Soil and manure samples, and detection of Cs-137 in soil from weapons testing fallout (9/6/2011)

9/6 (5:26pm): We tested a topsoil sample and a dried manure sample from the Sacramento area. The manure was produced by a cow long before Fukushima and left outside to dry; it was rained on back in March and April. Both samples showed detectable levels of Cs-134 and Cs-137, with the manure showing higher levels than the soil probably because of its different chemical properties and/or lower density.

In addition, a soil sample from Sonoma county was tested. This sample had been collected in late April but we had not had the chance to test it until now.

One interesting feature of the Sacramento and Sonoma soil samples is that the ratio of Cesium-137 to Cesium-134 is very large — approximately 17.6 and 5.5, respectively. All of our other soil samples until now had shown ratios of between 1 and 2. We know from our air and rainwater measurements that material from Fukushima has a cesium ratio in the range of approximately 1.0 to 1.5, meaning that there is extra Cs-137 in these two soil samples. The best explanation is that in addition to Fukushima fallout, we have also detected atmospheric nuclear weapons testing fallout in these soils. Weapons fallout contains only Cs-137 (no Cs-134) and is known to be present in older soils (pre-1963). Both of these samples come from older soils, while our samples until this point had come from newer soils.

This direct comparison between Fukushima fallout and atmospheric weapons fallout in these soils shows that the fallout from Fukushima in Northern California is significantly less than the amount of Cs-137 that still remains from weapons testing, which has had nearly 50 years to disperse and decay.

Mark [BRAWM Team Member]


This is a LOT of Cesium-137

These two (2) data points, (old soil samples), in California, might point to the Fukushima contribution, relative to ALL previous Cesium-137/134 sources. The measured ratio is roughly 3/1, so prior to Fukushima the ratio was approximately 2/0.

Thus, for these two (2) California samples, the Fukushima contribution is roughly 1/2 ALL previous Cesium-137 aources.

This would include Rancho Seco, Chernobyl, all weapons tests and every manufacturing and medical release. This would include any natural sourcing from volcanic, satellite and/or meteoric contributions which was present in the (old) soil.

Certainly, the soil contribution of the Fukushima disaster, will be MOST of the Cesium-137, for Honshu Island, Japan.

"The measured ratio is

"The measured ratio is roughly 3/1, so prior to Fukushima the ratio was approximately 2/0.

Thus, for these two (2) California samples, the Fukushima contribution is roughly 1/2 ALL previous Cesium-137 sources."

According to your own assumptions the Fukushima contribution would be 1/3 of all the previous Cs-137 sources, right?

And then we have to take into account the time passed since the previous depositions, that is, almost two half-lives for the nuclear testing era and almost one half-life for the Chernobyl fallout. So roughly 30~35% of the Cs-137 from the nuclear testing era would still be around, 55% in the case of Chernobyl fallout.



The elapsed time and half-lives for Cs-137 and Cs-134, WERE referenced in the earlier comments, such as 'Good Science' and phrases using the term 'present', as in the measurable radionuclides as of March 9, 2011.

The 'ratio' of "2/0" also is such a reference...

In any event, this represents a grand total of two (2) data points... and blog discussion, NOT a peer-reviewed formal publication...

Once the prose is clear, the math is simple...

I still have not looked at the BRAWM data and/or methodology.

Oh, and the 'old soil' and cow-chip samples sat on the shelf, long enough for the short halflife radionuclides such as I-131 to vanish. While this would be correctable, that is not as satisfactory as measured values.

And now that I think of it,

And now that I think of it, have you actually checked the results or read the OP? The Cs-137 to Cs-134 ratio is not even close to being 3:1.

Here's what we have in the OP:

"One interesting feature of the Sacramento and Sonoma soil samples is that the ratio of Cesium-137 to Cesium-134 is very large — approximately 17.6 and 5.5, respectively."

And here's the data:

Cs-137: 2.590±0.259 Bq/Kg
Cs-134: 0.147±0.015 Bq/Kg

Cs-137: 1.905±0.190 Bq/Kg
Cs-134: 0.347±0.035 Bq/Kg

Sorry, the underlying data

Sorry, the underlying data is not in OP above and the summary was misinterpreted. Considered the 17.6/5.5 as the Cs-137/Cs-134 ratio, mistakenly.

