自然環境における²²²Rn, ²²⁰Rnおよびそれらの短半減期娘核種の濃度

抄録

Concentrations of ²²²Rn, ²²⁰Rn and their daughter products in the atmospheric air have been measured at various locations and altitudes. The results are as follows: (1) Daily geometric mean value of ²²²Rn daughters on the campus was 91.0pCi·m^-3 and the concentrations observed in the daytime, nighttime and all day showed logarithmic normal distributions. (2) The maximum concentration of ²²²Rn appeared between 600 and 800 hours, and the minimum in the afternoon through the year. (3) A seasonal variation of ²²²Rn daughters with winter maximum and summer minimum was obtained on the campus. (4) Annual variation for 13 years was not found clearly. (5) The concentrations of ²²²Rn in the outdoor air differ from place to place, and it amounted from 10 to 1370pCi m^-3 at different environments. (6) The concentration of ²²⁰Rn decreased rapidly with altitude and the inverse correlation was observed between concentration of ²²⁰Rn and the wind speed near the ground.