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Concentration of Strontium-90 at Selected Hot Spots in Japan

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This study measured the radioactive fission product strontium-90 alongside cesium-134 and cesium-137 in soil and vegetation from contaminated spots in eastern Japan after the Fukushima nuclear accident. Strontium-90 activity was low relative to radiocesium. The authors use the result to test the screening assumption used in Japanese food monitoring that strontium-90 does not exceed 10 percent of cesium-137 activity.

Key numbers

  • Strontium-90 activity concentrations did not exceed roughly 1 Bq per gram and were 1 to 4 powers of ten lower than cesium-137 in the same samples (Results, p. 2; Abstract).
  • In no sample was strontium-90 higher than 10 percent of cesium-137 activity (Results, p. 4).
  • Correlation of strontium-90 with cesium-137 was weak (power trend line, R squared 0.264; 0.41 when one sample was omitted) (Results, p. 4).
  • Chemical recovery of strontium, measured with a strontium-85 tracer, was 92.4 to 98.2 percent (Methods, p. 2).
  • Individual sample values are in Supplementary Table S1, which is not part of the archived PDF.

Methods (brief)

Air-dried soil and vegetation were leached with nitric acid and hydrogen peroxide with stable strontium carrier, strontium was isolated on a strontium-selective extraction resin, and strontium-90 was counted by liquid scintillation. Cesium isotopes were measured by high-purity germanium gamma spectrometry. An IAEA grass reference material was processed alongside samples.

Evidence fitness

Supports statements that strontium-90 released by the Fukushima accident was low relative to radiocesium in soil and vegetation, and that the 10 percent screening ratio held for these samples. It does not measure foods and does not address stable strontium.

Limitations

Sample numbers are small and per-sample results sit in a supplement not archived here. Older fallout from 20th-century weapons tests may contribute to low-level samples. Soil was leached rather than totally dissolved, which the authors justify for surface-bound fallout.

Update history

No substantive edit history is available in this build. The full commit record is available in git.

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