This article is an Advance Online Publication of the authors’ corrected proof. Note that minor changes may be made before final version publication.

The Horticulture Journal Preview e Japanese Society for doi: 10.2503/hortj.MI-132 JSHS Horticultural Science http://www.jshs.jp/

Translocation of Radiocesium Released by the Fukushima Daiichi Nuclear Power Plant Accident in Japanese Chestnut and Chestnut Weevil Larvae

Yoshito Sasaki*, Yasuo Ishii, Hironobu Abe, Katsuaki Mitachi, Takayoshi Watanabe and Tadafumi Niizato

Fukushima Environmental Safety Center, Japan Atomic Energy Agency, Fukushima 963-7700, Japan

To examine the translocation of radiocesium scattered by the Fukushima Daiichi nuclear power plant accident that occurred in March 2011 to the Japanese chestnut, we investigated the autoradiography and radiocesium concentration in each part of Japanese chestnuts. The Japanese chestnut fruit has a thin skin between the kernel (cotyledons) and shell; the kernel of the fruit is edible. The 137Cs concentration in each part of the fruit was found to be almost the same at about 1.0 × 104 Bq·kg−1 DW, as well as leaves. The radiocesium concentration in chestnut weevil larvae found on the fruit was approximately one-seventh of that in the kernel.

Key Words: cesium, chestnut, fruit, Fukushima Daiichi, .

trunks. The chestnut fruit is a forest product eaten in Introduction Europe, China, and Japan (Korel and Balaban, 2009). A large amount of radionuclides was released into After the CNPP accident, it was reported that chestnut the environment by the accident at the Fukushima fruits grown in Italy had a relatively high radiocesium Daiichi nuclear power plant (FDNPP) of the Tokyo transfer rate (Monte et al., 1990). Radiocesium released Electric Power Company, as a result of the Great East in the FDNPP accident detected from Japanese chest- Japan Earthquake on March 11, 2011 (Chino et al., nuts ( Sieb. et Zucc.) (Ministry of 2011). Radionuclides with short half-lives, such as 131I Agriculture, Forestry and Fisheries, http://www. (8.04 days half-life) decayed in a few months, whereas maff.go.jp/j/kanbo/joho/saigai/s_chosa/H25gaiyo.html, many of those with relatively long half-lives, such as January 4, 2016). Kusaba et al. (2015) also reported that 134Cs (2.06 years half-life) and 137Cs (30.2 years half- the radiocesium concentration of chestnut fruit has de- life), are still present in the environment. Potassium and creased year by year. We examined radiocesium con- cesium are congeners; cesium behavior is similar to that centrations in each part of the fruit of the Japanese of potassium, and these elements are easily incorpo- chestnut and the ratio of radiocesium concentrations in rated into plants. If a plant containing radiocesium is in- soil and chestnut fruit [i.e., the transfer factor (TF)]. gested by humans, then there is a possibility of internal Radiocesium transfer from chestnut fruit to insects exposure. Mushrooms, wild vegetables, and fruits, as parasitic to the fruit was also investigated in the study. well as wood, are important forest products. Elucidation It was reported that there was a decrease in the survival of radiocesium translocation to these products could re- rate and high malformation rate in aphids (Akimoto, duce exposure. At the time of the Chernobyl nuclear 2014) and pale grass blue butterfly (Hiyama et al., power plant (CNPP) accident (April 26, 1986), because 2012) in radiocesium-contaminated areas due to the the deciduous trees were budding, radioactive materials FDNPP accident. The web spider in the class of arach- were caught in the tree canopy. At the time of the nida (Ayabe et al., 2014) and aquatic insects FDNPP accident, because the deciduous trees were in a (Yoshimura and Akama, 2014) also incorporated radio- dormant stage and their leaves were falling, released cesium. However, little is known about the transfer of radioactive material was caught in the branches and radiocesium from food (primary producers) to insects (consumer) in the food web. The chestnut weevil [sci- entific name: Curculio sikkimensis Heller (Coleoptera: Received; November 11, 2015. Accepted; May 17, 2016. First Published Online in J-STAGE on August 11, 2016. Curculionidae)] is a parasitic found on the chest- * Corresponding author (E-mail: [email protected]). nut fruit. Chestnut weevils lay eggs in the fruit of the

