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Journal Articles

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

Dohi, Terumi; Omura, Yoshihito*; Yoshimura, Kazuya; Sasaki, Takayuki*; Fujiwara, Kenso; Kanaizuka, Seiichi*; Nakama, Shigeo; Iijima, Kazuki

PLOS ONE (Internet), 16(5), p.e0251828_1 - e0251828_16, 2021/05

https://doi.org/10.1371/journal.pone.0251828
 Times Cited Count：6 Percentile：41.49(Multidisciplinary Sciences)

Journal Articles

Radiocaesium activity concentrations in parmelioid lichens within a 60 km radius of the Fukushima Dai-ichi Nuclear Power Plant

Dohi, Terumi; Omura, Yoshihito*; Kashiwadani, Hiroyuki*; Fujiwara, Kenso; Sakamoto, Yoshiaki; Iijima, Kazuki

Journal of Environmental Radioactivity, 146, p.125 - 133, 2015/08

https://doi.org/10.1016/j.jenvrad.2015.04.013
 Times Cited Count：20 Percentile：52.45(Environmental Sciences)

Radiocaesium activity concentrations ($$^{134}$$Cs, $$^{137}$$Cs) were measured in parmelioid lichens collected within the Fukushima Prefecture approximately 2 y after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. A total of 44 samples consisting of nine species were collected at 16 points within a 60 km radius of the FDNPP. The activity concentration of $$^{134}$$Cs ranged from 4.6 to 1000 kBq kg$$^{-1}$$ and for $$^{137}$$Cs ranged from 7.6 to 1740 kBq kg$$^{-1}$$. A significant positive correlation was found between the $$^{137}$$Cs activity concentration in lichens and the $$^{137}$$Cs deposition density on soil, based on the calculated Spearman's rank correlation coefficients as $$r$$ = 0.90 ($$P$$ $$<$$ 0.01). The two dominant species, Flavoparmelia caperata and Parmotrema clavuliferum, showed strong positive correlations, for which the r values were calculated as 0.92 ($$P$$ $$<$$ 0.01) and 0.90 ($$P$$ $$<$$ 0.01) respectively. Therefore, they are suggested as biomonitoring species for levels of radiocaesium fallout within the Fukushima Prefecture.

Journal Articles

$$^{137}$$Cs concentrations in foliose lichens within Tsukuba-city as a reflection of radioactive fallout from the Fukushima Dai-ichi Nuclear Power Plant accident

Omura, Yoshihito*; Matsukura, Kimiyo*; Abe, Junichi*; Hosaka, Kentaro*; Tamaoki, Masanori*; Dohi, Terumi; Kakishima, Makoto*; Seaward, M. R. D.*

Journal of Environmental Radioactivity, 141, p.38 - 43, 2015/03

https://doi.org/10.1016/j.jenvrad.2014.11.014
 Times Cited Count：12 Percentile：35.16(Environmental Sciences)

$$^{137}$$Cs concentrations in ten species of foliose lichens collected within Tsukuba-city in August 2013 ranged from 1.7 to 35 kBq/kg. The relationships between $$^{137}$$Cs in two dominant species, Dirinaria applanata and Physcia orientalis, and the air dose rate ($$mu$$Sv/h) at the sampling sites were investigated. $$^{137}$$Cs in P. orientalis measured about 1 year after the Fukushima nuclear accident was correlated (r$$^{2}$$=0.80) more closely with the air dose rate than those measured after about 2 years (r$$^{2}$$=0.65), possibly demonstrating its continued value as a biomonitor to reflect ambient fall-out levels. In contrast, those of Dirinaria applanata were not correlated with the air dose rate in either year.

