Investigation on seasonal variations of Be-7 and H-3 in the rainwater of Korea

Abstract:

Both Beryllium-7 (Be-7) and Tritium (H-3) are produced by cosmic ray interactions in upper atmosphere by spallation reactions. We investigated these nuclides in rainwater along with sodium concentration in the region of Deajeon, Korea (36.32°N, 127.41°E) for 7 months during 2007 and 2008. The results of our study demonstrate that Be-7 in rainwater is inversely propotional to the amount of sodium, proportional to the amount of rainwater and air mixing of the stratosphere in sping. Both isotopes show their peaks during fall and spring seasons. The trend of H-3 variation is shifted about a month compared to that of Be-7. This could be due to the different residence time between H-3 and Be-7 in the atmosphere. The detection efficiency of uncorrected Be-7 concentrations in this area ranged from 0.06 to 14.13 Bq/L which is lower than the reference values of New Zealand (0.5 ~ 4.3 x 10⁷ (atoms/kg rain)) and Japan. The H-3 concentrations of this study ranged from 4.8±0.10 and 18.6±0.3 (TU). This range is well compared to the H-3 concentration of the Northern Hemisphere. Also, sodium variation of the rainwater is found to be inversely proportaional to Be-7 concentrations. This could be associated with air mixing phenomenon involved in the movement of salt in land of Korea. This presentation demonstrates details in both chemistry and data analysis along with other previously published data. This study will provide reference values of Be-7 for the Korean region and will guide a prospective geolgical application associated with atmospheric cosmogenic nuclide production.