In order to understand the regional property of tritium concentration in natural water at Hirosaki City, Aomori Prefecture Japan, natural spring water samples were collected from 15 sites in 2016 and tritium concentration was measured by low-level tritium counting procedure using a commercially available solid polymer electrolyte (SPE) tritium enrichment system. The limit of detection of this procedure was approximately 0.06 Bq/L. Findings showed tritium concentrations in natural spring water samples ranged from 0.30 to 0.55 Bq/L with mean value of 0.44±0.08 Bq/L. These results were within the range of reported concentrations in rain and surface and shallow groundwater in Japan including other places of Aomori Prefecture. The presently obtained data could be considered as the background level of the Hirosaki area. The annual effective dose would be negligibly small compared with the annual effective dose limit of 1 mSv, if the committed effective dose equivalent from drinking water to residents was calculated using the highest tritium concentration data.

Monthly precipitation samples were collected at Hirosaki, Aomori Prefecture from January 2018 to December 2020 to measure the ion species and stable hydrogen and oxygen isotope ratios in order to understand the regional properties. The tritium concentration ranged from 0.28 to 1.20 Bq/L, with mean values (±S.D.) of 0.52 ± 0.18, 0.67 ± 0.25 and 0.63 ± 0.21 Bq/L in 2018, 2019 and 2020, respectively. This concentration level was almost the same as for Rokkasho, Aomori Prefecture. The tritium concentration had clear seasonal variation: high in the spring and low in the summer. This trend was thought to arise from seasonal fluctuations in the atmospheric circulation. On the other hand, the pH tended to be low, and the electrical conductivity (EC) tended to be high from the winter to the spring. The ion components, which major ion species contained in sea salt, also tended to be high in the winter, and these components had a strong influence on EC. The d-excess values were high in the winter and low in the summer, and when this trend was considered from the viewpoint of the wind direction data in Hirosaki, these dust components were attributed to the northwest monsoon in the winter to the spring coming from the Asian continent.

In Japan, the deuterium plasma experiment using the Large Helical Device was started at the National Institute for Fusion Science (NIFS) in March 2017 to investigate high-temperature plasma physics and hydrogen isotope effects in research leading towards the realisation of fusion energy. The deuterium plasma experiment produces small amount of tritium by fusion reactions. To understand any impacts by the experiment to the surrounding environment, monthly precipitation samples have been collected at the NIFS site since November 2013 to assess the relationship between isotope composition and chemical species in precipitation including tritium. By comparing data before and after the deuterium plasma experiment start, it was found that tritium released from the main stack of the fusion test facility had no impact on the environment surrounding NIFS.