© 2016 The Japanese Society for Horticultural Science (JSHS), All rights reserved. 2 Y. Sasaki, Y. Ishii, H. Abe, K. Mitachi, T. Watanabe and T. Niizato chestnut, and the hatched larvae feed on the chestnut crispula Blume), and Japanese Chestnut (Castanea fruit. After the mature larvae exit from the fruit, they crenata Siebold et Zucc), as well as partially distributed burrow into the soil and grow in the soil until they be- Japanese red pine (Pinus densiflora Sieb. et Zucc.) in come adult worms (Imamura et al., 2004). The chestnut the ridges and forest edge. The average tree height and weevil larvae are used as fishing bait and a commodity tree density of the canopy layer are 11.6 m and 9.2 trees (Umeya, 2004). Since the larvae that crawl out of the per 100 m2, respectively. About 5% of the forest floor is chestnut fruit have eaten only the fruit prior to that covered by Dwarf bamboo (Sasa nipponica Makino et point, it is easy to evaluate the transition rate of radio- Shibata). The thickness of the litter layer is roughly cesium to the larvae from the chestnut fruit. We also ex- 1 cm, and the soil is classified as a brown forest soil amined the radiocesium concentration in the chestnut (IUSS Working Group WRB, 2015). The samples of the weevil larvae. Japanese chestnut tree (bark and wood), leaves and fruits were collected from the same tree. The sample Materials and Methods tree had a height of 12.3 m, a diameter at breast height Sampling of 21.8 cm, and a canopy projection area of 11.5 m2. Samples were collected in Yamakiya Kawamata Chestnut fruits were separated from the ripe spiny cu- Date-gun in Fukushima Prefecture (Fig. 1). The study pule and dropped to the ground in October 2013. Fallen area is located in a mountain forest on a crest slope leaves were collected immediately after defoliation in (Tamura and Takeuchi, 1980) of a valley-head area that November 2013. Chestnut tree samples were obtained faces west, and does not face the FDNPP. The study from branches of the canopy at a height of approxi- area is a mixed forest mainly composed of Konara oak mately 7 m in February 2014 (Sasaki et al., 2016). (Quercus serrata Murray), Mizunara oak (Quercus Fruits were dried to a constant weight at 90°C, and

Fig. 2. Picture of chestnut weevil larvae (Curculio sikkimensis). A shows chestnut weevil larvae exiting the chestnut fruit. B shows the chestnut weevil larvae.

Fig. 1. Air dose rates (μSv·h−1) at 1 m above the ground surface on Fig. 3. Distribution of radioactivity in the fruits and leaves of April 29, 2011 (http://ramap.jmc.or.jp/map/eng/map.html) and Japanese chestnuts. Optical photograph (A, C, and E) and auto- location of the sampling site in the Yamakiya area, Kawamata radiograph image (B, D, and F). A and B are the outer shell of town, Fukushima Prefecture. The symbol ▲ indicates the sam- the Japanese chestnut. C and D are the inner skin and kernel. E pling site. The GPS coordinates of the field are 37°35'17.7"N, and F are the leaves. The image toward the left in A and B is 140°42'08.3"E. FDNPP indicates the Fukushima Daiichi the inside of the shell and the one toward the right is the outside nuclear power plant. of the shell. Hort. J. Preview 3 the outer shell, inner skin, and kernel (cotyledons) were laser scanner (Typhoon FLA7000; GE Healthcare, separated. Each part of the fruit was placed in an 80 mL United Kingdom). capacity polystyrene container (V7 container, sanoya- sangyo, Japan) and subjected to radiocesium concentra- Transfer factor (TF) from the soil to chestnut tion measurements. Chestnut litter leaves were dried to Transition of radiocesium to plants was evaluated a constant weight at 90°C. The dried samples were using TF. TF was expressed by the ratio of the radio- placed in V7 containers to measure radiocesium con- cesium concentration in the fresh weight of the plant centrations. The soil surface at 5 cm depth was col- to the radiocesium concentration in the dry weight of lected in one location using a shallow soil sampler soil at a depth of 20 cm from the surface (Bq·kg−1)

