40 rf | f | | { | | f | J T J] 4 oO 35 -~— — x 30 }~- x —_] Xr x Ox 25 |. x Ww -— x 3 Ye a Q oO S 20 -~- ° = 4 x a. ° x wn O 4454 x - x x — 6 x 10 -— x x x x bern * Io o ° x * xy ° Oo x ° Oo x x ° ° oLt tl 90° 70° 60° | x 50° { 40° —~ oO [| 30° ° ° x oO oO P| 20° 40° o Xx o° NORTH LATITUDE oO ° o xk 410° 20° | xo — x O94 0 9 } | 30° x ° | ie 40° 50° 60° 70° 90° SOUTH LATITUDE Fig. 9—Soil data, 1956: ©, electroanalysis x 1.15; x, HCl extraction. Nevada and USSR tests. Their estimated contribution amounts to a very small part of the temperate latitude bump shown by the data.‘ Other less certain arguments all add up to the same picture: the bulk of the long-lived fallout in the temperate latitudes appears to have come from the stratosphere. However, the main evidence —age determination by short-lived fission products —suffers from possible defects due to fractionation and errors in radiochemistry. New measurements are being taken of the stratospheric Sr® distribution and other, and perhaps more certain, short-lived fission products to further check whether delayed fallout is uniform, or as proposed here, nonuniform over the globe. From existing evidence, it can be argued that, even if the intermediate fallout were subtracted, there would be little doubt that a marked peak of the stratospheric fallout in the temperate latitudes of the Northern Hemisphere would still appear. The polar region may show smaller values due to the smaller amount of precipitation or to the main injection into the troposphere entering the temperate rather than polar regions. _ A second prediction of the meteorology calls for a seasonal variation in the Sr” removal from the stratosphere with a peak in the late winter or spring. Although Fig. 11 shows the plot of 45-day fallout amounts for Milford Haven, England, in rain® (the solid line), similar results are found for all of the U. S. stations®that sample rain water and air concentration. The British were also able to sample and interpret air concentration of bomb radioactivity in the lower stratosphere for a short time in 1954 and 1955, the results being shown by the heavy dots. The left-hand ordinate is the concentration of Sr® per unit volume of rain water rather than deposition per unit area. A plot of deposition per unit area shows just about the same picture, indicating that the seasonai variation in deposition is not due to the fact that it rains 326 fs bi: