Deposition of gamma-emitting nuclides in Japan after the reactor-IV accident at Chernobyl'

The wet and dry deposition of gamma-emitting nuclides are presented for Tsukuba and eleven stations in Japan following the nuclear reactor accident at Chernobyl'. In Japan fallout from the reactor at Chernobyl' was first detected on May 3, 1986, a week after the accident. Abruptly high radioactive deposition, which mainly consists of¹³¹I,¹³²I,¹⁰³Ru,¹³⁷Cs and¹³⁴Cs, was observed in early May. The cumulative amount of¹³¹I,¹⁰³Ru and¹³⁷Cs in May at Tsukuba were 5854±838 Bq·m^–2, 364±54 Bq·m^–2 and 130±26 Bq·m^–2 (decay was corrected to April 26), respectively. The monthly¹³⁷Cs deposition in May corresponds to 2.5% of the cumulative¹³⁷Cs deposition during the period from 1960 through 1982. Most of the Chernobyl' radioactivities, especially¹³¹I, are scavenged from the atmosphere by the wet removal process.