Characteristics of tritium, stable isotopes and chemical components in monthly precipitation at Hiroshima, Japan.

This article focuses on the measurement and analysis of tritium concentrations in monthly precipitation in Hiroshima City during 2021. Tritium (³H), a beta-emitting radioisotope of hydrogen, was found to range from 0.16 to 0.78 Bq L⁻¹, with seasonal variations consistent with other regions of Japan but deviating from the expected latitude effect, which typically shows higher tritium levels at higher latitudes. The study also measured stable isotopes of hydrogen and oxygen and major ionic components, identifying some ions of continental origin, suggesting that Hiroshima's precipitation is influenced by Asian continental air masses. These findings imply that tritium levels in the westernmost region of Honshu, including Hiroshima, may be affected by continental sources rather than solely by latitude-related atmospheric processes. The article highlights the importance of continued monitoring to better understand tritium behavior in this region.