18
an
65
.
The presence of zn°? is corroborated by the 0.5-mev
peak.
peak.
Fig.
8 also shows the gamma-ray spectrum of noddy tern
guano collected in this area.
,
over the
1.17 peak of Co
.
;
60
The 1.12-mev peak predominates
and the 0.51 peak of Zn
.
.
65
,
,
,
is evident.
The foliar contribution to the litter contains only Cs
137
from
among the gamma-—-emitters.
.
In undisturbed areas Cs
137
and Sr
90
.
are being deposited
with the litter and are thus replacing at the surface some of
the Cs
137
and Sr
90
lost by leaching.
,
.
os
There is not sufficient
data from the field work to determine whether there eventually
will be a loss of these radionuclides from the soil-plant system,
or a steady state
(excluding physical decay of the radionuclides).
Long-term experiments, under simulated field conditions, with
monolith lysimeters
and controlled and uniform addition of the
radionuclides would define this point.
Young Soil
Fig. 9 gives the spectra of the 0 to l-inch,
.
and 9 to 10-inch increments of a young soil.
Pr
14
a
1 to 2-inch,
co,
an°>,
1
and Eu 39 were detected only in the surface layers,
L
Ce 44
and
with increasing depth the 0.60 to 0.66-mev photopeak region of
the spectra shifts toward the 0.60-mev peak of spt? .
The spec-
trum of the 9 to 10-inch increment is compared with that of an
spt? spike in Fig. 10, showing that the photopeaks of the soil
and spike gamma spectra are identical.