PRECIPITATIONVS. "cs IN MILK IN NORWAY
869
zone 2, Figure 5 shows the average concentrations of !*’Cs in the milk
for the three zones in each spring.
The precipitation rate and form vary widely in the three zones.
The primary purpose of our studies was to investigate whether or not
there was any correlation between the precipitation and the concentra-
tion of *°’Cs in milk.
57C5 IN MILK, PC/L
400
Fig. 9 —Average concentration of 13’Cs in milk in the
three zones in the springs of
1962, 1963, and 1964,
From
gamma
300
200
100
0
spectroscopic
ZONE 1
2 3
1962
measurement
1
2 3
1963
7
l]
l
yy
yZ
Y]
y]l
1
2 3
1964
performed
in
our
laboratory, we knew the amaurt of 3'Cs in the milk from the same
dairies at the same time ‘of.‘the year for three consecutive years. It
was presumed that the.. 17g deposited in the soil before the new
nuclear-weapon test series._4nythe autumn of 1961 would give the same
contribution to the milk’s @ontent in 1962, 1963, and 1964 because of
the long half-life of '°’Cs (80 years) compared to the time of observa-
tion (3 years). Cesium-137:¢g-strongly bound in the soil and diminishes
very slowly.® Besides, most” of the 137Cs ingested by cows originates
from '"Cs deposited directlyfremthe air to the leaves and, to a far
lesser degree, from the soil through the roots of plants.® Any increase
of the '*’Cs content of milk,therefore should be exclusively due to
increased fallout from the new fést series.
The year 1961 is used ag_the basic yearfor the studies, but, to
minimize local variations in thé precipitation for that year, we used
the
average precipitation for
1959, 1960, and 1961 instead of the
precipitation in 1961 only.
Several facts are important when one considers the precipitation
in the various districts from which the dairies receive their milk
supplies. The precipitation rate in Norway varies considerably from
one county to another and is measured by a large number of stations.