Thursday, June 7, 2018

Radiocesium in Tokyo Bay from Fukusima Daiichi Disaster

Maria Perez (201, June 7). Fukushima Nuclear Plant Radioactive Waste Flowed Into Bay for Five Years After Disaster. Newsweek,
Hideo Yamazaki, a former professor of environmental analysis at Kindai University told The Asahi Shimbun that 20,100 becquerels of cesium per square meter were found in the mud of the Kyu-Edogawa river five years after a tsunami caused the meltdown of the plant...

Yamazaki’s team measured a maximum of 104,000 becquerels of cesium per square meter from the mud he and his study team collected in July 2016 in the same area of the bay... The substances eventually moved downstream into the Tokyo Bay and seeped into the mud, Yamazaki told the publication....

The highest level of radioactivity that was found in the mud during the 2016 study was 350 becquerels, The Asahi Shimbun reported. 
The article notes as a basis for comparison that the Japanese government is allowing soil with up to 8,000 becquerels per kilogram to be used in road construction.

This most recent set of findings reported by  Newsweek contributes to a growing body of literature describing how radioactive particles concentrate in mud and brackish water, threatening tidal life:
Scientists find new source of radioactivity from Fukushima disaster October 2, 2017, Woods Hole Oceanographic Institution

Virginie Sanial el al., "Unexpected source of Fukushima-derived radiocesium to the coastal ocean of Japan," PNAS (2017).
I fear that if someone were to test US shorelines for radiocesium they would also find Cesium-137, which has an approximately 30 year half life, among many other long-lived radionuclides concentrated in the environment.

Research published by Timothy Mousseau and Anders Moller has explored the long term effects of increasingly radioactive environments and found transgenerational effects, with some species more impacted than others depending at least partially upon their capacities to mobilize antioxidants:

Anders Pape Møller, Andea Bonisoli-Alquati, Geir Rudolfsen, Timothy A. Mousseau. Chernobyl Birds Have Smaller Brains. PLOS, ( 

How resilient are humans to the effects of bioaccumulated toxins? I guess we are going to find out....

The plant looks quiet today:



  1. Japanese English
    Characteristics of Caesium-134 and Caesium-137
    font size decrease font size increase font size Print
    Radiological Characteristics
    Caesium-134 has a radioactive half life of 2.06 years. It decays by beta emission, yielding one beta particle per transformation with a mean energy of 0.157 MeV. It also emits an average of 2.23 gamma rays per transformation with a mean energy of 0.698 MeV.

    Caesium-137 has a radioactive half life of 30.2 years. It decays by beta emission, yielding one beta particle per transformation with a mean energy of 0.188 MeV. Its other emissions are negligible. In 0.944 of transformations, barium 137m (radioactive half life 2.552 minutes) is produced. This decays by gamma emission in 0.898 of transformations, emitting a gamma ray of energy 0.662 MeV.

    Behaviour of Caesium in Soils and Plants1)2)3)
    Caesium is a close chemical analogue of potassium and can substitute for it within the structure of clay minerals. Thus, it binds strongly to clays, tending to be both immobile and relatively poorly available to plants in clay rich soils. Conversely, it tends to be more mobile and available in soils that contain little clay and that are potassium deficient.

    Demonstration projects

    Demonstration projects

    Demonstration projects

    Depth distribution of radioactivity density in soil of schoolsand Playgrounds
    Behaviour of Caesium in Domestic Animals and Humans1)2)3)
    Caesium is well absorbed from the gastrointestinal tract of mammals and birds, with the fractional absorption typically being in the range 0.6 to 1.0. The element is then relatively uniformly distributed throughout all organs and tissues of the body, though it is concentrated to a limited degree in muscle, following the distribution of stable potassium. The biological half life of retention in the body differs between species and generally increases with increasing body mass both within and between species. Effective half-life of Cesium-137 in humans is approximately 110 days (ICRP Pub.78).

    Demonstration projects
    Fractional Systemic Retention of Caesium as a Function of Body Mass (applicable to mice, rats, guinea pigs, hens, dogs, monkeys and humans)

    1) Coughtrey, P J and Thorne, M C, Radionuclide Distribution and Transport in Terrestrial and Aquatic Ecosystems, Volume 1, A A Balkema, Rotterdam, 1983
    2) IAEA-TECDOC-1616, 2009
    3) IAEA Technical Reports Series No. 472, 2010

    back to top
    Background information

    Background Information relating to the Effects of Ionising Radiations and the Fukushima Dai-ichi Accident
    The Nature of Ionising Radiations and their Health Effects
    Everyday Exposures to Ionising Radiations
    Major Nuclear Accidents and Their Consequences
    International Guidance, Legislation and Regulations
    Remediation following Major Radiation Accidents
    Remediation following Major Radiation Accidents
    Characteristics of Caesium-134 and Caesium-137
    Remediation of Agricultural Areas
    Remediation of Semi-natural Areas
    Remediation of Urban and Other Built Areas
    Waste Management
    Copyright © 2014 Japan Atomic Energy Agency. All Rights Reserved.

  2. Hi Majia,

    Maximum activities of 137-Cs in sediments right offshore Fukushima and along the coast were 540 Bq/kg ( and 700 +/- 60 Bq/kg (Sanial et al. 2017, The partitioning/sticking of Cs to the sediments there occurred at seawater concentrations immediately (weeks) following the meltdowns that were millions to 10's of millions of Bq/meter cubed of seawater. Given that seawater concentrations here along the coast of North America are about a million times lower than those peak activities it is very unlikely that 137-Cs from Fukushima can be measured in sediments here along the coast owing to ocean transport of contamination. But I will collect some samples and have a look for you. Atmospheric transport of Fukushima contamination to soils on land was very minor here. Measurements by colleague Kris Starosta and his group show that only about 0.2-0.3 Bg/kg Fukushima derived 137-Cs could be detected. You can read about that study here

    Sediments here are unlikely to represent a significant vector for radiocesium to make its way into the food web or lead to exposure of human consumers or wildlife to Fukushima contaminants given the scientifically derived evidence already gathered.

  3. Better to have scientific evidence than hyperbole or sophistry, even though one may not agree some of it. I wish there were more published by Kaltofen, about radionuclides in air samples, he has gotten.


Note: Only a member of this blog may post a comment.