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Discovery of radioactive silver ([sup.110m]Ag) in spiders and other fauna in the terrestrial environment after the meltdown of Fukushima Dai-ichi nuclear power plant.

Introduction

After the Great East Japan Earthquake and resulting Tsunami on March 11, 2011, a sequential meltdown of the nuclear fuels occurred at the Fukushima Dai-ichi nuclear power plant (NPP) of Tokyo Electric Power Company (TEPCO), following the discharge of enormous amounts of radioactive materials into the environment. The main components were [sup.131]I, [sup.133]I, [sup.134]Cs and [sup.137]Cs, whose total amounts were estimated to be 1.5 x [10.sup.17] Bq for [sup.131]I, 1.2 x [10.sup.16]Bq for [sup.137]Cs, and also 6.3 x [10.sup.17]Bq in iodine equivalent. (1) Roughly half of the discharged activity had precipitated in soils and entered inland waters, where it was incorporated into flora and fauna in the terrestrial environment. (2) Among a number of attempts to reveal the scale and distribution of the fallout, our group also started to survey local and biological contamination with the radioactivity in the vicinity of the TEPCO's NPP. On Sept. 20, 2011, we visited one of the heavily contaminated area, Iitate village in Fukushima Prefecture, where had already been declared to be the "planned evacuation zone". It was a stormy day with heavy rain of typhoon and we had to abandon our original plan to collect vegetation samples, instead we collected the orb-web spider Nephila clavata (Joro-gumo in Japanese), which nested in abundance in a bamboo forest. Our initial conjecture was that the spiders might be contaminated with radioactive cesium reflecting contamination of the food chain. Unexpectedly, however, germanium-semiconductor analysis in the laboratory of the N. clavata specimens showed a sharp peak (657.8 keV) of [sup.110m]Ag distinct from the [sup.137]Cs peak (661.7keV). This was the beginning to recognize marked biological concentration of [sup.110m]Ag in the field fauna during this accident, which was publicized preliminary. (3)

In fact, radioactive silver, [sup.110m]Ag (half-life: 249.95 days), first attracted attention as the atomic weapon detritus, whose distinct biological accumulation was detected in the digestive tissues of a marine crustacean and mussels, barnacles, and fishes from the Pacific Ocean due to the repeated test explosions at Entwetok Atoll, Bikini Atoll etc., from 1946 to 1963. (4), (5) [sup.110m]Ag had also been detected as a minor radioactive nuclide contained in wastewater from NPPs, however, the Chernobyl accident on April 26, 1986 caused its discharge in a large amount into the environment. For example, in Cumbria, northwestern England located ~2000 km from Chernobyl, all vegetation in 18 varietal soils sampled in May 1986 was contaminated with [sup.110m]Ag with concentrations ranging from 190 to 480Bq/kg of dryweight (DW). (6) Many studies were conducted on the metabolism of [sup.110m]Ag in the fallout of the accident by aquatic biota especially in oceans. (7)-(9) Studies on cattle such as oxen, lambs and sheep revealed that distinct accumulation of [sup.110m]Ag was rather restricted to liver with the biological half-life of 35 days in the case of sheep. (6), (10)-(12) In contrast to these studies, contamination of terrestrial wild fauna involving small insects and animals remained very scarce.

Even in the accident at TEPCO's NPP, studies on the contamination of fauna were mostly restricted to cattle. After the accident, [sup.110m]Ag was detected in the liver of cattle at a concentration of 177 [+ or -] 176Bq/kg, (13) and a 3-month supply of clean hay as fodder to the contaminated cattle failed to decrease its contents in liver significantly. (14) In contrast, no published studies exist on the dynamics of [sup.110m]Ag in small faunal species comprising the food chain in terrestrial environments. Therefore, we conducted successive surveillance of [sup.110m]Ag in spiders as well as several small animals and insects during our visits to Fukushima once a month until November 2014. The obtained results confirmed the reproducible accumulation of [sup.110m]Ag in small faunal species. Here, we describe the contamination of 35 of these species by [sup.110m]Ag and [sup.137]Cs (or [sup.134]Cs) fallout and the fates of those radionuclides in the bodies of the orb-web spider N. clavata and the ground spider Atypus karschi in the 3.5 years after the NPP accident.

