Radiocaesium accumulation capacity of epiphytic lichens and adjacent barks collected at the perimeter boundary site of the Fukushima Dai-ichi Nuclear Power Station

PLoS One. 2021 May 24;16(5):e0251828. doi: 10.1371/journal.pone.0251828. eCollection 2021.

Abstract

We investigated the radiocaesium content of nine epiphytic foliose lichens species and the adjacent barks of Zelkova serrata (Ulmaceae, "Japanese elm") and Cerasus sp. (Rosaceae, "Cherry tree") at the boundary of the Fukushima Dai-ichi Nuclear Power Station six years after the accident in 2011. Caesium-137 activities per unit area (the 137Cs-inventory) were determined to compare radiocaesium retentions of lichens (65 specimens) and barks (44 specimens) under the same growth conditions. The 137Cs-inventory of lichens collected from Zelkova serrata and Cerasus sp. were respectively 7.9- and 3.8-times greater than the adjacent barks. Furthermore, we examined the radiocaesium distribution within these samples using autoradiography and on the surfaces with an electron probe micro analyzer (EPMA). Autoradiographic results showed strong local spotting and heterogeneous distributions of radioactivity in both the lichen and bark samples, although the intensities were lower in the barks. The electron microscopy analysis demonstrated that particulates with similar sizes and compositions were distributed on the surfaces of the samples. We therefore concluded that the lichens and barks could capture fine particles, including radiocaesium particles. In addition, radioactivity was distributed more towards the inwards of the lichen samples than the peripheries. This suggests that lichen can retain 137Cs that is chemically immobilised in particulates intracellularly, unlike bark.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cesium Radioisotopes / chemistry
  • Cesium Radioisotopes / isolation & purification*
  • Fukushima Nuclear Accident
  • Humans
  • Lichens / chemistry
  • Lichens / radiation effects
  • Nuclear Power Plants*
  • Plant Bark / chemistry
  • Plant Bark / radiation effects
  • Radiation Monitoring*
  • Ulmaceae / chemistry
  • Ulmaceae / radiation effects
  • Water Pollutants, Radioactive / adverse effects
  • Water Pollutants, Radioactive / isolation & purification

Substances

  • Cesium Radioisotopes
  • Water Pollutants, Radioactive
  • Cesium-137

Grants and funding

This work was financially supported by an internal budget of Japan Atomic Energy Agency for the Fukushima reconstruction research activity. This research was supported by the MEXT Nuclear Energy S&T and Human Resource Development Project through Concentrating Wisdom Grant Number JPMX15D15664655 operated by KI, and Grant-in-Aid for Challenging Exploratory Research of JSPS (no.16K12627) operated by TD. These funders did not play a role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. They provided only financial support in the research materials in this study. Nuclear Engineering Co., Ltd. employed SK, this commercial affiliation did not play a role in this study.