(sampling tube ϕ110 × 50 mm) at the base on the down- (International Atomic Energy Agency, 2010). Cp repre- stream side of the chestnut tree. Collected soil was sented the radiocesium concentration of the plant −1 dried to a constant weight at 105°C. After the soil was [Bq·kg FWplant], and Cn represented the radiocesium −1 evenly mixed, it was placed in a 100 mL polystyrene concentration of the soil [Bq·kg DWsoil-20 cm depth]. container (U8 container, Umano Kagaku Youki, Japan) (2) and subjected to radiocesium concentration measure- Cp = TF × C n ment. Collected chestnuts were placed at room tempera- Radiocesium concentration in soil at a depth of 20 cm ture for about a month. Chestnut weevil larvae were was one-quarter of the average radiocesium concentra- collected after they crawled out of the chestnut fruit tion in soil at a depth of 5 cm. Radiocesium concentra- (Fig. 2). Collected larvae were dried to a constant tion in the fresh weight of chestnut was calculated using weight at 90°C and then placed on a 0.45 μm pore size the moisture content of the chestnut fruit. membrane filter (HVLP4700; Merk Millipore, MA, Results and Discussion USA) with a diameter of 47 mm to measure radiocesi- um concentrations. The moisture content percentage (u) The results of autoradiography of the fruits and was determined by equation (1), where Wf represented leaves are shown in Figure 3. The radiocesium was uni- fresh weight and Wd represented dry weight. formly distributed in the entire shell, as shown in Figure 3A and B. Fallen leaves were collected immediately (1) u = Wf − W d /Wf after defoliation. The radiocesium in the skin and kernel peeled off the shell of the fruit was relatively more dis- tributed at the central portion, and the possible reason Measurement of radiocesium concentration for this is that a relatively large amount of nutrients ac- Radiocesium concentrations were measured using a cumulat in the central portion of the kernel (cotyledon) n-type high-purity Ge-detector (GMX40P4-76 germani- which is a nutrient storage organ (Fig. 3C, D). The re- um detector; Seiko EG&G ORTEC, Japan) with 40% sults of autoradiography of the leaves showed that the relative efficiency. Gamma-ray emissions at energies of amount of radiocesium at the midrib was higher than at 604.7 keV (134Cs), 661.7 keV (137Cs) were measured. the lamina (Fig. 3E, F). Since radiocesium was detected For the pulse-height analysis, a mulch channel analyzer in the veins, which are one of the routes of water and (MCA7600; Seiko EG&G ORTEC) was used in line nutrient passage in plants, there was a possibility that with the spectrum analysis software (Gamma Studio; radiocesium was translocated in the plant. Seiko EG&G ORTEC). Efficiency calibration was car- Radiocesium concentrations in the fruit, stem (bark ried out with a multiple gamma-ray emitting standard and wood), leaves, and larvae of the chestnut weevil source (including 10 nuclides) packed in the same type (billbug larvae) are shown in Table 1. The radiocesium of vessel (Eckert & Ziegler Isotope Products, CA, concentrations were nearly identical in each part of the USA) or a plastic disc which was the same active area fruit, shell, skin, and kernel, as well as leaves. This re- (φ 42 mm) as the membrane filter (Eckert & Ziegler sult was consistent with the results of autoradiography. Nuclitec GmbH, Germany). The decay of radiocesium Kusaba et al. (2015) also reported that the radiocesium was corrected on the dates of sampling of chestnut fruit. concentration of chestnut nuts (kernel and thin skin), Each analysis sample consisted of about fifteen chest- shells, burs, and current shoots were almost the same. nuts. Each analysis sample consisted of fourteen chest- The total amount of radiocesium was highest in the ker- nuts, weevil larvae. Due to the poor harvest, chestnut nel, which accounts for most of the fruit (Fig. 4). fruit was not harvested in 2014. The radiocesium concentration in the chestnut weevil larvae was about one-seventh that of the kernel, which Autoradiography measurement is eaten by the larvae. Ayabe et al. (2014) reported that For the autoradiography measurements, the sample a relatively high concentration of radiocesium was was covered by a thin polyvinylidene chloride film. detected in some large spiders. This fact indicated that After four days of exposure using an imaging plate radiocesium was transferred to the web spider, which (BAS-IP MS 2040; Fuji Film, Japan) with a pixel size is a secondary consumer in the food web. Our results of 100 μm, the autoradiograph image was scanned by a showed that radiocesium was transferred from produc- 4 Table 1. Radiocesium concentrationsY. Sasaki, Y. Ishii, in each H. partAbe, of K. the Mitachi, Japanese T. Watanabechestnut fruit and and T. Niizato tree, soil, and billbug larvae.

