T. M. neal, E._E. HELD and R. M. CONARD
1961-1962tests were maximal." Speeds of
surface currents in both the California and North
Equatorial Currents are sufficiently large to
accountfor transport of waters from 30 to 40°N
latitude to Rongelap Atoll!”in the time period
1961-1963; similarly, maximum surface de-
position of 55Fe occurred in 1963," and thus
the data ofTable 2 probably reflect contributions
from both sources. The higher specific activity
noted in goatfish liver in August 1963 may
reflect morenearly the specific activity ofwaters
at Rongclap Atoll than does the sample of
March 1963. Liversfrom immature goatfish
were used in the August specimen, while the
|
249
species important in the Rongeizres¢ diet. The
fact that livers from mature gc2:ish contzin
between 2-3 times as much stable iron per urit
wet weight as do livers of mazure selmon! is
consistent with this argument. Second, Jenntres) and more recently Pazsvoxl® have
suggested that large amounts cf *°Fe were introduced into the northern hemisphere 2s tropospheric fallout during the 1661-1052 test series
and that deposition may have occurred in rather
narrow latitudinal bands (maximum input at
.60°-70°N (Preston). Josepx ef c/.©) suggest
that subsequent stratospheric depesition of *5Fe
from these tests was similar to that observed for
March sample was obtained from mature fish. %Sr, i.e. maximum ceposition at =3°N. TransRecent measurements of the specific activity port of Fe from these high ladiruces by major
‘ofimmature and mature goatfish liver collected ocean current systems feecing the North
at Johnston Atoll in 1968 showed that immature
fish livers contained less stable iron and more
*5Fe per unit wet weight than did livers from
mature fish. We assume that the immature
Equatorial Current (in e2ddision to bioicgical
and physico-chemical factors; will deplete
northern waters of this radionuclide. As discussed earlier, transit time for these waters from
fish are in the process of forming their iron high. latitudes to Rongelap Azcil is measured in
stores and therefore more nearly reflect the - year, and itis therefore possible that the higher
environmental specific activities than do the. §5F'c¢ body burdensin the Rongelapese reflects 2
mature fish whose iron stores. are already
- formed. In thelatter case, exchange rates may
_ be slow.
so
Our measurements of ®5Fe in soils collected
from the samesites between 1959-1963 do not
“lag’’ time between the 55Fe specific activities of
Northern Pacific and Southern Pecifc Ocean
biota due to this transport. Finally it is possible
that the high **Fe Rongelapese bedy burdens
relative to the Japanese donors results from a
clarify either of the input sources mentioned combination of dietary intake and uptake and
above; the changes in concentrations are greater retention differences for iron bemveen the awo
than can be accounted for by physical decay. groups sampled. Unfortunately precise dietary
Natural processes which remove ®5Fe from the” information for both groupsis lacking and httle
upper 2.54 cm of soil may preclude its use as a
is known about the 55Fe specitic actvities of the ~
precise collector, and therefore the results are foods eaten by both groups. The Rongelapese
useful only to indicateorder ofmagnitude values -do not suffer from iron deficiency anemia, so
of 55Fe soil concentrations present at the collec- enhanced uptake of iron from the ciet is
tion time.
.
probablyinconsequential. Itis clear that further
Unfortunately it is not possible to offer a measurements of the specific activities of 55Fe in
- Clear argumentin explanation of the 55Fe body. -the diets of the Rongelapese and other maritime
burdens of the Rongelapese presented here, at cultures and the effective haiZiive thev display
this time. Samples from 1963 through 1969. for this radionuclide will be needed to clarify
would have shed light on the problem, but the questions raised here.
none are available for analysis. In a speculative
vein, several explanations can be advanced.
First, the possibility of Rongelap lagoon acting
23 a nutrient and trace-clement “trap” similar
to estuaries"® is intriguing. Removal and
retention within the lagoon of both stable iron
and ®Fe from the North Equatorial Current
could lead to high specific activities of 55Fe in
So
- oe
SULZ 1 eb
Acknowledgement—We thans Mr. T. A. Joxrta for
technical assistance and Dr. M. Feorra ior kindly
arranging for the blood specimens ‘rom Tokai-mura,
Japan. Dr. A. H. Seyvmocr and Mr. E. E. Parmer
provided helpful discussions during preparation of the
manuscript. Supported by AEC uncer Contract
No. AT(45-1)-2225-14 and AT {70-15-259.