L4
spies change with increasing depth.
In the 0.60 to 0.66 -mev
photopeak region of the 0 to l-inch increment, the relatively
broad peak is a combination of the 0.60-mev photopeak of sp25
and the 0.66-mev peak of Cs
137 palo7m
-
«
In the 1 to 2-inch
increment the peak becomes sharper and is oriented toward the
1
0.66-mev photopeak of Cs 37_yah37m
At the 9 to 10-inch incre-
ment there is almost complete orientation toward the cst?
pal37m peak, with little ght?5 remaining.
In Fig. 6 a comparison
is given of the spectrum of the 9 to 10-inch increment (Fig. 5)
and the gamma spectra of ast3? and sbt?5 spikes.
Fig.
7 shows the gamma spectra of increments taken from an
undisturbed area in 1958.
The first spectrum is from the 0 to
1/4—inch depth and the subsequent spectra are from 1/8-inch
depth increments to a depth of l inch.
spt??, the rare earths,
The highest levels of
and 60°, which move more slowly than
cst?” or sr??, are in the 1/2 to 5/8-inch increments, whereas
the est37, which moves most rapidly in this soil type, is in
the 3/4 to 7/8-inch increment.
Litter and Guano
The gamma-ray spectrum of litter, consisting of leaves,
twigs and floral parts splattered with tern droppings, collected
ta
io
:
os
be
|
t
from old soil in 1961 (Fig.
8) shows the cst37 photopeak to be
much higher than the spt?5 peak.
The 1.17 peak of 9°? is
skewed to the left, indicating the presence of the 1.12-mev