Nuclear Fallout

In order to fully appreciate how to manage environmental damage due to nuclear fallout events, it is important to appreciate how radioisotopes behave in the environment. 

 

Given disasters such as Chernobyl and Fukuyama this knowledge will help with approaches to manage the environmental damage they produce and cleanup. This study undertook experiments to determine the behavior of fallout after extended periods to determine if assumptions regarding the behavior of the isotopes were valid. Given that fallout from nuclear testing is over 50 years old it provides good information on the long term behavior of these isotopes. 

In This experiment they used two chore location that should have minimal effects from nuclear disaster one was in Thailand and one was in British Isle. Both of these locations are pine forests but different climates. They used different ways to test the soil depth but the main way was they used 210Pb to determine the depth that would correspond to nuclear testing era. The researchers looked into Cs 137 the most during their testing to determine the soil quality during their tests. Cs 137 is one of the most important radionuclides released to the environment by both reactor accidents and nuclear weapons. Internal exposure to Cs 137, through ingestion or inhalation, allows the radioactive material to be distributed in the soft tissues, especially muscle tissue, exposing these tissues to the beta particles and gamma radiation and increasing cancer risk. Cs 137 is a radioactive isotope of caesium which is formed as one of the more common fission products by the nuclear fission of uranium-235 and other fissionable isotopes in nuclear reactors and nuclear weapons. That is they the researchers looked closely into Cs 137.

The researchers tested the quality of the soil, types of soil, Ph level of the soils, and the organic matter and decay of the soil. They used x-ray diffraction to see soil contents through different depths in the soil. The soil samples were taking from approximately the depths of 1 cm - 18 cm. What they found at these two test sites was significant amounts of clay in the soil which retains the radioactive materials for a longer time. The clay slowed down the movement of the radioactive elements after deposition to the soil. This made the radioactive elements stay closer to the surface of the soil much more that it would have if the soil contained no clay. Due to large differences in vertical gradients of bulk densities in the soil of the two tests sights the peak activity inventories and half depths provide the most reliable measurements of the vertical migration of Cs 137 since deposition. High soil pH, good soil moisture and temperature conditions, good aeration. Decaying of plants and animals normally gives the soil natural nutrients which gives that soil a good pH level for plant growth. Low soil Ph, poor drainage, low soil temperature, permanent dryness, and nutrient poor soils. At the British Isle test location a well developed surface organic layer with a strong acidic pH. The organic carbon content ranged from 32% at the surface to 2% at 17cm. At the test site in Thailand the rapid decay of organic matter was much Higher than at the British Isle location. The results of the tests at the two locations provide evidence that even under different climates the long term downward movement of Cs 137 in the pine forest soil is limited to a few cm. Movement was particularly limited in a tropical pine forest soil in which fixation by illite is the mostly likely retention mechanism though a high bulk density may also help slow down the movement of Cs 137. At the test locations the Cs 137 remains associated with organic matter present when it was deposited.

In the more highly organic soil underlying the temperate pine forest some limited vertical movement of weapons fallout Cs 137 has occurred but the layer of peak Cs1 37 accumulation is still relatively shallow and clearly co-located with OM originating at the time of global weapons testing. The lack of significant migration over 50 years at both test sites has important consequences for long term forest management and radiation doses to humans and other organisms in forests. Levels of Am 241 was undetectable in Thailand strictly considerably smaller than that of British Isles.

The showing of these test can prove that nuclear weapon fallout can have a tremendous influence on the soil of the earth and can be stuck in the soil close to the surface for centuries after the fallout has occurred. This shows that even when we think it is safe to be on that soil because of how long ago the fallout may have happened we never know if the soil will fully recover from that.

The reason I am writing this blog is to show people how powerful these nuclear weapons are on people and our earth. These weapons release radioactive materials into our earth and can affect humans, plants, and animals for centuries after the nuclear weapon fallout has occurred. If these nuclear weapons start getting used out of control the earth will not be suitable for life on earth and people should learn about that because they may not know that and think once that nuclear weapon clears it is okay to live in these areas but it is not because the food and water will be contaminated and not save for people to eat or drink.

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Other references:
http://www.radioactivity.eu.com/site/pages/Caesium_137.htm
http://large.stanford.edu/courses/2012/ph241/wessells1/