-19DISCUSSION
The summary table of the radionuclides present in the soil samples
collected on Kabelle Island more than three years after the initial fallout shows that about 40 per cent of the total radioactivity is due to Cel44_
pr 144 and 40 per cent to a non-fission product, Fe55.
Since the latter
has a half life of 2.9 years one would expect this isotope to become important after the shorter-lived isotopes have disappeared.
This was
found to be the case in fish livers and clam kidney samples taken at the
Pacific Proving Ground in 1954 and 1956. v4 In one case, as much as
95 per cent of the total radioactivity in a fish liver sample collected at
Eniwetok Atoll in 1956 was attributed to Fe°”.
The presence of Sb!25 and Eu!5® also was clearly demonstrated in
this sample, the former contributing about twice as much radioactivity
as the latter.
Eu!®° was detected in only one sample, whereas gpi2s
was found in five other soil samples (Table 5).
Table 5. Island soil samples from the Marshall Islands containing
Sb125 as determined by gamma spectra
Sample
Top inch
Top inch
Date Collected
3/26/54
Top inch
Random sample
top two inches
Top two inches*
3/26/54
12/8/54
7/18/57
7/ 5/57
Island
Labaredj
Atoll
Rongelap
Kabelle
Rongelap
Kabelle
Rongelap
Kabelle
Janet
Rongelap
Eniwetok**
* Sb!29° separated by ion-exchange; other determinations were made
using whole samples.
** Lowman, F. G.