137Cs DEPOSITION AND DIETARY LEVELS
TTT TOT
—
24
_
20
74
r
28 t—
0
|
o
"5705, MC/ SQUARE MILE
32
785
Piety
JFMAMJJASOND
1963
Fig. 1—Monthly deposition of 4%"Cs during 1963 at Argonne. Totals:
from airy and precipitation data, 78 mc/square mile; from soil mea-
surements, 70 mc/square mile.
of the plant in question. This is illustrated’ in Fig. 3 by the '"Cs con-
tent of wheat grown at Chillicothe, Tex., during 1957 through 1960. Al-
though the total '°7Cs deposition on the ground was greater in 1960 than
in 1959, the '*"Cs in the grain was lower by almost an order of magni-
tude in 1960 relative to 1959. The high level present in the 1957 crop is
attributable to nuclear weapons testing at the Nevada Test Site during
the spring and summer of that year. Thus it is apparent that years of
heavy fallout result in corresponding elevation in the '"Cs level in
wheat and, presumably, in other plant material and, by inference, in
animals feeding on such plant material.
It is not surprising therefore that the levels of '°"Cs in the diet
shown in Fig. 4 increased rapidly after the resumption of nuclear test-
ing in September 1961. Foods were purchased quarterly in two supermarkets in the Chicago area according to a list supplied by the Health
and Safety Laboratory for the Tri-City Food Sampling Program.’ The
87Cs content of each food on the list was determined by a gamma-ray
spectrometric method analogous to that used for the soil cores.’ The
foods were counted in bulk amounts of 1to 2 kg without ashing or chemical processing prior to analysis. The results from April 1961 through
July 1964 expressed in picocuries of !°"°Cs per day are shown in Fig. 4.
The sudden increase in October 1961 is probably a transient effect due
to the heavy fallout that occurred in late September 1961, much of
which was dry deposition. In 1962 the highest level in the diet was observed in the July sampling and was largely due to the concentration of