14
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 spt25
and the 0.66-mev peak of Cs
137
-B a
L37m
-
in the l to 2-inch
increment the peak becomes sharper and is oriented toward the
0.66-mev photopeak of Cs
137
-B a
137m
-
At the 9 to 10-inch incre-
ment there is almost complete orientation toward the cst 37_
Ba 37m peak, with little spt?5 remaining.
1
.
¢
2
a
In Pig. 6 a comparison
is given of the spectrum of the 9 to 10-inch increment (Fig. 5)
and the gamma spectra of cst37 and spt?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.
sht?5, the rare earths,
The highest levels of
and co°?, which move more slowly than
cst?? or sr??, are in the 1/2 to 5/8-inch increments, whereas
the est?) 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
from old soil in 1961 (Fig.
8) shows the csi3? photopeak to be
much higher than the spt?5 peak.
skewed to the left,
The 1.17 peak of Co
60
is
indicating the presence of the 1.12-mev
AS