I
a
*
a
aid sucending series,
Curves 1-% represent the radio-decay of
sarpl.s co.lected 10-.1 months after March 1,
1954,
while curves
4-9 pertain to sumpies so.liected s.orvtly after the Redwing series.
The
two ,;rouns differ in both steepness and direction of curvature.
QThe first group, curves i-3,
decayed with a log-log slope of -1.3 to
-1.4 wiien asrees with tne slopes of the remarkably straight decay
2aurves ovir ilnost the aame period of time for the Eniwetok Atoll
pazikton sesiples (UWL+S3:21).
Yowever,
the Rongelap Atoll plankton
deciy curves differ rroin those of Eniwetok Atoll in having a down-
ward flexure.
In fact, curve 2 displays up to the 1350th day al-
most a uniform nalf-life of about 710 days, and from days 12350 to
1740, a 430-day nalr-life.
fron this pattern,
Curves |] and 3 deviate only slightly
being steeper in the early sections.
Gamma-
Spectrumetry of the sample of curve 2 on November 6 and December
3),
1957 showed cel4 of 235-day half life to be the primary con-
stituer.t,
which is presumable accompanied by small,
amounts of longer-lived isotopes,
life afser 1550 days.
undetected
contributing to the 450-day half
The second group, curves 4-6, decayed rapidly
(slopes -4.1 to -10.8) because of recent origin (Redwing), but with
a distinct upward flexure.
In studying tne decay rates it was evident that there was a more
rapid Gecay of the radioactivity in plankton from the part of the
lagson
neair Rongelap Island than occurred near Kabelle Island.
This
is interpreted as indicating the influence of recent Redwing detona-
tions probabiy within e month-preeeding-Pewa—+7-21.56} whose fallout
thus
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