Artificial Radionuclides in the East Sea (Sea of Japan) Proper and Peter the Great Bay

Over the past decade there has been growing concern over dumping of radioactive waste in the East Sea (Sea of Japan) proper and adjacent coastal waters. Here we show that the evolution of activity concentrations of 137Cs and 239+240Pu in the East Sea, and existing levels of radioactive contamination in waters, sediments and biota from Peter the Great Bay (Russia) can be largely attributed to global fallout deposition. The former sequence of data includes results from the AWARES cruise (Active Watch of Artificial Radionuclides in the East Sea) conducted between 26 October and 1 November 1993 about ten days after 14 GBq of liquid radioactive waste was dumped into the East Sea. The activity concentration of 137Cs and 239+240Pu in surface waters ranged between 2.7–3.5 Bq m−3 and 3.5–20.8 mBq m−3, respectively, and were not different to levels observed during August 1993 prior to the Russian dumping operation in October. Isotopic ratios also indicate the absence of any significant anthropogenic radioactive contamination in the region other than from global fallout deposition.