Abstract
Plutonium isotopes have primarily been injected to the stratosphere by the atmospheric nuclear weapon tests and the burn-up of the SNAP-9A satellite. Here we show by using published data that the stratospheric plutonium exponentially decreased with apparent residence time of 1.5 ± 0.5 years, and that the temporal variations of plutonium in surface air followed the stratospheric trends until the early 1980s. In the 2000s, plutonium and its isotope ratios in the atmosphere varied dynamically, and sporadic high concentrations of 239,240Pu reported for the lower stratospheric and upper tropospheric aerosols may be due to environmental events such as the global dust outbreaks and biomass burning.
Highlights
Residence time of gaseous chemical components such as CO2 and SF6, were calculated
The observed levels of 239,240Pu in stratospheric aerosols were from two to four orders of magnitude higher than that in the ground-level air. They suggested that the stratospheric mean residence time of plutonium and 137Cs should be 2.5–5 y, arguing that radionuclides attached to fine aerosol particles (< 0.02 μ m in diameter) could have a longer stay in the stratosphere, and radionuclides injected there mainly during the early 1960s have still been present during the 2000s in the stratosphere
(1964–2010) of plutonium isotopes in the stratosphere and surface air of the Northern Hemisphere we have found that the dominant processes affecting plutonium concentrations in the upper troposphere should be global dust events and biomass burning, and that its apparent residence time in the atmosphere did not change from 1.5 ± 0.5 years
Summary
Residence time of gaseous chemical components such as CO2 and SF6, were calculated. The obtained residence time of gaseous chemicals in the mid-latitude stratosphere was in the range of 1.1 to 2.1 y (ref. 15). (1964–2010) of plutonium isotopes in the stratosphere and surface air of the Northern Hemisphere we have found that the dominant processes affecting plutonium concentrations in the upper troposphere should be global dust events and biomass burning, and that its apparent residence time in the atmosphere did not change from 1.5 ± 0.5 years.
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