Journal Articles

Outline of Investigation for radiocaesium concentrations in lichens after Fukushima Dai-ichi Nuclear Power Plant accident

Dohi, Terumi; Omura, Yoshihito*; Kashiwadani, Hiroyuki*; Fujiwara, Kenso; Sakamoto, Yoshiaki; Iijima, Kazuki

Raiken, 18(1), p.11 - 13, 2014/12

no abstracts in English

Oral presentation

Concentration of radiocesium in lichens after Fukushima NPP accident

Dohi, Terumi; Omura, Yoshihito*; Kashiwadani, Hiroyuki; Sakamoto, Yoshiaki

no journal, , 

Most lichens grow on rocks and barks, and they are found in terrestrial ecosystems. We will present the radiocesium concentration in lichens sampled in Ibaraki and Fukushima Prefecture, etc. after the accident at Fukushima Daiichi Nuclear Power Station.

Oral presentation

Retention characteristics of radiocaesium in lichens and their applicability as fall-out indicator

Dohi, Terumi; Omura, Yoshihito*; Fujiwara, Kenso; Iijima, Kazuki

no journal, , 

Lichens are symbiotic organisms consisted of fungi and algae. A number of studies were carried out after the nuclear weapons tests and Chernobyl accident, and demonstrated that lichens were useful for indicator of radioactive fallout because they could take up large amount of radionuclides directly from their thallus due to lack of root system and retain them. However, in order to measure radiocaesium concentration in lichen, the lichen sample was collected from their habitat. Therefore, temporal change of radiocaesium concentration in same lichen individual has never reported. In addition, a retention of radiocaesium in lichens in Japan was unknown. The objective of this study is to investigate the temporal change of radiocaesium concentration in individual lichen. Lichen samples were parmelioid lichens which were grown on the trunk of Prunus spp. within Fukushima prefecture. The counting rate of surface of lichen was measured by using Geiger-Mueller (GM) survey meter with a lead collimator to evaluate the radiocaesium concentration. The contamination density in lichens increased from the initial measurement value after one year. It is considered that lichen may receive radiocaesium from stem flow including radiocaesium desorbed from canopy or stem.

Oral presentation

$$^{137}$$Cs in lichens after the Fukushima Nuclear Accident

Dohi, Terumi; Omura, Yoshihito*; Fujiwara, Kenso; Iijima, Kazuki

no journal, , 

Large quantity of radionuclides, including $$^{134}$$Cs and $$^{137}$$Cs, were released into the atmosphere caused by the Fukushima Dai-chi Nuclear Power Plant (FDNPP) accident on March 11, 2011. As lichens are known to be effective tools to monitor environmental radioelements in both time and space, lichen samples are expected to be used to examine and monitor radiocaesium fallout from FDNPP in Japan. The purpose of this study is to discuss the estimation of radiocaesium fallout in the ecosystem based on the following examinations using lichens. Fifty-eight samples including foliose and fruticose lichens were collected from northern to central Japan especially focusing on Fukushima Prefecture during 2012 and 2013. After correction for radioactive decay (on each sampling date), the detected radiocaesium concentrations ranged from 16.1 Bq kg$$^{-1}$$ (d.w.) to 510,000 Bq kg$$^{-1}$$ for $$^{134}$$Cs and from 33.8 to 880,000 Bq kg$$^{-1}$$ for $$^{137}$$Cs in lichens. $$^{137}$$Cs concentration in the lichen samples generally increased with increase in the amount of fallout estimated by the $$^{137}$$Cs deposition in soil. The positive correlation was supported between $$^{137}$$Cs in lichens collected from Fukushima Prefecture and $$^{137}$$Cs inventories on soil calculated by Inverse Distance Weighted with Spearman's rank correlation coefficient (0.90, p $$<$$ 0.01). The activity ratios of $$^{134}$$Cs and $$^{134}$$Cs for the lichen samples (${it n}$ = 44) collected within Fukushima Prefecture (decay corrected to March 11, 2011) were between 0.95$$pm$$0.04 and 1.08$$pm$$0.41. The ratios are consistent with those for radiocaesium derived from the FDNPP accident (reported as 0.89 to 1.2). The ratios obtained from lichen samples collected in outside of Fukushima Prefecture were 0.75$$pm$$0.23 to 1.48$$pm$$0.48. They were consistent with those from Fukushima. But one sample showing significantly small value, 0.48$$pm$$0.16, might be influenced by different origin from Fukushima.

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