Table 1. Radiocesium concentrations in each part of the Japanese chestnut fruit and tree, soil, and billbug larvae.

Sampling date 134Cs concentration (Bq·kg−1 DW) 137Cs concentration (Bq·kg−1 DW) Shell Oct. 2013 (4.98 ± 0.18)x × 103 (1.16 ± 0.02) × 104 (5.03 ± 0.17) × 103 (1.06 ± 0.02) × 104 (4.81 ± 0.16) × 103 (1.08 ± 0.02) × 104 Average (4.94 ± 0.09)y × 103 (1.10 ± 0.04) × 104

Skin Oct. 2013 (7.17 ± 0.40) × 103 (1.50 ± 0.05) × 104 (7.52 ± 0.39) × 103 (1.53 ± 0.05) × 104 (6.23 ± 0.33) × 103 (1.55 ± 0.04) × 104 Average (6.97 ± 0.55) × 103 (1.53 ± 0.02) × 104

Kernel Oct. 2013 (5.06 ± 0.10) × 103 (1.09 ± 0.01) × 104 (4.24 ± 0.09) × 103 (9.69 ± 0.12) × 103 (4.46 ± 0.09) × 103 (9.82 ± 0.12) × 103 Average (4.59 ± 0.34) × 103 (1.01 ± 0.05) × 104

Barkz Feb. 2014 (2.52 ± 0.07) × 104 (5.59 ± 0.09) × 104 (1.50 ± 0.03) × 104 (3.47 ± 0.05) × 104 (3.08 ± 0.06) × 104 (6.85 ± 0.07) × 104 Average (2.37 ± 0.53) × 104 (5.30 ± 1.40) × 104

Woodz Feb. 2014 (3.27 ± 0.17) × 103 (7.10 ± 0.21) × 103 (3.15 ± 0.13) × 103 (6.99 ± 0.16) × 103 (2.34 ± 0.09) × 103 (5.43 ± 0.12) × 103 Average (2.92 ± 0.41) × 103 (6.51 ± 0.76) × 103

Leafz Nov. 2013 (3.79 ± 0.21) × 103 (8.46 ± 0.26) × 103 (4.06 ± 0.24) × 103 (9.49 ± 0.30) × 103 (4.03 ± 0.25) × 103 (1.09 ± 0.32) × 104 Average (3.96 ± 0.12) × 103 (9.62 ± 1.01) × 103

Soil Nov. 2013 (1.07 ± 0.02) × 104 (2.45 ± 0.02) × 104 (1.09 ± 0.02) × 104 (2.48 ± 0.02) × 104 (1.08 ± 0.02) × 104 (2.43 ± 0.02) × 104 (9.85 ± 0.02) × 103 (2.23 ± 0.02) × 104 Average (1.06 ± 0.04) × 104 (2.40 ± 0.10) × 104

