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Pacific Ocean: Radionuclides

  1. Michio Aoyama

Published Online: 15 JUN 2010

DOI: 10.1002/0470862106.ia744

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Aoyama, M. 2010. Pacific Ocean: Radionuclides. Encyclopedia of Inorganic Chemistry. .

Author Information

  1. Meteorological Research Institute, Tsukuba, Japan

Publication History

  1. Published Online: 15 JUN 2010


The main sources of anthropogenic radioactivity to the Pacific Ocean are fallout from atmospheric nuclear weapon testing. The releases from the nuclear fuel reprocessing plant and from the Chernobyl accident in 1986 are minimal in this region. Consequently, the radionuclide levels in the Pacific Ocean are low, about a few becquerel per cubic meter for 137Cs in the surface water.

137Cs, 239, 240Pu (other transuranics), and 90Sr are discussed in this article for the following reasons: (i) 137Cs and 90Sr, conservative in the open sea, are the most abundant anthropogenic radionuclides and the main contributors to human exposure and (ii) 239, 240Pu are very long-lived, nonconservative, and the most abundant among transuranics. The distributions and temporal change in these radionuclides in seawater and sediment are described. The current radionuclide levels in the Pacific Ocean are low and, therefore, of no concern from the radiological point of view.


  • artificial radionuclides;
  • Pacific Ocean;
  • global fallout;
  • nuclear weapons tests;
  • subduction;
  • subsurface maximum;
  • 137Cs;
  • Pu isotopes;
  • transuranics;
  • 90Sr;
  • water column inventory;
  • sediment