specific activities
cesium in the soil
1.3 parts
(Table 3).
This is in spite of the fact that total
(radioactive plus
per million whereas
nonradioactive)
total
amounts to less than
strontium amounts
to
2000-4000 parts
7
*
:4
\
&
per million owing to its very much greater natural abundance.
a
)
1
Unfortunately
for
cleanup
purposes,
cesium-137
is
readily taken up by plants, moving in much the same way as potassium,
essential
element with which it might compete for uptake.
activity varies
with
the
in different foods,
specific-activity of
the
but
Plants,
concentrate cesium 3-6 times over the soil level
the concentration ratio
(plants/soil)
Its specific-
in each case will
soil.
rise
especially
(6).
an
and
fall
fruits, may
For strontium-90,
in edible fruits ranges
from
.01 to
.5 but in the leaves it may be as high as 10 (Appendix 8).
The cesium-137 surface-zone activity (0-10 cm}
individual
aerial
islands
survey,
of
the
Bikini
Atoll,
is given in Table 1.
estimates were confirmed
determined
by
a
for the
comprehensive
In the case of Bikini and Eneu, the
by terrestrial
measurements.
These measurements
Show that Bikini is among the most heavily contaminated islands, while Eneu
is in the lower range.
In
distributed
mean)
the
fell
soil,
cesium-137
exponentially
with
specific-activity
depth
on
both
(island
islands
as
illustrated in Figure 4, based on Table 2:
where
A, is
specific activity
(pCi/g)
at depth
Z
(cm),
activity at zero depth (Bikini, 80.5 pCi/g; Eneu, 5.5 pCi/g).
Although the surface activity of Bikini
than
10
times
that
of
Eneu,
the
fractional
decline
of
and
A
is
the
°
averaged more
activity
per
centimeter depth (4) was about the same (-.065 per cm vs. -.052 per cm).
5000019.
a9