131
in Asparagopsis was due to I 3 -
,
.
The half life of the isotope
contributing 90 per cent of the radioactivity in Asparagopsis
was found to be 7.6 to 8.5 days.
This compares well with the
The
accepted value for r3t which is given as 8.14 days (5).
lowest values obtained at Eniwetok may have been due to the
presence of ye?
r133)
and 1335,
isotopes whose faster decay
rates would tend to lower the value.
It was evident from the short half life and high level of
radioactivity of two samples of Asparagopsis collected on April
3,
1954 at Parry Island that these algae were concentrating a
recently formed isotope.
The values for the counts of these
samples were 12,400 and 11,400 d/m/g as opposed to an average
value of 260 d/m/g based on radioactive decay of samples collected in the same locality on March 6,
1954.
The increase in
Specific activity might have been due to material resulting from
the March 27 test at Bikini Atoll,
since it was observed that
the background count at Parry Island increased a few days after
this date.
Changes in the activity levels in the algae would
be expected to follow closely those of the environment,
for it
has been shown in laboratory tests that z+3? uptake reaches
equilibrium after the first hour in Ascophyllum
three hours in Laminaria (7).
(4)
and after
As laboratory tests have not been
conducted with Asparagopsis to determine this factor,
it cannot:
be stated with certainty that it would behave similarly.
vs
144094
aw
5
.
7c
AC