A lot of Radioactive Cesium

Restating this, to include the Cesium-137 PLUS the Cesium-134 for the two (2) California samples ...

Recently measured total cesium (134 + 137), to previous measured total cesium 137, where the 134 had half-lifed away.

(5 now)/(3 previous) for a 2011 contribution of 2. Thus the Fukushima cesium contribution to these soil samples was 2/3 of ALL previously present cesium.

If we add in the radioactive Iodine for the month of April 2011, the total Fukushima fallout contribution to these two (2) California soil samples ... would be MOST of the radionuclides in the soil.

This is notwithstanding the fact that the distance to San Francisco from Fukushima is 5024 miles / 8085.34 km.

Maps of fallout from weapons

Maps of fallout from weapons testing 1951-1970

Map of fallout from Chinese testing 1966

Looks like it had a small impact on California:

Good Science


Good science. The half lives of 30/2 years have depleted the Cs-134 from the weapons tests.

The aspect ratio of the Cs-137/Cs-134 in the older soils is skewed to 17.6/5.5, (about 3/1). The recent Fukushima Diachi Unit-1 and Unit-2 emission, presently have an aspect ratio of about 1.5/1.

The newer soils have been showing an aspect ratio of 2/1 for the two isotopes. These newer soils presumably have less weapons test cesium-137, as they were not directly exposed to the weapons fallout, and have only 2ndary deposition.

What is the aspect ratio for the Rancho Seco emissions?

Rancho Seco aspect ratio

Comparing dates and tests for EPA milk testing I-131 vs Cs-137 in Sacramento show a trend of 2/1 I-131 to Cs-137, although there is some fluctuation due to long half life of Cs-137. Many of the historical Rancho Seco test results are much higher than similar BRAWM Fukushima results.

Circa-1960's French Nuclear Program


Are we comparing apples to oranges? Perhaps it is appropriate to differentiate between localized and global radionuclide contamination events. So for example, the indicated French Bordeaux cesium peaks generally correspond to the French atomic energy development manufacturing activities and their 1960’s era Algerian nuclear weapon tests. Three (3)-cell and five (5)-cell climate models as well as local Mediteranean weather patterns can likely tie these French activities and wine measurements together.

The GE Fukushima Daiichi-1+2, and the more significant atomic explosions of the MOX laden Fukushima Daiichi-3 nuclear plant, and the USSR Chernobyl, plant have hemispheric, if not global radionuclide contamination implications.

Your Testing of "Older" Soils

Mark & Team BRAWM:

Thank you for your willingness to test some of the "older" soils in the Bay Area. As I understand it, the City of Alameda is mostly built upon newer & cleaner landfill. Thusly, your soil and grass samples from the City of Alameda are of "newer" soils. Correct?

It makes sense that our soils contain more C-137 from the weapons testing in Nevada...not to mention China, North Korea, Soviet Union, etc. After all, particulate matter is sometimes able to circle the globe multiple times after a nuclear explosion. (Although, Alameda should also contain some from the testing in China, North Korea, etc.)

I am interested in finding out just how much radioactive contamination we have been living with pre-Fukushima.

BC posted an interesting document on node 5556 with regard to C-137 deposition & concentrations "downwind" from the Nevada Test Site. It turns out that "we are all downwind" from the Nevada Test Site. The document is actually a master's thesis: The Blair Thesis. Circa 2008. It is a "must read"!! Thank you, BC.

Older soils

Yes, by coincidence we had only tested newer soils. The part of Alameda that the original soil samples are from is built on landfill, and the soil samples from San Diego were store-bought soils that had been recently laid down (and the control samples show no Cs-137).

We had been sent the Sonoma sample in late April, but hadn't tested it. If we had, we would have come across this earlier. Both that sample and the Sacramento sample are from farms, not gardens, so there shouldn't be a high turnover in the soils except for tilling and erosion.

I just got some samples of older soil from a yard in Oakland, and it appears to have more 137 than 134 as well. We have several layers from that yard, so we will be able to see the quantity of each isotope with depth.

