Misunderstanding Ocean Transport Models of the Fukushima Radionuclide Plume in the Pacific

by Jay T. Cullen

Introduction

This post is part of an ongoing series that endeavors to provide useful and accurate information about: 1) the fate of Fukushima derived radionuclides in the Pacific Ocean, and, 2) the impact of these radionuclides on the marine ecosystem and the west coast of North America. The purpose of this diary is to draw attention to a number of poorly researched posts about a recently published study (unfortunately this study is behind a publisher pay-wall) in a Chinese journal that predicts a concentrated plume of radioactive elements from Fukushima arriving on the west coast. It is an unfortunate but common example of how news aggregation sites can misinterpret the results of a scientific study and misinform the public.


What models can and cannot say about the Fukushima plume

The study in question by Fu and co-workers published in the Journal of Ocean University of China in 2014 (behind pay-wall unfortunately) is wholly incapable of describing the behavior of dissolved radionuclides in the plume that is now arriving on the west coast of North America.

From the paper the authors themselves state in the methods that:

“In the study, the radioactive pollutant in the ocean is treated as a mixture of multiple Lagrangian particulates, and each particulate represents a radioactive element. The particulates can move in both horizontal and vertical directions, but cannot diffuse and mix with surrounding seawater.”

What this means is that rather than being allowed to mix and diffuse (or decay or sink after becoming associated with particles) the radionuclides are treated as neutrally buoyant drifters. The model, therefore, greatly overestimates the concentrations of radionuclides reaching the west coast of North America in the plume.

For those interested in models using accurate physics that will allow for an accurate prediction of radionuclide concentrations consult the following studies:

Behrens et al. (2012) and Rossi et al. (2013) (behind pay-wall)

Snapshot of the high-resolution (0.1°) model field, taken at the end of the tracer injection period (end of April, model year 0): shading indicates the thickness of the surface mixed layer (in m); contouring illustrates the surface velocity field indicated by local stream lines.
Snapshot of the high-resolution (0.1°) model field, from Behrens et al. taken at the end of the tracer injection period (end of April, model year 0): shading indicates the thickness of the surface mixed layer (in m); contouring illustrates the surface velocity field indicated by local stream lines and clearly identifies the high velocity Kuroshio and Kuroshio extension.

The Behrens et al. study is open-access while the Rossi et al. study is not. Measurements taken in the North Pacific by Canada’s Department of Fisheries and Oceans and InFORM team member Dr. John Smith indicate that the Rossi et al. study predicts the arrival time of the plume on the west coast but overestimates the activity of the Fukushima derived radionuclide 137-Cs. Behrens et al. predict a too late time of arrival but with lower activities that appear to more realistic. It important to note that these models carry the own simplifications and assumptions (e.g. see section 3.4 Caveats of the Behrens et al. (2012) study) and that recent measurements suggest that some of the Fukushima plume is being dispersed to the south rather than to the east in the Pacific (e.g. Kumamoto et al. (2014) open-access; more on this study in a forthcoming post).

Articles that confuse the conclusions of the Chinese study are a good example of poor reporting on an important subject. The example here was originally spawned by Energy News who have a history of inaccurate reporting on Fukushima and then propagated through the web by uncritical followers of the site.

Advertisements

9 thoughts on “Misunderstanding Ocean Transport Models of the Fukushima Radionuclide Plume in the Pacific”

  1. You slag enenews but where have you and health Canada been since March 2011? Also you talk about ‘allowable levels’ of c137 etc in food/drinking water set by health Canada which are 10 times higher than in Japan and based on what? And from samples taken from 62 fish in 2013 you magically come up with comparisons to background radiation and smoking radiation levels? Good luck with your site, I will go back to getting my info from those shady online sites thank you.

    Like

    1. Hi Rick,
      Thanks for your comment. The short answer to your question with respect to Health Canada and myself is that along with Fisheries and Oceans Canada there has been a seawater monitoring program and assessments made of radionuclides measured in fish here and in Japan by Health Canada since the disaster began in 2011. Your can read the study by Dr. Jing Chen summarized above and an earlier publication she wrote in 2013 where she evaluated the likely risk to seafood consumers based on Japanese monitoring of their food supply (open-access in Radiation Protection Dosimetry http://rpd.oxfordjournals.org/content/early/2013/09/28/rpd.nct239.full) which is one of the 5 most downloaded studies in that journal for 2013.

      It takes time and resources to make measurements so I think it is unreasonable to fault the scientific community for not being able to measure everything everywhere. Scientific understanding of the activities of Fukushima derived radionuclides is increasing incrementally. The Japanese have been making many measurements of radionuclides in fish. The Japanese Fisheries Agency has made over 47,000 as of July 31, 2014 (http://www.jfa.maff.go.jp/e/inspection/).

