RADIATION STANDARDS, INCLUDING FALLOUT
77
Similar studies in the Soviet Union have suggested the same overwater fallout excess. The best hypothesis for the extra fallout is
that there are salt particles near the surface of the ocean to which the
strontium 90 aerosols attach themselves, and these are brought back
to the seas and oceans.
There are additional mechanisms besides rainfall which may deposit material over the oceans. There is evidence that fallout over
the ocean is greater than extrapolation from land and rainfall data.
In placard 6, the North Pole lies on the left, the Equator on the
center, and the South Pole on the right. This irregular scale is such
that. equal lengths cover equal areas on the earth rather than a linear
latitude scale. The total amountof fallout to mid-1961 is the upper
line. This has been derived from the previous placard plus fallout
collected in the pots and funnels on a monthly basis. We have taken
soil accumulation to mid-1960 and added this to the AEC potresults.
The peak occurs from 30° to 60° N.as already suggested yesterday
by Dr. Dunham.
The middle curve showsthe distribution of fallout from the U.S.S.R.
fall 1958 test series. This likewise shows a peak in the temperate
latitudes from 30° to 60° N. and virtually nothing appears in the
Southern Hemisphere. The bottom curve showsthe fallout from our
Hardtack summer 1958 test series. This has been identified by the
unique tracer, radiotungsten, which was injected into the lower equa-
torial atmosphere at the Eniwetok Proving Grounds.
Again there is a tendency for a peak in the temperate latitudes in
the Northern Hemisphere and a suggestion of one in the Southern
Hemisphere.
Representative Price. But you don’t show muchof a curve anyplace.
Dr. Macnta. No. This fajlout has been more uniformly distributed
over the globe than the fall 1958 Soviet tests. The peak in the temperate latitudes of the Northern Hemisphere is about twice that of the
Southern Hemisphere, although there is a paucity of data in the Southern Hemisphere. It is clear that no matter where the stratospheric
injection takes place, whether it is near the Equator or the polar regions,it is the temperate zone whichseemsto get. the greater bulk of the
fallout. This placard is evidence for this conclusion.
Mr. Ramey. That is the banding?
Dr. Macurta. This is the banding referred to many years ago and
which has now been definitely confirmed.
Placard 7 introduces the next subject; the seasonal variation of fallout. The month of the year is shown on the horizontal axis, and the
amount of strontium 90 fallout is on the vertical axis. The units are
megacuries because the total amount of fallout on the entire northern
hemisphere is under consideration.
The spring period is shown in the shading. Thetotal fallout in
the year 1959 is shown by the uppermost. curve labeled “total.” It.
shows a peak in the months of March, April, and May. The second
curve, labeled “U.S.S.R. fall 1958,” shows a pattern very similar to
the “total.”
Using the radio tungsten data, one is able to obtain a seasonal
trend in the fallout from the United States 1958 summerPacific tests
in the lower equatorial stratosphere. This is shown by the lower
curve. It likewise tends to peak in the spring season of the year, but
the peak is much less marked than the other two curves.
GEIB EE” oncetataSy