such
metallic
as
ions
mollusks
at
levels
concentrate
many
times
higher than the levels found in the
surrounding water.
The concentration
of Ce“ in clams during April 1959 was
about 7 X 10° pyc per kilogram of
clam muscle (wet weight). It had de-
creased to 7 X 10 pyc by July 1959.
The gross radioactivity of surround-
ing water during the time from August
1958 to February 1959 was about
3+3 ype per liter, but it increased
to 21£3.2 pyc per liter in March
1959. The radioactivity of the water
has
not
been
measured
since
April
1959, but radioactivity in rain and fall-
out in this region increased from March
1959 and reached a maximum in April
1959. Since August 1959, there has
been less radioactivity in rain and
fallout.
It has been reported that the concen-
tration of Ce™ in the sediment of the
sea in the year 1960 was | puc per gram
ties of both radionuclides. The presence
of Ce™ in food was at a quite trivial
level compared to the maximum per-
This amount corre-
missible concentration of Ce(1 x 10°
surrounding sea water. The concentra-
N. NEzu
M. ASANO
S. OuCHI
Ibaraki Prefectural Institute of Health,
Mito, Ibaraki, Japan
of dried sample.
sponded to that found in 5 liters of
tion of Ce™ in sediment was about 100
times higher than that of Sr” (6).
A clam is a marine organism that
makes its home in brackish water, and
thus can be found in marsh sediment.
Since radioactive contamination in a
marsh bed hasits origin in fallout, it
may safely be assumed that Ce’ was
deposited in the marsh bed by fallout
and then absorbed by the clams.
.
The concentration of Sr was generally at a higher level in bone than in
other biological samples, whereas Ce™
was more concentrated in clams. Cattle
and horse bone contained large quanti-
pue per liter of water).
References
1. H. F. Hunter and N. E. Ballou, Nucleonics 9,
No. 11, c-2 (1951).
. M. A. Van Dilla, Science 131, 659 (1960).
. I. Puliman and P. Axel, Phys. Rev. 102, 1366
wn
isms
(1956).
4. E Bleuler and W. Zunti, Helv. Phys. Acta, 19,
375 (1946).
5. E. D. Goldberg, Geol. Soc. Am., Mem. 67,
345 (1957).
6. Y. Higano et al., Japan Radiation Research
Soc., rd Meeting Mem. (1961), p. 20.
19 October 1961
ute | 9 P Health) |
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Tbaraki ken, Japan
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