76
northern and eastern sectors of the atoll, respectively.
In addition, in
groups of stations (within the dotted lines in Fig. 18) the relative ordering
of 6069, 1370, and 207
Bi changed, delineating still smaller areas.
The
sequetces found may thus serve as discrimirants for groups of stations where
the ordering sequence of radionuclides concentrations are the same.
additional discriminant, the ratios of
As an
2394240, 2385), found in sur
face sedi-
ments at each station are added to the figure, since these ratios may also
retain the signature of debris from individual devices.
Comparison of these
two "discriminant functions" show that although individual detonations may
have disseminated unique proportions of radionuclides, mixing and/or fractionation of the radionuclides and debris from the several tests have left few conclusive signatures of individual sources in the laaoon sediments.
The relatively high abundance of
185
Eu in north central lagoon sediments
may j]ltustrate the area over which debris ejected from the Station B-18 and
C-8 test areas has had major influence on the concentrations present in surface
sediments.
It may also be of significance to note the possible correlation
between the distributions of high
to the distribution of high
2394240,
2394240
Pu/
238
Pu ratios south of Tewa Crater,
pyri, 1 137%e5/88co and ow
23942405)
W95e 4 ratios which are common both this area and the test areas around Station
B-18 and Tewa Crater.
5.1-8 Uranium, Radium-226 and Polonium-210
The naturally occurrina isotopes
210
Po are members of the
238
U decay series (Fig. 19).
238
U and
234,,
U,
226
Ra and
The structures of orga-
nisms which comprise the sediments of coralline atolls accumulate these radionuclides from sea water.
In addition, deposition of
210 Pb and 210 Po in the
Sediments results from aeolian and pluvial transport process.
Because the
activity ratio 2307, 234), in recent coral is less than 0.005 (Thurber et al.,