14
L
rc
Sb 25 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 spi?5
and the 0.66-mev peak of Cs 137 -B a 137m -
In the 1 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 es 3?_
za?" yeak, with little sb!?> 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 Cs 137 and spt? 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 coo? which move more slowly than
e313? or sx?°, are in the 1/2 to 5/8-inch increments, whereas
the cst37 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,
twi,s and floral parts splattered with tern droppings, collected
from old soil in 1961 (Fig.
8) shows the Cs
:
much higher
than the Sb 125 peak,
13
7 photopeak to be
The 1.17 peak of Co 50 is
skewed to the left, indicating the presence of the 1.12-mev