorry to say it but the "bamboo spear" spirit seems to be alive and well in Japan, even after 67 years.

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Minami Soma's "Black Dust" with Over 10 Million Bq/kg of Radioactive Cesium, Says Assemblyman Ooyama (Just Don't Multiply by 65!)

He keeps finding "black dust" in his city with ever higher radioactivity. That's extremely high, even though Mr. Ooyama hasn't given the details as to the exact measurement or the location in his blog post.

But one thing the readers had better keep in mind: YOU DO NOT MULTIPLY THIS NUMBER BY 65 TO CONVERT TO BQ/M2.

As I said in the previous post on Tokyo's "black dust", the multiplier of 65 is only applicable if:

• The soil sample is taken from the surface to 5 centimeter deep; and

• The soil's relative density is about 1.3 gram/cm3 (cubic centimeter).

In case of the samples that Mr. Ooyama has been collecting,

• The samples are taken from the surface, as in most cases the "black dust" is scattered on the paved road; and

• The soil's density is extremely light, 0.45 gram/cm3.

By automatically multiplying the Bq/kg numbers for Minami Soma's samples by 65 (or worse, 150), you would be grossly exaggerating the Bq/m2 numbers.

Japan Health Physics Society has a Q&A post detailing the step-by-step calculation to convert Bq/kg to Bq/m2. Let's figure out what kind of multiplier would be appropriate (if at all) to use for the Minami Soma "black dust" samples.

First, this is how the multiplier of 65 for the soil sample taken from surface to 5 centimeters and with the relative density of 1.3 gram/cm3 is calculated:

Calculate volume for 1 kg of a given soil sample using the relative density (or specific gravity). Then divide the volume by the depth to get the area. So,

Volume (cm3) = 1000 (g) / 1.3 (g/cm3) = 769 cm3
Area (cm2) = Volume (cm3) / Depth (cm) = 769 / 5 = 154 cm2
Area equivalent to Bq/kg = Bq/154 cm2
Converting this into Bq/m2 (which is 10000 cm2), with the multiplier "x",
Bq/154 cm2 = x Bq/10000 cm2
x = 10000/154 = 64.9 ≒ 65

Variables are "relative density" and "depth".

Now, in case of Minami Soma's "black dust", let's assume the sample is taken from surface to 1 centimeter deep (I suspect it's thinner than 1 centimeter). The density is 0.45 gram/cm3, as one of Mr. Ooyama's Youtube video states (100 ml for 45 gram):

Volume (cm3) = 1000 (g) / 0.45 (g/cm3) = 2222 cm3
Area (cm2) = Volume (cm3) / Depth (cm) = 2222 / 1 = 2222 cm2
Area equivalent to Bq/kg = Bq/2222 cm2
Converting this into Bq/m2, with the multiplier "x",
Bq/2222 cm2 = x Bq/10000 cm2
x = 10000/2222 ≒ 4.5

If it is possible to take the sample from 1 millimeter,

Volume (cm3) = 1000 (g) / 0.45 (g/cm3) = 2222 cm3
Area (cm2) = Volume (cm3) / Depth (cm) = 2222 / 0.1 = 22220 cm2
Area equivalent to Bq/kg = Bq/22220 cm2
Converting this into Bq/m2, with the multiplier "x",
Bq/22220 cm2 = x Bq/10000 cm2
x = 10000/22220 ≒ 0.45

So, if the "black dust" sample is taken from the surface to 1 centimeter deep, the appropriate multiplier would be NOT 65 BUT 4.5. If the sample is taken from 1 millimeter, the multiplier would be 0.45.

The numbers, whether they are in Bq/kg or Bq/m2, are extremely high, particularly in Minami Soma City. I don't understand why the municipal governments, whether it is in Minami Soma City or in Tokyo, aren't removing the substance, particularly from the school routes and parks.

But it is plain wrong to hype the already bad numbers by multiplying by 65. As the "black dust" is not uniformly spread over wide areas, I'm not sure if doing the conversion from Bq/kg to Bq/m2 makes any sense.

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"Black Dust" in Tokyo? With 243,000 Bq/Kg of Radioactive Cesium

Freelance journalist Rei Shiva [Shiba] writing for Nikkan Spa, a daily tabloid in Japan (part; 5/15/2012):

福島県南相馬市内で発見された超強力な放射能を持つ謎の“黒い粉”が話題になったのは今年２月のこと。

It was this February when the super-radioactive and mysterious "black dust" found in Minami Soma City in Fukushima Prefecture was in the news.

1kgあたり108万ベクレル」というケタ違いの線量は衝撃的なものの、「南相馬での特殊な事例」として受け止められていた。ところが、その「黒い粉」は東京都内の至るところに存在しているという。

Although 1.08 million Bq/kg was shocking, it was considered to be specific only to Minami Soma. However, I've been told that "black dust" exists everywhere in Tokyo.

