Effects of bark washing and epiphytic moss on 137Cs activity concentration in bark and stemflow in Japanese persimmon (Diospyros kaki Thunb.)

Publication date: November 2017
Source:Journal of Environmental Radioactivity, Volumes 178–179
Author(s): Mamoru Sato, Tsugiko Takase, Katsuhiko Yamaguchi
The effects of bark washing, and of epiphytic moss growing on the bark surfaces, on the ¹³⁷Cs activity concentrations in bark and stemflow samples were evaluated at two Japanese persimmon orchards located in Fukushima City and Date City, both approximately 60–65 km northwest of the Fukushima Dai-ichi nuclear power plant. The means of ¹³⁷Cs in stemflow captured by 1 g of sphagnum placed on the main trunks of washed and unwashed trees, and on sites with moss and with no moss growing on bark of the non-washed trees in Date City, were 0.37 Bq, 1.08Bq, 0.77 Bq and 0.52 Bq respectively. The ¹³⁷Cs was significantly lower in the washed bark and in the absence of moss at p = 0.00031 and p = 0.0443 by t-test respectively. The ¹³⁷Cs in directly-collected stemflow on the main trunks was significantly higher for the unwashed tree at 6.0 Bq L⁻¹ compared with the washed tree at 1.1 Bq L⁻¹ (p = 0.017 by Tukey's test). The extraction rate of dissolved ¹³⁷Cs with deionized water was 7.3% even after stirring for 40 h. These results indicate that the moss acts as reservoir of ¹³⁷Cs, and that bark-washing decontamination can reduce the additional ¹³⁷Cs supply from moss in subsequent years following the radioactive fallout.



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