GENERAL INTRODUCTION
Gross beta is a useful criterion of the amount of persisting radioactivity.
Plotting the logarithm of this value against the logarithm of
the time after detonation
depicts the trends of both physical decay and
of decline in radioactivity due to a combination of physical decay and
various biological and environmental factors.
The term decline as
used here indicates the trend with time in the amount of radioactivity
in successive samples of a particular type of substance at a particular
locality.
with time.
The term is appropriate because the amount usually decreases
However, the amount may increase or remain constant for a
while if there is an influx of radioactivity into the environment, so that
minor fluctuations in decline are to be
expected.
In this
respect de-
cline differs from physical decay, which can not remain constant or increase but can only decrease.
The three sections of this paper deal respectively with decay data
of early samples from Eniwetok Atoll, and with decline of plankton and
fish samples from Rongelap Atoll.
All have the feature in common that
their radioactivity was derived primarily from a single, though not the
same,
detonation rather than from two or more successive detonations.
-Ve-