「放射線検知器を近づけてみると、明らかに反応があるので、汚染度が高いのかなとは思っていたのですが、まさかここまでとは……」「黒い粉」を都内で発見した、市民団体「NO！放射能 江東こども守る会」の石川あや子代表は驚きを隠せない。「江戸川区のJR平井駅周辺で『黒い粉』らしきものを見つけ、採取したサンプルを神戸大学の山内知也教授に検査してもらったところ、最大で１kgあたり24万3000Bqという数値が出たんです」。

"When I brought the radiation detector closer, it visibly responded. So I knew it might be highly contaminated, but didn't know it was this contaminated...", says Ayako Ishikawa incredulously. Ishikawa is the head of the citizens' group "No! to Radiation, Protect Children in Koto". [Koto-ku is one of the eastern Special Wards of Tokyo]. She says, "We found something that looked like "black dust" near the Hirai JR station in Edogawa-ku. We collected the sample and and asked Professor Tomoya Yamauchi of Kobe University to measure the radiation. The result was that it had the maximum 243,000 Bq/kg [of radioactive cesium]."

これは原子炉等規制法で定められた「安全基準（クリアランスレベル）」の約2430倍という、途方もない数値だ。

It is 2,430 times the clearance level [100 Bq/kg] specified by the Nuclear Reactor Regulation Law.

「注意して見ると、『黒い粉』は都内の至るところにあります」と石川さんは言う。そんなにあちこちに高汚染の物質が転がっているのだろうか？　という疑問を抱えつつ、「黒い粉」の調査に本誌記者も同行した。

"If you look carefully, "black dust" is everywhere in Tokyo", says Ishikawa. Such highly contaminated materials are everywhere? I decided to accompany her to look for "black dust".

まずは、JR平井駅から徒歩10分ほど。公営団地そばの運動場で「黒い粉」を発見した。フェンス近くで何か所にもわたって吹き溜まっていた「黒い粉」は、一見すると黒い土のように見える。近づいてよく見てみると、乾燥して干からびたコケやカビのようなものであるとわかる。

First, [to a location] about 10-minute walk from the JR Hirai Station. We found the "black dust" on the playground near the public housing. There were several drifts near the fence, and they looked like just "black soil". When I took a closer look, they were revealed to be something like a dried moss or mold.

「この前来たときと微妙に場所が変わっていますね。風雨で移動したのかもしれません」と石川さん。ガイガーカウンターよりも信頼性の高い、国産のシンチレーション式放射線検知器を「黒い粉」に近づけてみた。すると数値が急上昇し、毎時2μSvを超えた。東京都の平均的な空間線量（地上１ｍ）の約20倍だ。山内教授は「一般的に携帯式の放射線検知器は周囲の放射線量の平均値を表示します。つまり、少量の物質に検知器を向けて数値が急上昇するならば、その物質が極めて強い放射線を出している可能性があります」という。

Ishikawa said, "They are at slightly different locations. Rain and wind may have moved them." We measured the radiation with the scintillation survey meter made by a domestic manufacturer because it is more reliable than a geiger counter. The number shot up quickly, and exceeded 2 microsieverts/hour. That is twenty times more than the average air radiation level (at 1 meter off the ground) in Tokyo. Professor Yamauchi says, "In general, a scintillation survey meter shows the average radiation level. If the number rises rapidly when the survey meter is directed toward a small amount of substance, it is possible that the substance is emitting extremely strong radiation."

...

果たして、「黒い粉」の正体とは何なのか？　そして、「黒い粉」の性質を利用した効率良い除染方法とは？　5月15日発売の週刊SPA！「首都圏を襲う［放射能の黒い粉］」では、「黒い粉」の元になる物質の怖さのみならず有用性もまた報じている。

What is this "black dust"? What is the efficient decontamination method using the unique properties of the "black dust"? Shukan Spa [weekly magazine] that will go on sale on May 15 has the article "Radioactive black dust striking the Tokyo Metropolitan area", which will report on the danger of the substance that makes up the "black dust" as well as its usefulness.

I don't see much point in comparing it to the clearance level of 100 Bq/kg which is applicable only to enclosed nuclear facilities. After the Fukushima nuclear accident, it's a whole new ballgame where the disaster debris exceeding that clearance level is being shipped to Kyushu to be burned in a regular incinerator and the soil samples in Kanto and Tohoku easily exceed that level in many locations.

Even though I have reported on the "black dust" in Minami Soma City (most recently, here), I am not completely convinced that this "black" substance is any different from a drift of dirt that one often saw on the road surface or near the drains even before the Fukushima nuclear accident. Cyanobacteria that supposedly make up the "black dust" are ubiquitous.