Materials and methods

Sampling of fauna species and soils. From Sept. 20, 2011 until Nov. 3, 2014, we collected 35 faunal species from Benten-yama and Hanami-yama in Fukushima city, Oguni, Miyuki-yama and Ryozen in Date city, Tsushima and Akougi in Namie town, Yamakiya in Kawamata town and Nimaibashi, Iitoi, Hiso, Maeda, Sasu, Usuishi and Nagadoro in Iitate village in Fukushima Prefecture (Fig. 1). The sampling sites were located more than 30 km from Fukushima Dai-ichi NPP. Most of the collected species were separately stored in plastic 100-mL cups to avoid their preying on each other. Names of all collected species are listed in Table 3. The collected fauna were starved at room temperature for ~3 weeks in the U8-cups, which were stored in desiccators. During the starvation process, some of the fauna excreted feces and urine before their death. Starvation was necessary to allow measurement of the true radioactivity in the body tissues of the collected fauna, after they had excreted residual, non-metabolized contamination in their feces and urine. For some of the fauna, the radioactivity in the desiccated feces was also measured.

Our visit to the Hiso on Oct. 13, 2013 coincided with the pregnancy phase of N. clavata females. We collected 85 of the pregnant spiders, separately storing them in U8-cups. These spiders were starved under dark conditions until some of them had spun webs and shed their egg sacs into the cups. Spider bodies, excrement (feces D urine), web thread, and egg sacs were separately collected and their radioactivity was measured. We also collected soil from the sites where N. clavata and A. karschi had been sampled. Surface soils were collected from an area of 10 x 10 x 2 cm. A vertical depth of 2 cm was chosen because >95% of nuclear fallout accumulates within a vertical depth of 2 cm from the soil surface. (15), (16)

Measurement of radioactivity. The detection of the discharged [sup.110m]Ag in the atmospheric dust from the TEPCO's NPP was first recognized by several institutions from March to May in 2011, (17)-(19) and its total amount was estimated to be 4.04-6.41 x [10.sup.15]Bq in the cores of Units 1-3 of the NPP. (20) The Ministry of Education, Culture, Sports, Science and Technology, Japan, published a rough distribution map of [sup.110m]Ag in soils on Oct. 31, 2011 (Fig. 1), (21) and its distribution in surface soils in a wide area around the power plant (22)-(24) as well as the vertical distribution profile in Fukushima soils16) were described a year later the accident.

The aerial dose (pSv/h) was measured in the contaminated fields at a height of 1 m from the sampling sites using an Aloka .-survey meter (TCS-172; Hitachi-Aloka, Tokyo, Japan). In the laboratory, all materials were analyzed on germanium-semiconductor detectors (GEM type and GMX type, Seiko EG&G, Tokyo, Japan). The counting time was set at 220,000 s. [sup.110m]Ag, [sup.137]Cs, and [sup.134]Cs activities were determined using the [gamma]-ray detector, detecting peaks at 884.7, 661.7, and 604.7keV, respectively. Multiple number of animals in each sample (Table 3) was put together in a cup and measured. Therefore no statistical errors were expressed in Tables. The concentration of the measured radioactivity was expressed as Bq/kgDW. Radioactivity in snakes, slugs, and tadpoles, all of which had high water content, and melted during starvation process was measured without desiccation of the specimens and expressed as Bq/kgFW, where FW is the fresh weight.

Imaging analysis. N. clavata specimens were gently flattened between paper towels, allowed to air-dry completely, and then exposed to BAS imaging plates (IP-plate; FujiFilm, Tokyo, Japan). An image of the vertical distribution of the radioactivity in the soil profile was obtained by exposing the vertical soil layer collected in a lunchbox (13 x 7.5 x 6 cm) to an IP-plate. In both cases, polyethylene film was placed between the sample and the IP-plate to avoid chemical- or water-related disturbances of the sensitivity of the IP-plate to the samples. After ~1 month of exposure, the IP-plates were scanned using an Image-analyzer (FLA-5000; FujiFilm). The feces of lizards and other fauna were observed by digital microscopy (KEYENCE VH-6300).

Results

Detection of [sup.110m]Ag in N. clavata. Figure 2 shows the [gamma]-radiation from N. clavata (sample no. 3 in Table 3) detected by Ge-semiconductor analysis. Energy peaks corresponding to [sup.137]Cs (661.7 keV), [sup.110m]Ag (657.8keV), and three other peaks characteristic of [sup.110m]Ag (884.7, 937.5, and 1384 keV) were obtained from the same sample. The radioactivity ratio of [sup.110m]Ag/[sup.134]Cs/[sup.137]Cs was 1/1.12/1.50.

