Chemical and Radioactive Properties 



Physical radiometric methods are now adequate for the two important 

 alpha-emitting nuclides (Miyake and Sugimura, 1968), and although 

 internal standards have been used in most cases, there is little indication 

 that equilibration with the plutonium in seawater has been estabUshed. 

 Plutonium's attraction to surfaces may be one of its most characteristic 

 properties and needs additional study, beginning with the relatively 

 simple surfaces of the large algae. 



Describing oceanic distributions has been limited by low and variable 

 analytical yields, especially in sediments and complex living tissues. 

 Improved analytical methods are needed; one promising technique is 

 the recovery of traces of plutonium from tissue by electroplating. 



There are still other puzzles related to plutonium in the ocean. Why 

 is it often associated with high concentrations of natural polonium on 

 surfaces, and what brings them to these surfaces? Are the concentrating 

 agencies physical, chemical, or biological? Do the nuclear properties 

 (the alpha emissions) contribute anything to the processes? Has natural 

 polonium-210 been significant in shaping the biosphere? Will the plu- 

 tonium that may be added significantly increase the ionizing burdens? 



FACTORS GOVERNING THE COMPOSITION 



OF SEAWATER BELOW THE POLAR ICE COVER 



The intermittently ice-covered polar seas may be areas of strong 

 air-sea gas exchange, as evidenced by the intense air-sea gradients 

 observed there. These areas have been poorly investigated because 

 of the sampling difficulties. The freezing process and the biota, unique 

 to the ice-seawater system, many produce chemical conditions distinct 

 from those of open sea regions. 



The freezing of seawater and its eifect on the chemistry of the water- 

 ice interface is not well understood. There have been too few systematic 

 field observations of the composition of surface seawater under freezing 

 conditions to compare with data from laboratory investigations (Wiere, 

 1930; Thompson and Nelson, 1956; and Bennington, 1962). 



Marine plants are abundant within and under the sea ice (ApoUonio, 

 1961, 1965; Meguro et al., 1967; and Clasby et al., 1972), and their 

 chemical interactions may differ noticeably from those of open ocean phy- 

 toplankton. It is important to determine the horizontal chemical gradients 

 that may be produced under the ice and within the open water, and the 

 rates of transfer of gases across the water-air interface in the open 

 water. Adequate investigations of horizontal chemical gradients on 

 scale lengths of a few meters to kilometers and of small-scale vertical 

 gradients directly under the ice are difficult to carry out. The difficulty 

 arises from 



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