Radiocesium contamination of the moss Hypnum plumaeforme caused by the Fukushima Dai-ichi Nuclear Power Plant accident

Abstract

We investigated ¹³⁴Cs and ¹³⁷Cs activity concentrations in the common Japanese moss species Hypnum plumaeforme collected from 32 sites within ca. 100 km radius of the Fukushima Dai-ichi Nuclear Power Plant. A total of 32 samples of H. plumaeforme were collected during the field surveys from November 2013 to September 2014. The maximum radiocesium activity concentrations in H. plumaeforme were 60.9 ± 1.8 kBq kg^-1 for ¹³⁴Cs and 123 ± 2.3 kBq kg^-1 for ¹³⁷Cs. The mean value for the ¹³⁴Cs/¹³⁷Cs was 1.17 ± 0.05, and the mean T_ag value was 0.09 ± 0.13. Positive correlations were obtained between total ¹³⁴Cs + ¹³⁷Cs activity concentrations in H. plumaeforme and the air dose rate with a correlation coefficient (r) of 0.55 (P = 0.001), and between ¹³⁷Cs activity concentration in H. plumaeforme and ¹³⁷Cs deposition density on soil with r of 0.55 (P = 0.001). These results suggest that the perennial moss species H. plumaeforme could be more suitable and useful as a qualitative indicator for the radiocesium pollution compared to vascular plants spreading over the lowlands including human habitation in Fukushima Prefecture.

Keywords: Contamination; Fukushima Dai-ichi Nuclear Power Plant accident; Hypnum plumaeforme; Radiocesium.