Concentration of radioactivity in N. clavata and A. karschi. We collected N. clavata and surface soils from three different locations in Fukushima Prefecture and calculated the radioactivity concentration ratios, defined as ([sup.110m]Ag Bq/kg N. clavata)/ ([sup.110m]Ag Bq/kg soil). A similar ratio was calculated for [sup.137]Cs. As shown in Table 1, the radioactivity concentration ratios were 27.8, 74.5, and 87.3 for [sup.110m]Ag and 0.036, 0.078, and 0.071 for [sup.137]Cs at Oguni, Benten-yama, and Nimaibashi, respectively. These data were then used to calculate the radio activity concentration ratios of [sup.110m]Ag to [sup.137]Cs, defined as ([sup.110m]Ag Bq/kg spider/[sup.110m]Ag Bq/kg soil)/([sup.137]Cs Bq/kg spider/[sup.137]Cs Bq/kg soil). The values were 774, 960, and 1234, at Oguni, Bentenyama, and Nimaibashi, respectively.

We also measured the radioactivity concentration ratio in A. karschi living only on the soil surface as a ground spider, which would have received [sup.110m]Ag directly from the soil-based food chain, while N. clavata resides in aerial webs mainly depending on flying preys. As shown in Table 1, the concentration ratios of [sup.110m]Ag and 1[sup.37]Cs in A. karschi in samples collected at Benten-yama and Iitoi were 448 and 166, and 1.30 and 0.45, respectively, corresponding to [sup.110m]Ag to [sup.137]Cs radioactivity concentration ratios of 344 and 369 (Table 1). Thus, in both spider species, the concentration ratio of radioactive [sup.110m]Ag was two-three orders higher than that of [sup.137]Cs.

Distribution of radionuclides in the body, thread, excrement, and egg sac of N. clavata. Figure 3 shows the lifestyle of the female N. clavata spiders in the U8-cups. All N. clavata collected from Hiso on Oct. 13, 2013 were pregnant. During starvation in the U8-cups incubated at room temperature, one N. clavata delivered one egg sac containing many larval spiders (Fig. 3a). The egg sac was covered with a silky thread and hung on the web strung across the cup interior (Fig. 3d). Table 2 shows that the spider's body and excrement contained equivalent concentrations of [sup.110m]Ag, whereas the concentration in the egg sacs was more than twofold higher. Web silk did not contain [sup.110m]Ag. However, the concentration of [sup.137]Cs (and [sup.134]Cs) in the spiders' body and thread was nearly the same. Cesium might be incorporated as a contaminant into thread, replacing potassium. Spider excrement contained 4.5 times more [sup.137]Cs (and [sup.134]Cs) than measured in the spider body. Concentrated radioactivity was observed possibly at the midgut gland of N. clavata, while with lower concentrations of radioactivity in other body parts (Fig. 4).

Radionuclide contents in N. clavata during the 3.5 years after the NPP accident. Figure 5 shows the trend in the radionuclide contents of N. clavata over the sampling period. Although the dates and sites of N. clavata collection differed, the concentration of [sup.110m]Ag in the spiders clearly decreased rapidly within 3.5 years after the NPP accident, except in sample no. 11, which still had a detectable amount of [sup.110m]Ag and a very high amount of [sup.137]Cs (and [sup.134]Cs). This sample was collected at Tsushima, where aerial doses were higher (8.2 pSv/h) than those (1.3-4.6 pSv/h) at other sampling sites (Table 3a).

Amounts of [sup.110m]mAg, [sup.134]Cs, and [sup.137]Cs in various faunal species. Table 3a shows the original [sup.110m]Ag, [sup.134]Cs, and [sup.137]Cs data obtained at the faunal sampling times between Sept. 20, 2011 and Nov. 3, 2014, and Table 3b presents the decay-corrected data of Table 3a with reference to March 15, 2011, when the NPP discharged gaseous materials and the plume spread to the northwest. The [gamma]-ray peak patterns of most of the faunal samples collected in 2011-2012 were similar to that of N. clavata (Fig. 2, Table 3a). As shown in the column "[sup.110m]Ag Bq/kg" of Table 3b, silk spiders (sample no. 11), ground spiders (14, 16), pill bugs (24, 25), snails (30), dragonflies (54), crabs (60) and centipede (65) contained more than 5000Bq/kg, whereas silk spiders (1, 2, 3, 4), ground spiders (15, 17, 19), other spiders (21, 22), the beetle Seaka-gomimushi (23), ants (28), frogs (34), millipedes (42), slugs (44), dragonflies (56), and river shrimp (57) contained 1000-5000 [sup.110m]Ag Bq/kg. In contrast, [sup.110m]Ag was not detectable in lizards, locusts, beetles, longicorn beetles, honeybees, butterflies, tadpoles, and newts, although [sup.137]Cs (or [sup.134]Cs) was detected in all of them. Table 3b also shows that ground spiders, pill bugs, ants, snails, frogs, lizards, slugs, hornets, crabs, and dragonflies contained more than 10,000 [sup.137]Cs Bq/kg. The [sup.110m]Ag/[sup.137]Cs ratios of silk spiders, Argiope amoena, Seaka-gomimushi, millipedes, river shrimp, crabs, and the diving beetle Gengoro were above 1.0. Note that all of those species are members of Arthropoda.

