{both areally and with depth) indicate that multiple locations have been
the sources for the high specific activity sediments deposited at the
different locations in the northwest quadrant.
Compared to the concentrations of radionuclides in the very fine
sejiments collected in the northwestern lagoon, the high concentrations
of radionuclides measured in the naturally coarse sediments from two midlagoon stations directly downstream from the region of high radionuclide
concentrations cannot be explained by a linear correlation of the
radionuclide concentration with the proportion of fine sediment present
in the sample.
Either a particle size or biogeochemical fractionation of
the debris and/or radionuclides is suggested to explain this observation.
Evidence that the differences in the spatial distributions of
137 Cs and
207
Bi (from those of
2394240,
,
238
Pu,
24}
Am an
60
Co,
d 155 Eu) are
partly related to their chemical properties is suggested from thier distributions in sediment cores and from differences in their distribution
between the sediments and bottom waters of the lagoon.
The ratios for
the latter comparison were made by computing the ratio (pCi radionuclide/m=
bottom water):(pCi radionuclide/g surface sediment) at each station in the
Yagoon where the radionuclide concentrations in total, particulate
(>0.3 pm) and soluble (<0.3 ym) fractions of bottom water samples have
been measured hy other investigators.
24
The ratios for 23942405, 238pu
.
.
Lam and 155¢, (especially those between the concentrations measured
between suspended particulates and sediments) were found to be very similar
at any given station in the lagoon.
Compared to the actinide and
lanthanid&cosfficient? for total water samples (the range across the
lagoon is from 0.5 to 10), the ratios for 6069, 137¢5 and 20734
were
higher, by an average of about 7.3 times for
60¢0, 22 times for 20785,