抄録
Three chemical forms of atmospheric tritium, i. e., tritiated water vapor (HTO), hydrogen gas (HT), and hydrocarbons (CH3T), were measured at Kumamoto, Japan during the period between 2003 and 2005. The average concentrations were in the order of HT, CH3T, and HTO. The yearly average HT concentrations were not so different in each year, while that of CH3T showed a large variation. The concentrations of all chemical species have decreased compared to those measured during the period between 1984 and 1995 at Fukuoka, about 100 km north of the present sampling location, suggesting a decrease in emissions of HT and CH3T from their sources for these 8-10 years. The decrease in HTO concentration would be attributed to the decrease of the bomb-produced tritium and to a regional characteristic of the sampling locations; Kumamoto showed lower tritium concentrations in rain than Fukuoka.
