One-year monitoring of airborne radionuclides in Wako, Japan, after the Fukushima Dai-ichi nuclear power plant accident in 2011

Copyright © 2012 by The Geochemical Society of Japan. atmosphere were evaluated to be 1.5 × 1017 Bq and 1.2 × 1016 Bq, respectively, from March 12 10:00† to April 6 0:00. Immediately after the announcement of the FDNPP accident, worldwide monitoring activities started. Major radionuclides such as 131I, 137Cs, and 134Cs were detected in Japan, e.g., at the monitoring stations in Chiba on March 15 (Amano et al., 2012) and in Fukuoka on March 17 (Momoshima et al., 2012). They were then transported with westerly winds to across the pacific and reached North American continent on March 15 (Diaz Leon et al., 2011; Zhang et al., 2011; Biegalski et al., 2012) and further reached to Europe on March 19–20 (Masson et al., 2011) despite dispersion and deposition along the route of the radioactive plumes. The plumes also arrived at nearby Asian countries such as Taiwan (Huh et al., 2012) on March 25, Vietnam (Long et al., 2012) on March 27, and Korea (Kim et al., 2012) on March 28. Huh et al. (2012) suggested that the radionuclides were transported to Taiwan and its vicinity via two pathways at different altitudes: one was transported in the free troposphere by the prevailing westerly winds around the globe, and the other was transported in the planetary boundary layer by the northeast monsoon wind directly to Taiwan. One-year monitoring of airborne radionuclides in Wako, Japan, after the Fukushima Dai-ichi nuclear power plant accident in 2011