Characteristics of 129I and 127I distributions in the atmosphere

Atmospheric aerosols were collected by means of an Andersen sampler for 7 and 12 months in order to determine the particle size distributions of atmospheric 129I and 127I aerosols. The particle size distribution of 129I aerosols was rich in the fine mode and had a similar pattern to that of 127I aerosols. The median aerodynamic diameters were approximately 0.4 μm for both aerosol types. The coarse mode 129I and 127I aerosols were both assumed to be the result of resuspension from soil particles. Therefore, the fate of 129I in the atmosphere follows the behavior of stable 127I. The water soluble fraction of 127I in atmospheric aerosols was approximately 50%, and 10% or less of soluble 127I was in the form of iodate, IO3-. The particulate and gaseous 127I samples were also collected every 2 weeks for 9 months to determine the gas and particle distribution of 127I in the atmosphere, which varied over the collection period. The seasonal variation in particulate 127I concentrations seemed to be complementary with that for gaseous 127I in the atmosphere, and the gas-to-particle conversion of 127I was dependent on temperature. (author)