712
HAW THORNE
among representative samples collected in 1962 and 1963 is the subject
of this preliminary report.
The study was made on a privately owned dairy farm located near
St. George, Utah. Thirty-three acres of cultivated land Support a milking herd of 17 to 24 cows in a dry-lot operation. Alfalfa is the principal
crop and feed, with small acreages of barley and sorghum grownfor
silage to use as feed supplements. The sizes and brief cropping histories of the fields used in this report were: field 4, 5.8 acres, plowed
in July 1961 for sorghum and in November for barley with alfalfa;
field 5, 8.0 acres, last plowed in 1960 andin alfalfa thereafter; field 6,
6.6 acres, in continuous alfalfa for 11 years. An annual mean precipitation of 12 in. is augmented by irrigation water from the Virgin River.
Small samples, consisting of 6 to 8 specimens from each material
of interest, were analyzed for *Sr and '?’Cs according to the methods
for wet chemistry! given in USAEC Report NYO-4700(Rev.).
The vertical distributions of “Sr and "Cs were determined for
soil in the cultivated fields from samples taken in November of 1962.
The distribution of radionuclides is shown in Fig.1 as mean millicuries
per square mile per inch depth of the profiles of fields 4 to 6. In field 4
Sr and "Cs were at a maximum inthe surface inch with a gradual decrease through the plowed layer. In field 5, "Sr decreased with depth
whereas '°’Cs peaked in the lowest part of the plowed layer. Both “Sr
and "Cs were more uniform in the profile of field 6 than in the other
fields, but the '°"Cs in the surface inch exceeded that in fields 4 and 5.
The mean summation of nuclides with depth in these fields was 160 and
460 mc/square mile for Sr and *"Cs, respectively. The radioactivity
in specimens taken from below 18 in. was beneath the detection limit of
the chemical processes used.
Characterizations of radioactivity may be given in various dimensional units. The collection unit for specimens is often a mass unit that
is combined with its
dimensions. In Fig.
from the mass of soil
the radioactivity per
tion is
radioactivity and then extrapolated into suitable
1 the millicuries per square mile were derived
per unit areain kilograms per square meter and
unit mass in picocuries per kilogram. The equa-
Kg of soil/m? x pe/kg of soil x constant = mc/square mile
There are uncertainties concerning the precision and the reliability
with which a mean value can describe several specimens collectively.
These uncertainties, or variances, in a sample of specimens may be
extremely difficult to partition successfully among the factors contributing to it.
In the equation given, the independent variables are the kilograms
of soil per square meter and. the millicuries per square mile. The
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