23
amounts of ©9¢o and 137cs and lower amounts of 5°Fe than did mullet from Nam.
However conyict surgegn and mullet (Appendix Table 22) from Nam had higher
amounts of
©%Co and 13/cs than did convict surgeon fron Eneu Island the least
contaminated area of Bikini Atoll. It is likely that the mullet range more
widely within the lagoon than do the smaller convict surgeon, hence mullet
captured in one area may have accumulated the
another area.
radionuclides while in
Comparison of Radioactivity between Islands in Rongelap Atoll
At Rongelap Atoll radionuclide concentrations in the soil increase as one
moves northward along the east side of the atoll (Figure 5, Table 4). Of the
islands sampled at Rongelap Atoll, soil from Rongelap Island has the least
amount of radioactivity, while soil from the northern islands of Lukuen,
Gejen, and Lomuilal has the most.
Islands (Mellu, Kabelle) on the east
side of the atol] have intermediate amounts of radionuclides in the surface
soil. This soil distribution pattern corresponds with the fallout pattern
determined shortly after the Bravo test at Bikini Atoll] on 1 March 1954.
On the second of March 1954 gamma dose rates were estimated to be 3.5
roentgens per hour (r/hr) at Rongelap Island, 19 r/hr on Kabelle Island,
and , r/hr on Lomuilal Island in the northern part of the atoll (Held,
1965).
Ratios of
137¢5/90sr and 241Am/239»240py jin soil from Rongelap Atoll
are Similar (1 to 2) to the ratios found in soil from Nam and Bikini Islands
at Bikini Atoll again indicating the major source of these radionuclides was
the Bravo test.
Radioactivity in the biota also varied with island. Coconut crabs (Appendix
Table 6), fish (Appendix Table 9) and plants (Appendix Table 13) from the
southern islands of Rongelap Atol] had less radioactivity than did similar
samples from the northern island.
However, the amounts of radioactivity in the
biota did not differ as much as was noted for the surface soil.
Cesium-137
and 90Sy amounts in soil from the northern islands were 4 or more times the
amgunts found in soil from Rongelap Island, while the usual differences in
Cs and 90Sr amounts in plants and coconut crabs from these two areas were
factors of 2 to 4.
Differences in Radioactivity due to Sample Type
As noted for surveys since 1964 (Welander, et al.,1967; Held, 1971; Lynch
137cs are the primary radionuclides in biological ang
soil samples from the terrestrial environment.
In addition
Am and
¢39.240py
are important in soil, especially from Bikini and Rongelap atolls, both because
of the quantity of these radionuclides present in soil and because they are
alpha-emitting radionuclides, which have a higher potential health hazard than
most of the gamma-emitting radionuclides. Of the plants sampled, Pandanus
leaves are the best indicator species for 137Cs because they concentrate 13/Cs,
are abundant and are easily sampled throughout the year. The fruit of the
Pandanus contains greater amounts of 137Cs than do the leaves, however, the
fruit is available for only part of the year.
Pandanus leaves may also be
used as an indicator for %0sr, if coconut crabs are not available.
The exo-
also good indicator organisms since they integrate 137¢ gs well
90Sr, from a
skeleton of this crab contains the most 90Sr of any sample type analyzed, however,
coconut crabs are not present in all areas. When available coconut crabs are
wide area on an island, whereas the Pandanus integrate 13 Cs and
885, from a
relatively small area of an island.
DOE ARCHIVES
AN Re tenerhe wena aye
et al., 1975), 9%Sr and