__
roncantrations at Bikini and Eneu Islands:
the mean from the aerial survey,
collected for
the mean and median of the O- to 10-cm depth from all profiles
att i4land, and the distributed mean, which is calculated by dividing each
safand into six regions, determining the median 137¢s concentration for the
profiles jn each region, and then calculating the mean value of the medians
prom the six regions. For all other islands, the mean from the aerial survey
ang the mean and median from the soil profile data are given.
as
shown in Figs.
concantrations is
inc ramEents .
Thus,
3 to 10,
lognormal;
the aerial
the distribution of soil
radionuclide
this distribution is observed for all depth
data are
compared more appropriately to
the
median and distributed means than to the mean value, which over-emphasizes the
raw high 137Cs soil concentrations observed in the lognormal distribution of
sol |
For
cadionuclide concentrations at the Atoll] (Robison et al., 1981c).
gxample,
the average 137¢s soil concentration at Bikini Island from the aerial
survey 45 45 pCi/g; the median value from the terrestrial soil profile data is
5Y pul/g and the distributed mean is 60 pCi/g, both in good agreement with the
For Eneu Island, the aerial survey result is 3.4 pCi/g, and
the madian and distributed mean are 3.6 and 3.8 pCi/g, respectively, for 273
aprial survey.
sol! profiles.
for most other islands, the aerial survey gives higher !37Cs soil
concentrations than does the terrestrial soil profile survey. There are two
peanons that could account for this observation. First, the number of soil
profiles collected at islands other than Bikini and Eneu are limited.
This is
bacause, aS We mentioned in the Introduction, the time available at the other
The distribution of the
telands was short and dictated by the aerial survey.
raw soil profiles taken at each island during the NMIRS is critical; soil
radtonuc lide
concentrations are generally higher in the interior than at the
periphery of an island.
However, in many cases, the field team could not
reach the interior of the islands because of the very dense vegetation and,
A,
a took the profiles nearer the periphery of the islands (see Appendix
Elys. Al to A-14, for sample locations).
In contrast, for Bikini and Eneu
islands, We have a major, continuing program that provides a constant source
at samples.
Second, each soil profile represents a very small area of the
ys and and just a few kilograms of soil.
The aerial survey detector system,
ay the other hand, views large areas of the island and tons of soil.
error tively
5000321
integrates
the activity over
a
large
surface areas.
It
For small