nearly the same value, about 200 dpm/1000 scf. By May-June 1960 the values for these altitudes in the tropi- cal stratosphere had dropped to about 120 dpm/1000 scf while those in the northern polar stratosphere remained about 200 dpm/1000 scf. The distribution of nuclear debris in the northern hemisphere during March-April 1960 is shown in Figure 7, in the form of cross sections of the atmosphere. The data presented include tungsten-185 concentrations, rhodium-102 concentrations, and ce! 44jg9° ratios, The cet #4 7,99 ratios indicate that Teak and Orange contributed more than 20 percent of the strontium-90 above 50,000 feet in the northern polar stratosphere during early 1960. Integration of the strontium-90 distribution yields approximately 0.37 megacuries of strontium-90 in the lower atmosphere of the Northern Hemisphere during early 1960, of which about 0.053 megacuries was from Teak and Orange. Unfortunately, HASP has no data for the Southern Hemisphere between August 1959 and May 1960 and the data which exist for May and June 1960 do not provide sufficient coverage of the hemisphere to permit an accurate calculation of the contribution of Teak and Orange to the strontium-90 burden in that region, Thus, for want of a better procedure it is tentatively assumed that about 0.05 mc of Teak and Orange were also present in the lower atmosphere of the Southern Hemisphere by the end of the 1960 winter season in that hemisphere. This gives a very crude estimate of 0.1 mc of strontium-90 from Teak and Orange in the lower stratosphere (below 70, 000 feet) by the latter half of 1960. Teak and Orange Debris in the Stratospheric Aerosol A rather unique opportunity to observe particles bearing Teak and Orange debris was afforded by the use of impaction probes mounted on the sampling aircraft. 25 and May 19, 1960. A total of ten samples were obtained between February Of these, three were taken from the region of the northern polar stratosphere in which Teak and Orange debris was detected as previously described. The samples were examined by electron microscopy and electron diffraction, From the electron diffrac- tion patterns it was determined that most of the particles consist of ammonium sulfate and ammonium persulfate. Figure 8 shows electron micrographs of some typical particles of the sulfate and persulfate types. The particles in the electron micrographs were classified according to radius (or equivalent spherical radius in the case of flat particles). The number of particles in each class was corrected for impaction ef- ficiency for a cylindrical surface according to the method of Ranz and Wong. 3 This procedure made possible computations of the number concentrations (in particles per cubic centimeter of air) and volume concentrations (in cubic centimeters of particles per cubic centimeter of air) of the aerosol. calculations. Table 1 shows the results of these Also shown are the ratios of strontium-90 concentrations to aerosol volume concentrations, i.e., the calculated concentration of strontium-90 (in dpm per cm? of solid) in the particles. The strontium-90 con- centrations (in disintegrations per minute per cubic centimeter of air) were computed by averaging the concentrations as determined from the filter papers over the flight path for the duration of the probe sampler exposure. Except for sample P-5 all of the samples in Table 1 which were collected in polar air have strontium-90 concentrations in the particles which are at least a factor of two higher than the average for samples collected in tropical air. The average strontium-90 concentration in polar samples (except for P-5) is 2.18 x 10° dpm fem® of aerosol while the average for tropical samples is 4.49 x 10! dpm fem? of aerosol, 63