Determination of plutonium 240/239 ratios in Lake Ontario sediments.
A thermal ionization mass spectrometric procedure was developed for determination of 240/239 ratios in subpicogram quantities of plutonium (Pu), and was applied to Pu extracted from Lake Ontario sediment. The detection limit was ∼ 4 fg of Pu and the precision of 240/239 ratio measurement was ∼ 7% in the 0.07-0.42 pg range. Results of sediment analyses at various depths showed in all cases 240/239 ratios near the mean global fallout value of 0.176 ± 0.014. The lack of variability of the ratios with depth negated the use of Pu, present in excess in the near-surface samples due to leakage from a nearby reprocessing plant, as a geochronological meter. The 240/239 ratio of the leakage Pu appeared to be very similar to that of fallout Pu.
General Chemistry Branch, Chalk River Nuclear Laboratories, Atomic Energy of Canada Limited, Research Company, KOJ 1J0, Chalk River, Ontario, Canada.
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Green
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Miller
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Sparling
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Joshi