Table 9.
Mean concentrations of 59Co in the muscle tissue of reef and pelagic
fish collected at different times.
Collection
year
intervals
All reef species
60Co (pCi/kg wet wt)
Number of
samples
Mean
concentration
Range in
concentrations
1977-1978
27
2352209
19-897
1980-1981
12
146+110
31-430
1982-1984
12
60+51
7-180
’
w
All pelagic species
1977-1978
4
166+124
1981-1984
6
81+56
43-199
collections to those detected in the same tissues of the species collected
from the same locations during 1964 and 1969.!1.13 A least-squares fit of the
The effective
decay constant is the sum of the physical decay constant (0.1317 y~!) and an
environmental loss rate term that reflects the removal rate of 60Co. This
removal rate is usually expressed as the ecological half-life (or decay
Constant) and has a value for [Co of 7.8 y.
The disappearance of ®0Co from
Bikini lagoon and its availability to fishes is controlled both by
radiological
dilution.
decay
and
by
processes
of
remobilization,
transport,
and
If 60¢q continues to decline in the environment at the present
rate, the mean concentration of 50Co in the edible muscle tissue of fish from
the lagoon should be less than 20 pCi/kg wet weight by the year 1990.
BISMUTH-207 IN FISH
The
presence
of 207p;
(tj/2 = 33.4 y)
was
first
reported
in marine
Samples obtained from the Pacific Proving Grounds in 1961.2! It was formed
Possibly from a series of nuclear reactions such as 207Pb(p,n) or 206pb(p,y),
assuming stable lead was present during testing as shielding material near the
Nuclear devices.22
5000511
Other than a recent report describing 297Bi as a component
ou
ee
Se
inertia
constant of 0.22 + 0.05 y-! (effective half-life of 3.2 y).
aos
been declining in the tissues of fish from Bikini with an effective decay
atin stan at
| appropriate present and historical data shows that the mean level of ®[Co has