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At the Largo, Md. Site listed in Table IV, a depth profile
soil sample was taken directly after our measurement by
Alexander of the U. S. Department of Agriculture.
The soil
density and moisture content were also measured.
The radiochemical determination of the 13’cs activity at this site and
its distribution in depth should be valuable in testing our
model.
These results together with the radiochemistry results
for the other sites measured will be compared with our
spectrometric estimates of 137?cs soil concentrations as soon
as the radiochemistry is completed.
Measurements
over Solid Rock
Since solid rock
is usually more homogeneous
than soil,
samples of the rock when analyzed y spectrometrically in the
laboratory for potassium,
238uU, and 232Th should allow a
reasonable comparison with our field spectrometric estimates
of the activity present.
Two of the sites for which data
are given in Table IV, at Shaver Lake, Cal. and Courtright
Reservoir,
Cal.,
were on
solid
rock outcrops.
Laboratory
analyses of the rock were done by Smith and Wollenberg of
the Lawrence Radiation Laboratory
(LRL).®
Adams of Rice University obtained data at these sites
with his field spectrometer system’® and the NYU group made
measurements of the total ionization intensity in air using
their thin-walled ionization chambers.
Although all the results of the other groups have not
yet been received, it appears that our values for potassium
and 232Th concentration agree reasonably well with the
analysis by LRL considering the fact that the sites
geometrically were not very good half spaces,
thus affecting
our conversion from dose rate to concentration.
Our inferred 238U concentrations disagree considerably,
however, this may be due to a substantial radon migration
from the rock in the field situation.
It is also possible
the laboratory samples may not have been representitive due
to lack of homogeneity.