Quarterdeck 3.2

Plutonium and Cesium in the Kara Sea

by Mahalingam Baskaran

Sidebar to Studies of nuclear contamination in the Russian Arctic

Plutonium and radioactive cesium in the Kara Sea come from several sources. A few major ones include fallout from nuclear weapons testing worldwide, river run-off containing eroded fall-out from land and leached materials from nuclear waste sites, direct dumping of nuclear effluents, effluents from other areas transported to the Kara Sea from the Barents Sea through the Novaya Zemlya strait, released radioactive contaminants from nuclear materials dumped in the Kara and Barents Seas since 1959, and fallout of "hot" particles from the nuclear weapons testing on nearby Novaya Zemlya island.

Effluents transported from elsewhere come from nuclear facilities in Europe such as Sellafield in the United Kingdom which discharges into the northeastern Irish Sea, Dounreay in northeast Scotland which discharges into the Pentland Firth, and La Hague reprocessing plant near Cherbourg, France which discharges into the English Channel.

The relative contribution of different plutonium sources to the total radioactive material in surface sediments of the study area can be evaluated using the atomic and activity ratios of different plutonium isotopes.

Radioactive materials from different sources exhibit distinctive proportions of the plutonium-239, 240 and plutonium-238. The table below shows Pu-238/Pu-239, 240 activity ratios for nuclear effluents from Sellafield (U.K.) and Cap de la Hague (France), discarded reactors in the Kara Sea, global fallout, and the surface sediments in the Kara Sea and adjoining areas. The latter ratio was measured at Texas A&M University.

The activity ratios of plutonium-238 to plutonium-239, 240 and plutonium-239, 240 to cesium-137 in the surface sediments we analyzed match that of nuclear materials derived from global fallout, suggesting that most radioactive cesium and plutonium in the Kara Sea is a result of global nuclear weapons testing. Fortunately, the concentrations of radioactive isotopes remain so low that they pose no immediate threat to the Arctic environment.

Table optimized for Netscape 1.1 [Text version]

Sample Location Pu-238 to Pu-239,240 Activity Ratios in 1993 Source
Effluents from Sellafield Irish Sea .29±0.02 British Nuclear Fuels, 1985
Effluents from Cap de la Hague English Channel 0.46 Calmet and Guegueniat, 1985
Dumped reactors in the Kara Sea Kara Sea 0.26-0.49 Mount, et al. 1993
Global fallout (+SNAP) Northern Hemisphere 0.30 Aarkrog, 1989
Surface sediments Kara Sea and the Ob and Yenisey Rivers 0.035±0.003 TAMU study

Editor's Note: A peer-reviewed article by Dr. Baskaran and others which reports the results of this research will appear later this year in Applied Radiation and Isotopes. A similar article has been submitted to Earth Planetary Science Letters.


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Updated September 13, 1995