Tritium concentrations in atmospheric water vapour, hydrogen and hydrocarbons in Fukuoka

Tritium concentrations of tritiated water vapor (HTO), tritiated hydrogen (HT) and tritiated hydrocarbons (CH3T) in the atmosphere in Fukuoka were measured once a week from 1984 to the present to evaluate the present background levels of atmospheric tritium. Atmospheric HTO concentration varies within a wide range from 5.6 to 61 mBq/m3-air or from 0.8 to 3.2 Bq/L-H2O. HTO concentrations expressed in pCI/m3; they are higher in summer and lower in winter. On the other hand, HT and CH3T concentrations generally show no seasonal variation with almost constant values of 26-70 mBq/m3 and 6.7-34 mBq/m3, respectively. Annual averaged values of the specific activities written in tritium units (TU) are about 16, 9 x 105 and 4 x 104 for HTO, HT and C3T, respectively. The results obviously indicate that not only HTO but also HT should be considered in estimating the radiation effect of tritium on human beings. (author)