Radioactivity of the atmospheric aerosols detected by CTBTO stations in Africa following the accident at the Fukushima Daiichi nuclear power plant

Abstract

Radionuclides from the reactor accident Fukushima Daiichi nuclear power plant were observed in the airborne aerosols at CTBT International Monitoring System (IMS) stations (MRP43, CMP13) in Africa. The maximum activity concentrations in the air measured in Mauritania were 186.44 10−6 Bq.m−3, 264.16 10−6 Bq.m−3 and 1269.94 10−6 Bq.m−3 for 134Cs, 137Cs and 131I respectively, and in Cameroon 16.42 10−6 Bq.m−3, 25.53 10−6 and 37.58 10−6 Bq.m−3 respectively for 134Cs, 137Cs and 131I. The activity ratio of 134Cs/137Cs is almost constant throughout the period of time relevant to this study due to their long half-lives of 30.2 years for 137Cs and 2.06 years for 134Cs. Whereas the 131I/137Cs activity ratio varies in time according to the radioactive decay with a half-live of 8.06 days for 131I and different removal rates of both radionuclides from the atmosphere during transport. The EMAC atmospheric chemistry-general circulation was used to simulate the emission and transport of the isotope 137Cs and map the deposition of the 137Cs deposition over Africa.