Estimate of Fukushima-derived radiocaesium in the North Pacific Ocean in summer 2012

Abstract

Distributions of radiocaesium (134Cs and 137Cs) derived from the Tokyo Electric Power Company (TEPCO) Fukushima Dai-ichi Nuclear Power Plant (FNPP1) accident in the North Pacific Ocean in the summer of 2012 were investigated. We have estimated the radiocaesium inventory in the surface layer using the optimal interpolation analysis and the subducted amount into the central mode water (CMW) by using vertical profiles of FNPP1-134Cs and mass balance analysis as the first approach. The inventory of the 134Cs in the surface layer in the North Pacific Ocean in August–December 2012 was estimated at 5.1 ± 0.9 PBq on 1 October 2012, which corresponds to 8.6 ± 1.5 PBq when it was decay corrected to the date of the FNPP1 accident, 11 March 2011. It was revealed that 56 ± 10% of the released 134Cs into the North Pacific Ocean, which was estimated at 15.3 ± 2.6 PBq, transported eastward in the surface layer in 2012. The amount of 134Cs subducted in the CMW was estimated to be 2.5 ± 0.9 PBq based on the mass balance among the three domains of the surface layer, subtropical mode water, and CMW.Electronic supplementary materialThe online version of this article (10.1007/s10967-018-6249-7) contains supplementary material, which is available to authorized users.

Reproducibility of Surface Wind and Tracer Transport Simulations over Complex Terrain Using 5-, 3-, and 1-km-Grid Models

“…The tracer (Cs-137) transport simulations were performed by an offline Eulerian regional air quality model, which was driven by the 5-, 3-, and 1-km-grid meteorological analyses mentioned above. The offline Eulerian regional air quality model was originally developed by Kajino et al (2012Kajino et al ( , 2019a for nonradioactive aerosol simulations and has subsequently been used for Fukushima nuclear pollutant simulations by Adachi et al (2013), Sekiyama et al (2015Sekiyama et al ( , 2017, Kajino et al (2016Kajino et al ( , 2018Kajino et al ( , 2019b, Inomata et al (2018), Kitayama et al (2018), Mathieu et al (2018), Sato et al (2018), Sekiyama and Iwasaki (2018), and Iwasaki et al (2019).…”