EGU21-13886, updated on 04 Mar 2021
https://doi.org/10.5194/egusphere-egu21-13886
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Radiocesium-bearing microparticles cause a large variation in 137Cs concentration in the aquatic insect, Stenopsyche marmorata, in the Ota River, Fukushima, Japan

Yumiko Ishii1, Hikaru Miura2, Jaeick Jo1, Hideki Tsuji1, Rie Saito3, Kazuma Koarai4, and Seiji Hayashi1
Yumiko Ishii et al.
  • 1National Institute for Environmental Studies, Japan (ishii.yumiko@nies.go.jp)
  • 2Central Research Institute of Electric Power Industry, Japan
  • 3Fukushima Prefectural Centre for Environmental Creation, Japan
  • 4Japan Atomic Energy Agency, Japan

Radiocesium-bearing microparticles (CsMPs), which are insoluble, Cs-bearing, silicate glass particles, have been found in terrestrial and freshwater environments after the TEPCO's Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in Japan. Few studies have investigated the distribution of CsMPs in freshwater ecosystems and their uptake by aquatic organisms. In this study, we determined the uptake of CsMPs by aquatic insects in the Ota River in Fukushima. Although aquatic insects are usually measured for radioactivity in bulk samples of several tens of insects, we investigated the variability of 137Cs concentration in individual aquatic insects, and the influence of CsMPs on them. Measurement of 137Cs concentrations in detritivorous caddisfly (Stenopsyche marmorata) larvae and carnivorous dragonfly larvae showed that 3 of 47 caddisfly larvae had considerably higher radioactivity, whereas no such outliers were observed in dragonfly larvae. These caddisfly larvae were confirmed to contain the CsMPs emitted from Unit 2 of the FDNPP, using a scanning electron microscope and radioactivity measurements after isolation of the CsMPs. CsMPs were also found in potential food sources of caddisfly larvae, such as periphyton and drifting particulate organic matter, indicating that larvae may ingest CsMPs along with food particles of similar size. Our study demonstrated that CsMPs could be taken up by aquatic insects and possibly by the fish consuming them. The existence of CsMPs can result in sporadic, extremely high 137Cs concentrations, and large variations in samples, and consequently obscure the actual transfer and temporal trends of 137Cs in freshwater ecosystems.

How to cite: Ishii, Y., Miura, H., Jo, J., Tsuji, H., Saito, R., Koarai, K., and Hayashi, S.: Radiocesium-bearing microparticles cause a large variation in 137Cs concentration in the aquatic insect, Stenopsyche marmorata, in the Ota River, Fukushima, Japan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13886, https://doi.org/10.5194/egusphere-egu21-13886, 2021.

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