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Since the mid-20th century, plutonium in the environment has been primarily produced by human activity. The first plants to produce plutonium for use in cold war atomic bombs were at the Hanford nuclear site, in Washington, and Mayak nuclear plant, in Russia. Over a period of four decades, “both released more than 200 million curies of radioactive isotopes into the surrounding environment -- twice the amount expelled in the Chernobyl disaster in each instance”.〔 The majority of plutonium isotopes are short-lived on a geological timescale, though it has been argued that some natural plutonium, like the long-lived 244Pu isotope, can be found in nature.〔P.K. Kuroda, ''Accounts of Chemical Research'', 1979, 12(2), 73-78 ()〕 This isotope has been found in lunar soil,〔KURODA, P.K., MYERS, W.A., "Plutonium-244 Dating III Initial Ratios of Plutonium to Uranium in Lunar Samples." Radioanalyt Chem. 150, 71.〕 meteorites,〔MYERS, W.A., and KURODA, P.K., "Plutonium-244 Dating IV. Initial Ratios of Plutonium to Uranium in the Renazzo, Mokoia and Groznaya Meteorite." J. Radioanalyt. Nucl. Chem. 152, 99.〕 and in the Oklo natural reactor.〔KURODA, P.K., "(Plutonium-244 in the Early Solar System and the Pre-Fermi Natural Reactor ) (The Shibata Prize Awardee's Lecture)". Geochem. J. 26, 1.〕 However, one paper on marine sediments for plutonium in marine sediments, atomic bomb fallout is responsible for 66% of the 239Pu and 59% 240Pu found in the English Channel, while nuclear reprocessing is responsible for the majority of the 238Pu and 241Pu present in the Earth's oceans (nuclear weapons testing is only responsible for 6.5 and 16.5% of these isotopes respectively).〔O.F.X. Donard, F. Bruneau, M. Moldovan, H. Garraud, V.N. Epov and D. Boust, ''Analytica Chimica Acta'', 2007, 587, 170-179 〕 ==Plutonium production== Richland, Washington was the first city established to support plutonium production at the nearby Hanford nuclear site, to power the American nuclear weapons arsenals. Ozersk, Russia supported plutonium production to power the Soviet nuclear arsenals at the Mayak nuclear plant. These were the first two cities in the world to produce plutonium for use in cold war atomic bombs. In the 2013 book on a history of these two blighted cities, ''Plutopia: Nuclear Families, Atomic Cities, and the Great Soviet and American Plutonium Disasters'' (Oxford), Kate Brown explores the health of affected citizens in both the United States and Russia, and the “slow-motion disasters” that still threaten the environments where the plants are located. According to Brown, the plants at Hanford and Mayak, over a period of four decades, “both released more than 200 million curies of radioactive isotopes into the surrounding environment -- twice the amount expelled in the Chernobyl disaster in each instance”.〔 Most of this radioactive contamination over the years at Hanford and Mayak were part of normal operations, but unforeseen accidents did occur and plant management kept this secret, as the pollution continued unabated. Even today, as pollution threats to health and the environment persist, the government keeps knowledge about the associated risks from the public.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Plutonium in the environment」の詳細全文を読む スポンサード リンク
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