239+240
concentrations of
Pu (120 pCi/q) and
24
Lam (103 pCi/q) measured in
any samples, occur at the focus of the “ellipse” at a location in the
northwest quadrant of the lagoon about 6 km SSE of the Bravo crater.
The highest concentrations of
155
Eu (139 pCi/a) were measured in samples
collected along the northern rim of the lagoon.
correction is made for the
155
If a radiological decay
Eu concentrations measured around the
northern rim of the atoll, it is found that the distribution patterns
fo
r 239+240
241
Pu,
Am and
155
Eu across the lagoon are very similar.
To the east of the focus of the "ellipse", the concentrations of
2394240,
>
241
Am an
d 155
Eu decrease approximately exponentially to: 2-5%
of the concentrations found near the focus.
tration of 137 Cs
137
Although the highest concen-
measured (29 pCi/g) also occurs near the focus, the
Cs concentrations decrease at a rate about 3.5 times faster per km than
the 239+240
Pu,
24}
Am and
155
Eu concentrations measured.
In the northwest quadrant of the lagoon, a layer of fine sediments
from 8 to 11 cm in depth was found covering the normal sedimentary deposits.
Measurements of
234,238
U and
226).
Ra:~~
.234
U ratios in samples of these
finely divided sediments show them to be very old corals, presumably from
the detonation craters.
In two cores collected from this region of
high radionuclide concentrations, the concentrations of
and
155
239+240
Pu,
241
Am
Eu decrease linearly with depth at a rate of about 50% through
the layer of finely divided sediment.
Sedimentation rates measured in
one of these cores (using the distribution of unsupported 210 Pb concen-
trations) show that the layer of finely divided sediment collected was
deposited at an uniform rate between the 1950's and 1972.
However, large
differences in the ratios of 2394240, Pu: 238 Pu across the northwest quadrant