[sup.110m]Ag/[sup.137]Cs ratio of feces and soil. The feces of some of the fauna were collected and the radioactivity content was measured. As shown in Table 4, earthworms, lizards, Seaka-gomimushi, and dragonflies (Akiakane) concentrated [sup.110m]Ag in their feces, based on feces/soil radioactivity ratios of 15, 746, 45, and 101, respectively. The feces of earthworms, ground spiders, and lizards also contained [sup.137]Cs (feces/soil ratios of 18, 19, and 4.3, respectively). The [sup.110m]Ag/[sup.137]Cs ratios in the feces of lizards and dragonflies were 0.23 and 0.46, respectively, which were two orders of magnitude higher than in any of the contaminated soils examined (see [sup.110m]Ag/[sup.137]Cs in Table 6). Thus, lizards and dragonflies concentrated large amounts of [sup.110m]Ag, which they ingested via the soil-based food chain.

Radionuclide contents of A. karschi during the 3.5 years after the NPP accident. A. karschi was collected as the representative spider to monitor radionuclide accumulation in spider bodies in the area of Iitoi, Iitate village, from Oct. 18, 2011 to Oct. 13, 2014. As an inhabitant of the surface soil, A. karschi was assumed to more directly reflect soil radionuclides available through the food chain than N. clavata, which mostly resides in aerial webs. The fixed sampling site, where the aerial rate of radioactivity accumulation was 5.37 [micro]Sv/h on the first sampling date, Oct. 18, 2011, but had decreased to 2.75 [micro]Sv/h on the fourth sampling date, Oct. 13, 2014. As shown in Table 5, during the 6 months from Oct. 18, 2011 to May 5, 2012, the radioactivity of [sup.110m]Ag, [sup.134]Cs, and [sup.137]Cs decayed from 3211 to 618 Bq/kg, 6346 to 1912 Bq/kg, and 8016 to 3169 Bq/kg, respectively. If each radionuclide found in A. karschi on Oct. 18, 2011 had decayed following its physical half-life, then the values on May 5, 2012 should have been 1859, 5294, and 7916Bq/kg, respectively. However, the detected radioactivity was far less. Moreover, on Oct. 13, 2014, [sup.110m]Ag was no longer detected in A. karschi, although [sup.137]Cs and [sup.134]Cs were still present in large amounts.

Radioactivity in soils. In contrast, the [gamma]-ray traces of all surveyed soils showed very low peaks for [sup.110m]Ag. [sup.110m]Ag was detected in soils at concentrations between 22 and 238 Bq/kg (Table 6). For example, the radioactivity ratio of [sup.110m]Ag/[sup.134]Cs/[sup.137]Cs in Nimaibashi soil collected on the same day as N. clavata was 1/675/703, which was very different from that of N. clavata (1/1.12/1.50. See Results). The radioactivity ratio of [sup.110m]Ag/[sup.137]Cs was between O. 0014 and 0.0023. These values were almost the same as those of the riverbed sediments of the four sampling locations of Nitta River (0.0016-0.0036), Takanokura Dam (0.008) of the Nitta River, and Tetsuzen Dam (0.01) of Ota River. (16) These sampling places are located in Minamisoma city, Fukushima Prefecture and to the northwest from Fukushima Dai-ichi NPP. The almost constant [sup.110m]Ag/[sup.137]Cs ratios in those soils suggested that our research area (100 km x 60 km) was contaminated with [sup.110m]Ag and [sup.137]Cs (and [sup.134]Cs) all at once shortly after the release of huge amount of radioactivity on March 15, 2011, with contamination occurring by precipitation. Figure 6 shows the autoradiograph of the forest soil profile at Tsushima. Radioactivity is distributed within 2 cm of the top soil, which includes a litter layer of ~1 cm at the surface.

