ABSTRACT 
Radiochemical separations were made on plankton samples 
collected in and west of the Eniwetok Proving Ground in Sep- 
tember 1956. Ion exchange resin column and precipitation 
technicues were used. Fission products, mainly Zr?5-Nb25 
and Cel44-pr144, contributed an average of 29 per cent of 
the total radioactivity. The remaining 71 per cent of the 
activity was contributed by the non-fisston radioisotopes 
zn©5, Co57,58,60, Fe55 and Mn>+. Radioactive zinc, cobalt, 
and iron accounted for averages of 24, 26 and 21 per cent 
respectively of the total radioactivity. Mn54 was present 
in trace amounts. Variations in ratio of occurrence for 
the different non-fission products with change in geographi- 
cal location was observed. Relatively high levels of gn©5 
were centered in the area near Bikini and Eniwetok Atolls. 
The area of high levels of radioactive cobalt and iron in 
comparison to gn©5 was located approximately 480 miles west 
and slightly north of Eniwetok Atoll. 
