674
THATCHER, PAYNE, AND CAMERON
leave a stratospheric inventory of 124 kg. When tritium deposition by
oceanic exchange is also considered, the possible deposition becomes
19 and 77 kg to give a total of 96 kg. This would leave a stratospheric
inventory of 72 kg.
Continued observations of tritium fallout in 1964 and 1965 should
permit a more accurate analysis of the vapor-exchange effect. The
rate of fallout is presumed to be approximately a first-order function
of the stratospheric concentration. Therefore the tritium fallout con-
centration in 1964 should have average values that reflect a stratospheric inventory between the two extreme values of 124 and 77 kg.
The IAEA is continuing the record of tritium in precipitation and is
applying the information to the analysis of vapor exchange and other
Significant aspects of environmentaltritium.
ACKNOWLEDGMENTS
The IAEA and the WMOare indebted to the International Meteoro-
logical Institute; the Environmental Group, AECL, Chalk River; the
Scripps Institute of Oceanography; the Weizman Institute; the Tata
Institute of Fundamental Research; and the New Zealand Institute of
Nuclear Science for tritium measurements over the years. Their
continued cooperation has made the project discussed in this paper
possible. Appreciation is expressed to the U. S. Geological Survey and
to the many other groups who have contributed data from national
projects.
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Phosphate Treated Mild Steel Cathodes, Report presented at the IAEA-WMO
panel on World-Wide Survey of Hydrogen and Oxygen Isotopes in Precipita-
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3. E, A, Martell, On the Inventory of Artificial Tritium and Its Occurrence in
Atmospheric Methane, J. Geophys. Res., 68(13): 3759 (1963).
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