Estimates of seasonal uariations of ~(222)Rn from different origins by using the correlation between ~(222)Rn and ~(212)Pb concentrations in air

摘要

Continuous measurements of ~(222)Rn (T_(1/2) = 3.82 d) and ~(212)Pb (T_(1/2) = 10.6 h) concentrations in outdoor air were carried out in Tokyo from December 1993 to November 1996. Positive correlations were found in the relation between ~(222)Rn and ~(212)Pb concentrations. Using the intercept values obtained from the regression line, a new method is proposed to separate the seasonal variation of monthly mean ~(222)Rn concentration by its origin. The estimated concentration of ~(222)Rn originating from distant regions in 1994 agreed with the calculations by the long-range transport model, which verified the method reliability. The present method would be useful as a means to study the cause of the seasonal variations of ~(222)Rn concentration.