Tritium concentration in unpolished rice

Inoue and Iwakura recently reported that the specific activity ratio of organically-bound 3H to free water 3H in polished rice samples collected in Japan and China was lower than unity. Their paper was the first to report the systematic apparent elimination of 3H for incorporation to organically-bound form in samples collected from the general environment. To confirm their result, seven unpolished rice samples obtained just after harvesting were analyzed for 3H. The mean specific activity ratio of organically-bound 3H to free water 3H was found to be 0.57, somewhat lower than the data by Inoue and Iwakura. This small difference may be caused by the different sampling years and/or the possible replacement of free water by atmospheric water vapor after harvesting.