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76
RADIATION STANDARDS, INCLUDING FALLOUT
area. The points of observation are shown by the black dots. It does
not showthose in continental United States or Canada because there
are too many ; approximately 80 or90.
The heavy shading showsthe area of the heaviest fallout. The lines
join points along which the fallout is equal. The interpolation has
been performed by the Weather Bureau assuming that the amount of
fallout is more or less proportional to the amount of rainfall in the
same climatic region.
Onecan see that the highest fallout is clearly in the temperate zones
of the Northern Hemisphere. There is a slight maximum in the temperate zone of the Southern Hemisphere.
The placard also showsthat there is a minor peak in the Midwest and
south-central part of the United States. It has been suggested that
this may be due to additional fallout from the Nevada tests. This is
probably partly true. But between 1959 and 1960, soil samples have
been collected by Dr. Alexander of the Department of Agriculture,
who hascollected all the samples shown on this chart, and analyzed
by the Health and Safety Laboratory of theAEC. The increase from
the 1959 to the 1960 values showed that there was also a peak at about
latitude 40° N., the same latitude at which the peak appears on the
chart. During this interval there were no Nevadatests.
Apparently the worldwide fallout does tend to peak in the temperate
zone at about 40° N. in the United States, possibly due to the fact
that we have intense thundershowers, which may bring debris from
higher altitudes in addition to other processes which generally increase fallout in the 30° to 60° N. band.
Representative Price. Mr. Ramey has question.
Mr. Ramey. This confirmsthe sort of theory you expressed in 1957,
that this would be the case; is that not correct ?
Dr. Macura. I am not sure I can take credit for having predicted
this particular phenomena.
Mr. Ramey. Theso-called banding phenomena.
Dr. Macuta. Thereis no question but there is a banding phenomena
taking place, virtually all of which has been derived from the stratosphere. This much has nowbeen amply confirmed. But whether or
not one should have found a peak in the midsection of the country,
this I don’t think I have predicted.
The two oceanic maximumsare associated with the storminess which
occurs with the Icelandic and Aleutian low pressure areas. ‘These are
regions of very heavy rainfall.
Chairman Houirtetp. Fortunately, that fallout occurs over the ocean
and very thinly populated islands.
Dr. Macura. Yes. I may point out that this chart shows fallout
over the oceans based on a fewstations, for example, in Scandinavia
and Bermuda, butit is likely that the fallout is heavier than is shown.
Dr. Bowen, of Woods Hole Oceanographic Institution, has been
sampling various depths of the ocean for the strontium 90 concentration in water.
While the water is in constant motion and it 1s 1m-
properto integrate in the vertical to find the total amount of deposition
at a given point, nevertheléss he has enough sampling points to suggest
that the fallout is greater than has been suggested by extrapolation
from land-based stations by a factor of roughly two.
SSRIPAAAORAGSS