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ABSTRACT
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oes terme
The trend in beta radioactivity as measured vith sethane
flow counters over a period of about two years is shown,
starting vith the 1958 Castle series of nuclear detonations,
up to but not including the series of 1956. The results are
presented as grephs each shoving the logarithm of the radioactivity of an organism or of a particular tissue of an organism, related to the logarithm of the time sfter the date of
detonation, when nearly all of the radioactivity vas assumed
to have originated.
Invertebrates are considered in greatest detail, and
other organisms and materials arw included for comparisoa:
island soil, beach sand, sea water, plankton, algae, land
plants, reef fish, birds, and rats.
It is proposed for most organisms studied that after a
period varying with the organism up to two to four veeks
following detonation, a maximum level of redtoactivity in the
field samples collected {s attained, followed by a decline
approaching linearity on log-log plots with slopes over the
ma jor portion of the two-year period that can be represented
es the negative exponent of the time after detonation. These
decline slopes varied greatly with different localities and
organisms, reaching 4 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 can be ac-
counted 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.