stituents. Sulfate is thought to be removed following biochemical re- 

 duction to sulfide, but the quantitative importance of this mechanism 

 has not been evaluated. 



Sodium and chloride leave the ocean waters primarily dissolved in 

 pore water of sediments, and potassium by uptake by clays, but the 

 quantitative aspects remain to be worked out. Practically none of 

 the details of how magnesium or any of the minor constituents are 

 removed from the system is known. 



PLUTONIUM CHEMISTRY OF THE OCEAN 



Plutonium is an extremely toxic, radioactive man-made element 

 whose behavior in the marine environment is inadequately known, 

 although it has been studied intensively in connection with production 

 of weapons and power sources (Olafson and Larson, 1963; Miner, 1964; 

 and Colemen, 1965). Only a few determinations of its concentration 

 in seawater and in associated organisms and sediments have been made, 

 the first being as recent as 1964 (Pillai et al., 1964). Its chemical be- 

 havior in the marine environment will be difficult to predict from that 

 observed on land, especially its involvement with the organisms of the 

 sea. 



Plutonium is a member of the actinide series and chemically similar 

 to the rare earths. It forms insoluble fluorides and hydroxides, and a 

 quite insoluble oxide. It can exist in several oxidation states, commonly 

 as tri- and tetravalent cations, or in the hexavalent form Pu02+^. It 

 forms soluble complexes with citrate and is strongly chelated (Olafson 

 and Larson, 1963). 



The use of plutonium is expected to expand so rapidly that several 

 serious hazards and management problems can be foreseen. Two of 

 its nuclides, Pu-239 and Pu-238, are employed as fuels. Accidents 

 released both of these into the environment, and, considering the large 

 scale of projected nuclear power programs, more such accidental re- 

 leases can be expected. The transport of this valuable major fuel across 

 oceans and continents may invite thievery and hijacking. 



It is important to accelerate studies of background levels and to 

 investigate chemical phenomena that might suggest the results of large 

 additions of plutonium nuclides to the ocean. These studies should 

 include consideration of its enrichment within the marine biosphere 

 and its known affinities for inorganic surfaces and particles. 



Present Conditions in the Ocean 



The time of entry of most of the ocean's plutonium is fairly well 

 known, as is its probable character on arrival at the sea surface. The 

 largest fraction originated during 1950-1970 as global fallout which has 



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