Recent Radiocarbon in Plants

概要

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Recent increase in radiocarbon in essential oil: menthol and thymol, and ethanol fermented from starch and sugar was assayed. Menthol and thymol were converted to P-cymene and thymol methylether respectively and counted by liquid scintillation techniques. Ethanol was mixed with toluene scintillator and counted by mean of large volume aluminum chamber to improve counting conditions. The results show that the carbon-14 activity in plants began to rise above normal in 1957 and the rate of increase was 7% per year to a level in 1959. A steep increase of the level to a peak in 1963, 80% above normal, which was caused by the large scale nuclear explosions through the end of 1962 was observed. The cause of the large variance among the samples in the same year and the difference of the data from that of the atmospheric carbon-14 presented a number of laboratories were discussed.
日本放射線影響学会の論文