Natural and artificial radionuclides in environmental samples collected from the McMurdo Sound region in South Victoria Land, Antarctica

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Natural and artificial radionuclides in the soils collected from Ross Island and the Dry Valleys area and water filters used at the Scott Base have been studied by non-destructive γ- and α-spectrometry. The U, Th and K contents in the soils from Cape Royds were found to be several times higher than those from the Dry Valleys area, while the K/Th and U/Th ratios were nearly the same independent of the sampling location. Accumulation of ^<137>(Cs) in surface soils was estimated to be 1-5mCi/(km)^2,which is one to two orders of magnitude lower than those measured for the surface soils in Japan. In spite of the great difference of the fallout accumulation in surface soil, the ^<239,240>(Pu)/^<137>(Cs) activity ratio (0.016-0.022) was almost the same as the global fallout value. On the other hand, various artificial radionuclides were detected in the water filter samples. Among them, exsistence of ^<207>(Bi) is remarkable in the Antarctic samples. No appreciable difference from the global fallout value was found for the ^<239,240>(Pu)/^<137>(Cs) and ^<241>(Am)/^<239,240>(Pu) activity ratios. However, the ^<238>(Pu)/^<239,240>(Pu) ratio was found to be 3 to 5 times higher than those measured in the northern hemisphere, which can be attributed to the accidental release of ^<238>(Pu) by the burn-up of SNAP-9A satellite in 1964.
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