The rate of decline of radioactivity in some biological samples from
(6
Rongelap Atoll also has been observed to follow a similar pattern
Therefore, the decay and decline slopes were plotted logarithmically.
RESULTS
Studies at Belle Island
A.
Rate of Decline of Radioactivity in the Algae
Inorder to determine the levels of radioactivity in several genera
of algae during the period from April 1954 to April 1956, samples were
collected on thirty-six different dates,
May 14,
1954.
three of these before the test of
The results of these surveys are summarized in Table 1,
and a log-log presentation of the average decline in radioactivity is illustrated in Figure 2.
The values plotted are based on the average of
seventeen samples for each date after May 14, 1954.
The individual rates
of decline for representatives of six genera of algae (Halimeda, Caulerpa,
Spyridia, Dictyota, Lyngbya, and Udotea) were found to be approximately
the same.
The radioactivity in the samples collected before May 14, 1954,was
due to the residual radioactivity of the 1952 test series at Eniwetok Atoll
(Operation Castle) plus some airborne contamination from the early tests