Billbug larvae Nov. 2013 (6.13 ± 1.18) × 102 (1.55 ± 0.10) × 103 (8.54 ± 1.08) × 102 (1.17 ± 0.09) × 103 Average (7.33 ± 1.21) × 102 (1.36 ± 0.20) × 103 z Data from Sasaki et al. 2016. y The radiocesium concentration is shown by mean ± 1σ standard deviations. x The radiocesium concentration measurements showed a 1σ counting error, and were corrected for radioactive decay to the sampling data of the chestnut fruit. ers (plants: chestnut fruits) to primary consumers (in- 2004)). Many insects are present in the natural environ- sect: chestnut weevil). The biological half-life of 137Cs ment, but there are few reports of radiocesium transi- of herbivorous insects and predaceous insect is about tion to insects. Since insects are one of the important 6 days (Ayabe et al., 2015). One possible reason that factors in the food chain as potential prey of fish and radiocesium was not concentrated in the chestnut , accumulation of information about the radio- weevil may be that herbivorous insects had a short bio- cesium transition to insects is important. logical half-life of radiocesium. Note that the radiation Monte et al. (1990) reported that the main radiocesi- resistance of lower organisms such as insects is high um, (released from the CNPP accident) transfer route of (e.g., the LD99.9 of the chestnut weevil larvae by edible fruit including chestnuts grown in Italy was from gamma-ray irradiation is about 500 Gy (Imamura et al., the plant surface (leaf and bark). Transfer factors of Hort. J. Preview 5

(Yamagata et al., 1969). Radiocesium remains in the soil surface (Takahashi et al., 2015) due to being strongly incorporated to clay minerals in soil (Sawhney, 1967; Schultz et al., 1960). Litter is deposited on the ground in the forest. Radiocesium is eluted from radiocesium-containing litter (Sakai et al., 2015). How- ever, it would be difficult to find dissolved radiocesium in the soil surface because most of it is adsorbed on the clay minerals. In stems that were present at the time of the accident, the radiocesium concentration of the bark was relatively high and approximately 10 times that of the wood (Table 1). The average 137Cs concentration of the dis- solved fraction (< 0.45 μm) in the stemflow was mea- sured to be around 10 Bq·L−1 (Sasaki et al., 2016). This Fig. 4. Total amount of radiocesium in one Japanese chestnut fruit. result indicated that radiocesium deposited to the bark The dry weight of the fruit was 2.1 ± 8.9 × 10−2 g. The error in was eluted as dissolved radiocesium. As in the case of radiocesium concentrations showed 1σ standard deviations. radiocesium transfer from the bark to stemflow, radio- cesium transfers from the bark to the wood. In trees that were present at the time of the accident, it was assumed European chestnut species were 0.7–1.4, which were that the incorporation rate of radiocesium into the trees calculated from Monte et al. (1990) data (International was more from the bark than from the roots. Takata Atomic Energy Agency, 2003). (2013) reported that the main route of the transition of Radiocesium concentration in the fresh weight of the radiocesium to the fruit of the grape was absorption chestnut kernel was calculated using the moisture con- through the bark. Sato et al. (2015) showed that radio- tent