The activity size distributions of 134Cs and 137Cs in aerosols measured from the first sample (LPI-AIST-1) reside mostly in the accumulation mode size range and showed the double peak structure. These activity size distributions almost overlapped with the mass size distribution of non-sea-salt sulfate aerosol. We further conducted the successive extraction experiment of radiocesium from the aerosol deposits on the aluminum sheet substrate (8th stage of LPI-AIST-1, 0.50.7 µm in aerodynamic diameter) with water, 0.1M HCl, and 1M HCl. In contrast to the relatively insoluble property of Chernobyl radionuclides, those in in the accumulation mode aerosols collected at Tsukuba are completely water-soluble (100%).
From the results, we regard that sulfate is the main transport medium of these radionuclides, and re-suspended soil particles that attached radionuclides were not the major airborne radioactive substances by the end of May, 2011 (Kaneyasu et al. ES&T, 2012). The changes in the activity size distributions of radiocesium and the mass size distribution of major aerosol components for aerosol samples collected by the end of August, 2011, will further be discussed in the presentation.