Thirty-year simulation of environmental fate of 137Cs in the Abukuma River basin considering the characteristics of 137Cs behavior in land uses

Tsubasa Ikenoue; Hikari Shimadera; Takahiro Nakanishi; Akira Kondo

doi:10.1016/j.scitotenv.2023.162846

Thirty-year simulation of environmental fate of ¹³⁷Cs in the Abukuma River basin considering the characteristics of ¹³⁷Cs behavior in land uses

Sci Total Environ. 2023 Jun 10:876:162846. doi: 10.1016/j.scitotenv.2023.162846. Epub 2023 Mar 15.

Authors

Tsubasa Ikenoue¹, Hikari Shimadera², Takahiro Nakanishi³, Akira Kondo²

Affiliations

¹ Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan; Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan. Electronic address: ikenoue.tsubasa@jaea.go.jp.
² Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
³ Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.

PMID: 36924964
DOI: 10.1016/j.scitotenv.2023.162846

Abstract

The Fukushima Daiichi Nuclear Power Plant accident caused a radioactive contamination of deposited radionuclides, including ¹³⁷Cs, on the land surface. Cesium-137 deposited on the land surface was strongly adsorbed on soil particles and was then washed off through soil erosion. Trends of temporal variation of ¹³⁷Cs wash-off varied greatly depending on land use. Therefore, it is important to reflect the characteristics of ¹³⁷Cs migration processes in each land use to clarify the long-term fate of ¹³⁷Cs. In this study, a 30-year simulation of environmental fate of ¹³⁷Cs was conducted using a distributed radiocesium prediction model, taking into account the characteristics of the ¹³⁷Cs behavior in each land use. Overall, in the Abukuma River basin, the ¹³⁷Cs transported into the ocean for 30 years was estimated to correspond to 4.6 % of the initial deposition in the basin, and the effective half-life of ¹³⁷Cs deposited in the basin was estimated to be 3.7 years shorter (by 11.6 %) than its physical half-life. These results suggested that ¹³⁷Cs deposited from the accident could still remain for decades. Based on the analysis of the ¹³⁷Cs behavior in land use, in 2011, the contribution of ¹³⁷Cs export to the ocean from urban lands was estimated to correspond to 70 % of the total ¹³⁷Cs export. Meanwhile, from 2012 to 2040, the contribution of ¹³⁷Cs export from agricultural lands was estimated to correspond to 75 % of the total ¹³⁷Cs export. The reduction ratios excluding radioactive decay of ¹³⁷Cs remained in areas with and without human activities for 30 years after the accident, defined as the ratios of the total outflow to the initial deposition, were estimated to be 11.5 %-17.7 % and 0.4 %-1.4 %, respectively. These results suggested that human activities enhance the reduction of ¹³⁷Cs remaining in land in the past and future.

Keywords: (137)Cs transport; Fukushima nuclear accident; Land use; Long-term simulation; Sediment transport.