Junge, Chagnon, and Manson® have shown that a stratospheric aerosol layer exists between the tropopause and about 76, 000 feet, above which the particle concentration decreases rapidly with increasing altitude. If it is assumed that the nuclear debris, and therefore strontium-90, from testing prior to Teak and Orange had been mixed throughout the altitude range in which the aerosol exists, then the strontium-90 had become incorporated into the stratospheric sulfate particles. The value of the average strontium-90 concentration in the tropical stratospheric aerosol of 4,5 x 10! dpm /em® of aerosol might then be used to characterize particles containing pre-Teak and Orange debris in the lower stratosphere. It thus appears, in view of the previous arguments concerning the origin of the debris in both polar and tropical stratospheric air, that with the possible exception of sample P-5, all of the listed "polar'' samples contained material from Teak and Orange shots. However, it seems that the contribution of Teak and Orange debris in these samples is at least 50 percent, whereas from the cel 44) sr?? ratios, it was estimated that the Teak and Orange contribution between 60, 000 and 70, 000 feet was about 30 percent. One explanation of the apparently high proportion of Teak and Orange debris in the stratospheric aerosol may be that prior to the time when sampling of particles began some Hardtack debris from the altitudes in the tropical stratosphere above the aerosol region (~ 80, 000 feet) had mixed into the polar stratosphere at lower altitudes (60,000 to 70,000 feet). Particles with a higher strontium-90 content could have resulted from this process since the debris from the tropical stratosphere could have been associated with relatively small concentrations of sulfate aerosol until it became mixed to lower altitudes in the polar stratosphere. That such a mixing process can occur has been indicated by Feely and Spar” based on studies of the stratospheric distributions of tungsten-185 produced by Hardtack tests. Of course it is not pos- sible to extract detailed knowledge of the relationships among nuclear debris, aerosol concentrations, and atmospheric transport properties since there exist uncertainties in estimating the particle volume concentra- tions and the average strontium-90 concentrations. The scanning of the electron micrographs fails to reveal significant differences in particle shape or type between samples containing Teak and Orange debris and those not containing that debris. found in most samples which were different in appearance fromthe sulfate particles. nantly of radii greater than one micron, some spherical, some irregular in shape. not be determined by electron diffraction. Some particles were These were predomi- Their composition could These larger particles contributed less than 10 percent of the cal- culated volume concentrations, While there is no direct observational evidence to provide detailed knowledge of the trajectories of the particulate matter resulting from the high altitude nuclear detonations, some reasonable speculations may be made to explain the observations described above. It is assumed that most of the mass of a nuclear weapon detonated in the atmosphere appears in particles of less than 0,1 micron diameter and that, in the absence of indigenous particles, most of the fission products, even those with noble gas precursors, eventually reside in the particles of weapon debris, These small particles, which have low sedimentation (about 0.01 cm/sec) also exist in concentrations low enough so that coagulation to produce particles with appreciable settling velocities is not a significant factor in the ultimate history of most of the debris. It is thus possible that the dis- tribution of nuclear debris in the upper atmosphere has been primarily governed by the motions of the air. Initial horizontal sperading of the debris (most likely by turbulent mixing) followed either by large scale vertical mixing or by subsidence in the polar regions especially during the winter season, would be consistent 144 . . 90 .o, : . with the observations of the Ce /St°” ratios in debris in the lower polar stratosphere, It is most likely that as the debris from the upper atmosphere detonations reaches the lower altitudes at which the sulfate 67