-L4ratios for other biological samples from within Eniwetok and
Pikinit Atolls,
reported in an earlier paper,
are given (16).
Co5T and Co60 were present at Bikini Atoll in a 1:1 ratio; at
Eniwetok in a 5.3:1 ratio.
A similar difference in levels of
the two cobalt isotopes also occurred in the plankton taken
in the open sea in the vicinity of the Pacific Proving Ground.
Thus, at stations 57, 58, 59, approximately 200 miles northwest
of Bikini Atoll, the ratio Co57/Co®° is 4.6:1.0 and the value
150 miles northwest of Eniwetok Atoll is 7.6:1.0.
The ratio
of CoD? /co©9 in an area 300 miles wide north to south and 200
to 500 miles west of Eniwetok was constant at a ratio of approximately 11:1.
The ratios of C057 /zn®5 for the plankton stations are
shown in Figure 4b.
on which ion-exchange
The values for the five plankton samples
separations were made are shown cross-
hatched; the remeining Cod? /zn®5 ratios for plankton were
calculated from the gamma spectra on total samples.
The
ratios for Eniwetok and Bikini samples were taken from lonexchange separation data in an earlier report (16).
The ratio of Co57/zn®5 at both atolls was 0.06:1.0, indicating a relatively high level of zn65 with respect to Cor”
The same condition prevailed at stations 3, 4, 5, and 6, 200
miles south and
west of Eniwetok Atoll.
However, the ratio
north of Eniwetok and Bikini along the northern boundary of
the restricted zone was slightly higher (0.1:1.0) than that of
the atolls.
The center of high Co>’/gn®5 ratio (5.5:1.0) was
an
cco