Thursday, May 17, 2012

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.


Anonymous said...

so .. a square-meter sheet of 1 mm thickness is decaying at a rate of ~4'500'000 atoms per second?
one, two, three, four, five, six, seven, eight ...

Anonymous said...

Are you sure you are reading his post correctly? I thought he said explicitly that it wasn't a soil sample, but a sample from a particular algae.

Anonymous said...

Ooyama seems to think the algae is "concentrating" the radioactive cesium. That algae is everywhere, including water and soil. The algae has been around for 2, 3 billion years.... All his samples are the soil that contain the algae. In his previous posts, he labeled all his samples as "soil". He's inconsistent.

Unfortunately, it is more sensational to call attention to the algae, as if it were some kind of mutation because of radioactivity, so that's what he seems to be doing.

Anonymous said...

There are fungi that feed off radiation. Not sure if they turn into black dust though.

Anonymous said...

I am so sorry to hear of this contamination. If there is any silver lining to this dark cloud it might be the awesome news of Japan's shutting down their entire nuclear reactor fleet. Way to go Japan for that!!!

Anonymous said...

Thank you to Ex SKF for debunking this nonsense. Not that black dust does not exist and not that it is not highly radioactive, but one thing I would like to now say very clearly is that the internet is full of information that AMPLIFIES danger using WRONG facts. Period. I think you get what I am saying. Thanks for clarifying, debunking this misinformation. Yesterday I saw a headline that said all of Western Japan is more contaminated than Belarus. What they meant was some of the West coast of Fukushima is very radioactive This is just nonsense reported as FACT. Ha. Fukushima Diary does a lot of good work but unfortunately a lot of sloppy half baked info is also promulgated from that site. I do not think the author of the site has bad intentions but he is a bit overly eager and does not always verify where info is coming from....

Anonymous said...

Very good points about Fukushima Diary, they really need to do some quality control on their facts there...

Anonymous said...


Have you done any research to establish what the "black dust" actually is? It appears the BLACK DUST IS RADIOTROPHIC FUNGUS such as the kind that was found thriving on the walls of the CHERNOBYL reactor in 2007. Scientists have studied it extensively since then.

Radiotrophic fungi are fungi which use the pigment melanin to convert gamma radiation into chemical energy for growth. This particular fungus (crytococcus neoformans) is widely distributed throughout the world and PROLIFERATES WHEN EXPOSED TO IONIZING RADIATION. However, researchers stress that this does not mean fungi can eat radioactive matter and somehow cleanse it. Rather, the fungi can simply harness the energy that radioactive materials give off.

~ LINK, original research article, lead author Ekaterina Dadachova, Albert Einstein College of Medicine, published May 23, 2007: "Ionizing Radiation Changes the Electronic Properties of Melanin and Enhances the Growth of Melanized Fungi". []

~ LINK, a lay-language article about the research paper form Science News Online, May 26, 2007: []

Cheers, JP

Anonymous said...

It's not just "there".

Anonymous said...

Ooyama says in his blog:

"For the avoidance of misunderstanding, we are not conducting a wide area soil survey. We are studying a type of cyanobacteria that has the potential to disperse bio-concentrated spores. This is rarely found in "black sand" or dust."

Its quite a different message to the headline on SKF.

Anonymous said...

Having 'Black Dust' accumulate in undisclosed water courses prior to conversion to drinking water is a concern.

Anonymous said...


If what anon (11:23 AM) said is accurate, please update/amend your comments to accurately reflect Mr. Ooyama's description of his process. As it stands, this current piece reminds me of the post you previously wrote attempting to quibble with the radiation readings that Gundersen got from the samples he took in Tokyo this spring.

Anonymous said...

Anon above, since when only 8 grams of sample tested using NaI scintillation survey meter is any accurate? Quibble? Excuse me?

La terra non ha uscite di emergenza. said...

gr/cm3 * depth cm * 10 = ratio
(0.45/1) * 10 = 4.5


kg/m3 * depth m = ratio
450 * 0.01 m = 4.5

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