EGU2020-12477, updated on 20 Jan 2021
https://doi.org/10.5194/egusphere-egu2020-12477
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Plot-scale wash-off of Cesium-137 and Strontium-90 after three decades since the Chernobyl accident

Yoshifumi Wakiyama1, Yasunori Igarashi1, Yuichi Onda2, Dmitry Samoilov3, Hlib Lisovy4, Volodymyr Demianovych3, Gennady Laptev4, Alexei Konoplev1, Kenji Nanba1,5, and Serhii Kirieiev3
Yoshifumi Wakiyama et al.
  • 1Fukushima University, Institute of Environmental Radioactivity, Fukushima, Japan (wakiyama@ipc.fukushima-u.ac.jp)
  • 2Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, Japan
  • 3Chernobyl Ecocentre, State Agency of Ukraine on Exclusion Zone Management, Ukraine
  • 4Ukrainian Hydrometeorological Institute, Ukraine
  • 5Faculty of Symbiotic Systems Science, Fukushima University, Japan

Long-term behaviors of Cesium-137 (137Cs) and Strontium-90 (90Sr) have been of great interest in Chernobyl and its downstream area. This study presents plot-scale observations of 137Cs and 90Sr wash-off in the Chernobyl exclusion zone since 2018 to date. Runoff plots were established on a pine forest in the Kopachi area (PF-KP), an abandoned farmland in the Korogod area (AF-KR) and a post wild fire territory in the Red Forest (WF-RF) in December 2017. Each runoff plot consists of eroding surface of 22.13 m length and 5 m width, a 30° V-notch weir with water level sensor for monitoring surface runoff and tanks for collecting runoff water and sediments. Since February 2018, runoff water and sediment samples trapped in the weir and tanks have been collected after rainfall events and analyzed for particulate 137Cs concentration, dissolved 137Cs concentration, and dissolved 90Sr concentration. Analyses of samples in 2, 4, and 3 wash-off events were completed for PF-KP, AF-KR, and WF-RF, respectively. The ash/litter on soil surface, soil of 0-1 cm depth, soil of 1-2 cm depth, and soil of 2-3 cm depth were sampled with a scraper plate and subject to measurements of 137Cs and 90Sr concentrations.  Total volume of surface runoff from PF-KP, AF-KR, and WF-RF were 0.97, 0.73, and 3.2 mm, respectively. Total sediment discharge from PF-KP, AF-KR, and WF-RF were 0.29, 0.015, 1.7 g m-2, respectively. The runoff and sediment discharge from PF-KP and WF-RF were mainly observed in summer and attributed to severe water repellency of the surface soils. Total particulate 137Cs wash-off from PF-KP, AF-KR, and WF-RF were 51, 0.082, 270 Bq m-2, respectively. Total dissolved 137Cs wash-off from PF-KP, AF-KR, and WF-RF were 7.4, 0.024, 9.8 Bq m-2, respectively. Total dissolved 90Sr wash-off from PF-KP, AF-KR, and WF-RF were 55, 0.31, 230 Bq m-2, respectively.  These results indicate that wild fire enhances surface runoff and sediment yield and result in greater wash-off of 137Cs and 90Sr. In comparisons between PF-KP and WF-RF, apparent Kd value for 137Cs at WF-RF was higher than at PF-KP. Ratio of dissolved 137Cs and 90Sr concentration to those in ash/litter layer at PF-KP was lower than those of WF-RF. The dissolution of these radionuclides into runoff water appeared to be restrained in the post wild-fire site.

How to cite: Wakiyama, Y., Igarashi, Y., Onda, Y., Samoilov, D., Lisovy, H., Demianovych, V., Laptev, G., Konoplev, A., Nanba, K., and Kirieiev, S.: Plot-scale wash-off of Cesium-137 and Strontium-90 after three decades since the Chernobyl accident , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12477, https://doi.org/10.5194/egusphere-egu2020-12477, 2020

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