Discussion

During our field research on the contamination of flora in Ibaraki, (25) and Fukushima, (26) we coincidentally detected large amounts of [sup.110m]Ag in the spider N. clavata (Fig. 2). This finding was subsequently confirmed in other faunal species. Among the many species surveyed (Table 3a), those belonging to Arthropoda contained more [sup.110m]Ag and had a higher radioactivity ratio ([sup.110m]Ag/[sup.137]Cs > 1) than faunal species from other phyla, when decay was corrected to the date of release of these radioactivity, March 15, 2011 (Table 3b). In contrast, [sup.110m]Ag concentrations in soils were very low, along with the [sup.110m]Ag/[sup.137]Cs ratio in soils (0.0014-0.0023) (Table 6) compared to the concentrations of these two radionuclides in all faunal species in which [sup.110m]Ag were detected (Table 3b).

In both spider species (N. clavata and A. karschi), the radioactivity concentration ratio of [sup.110m]Ag was three orders of magnitude higher than that of [sup.137]Cs (Table 1). The most plausible explanation for this unexpected result is that [sup.137]Cs was more rapidly bound to soil clay minerals, especially mica (15) or illite, (27) than [sup.110m]Ag, resulting in less [sup.137]Cs available to flora and/or fauna in the soil. Indeed, the [sup.137]Cs content of most of the vegetables and rice in Fukushima Prefecture has decreased very quickly in the 3 years since the NPP accident. (28) Alternatively, the Ag-transporter activity of both spiders may be much higher than their Cs-transporter activity, resulting in the more efficient uptake of [sup.110m]Ag. Otherwise, as mentioned later the binding activity of [sup.110m]Ag to hemocyanin in lymph fluid in both spiders may be very strong, thus [sup.110m]Ag may be more slowly metabolized than radioactive Cs to be excreted. Another explanation is that [sup.110m]Ag is more quickly turned over through the food chain to spiders in terrestrial environments than [sup.137]Cs. To confirm the latter three possibilities will require advanced biochemical and molecular biological works on mineral (Ag and/or Cs) transporters in flora and fauna.

Although we could not segregate the radioactivity sources in the labeling image of N. clavata and thus unable to localize [sup.110m]Ag and [sup.137]Cs (or [sup.134]Cs) anatomically, the image shown in Fig. 4 suggests that [sup.110m]Ag is circulated in the lymph fluid, thus binding to hemocyanin, the [O.sub.2] carrier protein that also plays an important role in metal transport and distribution in decapod crustaceans. (29) The trunk, head, and legs of N. clavata, as depicted in Fig. 4B, were probably labeled mainly with radioactive Cs. Autoradiographs (BAS-images) of many small animals collected from the contaminated field were taken by one of the authors (S. Mori) and published online. (30), (31) The muscles of frog and snake are very strongly labeled with radioactive Cs. (32) These observations are consistent with the very low [sup.110m]Ag/[sup.137]Cs ratio of those fauna (see the [sup.110m]Ag/[sup.137]Cs ratio of snake no. 38 and frog nos. 32-34 in Table 3a).

The fact that the concentration of [sup.110m]mAg in the egg sac of N. clavata (Fig. 3a) was more than twice that of the spider's body (Table 2) suggests that [sup.110m]Ag was transferred from the female spider to the egg sac. Because one egg sac incubates hundreds of larval spiders, separating them from the fragile sac after it was crushed was difficult (Fig. 3a). Thus, the portion of [sup.110m]Ag transferred from female spiders to its larvae could not be determined.

In Arthropoda and Mollusca that inhabit the sea, such as crab, octopus, and squid, etc., [sup.110m]Ag was suggested to replace copper in the active center of hemocyanin. It is reported that the regeneration of holohemocyanin by the combination of apoprotein with added cuprous chloride was inhibited by [Ag.sup.+], 33) although this has yet to be proven more directly using [sup.110m]Ag. The same may be true in the case of land fauna species living in freshwater, such as river shrimp, crab, and diving beetle Gengoro, whose [sup.110m]Ag contents and [sup.110m]Ag/[sup.137]Cs ratios were relatively high (Table 3). The amount of [sup.110m]Ag concentrated by phytoplankton or zooplankton may be a determining factor, as both would serve as the primary source of [sup.110m]Ag in the food chain of freshwater ecosystems. It was interesting that snail (sample no. 30 in Table 3) belonging to Mollusca had also relatively high [sup.110m]Ag content and [sup.110m]Ag/[sup.137]Cs ratio.

