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Potassium: Radonuclides

  1. Taehong Jun,
  2. Olga G. Tsay,
  3. David G. Churchill

Published Online: 15 DEC 2011

DOI: 10.1002/9781119951438.eibc0414

Encyclopedia of Inorganic and Bioinorganic Chemistry

Encyclopedia of Inorganic and Bioinorganic Chemistry

How to Cite

Jun, T., Tsay, O. G. and Churchill, D. G. 2011. Potassium: Radonuclides. Encyclopedia of Inorganic and Bioinorganic Chemistry. .

Author Information

  1. Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea

Publication History

  1. Published Online: 15 DEC 2011


There are currently 28 known nuclides of potassium (K). Three of these are naturally occurring: 39K, 40K, and 41K of which potassium-40 is the only naturally occurring radionuclide. With its long half-life of 1.28 × 109 years and an abundance of 0.012%, 40K is a discrete source of natural radiation. Thus, in potassium-rich foods, minerals, etc., a distinct natural dose is unavoidable for humans and all living creatures on Earth. Thus, it may be quantified in soil, plants, and animals and allows for various studies. Potassium-40 may decay to calcium-40 (89% probability) or may undergo electron capture (EC) to give argon-40 (11% probability). The biological half-life (excretion time decay) of 40K, however, is 30 days. As it is often found in many mineral forms, potassium-40 is a common constituent of soil and water, but not air. There are various reports in which 40K is tracked migrating from soil(s) into various plants. In countries such as Europe and Brazil, drinking water was also scrutinized and found to contain abnormal levels of 40K. The abundance of 40K in human diet and foods from places such as China, Pakistan, and Ukraine has also been studied.


  • radioisotope;
  • radionuclide;
  • half-life;
  • β-decay;
  • γ-decay;
  • γ-spectrometry;
  • cesium