In this study, we estimated the total releases of the radioac- tive isotopes 133Xe and 137Cs as well as their temporal emis- sion patterns from the damaged Fukushima Dai-ichi nuclear power plant (FD-NPP) in March and April 2011. The es- timate is based on an inverse modeling method, using the transport model FLEXPART and a large number of avail- able concentration and deposition measurements in Japan, North America, Europe, and a few other locations. De- spite the significant uncertainties in simulations as well as measurements, the inversion method was able to produce
(UNSCEAR, 2000a). That value is exceeded by deposition from FD-NPP over large parts of Honshu Island and the west- ern Pacific Ocean. However, deposition of FD-NPP 137Cs emissions over other parts of Asia, North America and Eu- rope is minor compared to this pre-existing background.
To determine the deposition amounts in Japan and other regions, we combined our gridded accumulated deposition
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