ABSTRACT
The trend in beta radioactivity as measured with methane
flow counters over a period of about two years is shown,
starting with the 1954 Castle series of nuclear detonations,
The results are
up to but not including the sertes of 1956.
presented as graphs each showing the logarithm of the radioactivity of an organism or of a particular tissue of an organism, related to the logarithm of the time after the date of
detonation, when nearly all of the radioactivity was assumed
to have originated.
Invertebrates are considered in greatest detail, and
other organisms and materials are included for comparison:
island soil, beach sand, sea water,
plants, reef fish, birds, and rats.
plankton, algae,
land
It is proposed for most organisms studied that after a
period varying with the organism up to two to four weeks
following detonation, a maximum level of radioactivity in the
field samples collected is attained,
followed by a decline
approaching linearity on log-log plots with slopes over the
major portion of the two-year period that can be represented
as the negative exponent of the time after detonation. These
decline slopes varied greatly with different localities and
organisms, reaching & maximum of > 3.
A few decay rates of individual samples of each organism
or material are included for comparison, and these generally
were equal to, or less steep than, the declines, suggesting
that for some organisms or tissues,
the level of radioactivity
in the environment decreases more rapidly than oan be accounted for solely by physical decay while for others the rate
of decline can be accounted for solely by the rate of physical
decay.
Dilution by natural water currents and rain is pre-
sumed to account for the many cases of more rapid decline than
decay.