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Update:November 14, 2018

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Radiocesium concentrations in wild zenmai (Osmunda japonica) and fuki (Petasites japonicus)


Article title

〔1〕 The transfer of radiocesium released in the 2011 Fukushima Daiichi Nuclear Power Station accident to leaves of wild Osmunda japonica, an edible fern

〔2〕 The transfer of radiocesium released in the 2011 Fukushima Daiichi Nuclear Power Station accident to petioles of wild butterbur (Petasites japonicus)

Author (affiliation)

〔1〕 Yoshiyuki Kiyono (a), Masabumi Komatsu (b), Akio Akama (c), Toshiya Matsuura (d), Masaru Hiroi (e), Munehiko Iwaya (f), Takashi Futamoto (f)
〔2〕 Yoshiyuki Kiyono (a), Akio Akama (c), Munehiko Iwaya (f), Yukio Yoshida (f)

(a) Department of Plant Ecology, FFPRI, Tsukuba, Ibaraki, Japan.
(b) Department of Mushroom Science and Forest Microbiology, FFPRI, Tsukuba, Ibaraki, Japan.

(c) Center of Forest Restoration and Radioecology, FFPRI, Tsukuba, Ibaraki, Japan.

(d) Department of Forest Management, FFPRI, Tsukuba, Ibaraki, Japan.

(e) Koriyama Women’s University, Koriyama, Fukushima, Japan.

(f) Japan Special Forest Product Promotion Association, Chiyoda, Tokyo, Japan.

Publication Journal

〔1〕 Bulletin of FFPRI, Vol.17No.3(No.447), 217-232, September 2018

〔2〕 Bulletin of FFPRI, Vol.17No.3(No.447), 249-257, September 2018

Content introduction

In 2011, the Fukushima Daiichi Nuclear Power Station accident caused radiocesium pollution in local forests. To date, 10 or more species of edible wild plants have been restricted from shipping. To evaluate the potential of using regional wild vegetable resources in the future, we collected wild zenmai (Osmunda japonica) and fuki (wild butterbur; Petasites japonicus) from more than 100 locations in the Fukushima prefecture and examined the factors influencing radiocesium concentrations in the plant bodies. The survey revealed that 81% of zenmai and 23% of fuki contained amounts equal or more than the reference value of the shipment limit for radiocesium (total value of cesium 134 and cesium 137 concentrations per kg of fresh plant material is 100 Becquerel), which confirmed that the shipment restriction is still required in the municipalities included in the surveyed sites. We observed that a) radiocesium concentrations in plant bodies of both zenmai and fuki were correlated with cesium concentrations in litter accumulated on the ground; b) cesium concentrations in fuki plant bodies were also correlated with cesium concentrations in the soil; and c) cesium concentrations increased by several magnitudes from spring to summer in some cases. In summer, the amount of radiocesium absorbed by roots increases because the decomposition of dead organic matter occurs relatively easily. Consequently, in the short term, edible wild plants could be more susceptible to environmental radiocesium concentration increase because of their relatively smaller sizes and more rapid metabolism compared with trees. In addition, we found that radiocesium concentration in the plant bodies largely fluctuated due to factors other than the radiocesium concentrations in litter and soil. One of the reasons for this could be the timing of the growth stages. For example, the sprouting times of wild plants are unequal, unlike those of cultivated plants.

Our results indicated that it is necessary to pay attention to a seasonal rise in cesium concentration in edible wild plants collected in the summer. We plan to continue examining other factors that influence cesium concentrations in edible wild plants.

Photograph: Sprout of zenmai
Photograph: Sprout of zenmai.