Zl
“a
5
the separated foraminifera and coral fragments from station 40C are,
growth increment from this coral since 1954 was the 2394240),
however, at least 2.5 times higher than those associated with their
concentration below 104 + 12 pci/kg.
respective components at station 3D,
The distribution of
2394240
Pu is
Lower concentrations are
associated with coral remains deeper in the sediment column,
From the
different among components in the sediment from different regions of the
radiological record retained in the skeletal matrix of the Favites
lagoon.
virens, coral labelled during 1954 and 1958, for example, should have
The fine fraction at these locations contained the highest
concentration of
2394240,
To within our analytical precision, the
2394240 Pu concentrations of 39x10 3 and 4.5 x 10° pci/ke, respectively
i
238, 239240, concentration ratio is identical in the components from
(No75).
both stations,
in any subsurface coral remains.
In the sediment column from Bikini station 3,
associated with all components that were separated,
2394240, is
At all depths in
These concentrations are orders of magnitude larger than those
This data, thereforc, does not support
translecation of labelled coral material deeper into the sediment column
by physical processes during or after testing.
Burrowing, organisms
the sediment column, the highest concentration of 23942400, in the
could redistribute some fraction of labelled sedimentary components tc
coarse components was associated with Halimeda fragments.
depths in the sediment column,
Sedimentation
of labelled material to the lagoon occurs at a rate that is too slow to
account for the buried activities below a few mm in the sediment
column.
Although the age of the Halimeda fragments, coral, and other
components at depths greater than a few cm must therefore predate
the test years, 2394240), , is associated with these components.
The possibility that subsurface remains labelled during testing
However, when the 2394246, activites
associated with each component at various depths are conpatred to the
activity in the corresponding component at the surface, the
activities differ.
23024
o
Spy
For exampic, between 5 to 10 em the PB H24G, |
concentrations associated with the coral, Halimeda,
foraminifera, and
shells are 1.29, 0.83, 0.43, and 0.34 times the concentrations
associated with those components in the surface layer.
Burrowing and
were buried later in the sediment column by large scale turbulence can
mixing processes by organisms are not likely to move specific component
be discounted.
selectively down through the sediment column.
Coral or Halimeda fragments directly subject to a
nuclear explosion probably would not retain their identity.
In recent
The data indicate that al] plutonium does not remain associated
yearly growth increments of a living sample of Favites virens coral from
with the sedimentary materai] with which it was originally deposited.
station B3, the 23942405, concentrations averaged 104 + 12 pCi/kg
Small quantities of plutonium are remobilized continuously from the
(No75)}.
sediments to the layoon water column by surface exchanve rechanisms.
This value agrees well with the 2397240, concentrations in
dead coral] remains in surface layers at station B 3.
In no yearly
Plutonium is also detected in the interstitial water extracted in situ
aor pncervee