[sup.110m]Ag was not detectable in lizards, locusts, beetles, longicorn beetles, honeybees, butterflies, tadpoles, and newts, which may have been due to very low Ag-transporter activity in the digestive organs of these species. The lizards were collected at the same fixed point where we also collected the ground spider A. karschi annually. As shown in Fig. 7, a major component of lizard feces comprised fragmented A. karschi. This spider highly concentrated [sup.110m]Ag in its body (sample nos. 14-20 in Table 3a), whereas the lizard did not (sample nos. 35-37 in Table 3a). This high amount of [sup.110m]Ag in the feces of lizards suggests that the lizards excreted highly concentrated [sup.110m]Ag without absorption of the radionuclide from the digested A. karschi. Thus, lizards may have very low intestinal Ag-transporter activity. A. karschi, however, almost completely absorbed [sup.110m]Ag into its body from unknown foods because no detectable [sup.110m]Ag was found in the feces of this spider (Table 4).

The radioactivity image of the soil profile (Fig. 6) agrees with the results of Lepage et al. (16) (see Figs. 5, 7 and 8 in their recent report). Although we could not differentiate [sup.110m]Ag from [sup.137]Cs and [sup.134]Cs in the image, the three radionuclides seemed to have co-localized in the topsoil within a depth of 2 cm. Silver tends to concentrate in the surface litter plus humus horizon, suggesting that it mixes with organic matter. Increased acidity facilitates the removal of Ag from this horizon, whereas at a pH above 4, Ag is relatively immobile. (34) If we define "the residence half time for [sup.110m]Ag in soil" as the time required for one-half of an acute [sup.110m]Ag deposit to pass through the soil layer of interest, the residence half time resulting from the migration velocity of [Ag.sup.+] within the 5-cm soil top layer would be 33 [+ or -] 3 years. (12) Therefore, the vertical migration of [sup.110m]Ag may be highly dependent on the soil type.

This study shows that faunal concentrations of [sup.110m]Ag released during the Fukushima Dai-ichi NPP accident are decreasing more rapidly than the physical half-life of the radionuclide in the contaminated terrestrial environment of Fukushima (Fig. 5, Table 5). Due to the Chernobyl and Fukushima disasters, the precise physicochemical dynamics of radioactive Cs with soil minerals have received considerable attention from soil scientists around the world. (15), (27) However, studies on the biological dynamics of radioactive Cs in the "soil sphere" are lacking. Clarification of not only the physicochemical dynamics of soil minerals, but also the biological dynamics of [sup.110m]Ag in the "soil sphere", will likely provide the information needed to explain why faunal concentrations of [sup.110m]Ag released by the Fukushima Dai-ichi NPP meltdown are decreasing faster through the food chain than predicted by their physical half-life.

doi: 10.2183/pjab.91.160

Acknowledgments

We thank Prof. Naoko K. Nishizawa (Ishikawa Prefectural University) for critical reading of this manuscript, and Prof. Tomoko Nakanishi (The University of Tokyo) for supplying the facilities for radioisotope studies by S.M., and Mr. Masamichi Kagaya for assisting the sampling of faunal species and soils at Namie town. We are deeply indebted to the Aichi Steel Corporation for financial funding of this study.

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(22) Watanabe, T., Tsuchiya, N., Oura, Y., Inoue, C., Hirano, N., Yamada, R., Yamasaki, S., Okamoto, A., Nara, F.W. and Nunohara, K. (2012) Distribution of artificial radionuclides ([sup.110m]Ag, [sup.129]Te, [sup.134]Cs, [sup.137]Cs) in surface soils from Miyagi Prefecture, northeast Japan, following the 2011 Fukushima Dai-ichi nuclear power plant accident. Geochem. J. 46, 279-285.

(23) Tazoe, H., Hosoda, M., Sorimachi, A., Nakata, A., Yoshida, M.A., Tokonami, S. and Yamada, M. (2012) Radioactive pollution from Fukushima Daiichi Nuclear Power Plant in the terrestrial environment. Radiat.

Prot. Dosimetry 152, 198-203.

(24) Petit, G.L., Douysset, G., Ducros, G., Gross, P., Achim, P., Monport, M., Raymond, P., Pontillon, Y., Jutier, C., Blanchard, X., Taffary, T. and Moulin, C. (2014) Analysis of radionuclide releases from the Fukushima Dai-Ichi Nuclear Power Plant Accident. Part I. Pure Appl. Geophys. 171, 629-644.

