The present study estimated the release rate of 131I and 137Cs during March 2011 and showed the results of the sensitivity analysis of the release rate to the deposition parameters. To estimate the release rate, the method applied is based on a simple inverse method by combining the measured daily deposition of 131I and 137Cs with regional range atmospheric dispersion calculations.

The present study showed that the release rates were reasonably estimated by using the measured daily depositions. It was found that the dry deposition velocity had only minor significance on the estimated release rate, predominately as a result of the inherently small contribution to total deposition when wet deposition occurred. The scavenging coefficient, on the other hand, showed a substantial effect on the release rate estimation. A three times larger scavenging coefficient resulted in increases of 10 and 21 fold in the estimated release rate for 131I and 137Cs, respectively, at maximum. The uncertainties of the release rate estimated by the inverse method might be large when the plume is transported through the rainfall area. It can be suggested that a more realistic parameterization of wet deposition processes is needed to refine the release rate estimation from environmental data.

Acknowledgments This work was partly supported by JSPS KAKENHI grant number 24110002. We thank JMA and CRIEPI for the JRA-25/JCDAS dataset.

Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.


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