No abstract

The average stratospheric residence half-time of particulate radioactive debris, as represented by strontium-90 and manganese-54, was approximately 10 months during the two years following the last atmospheric tests of high yield nuclear weapons. During this interval, the carbon-14 which was produced artificially by nuclear weapons tests showed a stratospheric residence half-time which increamed with time, but averaged about 18 months. It is suggested that the stratospheric residence half-time of particulate debris did not increase significantly during 1963 until early 1966 because in the upper stratosphere, above 20 km, the rate of particle settling of the debris exceeded the rate of upward diffusion, and as a result, this debris remained highly concentrated in the lower stratosphere throughout this period. It is also suggested that the relatively more rapid meridional movement of particulate debris, compared to the movement of carbon-14, into the stratosphere of the Southern Hemisphere during the second half of 1963 resulted to some extent from the partial separation of the particulate debris from the carbon-I4 in the equatorial stratosphere as a result of particle settling. 9t c c FIG. 2. Sampling corridor with Stardust and AEC balloon program flight tracks. TeiUus XVIII (1966), 2

From measurements made in the stratosphere and upper troposphere, atmospheric inventories of CCl3F, CCl4, and SF6 are calculated for April and July 1975. Mean Northern Hemispheric altitude profiles Of CCl3F and CCl4 in April 1975 show reasonable agreement with predictions of one‐dimensional diffusion models. From the distribution of these trace gases in the stratosphere, including comparisons with a few 85Kr and tritium measurements, we deduce a stratospheric circulation pattern consistent with patterns of a number of radioactive substances which have been injected into the stratosphere. The observed stratospheric and tropospheric inventories Of CCl3F and SF6 are consistent with an atmospheric residence time of 26 years and discount the existence of an important tropospheric sink.

No abstract

From measured distributions the inventory of CCl3F in the total stratosphere in April and October 1974 is 0.2 Tg. Assuming a box model of atmospheric transport, the observed stratospheric inventories agree with the measured tropospheric concentrations and the industrial production rates when the photolysis half‐life of a CCl3F in the stratosphere is 2–4 yr. This corresponds to a total atmospheric half‐life of 15–30 yr.