210 PERKINS, THOMAS, AND NIELSEN 100.000 ETT TTT TTT TTT — L 10,000 f= nee - a e * a, 2 ,*s — e — — = 4 = ® S890 _ — I24sb _ 1,000 - n° as. . ee" s = @ J ® —_— ee = 2 Sb Pe % 10,000 =-- Tle = 1,000; ° ~~ o®° 6 * e e ° Ce, °.° % == la7c, . Oe e? — = 5 oe” . . 7 eee °° ELitivirr rp ire s Pepe py yy 1,000 — f= as = a | 100 Le a — a po 4 + s& a 2 4 a | a a4e “a, a, C - a4 a a *.04 tee “as “| = = = = By = SS 4 eer tet tt ONDJFMAMJJASONDJFMAMJIJSASOND 1964 1963 1962 Fig. 7—Comparisons of the air concentration of ®Y and !4Sb with W7Cs. Yttrium-88 and '4Sb are corrected to the time of their probable injection, Nov. li and Dec. 31, 1962, respectively. which was followed by an activated charcoal trap for collection of gaseous radioiodine. These flights were limited to 12,000 feet altitude because of the type of airplane used, but they served to show that Significant variations in radionuclide concentrations did exist at these low altitudes. Figure 8 gives typical profiles of the concentrations of five radionuclides as a function of altitude showing comparatively high concentrations at 12,000 ft. The availability of stratospheric air filters, which were furnished by Isotopes, Inc,, Westwood, N. J., has made it possible to compare the air concentrations observed near ground level at our geographical position with those present in the stratosphere above. In Fig. 9 the _ ratios of the radionuclide concentrations for stratospheric air to those of ground-level air are compared for 12 radionuclides. These measurements were made on samples collected during January 1964, It is interesting that these ratios range from about 1500 to 3000 for all the radionuclides except *y, '4sb, and '!“Cs. The high stratospheric con-