To add to the list of literature about this, I posted a couple more articles below.

Mark [BRAWM Team Member]

Mark & Team BRAWM: Older Soils...and Newer Soils

Thank you, Mark, for your reply and for the additional articles that you posted!

Now, just a reminder, how about testing that "new soil" UNDER the grass samples you have been collecting and testing?

It would be great to find out whether or not ANY phytoremediation has taken place as the grass is watered, mowed, and the clippings removed from the site. If it is happening in Alameda, it is happening in my own backyard...and the backyards of other Forum followers.


Hi Mark and BRAWM Team Members,

Thank you so much continuing to test! I really appreciate all the the work that you do, as well as the feedback, comments, and analysis that you provide.

I have one question about the CS-137 in the soil and your analysis that the additional CS-137 may be from weapons testing fallout. I thought that the radioisotopes that you have been measuring had a specific signature, specific to the Fukushima fallout. I believe there were posts about this during the early days of this forum. Can you please explain?

Thank you!

Isotope ratio

Hi T.O. Mom,

I just made a comment below that also answers this question. It is the isotope ratio of the two Cesium isotopes (137 to 134) that allows us to conclude that the radioisotopes are from a Fukushima and not from something else. These soil samples are the first samples we have seen where the ratio was very far from 1, and the explanation comes from Cs-137 that remains in the soil from nuclear weapons testing, which is well-documented in the literature.

Mark [BRAWM Team Member]

Thanks for your reply, Mark,

Thanks for your reply, Mark, and also for the explanation. Much gratitude, as always:).

In the Sacramento sample,

In the Sacramento sample, Rancho Seco should also be considered:

Sacramento Cs 137

Reminds me of the time when

Reminds me of the time when TEPCO tried to say the plutonium they found must have come from atmospheric testing, haha.

Other Possibilities

Mark your analysis is comforting. The hard work (testing, sharing and engaging with us) is invaluable on many levels.

Thanks so much.

I also see a pattern of too many assumptions and a wiliness to minimize or a rush to minimize as your data set is a few specks in a sea of diverse emissions (the emitter is wildly unstable and multifaceted) and fallout distribution is another HUGE variable. The what and when of emissions is only partially known and a fraction of that has been made public. Placing another layer of variables from the process atmospheric transport and distribution makes the drawing almost any conclusions premature.

Isotope ratio allows us to draw these conclusions

Hi Red Mercury, I did not want to come off as minimizing the Fukushima fallout. I hope that I can try to explain a bit more clearly. The emissions from Fukushima have all had a Cs-137 to Cs-134 ratio of ≈1. This is true in our air and rainwater measurements, as well as the measurements of others in Japan and around the world. This ratio is what one would expect from cesium produced in a reactor — it simply is not possible to have radioactive cesium released from a reactor without this ratio being approximately 1. The two isotopes are chemically identical and would be transported in exactly the same way, so transport considerations do not factor in to the ratio. The only explanation for the large excess Cs-137 is that is remains from weapons testing. These levels are in the range that one would expect from previous measurements. For example, here's a review article about how researchers have used fallout Cs-137 for decades to track soil erosion: Application of radioactive fallout cesium-137 for measuring soil erosion and sediment accumulation rates and patterns: a review. Authors: Ritchie, J.C., McHenry, J.R. Source: Journal of environmental quality. Apr/June 1990. v. 19 (2), 0047-2425 In that paper, they show some data where the activity in soil is approximately 1 pCi/g = 37 Bq/kg. Another paper with data from the Central Valley of California shows measurements of Cs-137 that are about 20 decays per minute per cm2. Using their core depth of 40 cm, this translates to 8.3 Bq/kg, which is still larger than our measurements. Mark [BRAWM Team Member]

Only explanation?



It is perhaps premature for phrases like 'The Only Explanation'.

A small atomic explosion (prompt criticality) in the Fukushima Daiichi Unit-3, would produce a different transient radionuclide profile, quite distinct from the ongoing core meltdown emission processes.


