344 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



TABLE 1 Announced Nuclear Detonations at Bikini Atoll 



particles were observed adhering to these particles. Because of the dense property of the 

 CaO/Ca(OH)2 particles, their atmospheric hydration was dependent on the aqueous 

 environment encountered during fallout and sedimentation. Complete hydration, which 

 was observed in laboratory tests over several weeks' time, was found to be accompanied 

 by a 100% increase in particle volume and in the development of a crumbly, fluffy 

 structure. The CaO/Ca(OH)2 particles began to dissolve slowly when wet with seawater. 

 The freed calcium ions reacted with sulfate ions in the seawater to form calcium 

 sulfate-dihydrate (gypsum), whereas tlie hydroxyl ions reacted to form insoluble 

 Mg(0H)2 . A hard shell of Mg(0H)2 formed around the particle, which, during the period 

 of observation, apparently stopped any further reaction with seawater; a region of 

 Ca(0H)2 remained on the inner surfaces of the spherical particles. The remaining 

 radioactivity was associated with the Ca(0H)2 in the center of the sphere. Some of the 

 freed calcium ions in the spheres also formed CaCOs by reaction with bicarbonate ions in 

 seawater. The time history of the distribution and redistribution of transuranic elements 

 has been intimately associated with these particles and with their redistribution by the 

 physical circulation system of the lagoon. 