(25) Mori, S., Hirato, A., Tanoi, K., Takeda, K., Yamakawa, T. and Nakanishi, H. (2012) Radioactive cesium flow in Rhus vernicifera. Soil Sci. Plant Nutr. 58, 611-617.

(26) Nakanishi, H., Tanaka, H., Takeda, K., Tanoi, K., Hirose, A., Nagasaka, S., Yamakawa, T. and Mori, S. (2014) Radioactive cesium distribution in bamboo (Phyllostachy reticulate (Rupr) K. Koch) shoots after the TEPCO Fukushima Daiichi Nuclear Power Plant disaster. Soil Sci. Plant Nutr. 60, 801-808.

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(32) Mori, S. (2014) Reconstruction of the destroyed agriculture with evolution of agricultural sciences. Trends in the Science 19 (7), 56--59 (in Japanese).

(33) Moore, C.H., Henderson, R.W. and Nichol, L.W. (1968) An examination of the polymerization behavior of Jasus lalandii haemocyanin and its relation to the allosteric binding of oxygen. Biochemistry 7, 4075-4085.

(34) Boyle, R.W. (1968) The geochemistry of silver and its deposits. Geological Survey of Canada Bulletin 160, Geological Survey of Canada, Ottawa.

(Received Dec. 19, 2014; accepted Feb. 26, 2015)

By Hiromi NAKANISHI, * [1] Atsushi MORI, * [2] Kouki TAKEDA, * [1] Houdo TANAKA, * [1] Natsuko KOBAYASHI, * [1] Keitaro TANOI, * [1] Takashi YAMAKAWA * [1] and Satoshi MORI * [1] ([dagger])

(Communicated by Teruhiko BEPPU, M.J.A.)

* [1] Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.

* [2] The University of Electro-Communications, Tokyo, Japan.

([dagger]) Correspondence should be addressed: S. Mori, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan (e-mail: winep@ bird.ocn.ne.jp).

Table 1. Radioactivity concentration ratio between soil and
Nephila clavata or Atypus karschi. To calculate the concentration
ratio, the spider's radioactivity, as shown in Table 3b, was
divided by the corresponding soil radioactivity data shown in
Table 6. The results obtained using the [sup.134]Cs and
[sup.137]Cs data were almost the same (data not shown)

Species      Sampling place         Ratio of the radioactivity
             (Sample no.                concentrations:
             in Table 3)
                                   Spider (Bq/kg)/Soil (Bq/kg)

                                [sup.110m]Ag (a)   [sup.137]Cs (b)

Nephila
clavata
             Oguni (2)                27.8              0.036
             Benten-yama (1)          74.5              0.078
             Nimaibashi (3)           87.3              0.071
Atypus
karschi
             Benten-yama (16)         448                1.30
             Iitoi (14)               166                0.45

Species                          [sup.110m]Ag :
             Sampling place      [sup.137]Cs ratio
             (Sample no.             (a)/(b)
             in Table 3)
Nephila
clavata
             Oguni (2)                   774
             Benten-yama (1)             960
             Nimaibashi (3)              1234
Atypus
karschi
             Benten-yama (16)            344
             Iitoi (14)                  369

Table 2. Distribution of radionuclides derived from Nephila
clavata into four parts. It was sampled at Hiso on Oct. 13,
2013 (sample no. 9 in Table 3). See the culture conditions of
N. clavata in the U8-cup in the Materials and methods. Figures
of each part are shown in Fig. 3

N. clavata                       Radioactivity (Bq/kg)

                       [sup.110m]Ag    [sup.134]Cs    [sup.137]Cs

Whole body                78.5            546            1339
Excrement                 70.1            2480           6040
  (feces + urine)
Thread                    n.d.            756            1330
Egg sacs                  150             155            395

n.d.: not detected.

Table 3a. Radioactivity of faunal species collected from Sept.
20, 2011 to Nov. 3, 2014 at the sampling sites. Indicated number
of animals in each sample was put together in a cup and measured

Sample    Faunal species                Number of    Radioactivity
number                                   measured      (Bq/kgDW)
                                         samples     [sup.110m]Ag

