12 



Atomic Radiation and Oceanography and Fisheries 



remain in solution, while ruthenium 106, 

 cerium 144, zirconium 95, yttrium 90 and 91, 

 and niobium 95 are largely in the solid phase. 



The solid fractions, whether they be chemi- 

 cal precipitates or solids produced by accumula- 

 tion in the bodies of organisms, will tend to 

 settle out. As they settle, they may encounter 

 environmental conditions which will prevent or 

 hinder deposition. There will be, however, 

 some net transport toward the deeper water and 

 the bottom from the settling process. Because 

 of biological uptake, the removal of the par- 



TABLE 5 Physical States of Elements in Sea 

 Water 1 (From Greendale and Ballou, 1954) 



Percentage in given 

 physical state 



Element Ionic Colloidal Particulate 



Cesium * 70 7 23 



Iodine 90 8 2 



Strontium * 87 3 10 



Antimony 73 15 12 



Tellurium 45 43 12 



Molybdenum 30 10 60 



Ruthenium * 5 95 



Cerium * 2 4 94 



Zirconium * 1 3 96 



Yttrium * 4 96 



Niobium * 100 



1 Elements introduced by simulated underwater 

 detonation of atomic bomb, Greendale and Ballou, 

 1954. 



* Indicates element has important fission product 

 isotope. 



tides from the upper layers of the sea may be 

 quite slow. For example, cerium 144, a rare 

 earth which has a half-life of 275 days, and 

 which is present in the sea primarily in particu- 

 late form, and its daughter Pr 144 were found 

 to account for 80 to 90 per cent of the activity 

 in plankton samples from the upper layer taken 

 in the Pacific by the TROLL survey 1 3 months 

 after weapons tests (Harley, 1956). 



A very rough idea of the reduction in ac- 

 tivity that would eventually be obtained by 

 removal from the ocean can be gained from the 

 transfer percentages of Table 3. The fraction of 

 an introduced fission product remaining in the 

 sea will, at equilibrium, be equal to or greater 

 than the transfer percentages for the correspond- 

 ing element. (The transfer percentage reflects, 

 in part, retention on land as well as sedimenta- 

 tion from the sea.) An important factor is 

 the time required for equilibrium to be reached ; 

 if it is very long in relation to the half-life of 



the element in question, reduction of activity 

 may be negligible. The long-lived and danger- 

 ous isotope, strontium 90, has a relatively high 

 transfer percentage and a long equilibrium or 

 "residence" time; the same would be expected 

 for cesium 137, which is an alkali and should 

 behave somewhat like potassium or rubidium. 



Disposal of atomic wastes by deep sea burial 

 in various sorts of packages has been proposed. 

 Dispersion of the activity would then be by 

 slow diffusion from concreted wastes, or would 

 be delayed until rupture of an impermeable 

 container occurred. Because the deep ocean 

 sediments have appreciable exchange capacities, 

 much of the wastes would be retained in this 

 highly absorptive environment. The upper lay- 

 ers of the sediments would, presumably, tend 

 to become saturated, and the further removal of 

 radioactive elements by exchange or absorption 

 would be controlled by the rate of diffusion into 

 the deeper sediments. 



There are wide gaps in our knowledge of 

 many of the processes mentioned above. These, 

 and suggestions for research needed to fill them, 

 are discussed by Carritt and Harley (Chapter 6) . 

 Much of the required information can be ob- 

 tained by the use of radioactive tracers, intro- 

 duced in weapons tests and experimental waste 

 disposal operations, as well as in purposive 

 experiments. 



V. Physical Processes and Radioactive 

 Materials 



Physical structure of the sea 



The physical properties of sea water of im- 

 portance to the present study are functions of 

 temperature, salinity, and pressure. The tem- 

 perature ranges from about 30° C to about 

 — 2 ° C, which is the initial freezing point. The 

 highest temperatures occur at the surface or in 

 the mixed near-surface layer; below this the 

 temperature decreases to about 5° C at 1,000 

 meters and to 1° to 2° at greater depths. In 

 the deepest parts of the ocean there is a slight 

 increase of temperature due to adiabatic heat- 

 ing. Hydrostatic pressure increases about one 

 atmosphere for each 10 meters of depth. In 

 the open ocean in mid-latitudes the salinity gen- 

 erally decreases slightly with depth in the upper 

 few hundred meters, then increases slowly. In 

 high latitudes the salinity normally increases 

 with depth throughout the water column. 