of 50.8 ± 0.56% (mean ± SD, n = 3) of the chestnut cesium concentrations of fruit and leaves were reduced fruit, and was 5.0 × 103 Bq·kg−1 FW. The TF of by peeling off the bark of persimmons and peaches. Japanese chestnuts in this study, calculated from the Elucidation of the behavior of radiocesium in trees 137Cs concentrations of kernel and soil, was 0.8. The will be provided by long-term investigation of radio- value of the present study was consistent with the trans- cesium distribution in each part of radiocesium- fer factor to the chestnut fruit in Europe. contaminated trees and by the behavior of radiocesium Chestnuts of different varieties have been produced after transplantation of radiocesium-uncontaminated in Europe and Asia. The potassium content of the trees into radiocesium-contaminated soil. Japanese and European of chestnut is almost the same, Acknowledgements and potassium and cesium are congeners. Potassium contents of European and Japanese chestnut kernels are The authors wish to thank the members of the Sector 4.84 (National Nutrient Database for Standard Refer- of Fukushima Research and Development, Fukushima ence, http://ndb.nal.usda.gov/ndb/search/list, December Environmental Safety Center, JAEA. We would also 1, 2015) and 3.29 μg·g−1 FW (Standard Tables of Food like to thank Dr. H. Sato (associate professor of Composition in JAPAN, http://www.mext.go.jp/ Okayama University) for his helpful advice. Moreover, b_menu/shingi/gijyutu/gijyutu3/toushin/05031802.htm, we are grateful to Satoshi Maeda and Tsutomu Okazaki December 1, 2015), respectively. However, potassium (Sasakino Analytical laboratory, Fukushima Radiation and cesium are likely to show different behavior in Measurement Group) for their technical help in mea- plants. Actually, there are reports that there is no corre- surement of radiocesium concentrations. lation between the potassium and cesium content in rice (Tsukada et al., 2002; Yamaguchi et al., 2012). The 40K Literature Cited concentration in kernels was below the detection limit Akimoto, S. 2014. Morphological abnormalities in gall-forming 2 −1 (4 × 10 Bq·kg DW). aphids in a radiation-contaminated area near Fukushima Fine roots of chestnuts are abundant in the soil sur- Daiichi: selective impact of fallout? Ecol. Evol. 4: 355–369. face, and 65% of the fine roots are present at a depth of Ayabe, Y., T. Kanasashi, N. Hijii and C. Takenaka. 2014. Radio- 20 cm (Karizumi, 2010). Our study of the radiocesium cesium contamination of the web spider Nephila clavata distribution in forest soil in December 2012 indicated (Nephilidae: Arachnida) 1.5 years after the Fukushima Dai- that more than 99% of the total amount of radiocesium ichi Nuclear Power Plant accident. J. Environ. Radioact. 127: 105–110. was present in the surface layer to a depth of 10 cm Ayabe, Y., T. Kanasashi, N. Hijii and C. Takenaka. 2015. Moni- (Sato et al., 2013). About 80% of the radiocesium fall- toring radiocesium contamination of the web spider Nephila out of nuclear testing origin has been reported to be clavata (Nephilidae: Arachnida) in Fukushima forests. J. present in soil at up to 5 cm depth in pine forests Jpn. For. Soc. 97: 70–74 (In Japanese). 6 Y. Sasaki, Y. Ishii, H. Abe, K. Mitachi, T. Watanabe and T. Niizato

