-32Soil
a
——_—
The soil and sand samples included those from the islands
proper, from the beach,
and from the lagoon bettom.
The radio-
activity of a sample taken from the top inch of soit on
Labaredj Island March 26, 1954, was 6.8 microcuries per gram,
:
-
which is equivalent to one curie per 325 pounds of top soil.
The activity of this sample ten months later, January 29, 1955,
was one thirtieth its original value,
t.e.,
it had passed
The decay rate for this period
3
through nearly five half-lives.
4
is expressed by the formula, r = p23}, with March 1, 1954,
as the date of origin (Figure 12).
This rate approximates the
mixed fission product decay rate and in general approximates
the decay rate for many of the biological samples.
For these
reasons the decay factor for correcting counts back to the day
of collectionwas based on the decay curve of a similar soil
sample.
The decline in radioactivity of the soil samples can be
observed from the figures in Appendix Table X.
Considerable
variation in the activity of soil samples from the same area on
the same day can be expected because of the nature of the fallout pattern and should be kept in mind when interpreting reosuits.
If consideration ts given to the Kabelle samples only, the rate
of decline is greater than the decay rete from March to July
1954, but less from July 1954 to January 1955.
When the sample
counts from all islands are averaged, the relative decline in
activity of the March 1954 sanoles and the January 1955 samples
4s the same as the decline in activity of the aecay sample.
ue UNS
Usa