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marine environment have very short half-lives of anywhere from a 

 few minutes to a few yeao's. These isotopes, when released into 

 the ocean, will both disperse and radiodecay rather rapidly. 

 Some of the radionuclides that may have been released in the 

 Arctic could be fairly long-lived: for e:Kampie, plutoni\im-23a 

 has a half -life of approximately 86 years, plutonium-239 has a 

 half-life of 24,400 years, and plutoni\im-240 has a half-life of 

 6,850 years. Strontium-90 and cesium-137 have half-lives of 28 

 and 30 years respectively. 



Examination of the environmental impact resulting from the 

 1986 Chernobyl accident illustrates the effect of such 

 radiodecay. In 1989, EPA entered into a cooperative agreement^ 

 with the Institute of Biology of the Southern Seas (IBSS) in 

 Sevastopol, Uloredjie, to study the transport, partitioning, and 

 effects of Chernobyl's principal fallout radionuclides on the 

 Black Sea. In June 1990, at the invitation of XBSS, a joint 

 monitoring survey was conducted in the northern Black Sea aboard 

 the oceanographic survey ship Professor Vodvanifcalcv. The 

 radionuclides tracked by this effort were cesium-134, cesium-137, 

 ruthenium-106 , cerium- 144, and strontium-90. Dtaring the years 

 since Chernobyl, all of the radionuclide concentrations have been 

 decreasing through dilution and radiodecay until only the long- 

 lived Cesium-137 is at concentrations that are still easily 

 measiirable. 



project 02.06-31 under U.S. -Russia Bilateral 

 Environmental Agreement. 



