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RADIATION STANDARDS, INCLUDING FALLOUT
Wetherefore argue that, no matter whether the injection takes
place in the polar or equatorial region, there is a definite tendency
for peaking in the spring. However, when the injection is made in
the polar region, there is more of a spring peak than in the case of
the equatorial injection.
,
The figures in the upper righthand corner of the chart indicate the
fraction of the total fallout attributed to each of the sources. For
example, during the 8 spring months, March, April, and May, 73
percent of the fallout could be attributed to the Soviet 1958 October
test series, 13 percent to the Hardtack tests in the summerof 1958, and
all the other prior tests contributed only 14 percent. Most of the
fallout in the spring of 1959 came from the rapid fallout of the Soviet
Novoya Zemlyatests in the fall of 1958.
Placard 8 shows the fallout over a series of years from 1958
through 1961, and the zones for the spring of each year in the Northern
Hemisphere have been labeled in one sector, and those in the Southern
Hemisphere in another sector. March, April, May are the Northern
Hemisphere’s spring months, and September, October, November for
the Southern Hemisphere spring months.
The upper curve, identified by “Northern Hemisphere,” shows the
fallout in the Northern Hemisphere, and during each spring season
of the year you will find there is a definite peak. The most marked
peak occurred after the October 1958 Soviet. test series, in the spring
of 1959.
In 1960 and 1961 there were also spring maximumsdespite the fact
there were no previoustests in the autumn of 1959 or autumn of 1960,
suggesting that the mechanism which brings the strontium 90 down
from the stratosphereis a meteorological process.
In the Southern Hemisphere there is no evidence of any seasonal
variation at least to 1960. The wiggles on the placard for the Southern Hemisphere curve show no seasonal trends. In 1960 there is a
tendency for peak in the spring of the Southern Hemisphere, and the
suggestion of anotherone in the spring of 1961. Therealities of these
are still open to question because they are not particularly marked.
The reason for the absence of a spring peak in the Southern Hemisphere, which meteorologists would have expected on the basis of the
fact that the two hemispheres are similar, has two possible explanations. One is that there may be meteorological differences between
the hemispheres. The more likely explanation is the one to whichI
hold. There may be another source of fallout for the Southern
Hemisphere; namely, cross-equatorial flow from the troposphere of the
more highly contaminated Northern Hemisphere into the less contaminated Southern Hemisphere. This transfer may be irreguiar im
time. The Southern Hemisphere stratosphere may have a regular
fallout pattern, but the radioactivity derived from the Northern
Hemisphere troposphere may confuse this seasonal pattern. In
1960 and 1961 both hemispheres had about the same concentrations,
hence the Northern Hemisphere source became unimportant.
Theevidencefor this thesis is shown in placard 9, which shows data
collected by Dr. Gustafson of Argonne National Laboratory for an
isotope, rhodium 102, which was injected during the U.S. high-altitude
test of August 12, 1958. The fallout in both hemispheres was about
equal for this particular isotope. One hemisphere is not more heavily
contaminated than the other hemisphere.
Sis GGRODRICES osananeiagaeatisin