      The percentage of fish registering more than 100 Bq/kg (the more stringent Japanese regulation for food) has dropped from 53% to ~0.7% since 2011 until July 31, 2014 in Fukushima prefecture where coastal activities are many orders of magnitude greater than BC waters. The percentage has dropped to effectively 0% from 6.5% in the same time period in other prefectures. All the data is available for download at the site. These concentrations of Cs in fish result from many orders of magnitude higher activities of Cs in the coastal waters off of Japan immediately after the disaster. Such activities in seawater here will not occur based on modeling of plume transport and measurements being made in the North Pacific.

      All available measurements of fish caught off of the west coast of North America thus far suggest that there is little radiological health risk due to Fukushima radionuclides. That is what the evidence from the scientific community suggests.

      With respect to your second question the comparison of the dose experienced by consumers of fish above and other behaviours (smoking) is not magic but simply application of our best understanding of how radionuclide activity relates to dose experienced by Canadians.

      Thanks for your interest in the InFORM project.

      Like

      1. Dear person who responded; thank you for the response, it was most unexpected. My remarks were made with the expectation of being banned from commenting. As to your reply, I cannot possibly bandy numbers or statistics or peer reviewed studies with you as I am only a simple trades person, however I can point out that there are many high profile people in the scientific community out there who are taking the view that this crisis is far from over or improving (Arnie Gunderson, Dr. Jacques Repussard Director IRSN, Didier Champion IRSN, Doctors Gordon Edwards, Andrew S. Kanter, Brad Sample, and many Japanese and other Doctors and professors.) There are at least 400 tons of radio-active water leaking into the ocean everyday. They don’t know or are not saying where the 3 melted cores are, (in the ocean? because they are somewhere, and Tepco have admitted that containment is lost). Also, the IRSN studies are suggesting contamination of the North American coastline. If the Japanese limit for c134,137 contamination is 10bq per kg, why would I accept levels of up to 100bq per kg as per health Canada guidelines. As to cesium, why only talk about it? The IRSN also mention about 60 other radio-active isotopes leaking into the ocean, including uranium, plutonium, americium, strontium, tritium etc. So if you would like to win me over as a trusted source of information, please don’t patronize me with isolated statistics or cherry picked studies. There is a lot of information out there, and some of it is undoubtedly false or misinterpreted, but what is needed now for this crisis is not soothing words or more propaganda, but real scientific effort to contain these melted cores from doing any more damage. Since the technology does not exist to contain them Tepco needs to be removed from the lead role and some serious nuclear engineering firms brought in to deal with this. Also the public needs to have faith that this crisis is being taken seriously (hint; you are not doing that for me) by the powers that be. Thank you for the response. Rick Costello

        Like

      2. Hi Rick,

        My name is Jay Cullen and I am one of the PI’s of the InFORM program. You can find my contact information on the website and I urge you to email me with any questions you might have. One of the goals of the InFORM project is to get the best information about the impact of Fukushima derived radionuclides on the marine environment and people living along the west coast of Canada. I am not sure what blogs you are accustomed to commenting on but you won’t be banned from asking questions here. That being said there is a give and take here that will require some quantitative information be absorbed. My assessments here are based on the peer-reviewed studies published in academic journals by the international scientific community. I do my best to convey these findings to the public.

        With respect to your question about only talking about cesium there exist many studies of the other isotopes you mention. The main reason monitoring programs focus on Cs is that it is relatively easily measured by gamma-spectrometry, it was released in large quantities, it is relatively long lived (137-Cs half-life ~30 years), it is taken up by the biota and can represent a radiological health risk. The releases of the other elements you list above were relatively small in comparison and their radiological risks are not likely to be significant. I urge you to consult these posts based on measurements of strontium and plutonium in air, soil and water that compare their releases from Fukushima to those of Chernobyl and weapons testing in the 20th century. I also blog under the name MarineChemist at the DailyKos website.

        Plutonium
        http://www.dailykos.com/story/2014/03/30/1287608/-Plutonium-Released-from-the-Fukushima-Dai-ichi-Disaster

        Strontium
        http://www.dailykos.com/story/2014/04/14/1291864/-90-Strontium-Released-from-the-Fukushima-Disaster-Compared-to-Other-Human-Sources

        Plutonium releases were about 1-10 million times less than 137-Cs and 90-Sr was 30 to 10,000 times less. Researchers making measurements of plutonium in sediments and seawater directly off the coast from Fukushima could not detect the presence of Fukushima derived plutonium e.g. http://www.biogeosciences.net/10/2497/2013/bg-10-2497-2013.html

        We can detect Cs from Fukushima in seawater off the coast of North America now but the Cs present in fish caught off BC so far is almost exclusively from atmospheric weapons testing in the 1950’s and 1960’s.

        Thanks again for your comments. As I said please do not hesitate to write me about any of my posts. You are absolutely right that releases continue to the ocean from Fukushima. Measurements suggest that release rates are roughly 10,000-100,000 times lower now than they were in the weeks to month after the meltdowns in 2011. Our program will work to determine how much radioactivity is present off our coast and in the event that conditions change for the worse at the site allow response to increased risks associated with higher release rates.

        Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s