866
Table 1— TOTAL NUMBER OF DAIRIES IN NORWAY
AND NUMBER OF DAIRIES FROM WHICH
SAMPLES WERE TAKEN
Year
From
Dairies
Dairies supplying
samples
“1962
342
272
1963
342
297
1964
327
292
November
1958
until September
1961,
there were
no
atmospheric nuclear tests. Therefore it seemed reasonable to assume
that in the spring of 1962 we would find a smaller '*’Cs body burden in
cows and consequently a decreasing concentration of this nuclide in
milk for the next few years if nomore nuclear weapons were detonated
in the atmosphere. At that time the cows were fed supplementary
fodder and grass gathered before the bomb tests were resumedin the
autumn of 1961.
A systematical analysis of '*"Cs in milk was started, and these
analyses were repeated on the same scale during the springs of 1963
and 1964, (Spring means, in this connection, primarily the monthsof
March and April; however, a few of the milk samples were gathered
in February and May.)
The total number of dairies and the number of dairies from which
milk was sampled each year are given in Table 1. Practically all the
dairies in Norway were included in the investigation. Milk from 30 of
these dairies has been examined regularly every month since the
spring of 1963. Figure 1 shows their locations. Figure 2 shows that at
least in the period from March 1963 to March 1964 the lowest concentration of '°"Cs in milk occurred during spring.
Figure 3 is a map of Norway. Counties are outlined and numbered
1 to 18. Heavier lines have been drawn on the map dividing the country
into three zones. These lines follow the borders of the counties except
in Sgr-Trgndelag (14) and Nord-Trogndelag (15), which are divided into
two parts each—a western part near to the coast, included in zone 2,
and an eastern part, included in zone 1. The country was divided into
these three zones because of varying meteorological conditions, which
will be described later. Except in counties 14 and 15, no dairies are
situated near the zone lines since these lines run through very mountainous regions.
CORRELATIONS
Figure 4 shows the average concentration of }*"Cs in the milk for
each county in the three zones in the springs of 1962, 1963, and 1964.
It can be seen from this figure that concentrations of !°"Cs in zone 1
are different from those in zone 2; usually they are much higher in