Abundance and distribution of radioactive cesium-rich microparticles released from the Fukushima Daiichi Nuclear Power Plant into the environment

Deposition and Dispersion of Radio‐Cesium Released due to the Fukushima Nuclear Accident: 2. Sensitivity to Aerosol Microphysical Properties of Cs‐Bearing Microparticles (CsMPs)

“…The simulated activity fractions of the CsMPs to the total cumulative depositions for all the sensitivity tests are illustrated and compared against the observed values from the surface soil at 20 sites in Fukushima (Ikehara et al., 2020) in Figure 12. The simulated spatial distributions are shown in the top panels with the two combinations of sensitivity tests.…”

“…The simulated activity fractions of CsMPs to the total cumulative depositions were compared to those in the surface soil observed in Fukushima (Ikehara et al., 2020) for the first time. The observed activity fractions could have settled within the ranges of the simulated sensitivity tests for the locations under the influence of the type B CsMPs (near the F1NPP and NNW of the F1NPP).…”

“…The values are depicted where the simulated deposition exceeded 1 kBq m −2 . Bottom panel: The observed (O) activity fractions of CsMPs with measurement errors at the 20 sites in Fukushima based on a study conducted by Ikehara et al (2020) and ranges of the simulated (S) maximum and minimum activity fractions of CsMPs for all the sensitivity tests. 0.85%-16.2%), even though the emission during the events (0.475 PBq) was assumed to be 100% CsMPs.…”

“…The Fukushima Daiichi Nuclear Power Plant (F1NPP or FDNPP) accident released substantial amounts of fission products into the atmosphere (Chino et al., 2011; Hirao et al., 2013; Katata et al., 2015; Saunier et al., 2013; Stohl et al., 2012; Terada et al., 2020, 2012; Winiarek et al., 2014; Yumimoto et al., 2016). The contaminated air mass traveled over Japan and the radionuclides were deposited into and contaminated terrestrial ecosystems; this phenomenon was discovered by field measurements (Igarashi et al., 2015; Ikehara et al., 2020; NRA [Nuclear Regulation Authority], 2012; Oura et al., 2015; Sanada et al. 2014, 2018; Torii et al., 2012; Tsuruta et al., 2014, 2017, 2018, 2019) and has been investigated by numerical simulations (Kajino et al., 2018, 2019a; Morino et al, 2011, 2013; Nakajima et al., 2017; Sekiyama & Iwasaki, 2018; Sekiyama & Kajino, 2020; Saya et al., 2018; Sekiyama et al, 2015, 2017; Terada et al., 2020).…”

“…Recently, Ikehara et al. (2020) reported the activity fractions of CsMPs in the surface soil at 20 sites in the Fukushima prefecture, located 4.42–61.0 km from the F1NPP, which ranged from 1.63% to 80.2% of the total activity. As a result, we have observational evidence that the radioactivity of CsMPs was significant in the environment, and we can quantitatively compare those observational data with simulated CsMP deposition.…”