64 



Atomic Radiation and Oceanography and Fisheries 



lated by microscopic plankton organisms. Both 

 will be collected by filtration or centrifugation. 

 Goldberg (1956), however, noted that informa- 

 tion obtained during Operation WIGWAM 

 suggests a fractionation of a portion of the 

 fission product activities into solids that are col- 

 lected and concentrated by filter feeding or- 

 ganisms. The activity within the filter feeding 



TABLE 4 Fission Product Activity After 100 



Days Cooling from 10^^ Megawatt Hours of 



Nuclear Power Production i 



Revelle, et al. (1955). 



2 Based on tonnage shown in Table 3. 



organisms — ones adapted to the removal of 

 particulate material from suspension — showed 

 a high percentage of rare earth elements that 

 previously were noted as probably being pre- 

 dominantly dispersed as solids in the oceans. 

 These organisms were collected in the mixed 

 layer of the sea. 



About a year after the 1954 nuclear tests 

 were completed. Operation TROLL undertook 

 a survey of the region west from the test site, 

 including the region just off the Phillipines and 

 northward off the coast of Japan (U. S. Atomic 

 Energy Commission, 1956). Seventy water and 

 plankton samples taken during this cruise were 

 analyzed radiochemically. When compared on 

 an equal weight basis (1000 gms wet plankton 



vs. 1 liter of water) the plankton contained on 

 the average 470 times the activity of the water. 

 Significantly, 80 to 90 per cent of the activity 

 of the plankton was due to Ce^** (and its Pr^** 

 daughter) . Cerium is a rare earth. No informa- 

 tion is yet available concerning the species and 

 the relative quantities of organisms responsible 

 for the concentration of activity. A comparison 

 of the total activity per unit weight of macro- 

 and micro-plankton indicated approximately a 

 one and one half times greater concentration by 

 the micro-plankton. 



It is noteworthy that the observations made on 

 Operations TROLL and WIGWAM revealed 

 a system in which the properties, with the ex- 

 ception of radioactive element content, were es- 

 sentially those of normal sea water. The sys- 

 tem can be imagined as being essentially sea 

 water to which had been added the radioactive 

 material — a procedure which because of the 

 extreme dilution of the contaminant, in a 

 chemical sense, would not affect the sea water 

 properties. Furthermore, these observations were 

 made on samples taken in the mixed layer (the 

 upper 100 to 300 m) . 



These results, though largely qualitative in na- 

 ture, suggest the following conclusions regard- 

 ing the behavior of fission product elements in 

 the mixed layer of the open oceans: 



1. Radioactive material will be retained in the 

 mixed layer for periods of at least a year during 

 which time horizontal motion may carry them a 

 few thousand miles. (Operation TROLL and 

 SHUNKOTSU-MARU data.) 



2. Rare earth elements appear to be dispersed 

 primarily as solids and accumulated by the 

 plankton. (Operations TROLL and WIG- 

 WAM.) 



3. The initial accumulation of rare earth ac- 

 tivities is predominantly by filter feeding or- 

 ganisms, presumably by retention of finely di- 

 vided solids in their feeding apparatus. 



4. The cycle of rare earth activities through the 

 biota is unknown. Nevertheless, biological 

 agencies undoubtedly have an important influ- 

 ence in the deposition mechanisms. 



The physical state of fission product elements 

 in sea water is important in all of the processes 

 that have been previously mentioned. Table 5 

 sets forth several fission product elements, the 

 percent of total activity present one year after 

 removal from a reactor and an estimate of the 



