23
from sediments (No78b) at higher concentrations than those in the
weight, and the concentrations in the water where the algae were
overlying bottom water at Enewetak Atoll,
obtained ranged from 10 to 116 fCi/].
By equilibration, small
quantities of 2394240), | from the sediments are exchanged and released
.
Surface sediment concentrations
at the stations (No78a, Ne75) were compared to the algae concentrations
Vertical diffusion moves the radionuclides to the sediment water
at these sites.
interface where the plutonium mixes with the lagoon water mass.
associated with the Halimeda spectes (pCi/g dry weight)
Remobilized plutonium can then be concentrated by members of the marine
top 2.5-em sediment layer (pCi/g dry weight) was 0,24 + 0.13 aud the
food chain.
24d concentration ratio wus 0.32 # 0.24,
Vertical diffusion can also move the exchanged plutonium in
the interstitial fluid deeper into the sediment column,
Exchange of
The average ratio of the 2394240), concentrations
to that in the
Concentrations
and 24d an in the sediment ranged from 9 to 0? pli/y and irom 1.1
Plutonium with exposed carbonate surfaces might account for the
pCi/g, respectively,
concentrations associated with material decper in the sediment column,
algae have lower PSO cmd PAT Ay levels than sediments
immediate environment.
TRANSURANICS ASSOCTATED WITH THE CALCAREOUS ALGAE, HALIMEDA
Debris from the calcareous algae, Halimeda,
is the second most
of 23924,
ratio of
2394240
On an equivalent werght baste the
te 67
live henthic
in the
The average plant to sedinent concentration
24
:
:
Pu and * Van are uot statistically different.
.
‘Thus,
2394240, and 24d in
processes
there is no discrimination between
abundant component of Enewetak Lagoon sediments (£m54) and covers an
beginning with remobilization of the transuranics fron tie envaronrent
estimated 26% of the lagoon floor (Im54).
and ending with concentration by the algac.
Live species were collected
by divers and during dredging operations from numerous locations at both
Enewetak and Bikini.
Because algae were shown previously to concentrate
Table 4 summarizes data on transuranic concentrations in alae,
water, and sediment from Cactus Crater at Emnewetak,
The data show that
plutonium (No72), the role of this benthic algae is recycling the
the 238), 23240, ratio in the plants, water, and sediment are
transuranics at the Atoll should be assessed.
identical.
The mean concentration factor for 2394240 Pu associated with algae
In this crater ecosystem marine alyae do not discrinuinate
among the plutonium isotopes in the environment.
Tho plaunt:isedivert
species from both Atolls is 6 x 10° and ranges from 1 x to 32 x 104
concentration ratios of 2394240), and 241, are neariy
(No78a).
again shows that the processes of environmental release and plant uptake
To within the precision of our Measurements, the concentration
factors for plutonium at the two atolls and of different Halimeda
species from both atolls do not differ (No78a).
239+
24
Concentrations of
OBy associated with the live algac ranged from 0.4 to 22 pci/g wet
iventiceal, which
of the two transuranics are similar,
The mean surface sediment inventory of
Ci (Table 1).
The lagoon is 933 km”
Pu et FPrneretak is 249
in area and the average specific