Hi sad Anonymous, You are

Hi sad Anonymous,

You are correct that a prompt criticality (if such a thing occurred) would produce a different isotopic ratio. However, the cesium ratios we measured are actually the opposite of what you would see following an atomic explosion.

If fission were continuing, we would see more Cs-134 activity relative to Cs-137 (in this soil, we measured much, much less), and we would also be able to see other short-lived isotopes such as I-131 (just as we did immediately following the accident).

Tim [BRAWM Team Member]

Tim, I'm confused how it

Tim, I'm confused how it could be possible to distinguish so clearly between fallout from an atomic explosion 50 years ago and the fallout from a possible Reactor 3 explosion in March that was some kind of a 'dud/damp-squib' but still an atomic explosion too. Isn't the latter now a possible explanation because of this new soil measurement? The Cs-134 would be from the ongoing multiple reactor releases, and the unusual ratio of more Cs-137 in some samples could be due to additional fallout from a Reactor 3 small atomic explosion of some kind. Isn't this a valid interpretation of the readings too?

Global and Local


Merely pointed out that: Hemispheric contamination events, such as Fukushima and Chernobyl are quantitatively much larger than a single, localized event.

A four-ton (TNT equivalent) nuclear artillary shell or a similar yield prompt criticality in the Fukushima Daiichi Unit-3, would be an insignificant and local radiological release. Yet, the vagaries of wind, climate and water, might loft the radionuclides, by random processes, quite a distance from the small nuclear explosion.

Soil depth for sampling

Mark, have any of the articles you've recently reviewed changed your view on what soil depth samples should be taken from when looking for Fukushima isotopes in northwest coast soil that has experienced heavy precipitation?

So, is it likely that those

So, is it likely that those of us who grew up 40 years ago drank milk and ate more foods with more cesium in it than our children are currently from Fukushima?

I came across this on

I came across this on another website. Someone posted articles containing radioisotope data from Japan all the way back to 1963. They also posted 2 articles, one which shows levels of cesium 137 and other radioisotopes in the US and other countries. These articles are a good read and opens my eyes to what we are exposed to on a daily basis.
Radioactivity Survey Data in Japan
Evaluation of cesium 137 and elements intake from daily diets in residents of Kanagawa prefecture, Japan. (2009)

Contents and daily intakes of gamma ray emitting nuclides 90Sr and 238U using market-basket studies in Japan. (2007)

Yes -- a couple examples

Yes. For example, many weeks ago BC posted an article discussing cesium-137 in beef during the early 1960's. Milk levels were also discussed. Figures in the paper show sustained levels of Cs-137 in Colorado milk of about 1.5 to 7.4 Bq/L over a nearly three year period (1962–64). By contrast, the maximum Cs-137 levels we have seen in Berkeley after Fukushima are almost 0.6 Bq/L, and it was a brief, unsustained peak. A few months ago someone else brought up a dramatic example of how relatively large the fallout from atmospheric weapons testing was in a thread about dating Bordeaux wine using Cs-137. In particular, this plot of the Cs-137 activity versus the vintage year reveals, for example, how much larger the deposition from weapons testing was than the deposition from Chernobyl:
Original paper: "From the mass of the neutrino to the dating of wine," Ph. Hubert, F. Hubert, V. Raffestin Mark [BRAWM Team Member]

Thats some Hot manure !

May I ask was soil under manure or near tested or obtained for comparison?How can u be sure this manure sample was pooped pre Fukushima please explain ?

Collector told me

Hi Tdm, the person who collected the sample got it from the farm's dried manure pile. They apparently use the manure after it has set out for a year or so and becomes less foul... So that manure has cesium-134 and 137 in it mostly from post-Fukushima rain.

Mark [BRAWM Team Member]

Effects & Comparison?

Thanks for the latest data/post and all of your thoughts in the comments Mark.

Couple questions:

1) How do the current soil contamination levels compare to levels in Europe post-Chernobyl?

2) What are the implications for people living in California? I can't imagine this fallout in our soil/sand/playgrounds being beneficial.


And please also explain why

And please also explain why it is not possible the manure shows higher levels of contamination because the responsible cow may have eaten Fukushima-contaminated grass! Thanks!