Transport and fallout of stratospheric radioactive debris

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

Relationship between solar activity and Δ14C peaks in AD 775, AD 994, and 660 BC

“…The early (774 AD) rise in the Siberian and Altai Δ 14 C data is difficult to reconcile with 14 C results from the 1960s, when high-yield Soviet atmospheric nuclear tests in Novaya Zemlya (~74°N) in September-November 1961 and again in the latter half of 1962 produced very high burdens of excess 14 C in the NH stratosphere (Feely et al 1966). After each major injection, measurements of atmospheric 14 CO 2 in air samples from NH ground stations (Nydal and Lovseth 1983;Levin et al 1985) showed a sharp rise beginning in the early spring of the following year and continuing through the entire NH growing season.…”

On geoengineering with sulphate aerosols in the tropical upper troposphere and lower stratosphere

“…In the present context, some central results were obtained by analysis of observations made by a combination of WU-2 and RB57F highflying aircraft (up to about 21 km) augmented by a few balloon profiles to greater altitudes. Among these was the result that the radioactivity that was in gaseous form at 20 km, 14 C in carbon dioxide, had a stratospheric residence time of 16 months, while the many radionuclides that were attached to the stratospheric aerosol had a significantly shorter lifetime of 10 months (Feely et al 1966). The difference was attributed to gravitational settling by the aerosol, allowing the more effective dispersive motions at lower stratospheric altitudes to separate the gaseous and particulate radionuclides and yield a lower residence time for the latter.…”

Anthropogenic radionuclides in atmospheric air over Switzerland during the last few decades

“…The collected radionuclide data were nonetheless very useful for investigating atmospheric processes 19 . Results show that the transfer of radioactive debris from the stratosphere to the troposphere takes place mainly at the tropopause breaks, with a maximum in spring and a minimum in autumn 13,16,20 .…”

“…Radioactive particles with radius below 0.02 mm were typically found above 27 km, and particles of larger radius were found between the tropopause and 21 km. Mean residence times of the order of 1-4 years were reported for radioactive particle aerosols in the stratosphere 2,13,15,16,20 . These estimations were based on the rates of change of the stratospheric burden over short timescales (2-4 years), and numerous important factors/parameters were not taken into account.…”

“…Most information comes from early studies in the sixties and seventies on anthropogenic radionuclides in the atmosphere [10][11][12][13][14][15][16][17][18] . In these studies, tropospheric and stratospheric aerosols were sampled with the aid of aircraft and balloons.…”