Reprinted from Science, January 12, 1962, Vol. 135, No. 3498, pages 102-103
407933
Copyright © 1962 by the American Association for the Advancement of Science
Table 1. Results of Ce™ and Sr® analysis of different environmental samples.
Date
of
Sample
sampling
Soil (depth O-10cm)
Jan.
1960
Radish (root)
Clams, muscle
Cuttlefish (total)
Crucian carp bone
Mixed animal bone
Mar.
June
Feb.
Apr.
Jan.
1960
1960
1960
1960
1960
Spinach (leaves)
(cattle and horse)
Mar. 1960
pyc /kg (wet wt.)
(2670
+ 59)"
49.1+
puc /g of ash
3.4
99+ 5.0
68.0 + 3.6
77 + 9.0
31
+ 10
932 + 24
(130
+ 20)*
21.2 +
Sree
Ce
Sr”
Cet
pe
2.1
1242 10
28= 08
16+ 0.6
705.8 = §&.]
9293 + 60
(2.76 = 0.06)* (0.13 = 0.02)*
2.50 = 0,17
15
154
4.67
0.30
3.10
+08
+08
= 0.56
= 0.10
= 0.80
1.]
+= 0.)
1.98 += 0.16
0.65 + 0.19
0.10 + 0.038
6.937 + 0.081
30.98 + 0.20
* uuc/dried sample.
ratory have revealed the presence of
Ce'" in a wide variety of substances,
with prominent occurrence in animal
bone and clams.
Environmenta! substances, including
some food, obtained from Ibaraki,
Japan, during January to June, 1960,
have been analyzed for Sr and Ce™.
Strontium-90 concentration was determined by the “Method of Analysis for
Radioactive Strontium,” compiled by
the Science and Technics Agency of
Japan. This is a method of fuming
nitric acid separation.
The method of Cedetermination is
of Ce’ + Pr’, but the peaks due to
Prare only a few percent (3) of the
at 600° to 700°C. The oxides thus
obtained were dissolved in hydrochloric
harvested from Hinuma Marsh. In view
of the widespread occurrence of cerium-
144 in tested samples, it is assumed that
the presence of this radionuclide is due to
fallout.
The predominantfission product contributor to total radioactivity 0.85 to 3
years after detonation is Ce(Pr)
(7). Because Ce'™is abundant in fallout, it is reasonable to expect that food
will be contaminated by this radio-
nuclide,
Recently Van Dilla (2) reported that
although grazing animals ingest large
amounts of Ceand other radionuclides
as foliar contamination, very little Ce“
is absorbed. Investigations at our labo-
The Ce™ + Pr’ spectrum would be
expected to show peaks at 0.134, 0.100,
and 0.071 Mev due to Ce™, and at
tion of a cerium carrier solution to the
sample solution, rare earths were iso-
lated from the sample solution as hy-
tected in clams (Schizimi, Corbicura sp.)
peaks of the spectrum were consistent
with that of the Ce’™-+ Pr“ standard
sample.
2.18, 1.48, and 0.700 Mev due to Pr’.
The peaks due to Ce™ are more than
droxides. Oxalates were separated from
the hydroxides and converted into oxides by ignition in an electric furnace
Abstract. Small amounts of cerium-144
have been found in samples of food and
animal bone obtained from Ibaraki, Japan.
The highest level of radioactivity was de-
(T1) well-type crystal and a 256-chan-
nel pulse height analyzer. The distinct
as follows: A sample solution was prepared from the ashes of about 1 kg of
dried sample by hydrochloric acid ex-
traction and alkaline fusion. After addi-
Cerium-144 in Food
with a Geiger-Miller counter. The concentration of Ce’ was determined by
the chemical yield of added carrier and
by comparison with a standard sample
of known concentration.
The cerium fractions were combined,
and the gamma spectrum was determined by using a 1%4 by 2 inch Nal
acid, and hydroxides were again precipitated from this solution. This procedure was repeated two or three times
for removal of calcium, phosphate, and
other cations except for rare earths.
After being dissolved in concentrated
hydrochloric acid, the hydroxides were
passed through a column containing
anion exchange resin equilibrated with
concentrated hydrochloric acid. By this
procedure iron, uranium, and plutonium
are absorbed.
The effluent was dis-
solved in nitric acid solution (7.5M),
and again passed through a column
containing anion exchange resin equilibrated with nitric acid (7.544). By this
step thorium is absorbed. From the
effluent, rare earths were precipitated
as hydroxides.
Cerium was isolated
from other rare earths by the iodate
method and finally prepared as oxalate.
The radioactivity of each sample was
measured
under
standard
conditions
60 percent of the total gamma radiation
total.
Observed peaks on this spectrum
were 0.134, 0.100, and 0.069, Mev.
With our instrument, the ordinals lower
than 0.100 Mev are not in correct proportion to the energy. The gamma
Tadioactivity of the cerium fraction was
so low that the peaks due to Prcould
not be observed. From our data, the
individual peaks due to Pr’ cannot be
distinguished from the Compton background. The maximum energy of beta
rays, calculated from the beta-ray ab-
sorption curve of the cerium by the
method of Bleuler and Zunti (4), was
2.92 Mev. The decay curve of the
cerium fraction showed that the halflife was 282 days.
The radioactivity of the cerium fraction seems, therefore, to owe its origin
to Ce™ + Pr. The Ce’ concentrations of representative samples are sum-
marized in Table 1. This radionuclide
Was present in every sample tested. The
higher levels of Ce™ in clams, as compared with levels in the other biological
samples, are not unexpected, in view of
the findings of Goldberg et al. (5), who
demonstrated that some marine organ-