~29-
degrees of interaction of these variables upon tne decline of
radioactivity with increasing time after contamination are not
xnown, rigid interpretations of the shapes of the curves should
not be attempted.
However, the curves are useful in estimating
the levels of activity in the different organs on given dates
following the contamination of the atoll.
Decay curves were made for a limited number of samples.
these,
Of
only that of the thyroid evidenced a preponderance of a
single isotope, y232 which accounted for 99.9 percent or more
of the total activity.
In decay curves for bone, liver, and
kidney there was evidence of mixtures of isotopes.
nw prh28
for liver, rw t
~1.65
Slopes of
‘
for bone, and a curve for kidney,
vhich is not a straight line either logarithmically or semilogarithmically,
indicate that these organs do not contain similar
ratios of radioactive isotopes.
The decay curve slope for tern
liver is similar to that of Rongelap soil.
Chemical separation for strontium was done on two bird
samples collected March 26, 1954, at Kabelle.
Skins from two
different terns contained 2.9 percent and 3.5 percent of the
total activity as radioactive strontium.
In samples of total
muscle plus total bone from the same birds, 797 9° comprised
3.9 percent and 11.3 percent of the total activity (Table
VII).
The only collections at Rongelap Atoll containing birds
from both the northern and southern islands were made Janusry
26-30, 1955.
In view of the fact that the general levels of
contamination were higher on the northern islands,
it was ex-
pected that the northern birds would centain morg radloactivity
1 Ms 2
3T