as the depth increases the slope of the activity-vs-depth curve tends to
decrease,i.e., the activity levels do not go to zero, even at depths greater
than 100 cm.

Table 5 shows pertinent data for 905,

In an attempt to quantify this distribution and obtain an approximation of
the "average profile” for calculational purposes, 90... and 13766 data fer each oi
fourteen profile samples have been reproduced in Tables 6 and 7.
values for 905, for each sampling depth are plotted in Fig. 4.

The average
It is apparent t}

from the surface to about 30 cm the 9060 specific activity is decreasing with
a “soil half thickness" of 8.4 cm, while in the 30 to 85 cm depth range the
half thickness increases to 22 cm.

The levels to not pet as low as those found

on the southern islands (0.5 pCi/gm) at any depth down to 180 cm.

Those

profile samples which lie in or clesest te the subsistence agriculture areas
of Figure 2 have been averaced and plotted in Fig. 5.

In this set, the halt

thickness is only 4 cm from the surface to 10 cm. but increases to 25.5 a
in the 10 to 85 cm depth range.
piotted in Figs. 6 anc 7.

Similar treatment of the 1376, cata is

In Fig. 6, where all samples are averaged, the

half thickness is 4.5 cm down to about 10 cm, and 12 em from 10 to §5 cm.
Levels: equal to those found on the southern islands (*0.2 pCi/gm)} arc found
at depths below about 100 cm.

In Fig. 7, the subsistence agriculture case

gives a half thickness of 2.7 cm down to 10 cm, and 17.€ em frem 10 to 85 on.

For both 9055 and 137¢, it is apparent that the profile averaged over all
samples is more conservative than is the profile for subsistence agricultural
areas for estimating the affects of soil removal:

therefore the Task Grour

has used Figs. 4 and 6 for estimating dose reductions that might occur due

4,

to removal of soil.

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