Concentration of 137Cs in atmospheric coarse and fine particles collected in Fukushima Prefecture

Concentration of 137 Cs in coarse and fine aerosol particles was observed in the atmosphere around Fukushima and Date Cities, Fukushima Prefecture from August 2012 to July 2013. Airborne particles were collected once every 2 weeks and separated at a 50 % cutoff diameter of 1.1 µm. The averages of total 137 Cs concentration in coarse and fine particles was 183 and 166 µBq m −3 for Fukushima and Date sites, respectively. The average ratio of coarse to fine particle concentrations was approximately 2:1 at both sites. The particle-size distribution of 137 Cs was different from that collected immediately after the accident.