Chino, M., H. Nakayama, H. Nagai, H. Terada, G. Katata and H. power plant accident. J. Environ. Radioact. 161: 58–65. Yamazawa. 2011. Preliminary estimation of release amounts Sato, M., K. Abe, H. Kikunaga, D. Takata, K. Tanoi, T. Ohtsuki of 131I and 137Cs accidentally discharged from the Fukushima and Y. Muramatsu. 2015. Decontamination effects of bark Daiichi nuclear power plant into the atmosphere. J. Nucl. washing with a high-pressure washer on peach [Prunus Sci. Technol. 48: 1129–1134. persica (L.) Batsch] and Japanese persimmon (Diospyros Hiyama, A., C. Nohara, S. Kinjo, W. Taira, S. Gima, A. Tanahara kaki Thunb.) contaminated with radiocaesium during dor- and J. M. Otaki. 2012. The biological impacts of the mancy. Hort. J. 84: 295–304. Fukushima nuclear accident on the pale grass blue butterfly. Sato, H., T. Niizato, K. Amano, S. Tanaka and K. Aoki. 2013. Sci. Rep. 2: 570. Investigation and research on depth distribution in soil of Imamura, T., S. Todoroki, A. Miyanoshita and T. Hashimoto. radionuclides released by the TEPCO Fukushima Dai-ichi 2004. Effects of gamma irradiation on the emergence of nuclear power plant accident. 2012. MRS Proceedings 1518: larvae of Curculio sikkimensis (Heller) (Coleoptera: 277–282. Curculionidae) and kurokoi (Amsel) (: Sawhney, B. L. 1967. Cesium sorption in relation to lattice spac- ). Food irradiation, Japan. 39: 5–7. ing and cation exchange capacity of biotite. Soil Sci. Soc. International Atomic Energy Agency. 2003. IAEA BIOMASS-5. Am. Proc. 31: 181–183. Modelling the Transfer of Radionuclides to Fruit. p. 123, Schultz, R. K., R. Overstreet and I. Barshad. 1960. On the soil International Atomic Energy Agency, Vienna. chemistry of cesium-137. Soil Science 89: 16–27. International Atomic Energy Agency. 2010. Technical reports Takahashi, J., K. Tamura, T. Suda, R. Matsumura and Y. Onda. series No. 472: Handbook of parameter values for the pre- 2015. Vertical distribution and temporal changes of 137Cs in diction of radionuclide transfer in terrestrial and freshwater soil profiles under various land uses after the Fukushima environments. p. 39–82, International Atomic Energy Dai-ichi nuclear power plant accident. J Environ. Radioact. Agency, Vienna. 139: 351–361. IUSS Working Group WRB. 2015. World Reference Base for Takata, D. 2013. Distribution of radiocesium from the radioactive Soil Resources 2014, update 2015, International soil classifi- fallout in fruit trees. p. 143–162. In: T. M. Nakanishi and K. cation system for naming soils and creating legends for soil Tanoi (eds.). Agricultural Implications of the Fukushima maps. World Soil Resources Reports No. 106. FAO, Rome. Nuclear Accident. Springer, New York. Karizumi, N. 2010. The latest illustrations of tree roots (Japanese Tamura, T. and K. Takeuchi. 1980. Land characteristics of the title: Saishin jumoku konkei zusetsu: kakuron) (In Japanese). hills and their modification by man: with special reference to p. 358–361. Seibundo Shinkosha Publishing Co., Ltd. a few cases in the tama hills, west of Tokyo. Geogr. Rep. Tokyo. Tokyo Metropl. Univ. 14/15: 49–94. Korel, F. and M. Ö. Balaban. 2009. Chemical composition and Tsukada, H., H. Hasegawa, S. Hisamatsu and S. Yamasaki. 2002. health aspects of chestnut (Castanea spp.). p. 171–184. In: Rice uptake and distributions of radioactive 137Cs, stable C. Alasalvar and F. Shahidi (eds.). Tree Nuts: Composition, 133Cs and K from soil. Environ. Pollut. 117: 403–409. Phytochemicals, and Health Effects. CRC Press, New York. Umeya, K. 2004. Tsuri esa no “syoutyuu” retsuden (3). p. 293– Kusaba, S., K. Matsuoka, T. Saito, N. Kihou and K. Hiraoka. 306. In: Mushi wo taberu bunnkashi. Sorinsya. Tokyo (In 2015. Changes in radiocesium concentration in a Japanese Japanese). chestnut (Castanea crenata Sieold & Zucc.) orchard follow- Yamagata, N., S. Matsuda and M. Chiba. 1969. Radioecology of ing radioactive fallout. Soil Sci. Plant Nutr. 61: 165–168. cesium-137 and strontium-90 in the forest. J. Radiat. Res. Monte, L., S. Quaggia, F. Pompei and S. Fratarcangeli. 1990. The 10: 107–112. behaviour of 137Cs in some edible fruits. J. Environ. Yamaguchi, N., Y. Takata, K. Hayashi, S. Ishikawa, M. Radioact. 11: 207–214. Kuramata, S. Eguchi, S. Yoshikawa, A. Sakaguchi, K. Sakai, M., T. Gomi, R. S. Naito, J. N. Negishi, M. Sasaki, H. Asada, R. Wagai, T. Makino, I. Akahane and S. Hiradate. Toda, M. Nunokawa and K. Murase. 2015. Radiocesium 2012. Behavior of radio cesium in soil-plant systems and its leaching from contaminated litter in forest streams. J. controlling factor: a review. Rep. Natl. Inst. Agro. Environ. Environ. Radioact. 144: 15–20. Sci. Jpn. 31: 75–129 (In Japanese). Sasaki, Y., H. Abe, K. Mitachi, T. Watanabe, Y. Ishii and T. Yoshimura, M. and A. Akama. 2014. Radioactive contamination Niizato. 2016. The transfer of radiocesium from the bark to of aquatic insects in a stream impacted by the Fukushima the stemflow of chestnut trees (Castanea crenata) contami- nuclear power plant accident. Hydrobiologia 722: 19–30. nated by radionuclides from the Fukushima Dai-ichi nuclear