-27-
origin (Redwing) of part of the activity, but with a distinct upward
flexure indicating the effect of the original fallout from March 1, 1954.
Samples 6076-77 of plankton collected July 1956 from the Rongelap
Island vicinity of Rongelap lagoon were more radioactive when first
counted one month after collecting than the corresponding sample
(6079) from the lagoon near Kabelle Island.
One of the Rongelap
Island samples (6077) was about 2-1/2 to 9 times more radioactive than
the other two samples and decayed most rapidly of those studied.
Thus.
it was evident that there was a more rapid decay of the radioactivity in
plankton from the part of the lagoon near Rongelap Island than occurred
near Kabelle Island.
This is interpreted as indicating the influence of
recent Redwing detonations whose fallout affected the southern more
than the northern part of Rongelap Atoll.
Decay of March 1958 samples was negligible during the two months
from September to November 1958, while August 1958 samples decayed
during the month of November 1958 fairly rapidly, with a half life of
about 100 days, thus supporting the assumption that the increased levels
wereattributable to the Hardtack series of detonations.
eerirminerrina te =
The rate of decay of the samples collected in 1954 was less steep
than the rate of decline of radioactivity in Rongelap lagoon plankton.
In
Figure 9 the decay slopes of curves 1 to 3 range from -1.6 to a maximum
of -2.4, even in the steep portion from 660 to 1, 740 days, while in
Figure8
the decline slope shownby the dotted line is -3.5.
Compensating