Professor Yukio Hayakawa of Gunma University says if the top 1 millimeter of the soil is taken the radioactivity can be extremely high, though he seems to think that "black dust" is a very good indicator of urban contamination.

No matter what it is or how it came about, it is clearly highly radioactive, and it'd better be removed to avoid contact. No municipalities are doing that, as they should.

Just don't go multiply that number (243,000 Bq/kg) by 65 and exclaim "Look, Tokyo is more contaminated than Chernobyl exclusion zone!" The multiplier of 65 only applies to soil samples that are taken from the surface to 5 centimeters deep, and whose specific gravity is about 1.3g/cm3. If Tokyo's "black dust" has the same weight as Minami Soma's "black dust", it would be less than 0.5g/cm3.

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Minami Soma Assemblyman: "5.57 Million Bq/kg Cesium from Soil, and People Are Cleaning Out Their Homes"

Part of Minami Soma City in Fukushima was inside the "no-entry zone" but the designation was lifted as of April 16 this year and people are returning. One such area is Odaka District, and as NHK reported, the returning residents are being assisted by volunteers from all over Japan in cleaning up the damage from the March 11, 2011 earthquake and tsunami.

Minami Soma Assemblyman Koichi Ooyama says he went and collected soil samples (what he calls "black dust") in locations in Minami Soma, including several in Odaka District after the no-entry zone designation was lifted. He had them tested by the city's laboratory for radioactive cesium, and the result, as posted on his blog (5/10/2012) is shocking.  The maximum is 5,570,000 becquerels/kg of radioactive cesium in soil in Odaka District. In the same district, half a million becquerels/kg of cesium in cow dung was also found.

Mr. Ooyama lists those with high radioactive cesium content, because the numbers are not in sequence. English labels are by me. (Unit is bq/kg, dry weight):

①1,320,000 原町区牛越土壌 Haramachi District, soil
②1,960,000 鹿島区橲原土壌 Kashima District, soil
⑥5,570,000 小高区金谷土壌 Odaka District, soil
⑧　　16,200 原町区国見町土壌 Haramachi District, soil
⑪　793,000 小高区上町土壌 Odaka District, soil
⑫　430,000 小高区本町土壌 Odaka district, soil
⑬　583,000 小高区本町土壌 Odaka district, soil
⑭2,970,000 小高区金谷土壌 Odaka district, soil
⑰　522,000 小高区金谷牛ふん Odaka district, cow dung

Even if these samples are from areas where radioactive cesium is getting highly concentrated, I haven't seen numbers like this anywhere else in Fukushima outside the immediate vicinity of Fukushima I Nuclear Power Plant.

NHK News said the volunteers helping the home owners in Odaka District were scooping out the sludges - probably highly contaminated sludge - with hardly any protection other than flimsy masks and gloves. Who is going to be responsible if anything should happen to these volunteers later? Volunteers themselves.

Assemblyman Ooyama screams, "And they're going to do what? Spring athletic meets? Swimming pool opening? I can't take it any more!"

(For the mind-numbing routine in post-Fukushima Japan in spring and summer, see my previous post.)

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Professor Yukio Hayakawa Takes a "Radioactive Walk" In Abiko City and Kashiwa City in Chiba

The Gunma University professor took a walk in part of Abiko City and Kashiwa City, in the so-called "Tokatsu area" in the northwest corner of Chiba Prefecture with elevated radiation levels.

He says there is a statistically significant difference between the radiation levels on the ground levels and the levels at 1 meter off the ground, with the levels at 1 meter off the ground 20 to 30% less than at the ground levels.

The radiation levels of "black dust" he found along the way (in microsievert/hour):

2.676
3.767
2.489
1.556

Professor Hayakawa's walk from Abiko City to Kashiwa-no-ha in Kashiwa City on April 16, 2012:

我孫子-柏の葉

EveryTrail - Find hiking trails in California and beyond

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3.43 Million Bq/Kg of Radioactive Cesium in "Black Dust" in Minami Soma City, Fukushima

Whatever this substance is, the number is extremely high.

About this "black dust" in Minami Soma, see my past posts, here, here, here.

Minami Soma City's Assemblyman Ooyama reports on his blog (3/8/2012):

試料：ID:080 鹿島区ジサ原C
Cs-134 1,498,000 ± 1,586 Bq/kg
Cs-137 1,932,900 ± 2,481 Bq/kg
TOTAL 3,430,900± 2,945 Bq/kg

It seems to be part of the report by Professor Tomoya Yamauchi of Kobe University who did the measurement. Mr. Ooyama lists the result of 11 samples tested by Professor Yamauchi.

The NGO in Minami Soma, HCR, seems to have some kind of a fallout with the assemblyman's volunteer group over the "black dust", and they've been making rather wild announcements (telling residents that the black dust was plutonium, when there was no alpha emission was detected, for example). I am still trying to get the overall picture on this matter.

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