Atmospheric concentrations of212Pb were observed with aerosol samples intermittently from June, 1999, at Kawasaki. The atmospheric concentration of212Pb showed an unusual and temporal increase in the period from late August to early September, 2000, being inferred to be attributed partly to the212Pb fallout originating from the 2000 eruption of Miyake-jima volcano, Japan.
We have developed an air monitor for alpha-emitting particles released to the atmosphere at an accident of nuclear reprocessing plant. Selection of a suitable filter for the monitor is considerably important in order to achieve the high-sensitive measurement of radioactive concentration. We have examined surface collection efficiencies and pressure drops for the various filters that are commercially available in Japan. It was found that the PTFE membrane filter with backing had superior performance to the others, that is, a high surface collection efficiency and low pressure drop.