1         Nephila clavata                   5             731
            (silk spider)
2         Nephila clavata                   6             707
            (silk spider)
3         Nephila clavata                   6            1398
            (silk spider)
4         Nephila clavata                   10            400
            (silk spider)
5         Nephila clavata                   5            n.d.
            (silk spider)
6         Nephila clavata                   4            n.d.
            (silk spider)
7         Nephila clavata                   6            n.d.
            (silk spider)
8         Nephila clavata                   3             226
            (silk spider)
9         Nephila clavata                   35           78.5
            (silk spider)
10        Nephila clavata                   14           48.4
            (silk spider)
11        Nephila clavata                   4             139
            (silk spider)
12        Nephila clavata                   8            18.2
            (silk spider)
13        Araneus ventricosus               2             162
            (Onigumo)
14        Atypus karschi                    8            3211
            (ground spider)
15        Atypus karschi                    12            618
            (ground spider)
16        Atypus karschi                    10           2866
            (ground spider)
17        Atypus karschi                    13            232
            (ground spider)
18        Atypus karschi                    4            n.d.
            (ground spider)
19        Atypus karschi                    4            86.8
            (ground spider)
20        Atypus karschi                    4            n.d.
            (ground spider)
21        Argiope amoena                    10            140
            (Koganegumo)
22        Spider (Unknown)                  1             182
23        Doricus herensis                  6             491
            (Seaka-gomimushi)
24        Armadillidium                     23           2099
            vulgare (pill bug)
25        Armadillidium                     25           3906
            vulgare (pill bug)
26        Aphaenogaster                     20           n.d.
            famelica (ant)
27        Aphaenogaster                     10           n.d.
            famelica (ant)
28        Aphaenogaster                     32            317
            famelica (ant)
29        Oligochaeta (earthworm)           1            20.8
30        Euhadra (snail: Maimai)           43           3118
31        Bufo japonicus formosus           1             426
            (frog: Hikigaeru)
32        Rana rugosa (frog:                5             206
            Tsuchigaeru)
33        Frog (unknown)                    1             53
34        Frog (unknown)                    1            74.6
35        Lacertidae (lizard)               4            n.d.
36        Lacertidae (lizard)               3            n.d.
37        Lacertidae (lizard)               1            n.d.
38        Elaphe climacophora               1            18.2
            (snake) ([double dagger])
39        Patanga japonica (locust)         8            25.7
40        Patanga japonica (locust)         4            n.d.
41        Diestrammena apicalis             4             65
            (Kamadouma)
42        Thereuonema tuberculata           3             578
            (millipede: Geji)
43        Meghimatium bilineatum            5             165
            (slug) ([double dagger])
44        Meghimatium bilineatum            6             233
            (slug) ([double dagger])
45        Allomylina dichotoma              1            n.d.
            (female)(beetle)
46        Allomylina dichotoma              1            n.d.
            (male)(beetle)
47        Cerambycidae (longicorn:          1            n.d.
            Kamikiri)
48        Graptopsaltria                    10           n.d.
            nigrofuscata (Aburazemi)
49        Pentatoma japonica                4            n.d.
            (Kamemushi)
50        Vespa mandarinia (hornet:         4             273
            Suzumebachi)
51        Apis cerana japonica Rad          7            n.d.
            (honeybee)
52        Rhopalocera (butterfly:           10           n.d.
            Unknown)
53        Rhopalocera (butterfly:           5            n.d.
            Monshirocyo)
54        Anotogaster sieboldii             5             838
            (dragonfly)
55        Sympetrum croceolum               6             180
            (dragonfly)
56        Sympetrum frequens                4             610
            (dragonfly)
57        Palaemon paucidens                35           81.7
            (river shrimp)
58        Geothelphusa dehaani              3             162
            (crab: Sawagani)
59        Geothelphusa dehaani              3             185
            (crab: Sawagani)
60        Geothelphusa dehaani              5             664
            (crab: Sawagani)
61        Bellamya quadrata                 12           10.2
            histrica (Tanishi)
62        Cybister japonicus                8            46.7
            (Gengoro)
63        tadpole ([double dagger])         86           n.d.
64        Cynops pyrrhogaster               2            n.d.
            (Akaharaimori)
65        Epimorpha (centipede:             1             425
            Mukade)

Sample           Radioactivity           Date of       Sampling
number            (Bq/kgDW)              sampling        place

          [sup.134]Cs    [sup.137]Cs

1             989            1052        2011/9/20    Benten-yama

2             949            1180       2011/10/18       Oguni

3             1559           2096        2011/11/9     Nimaibashi

4             980            1340        2011/11/9    Benten-yama

5             772            1653        2012/7/11        Hiso

6             512            1093        2012/7/11        Hiso

7             538            1077        2012/7/11        Hiso

8             993            2163        2012/7/11       Oguni

9             546            1339       2013/10/13        Hiso

10            107            385         2013/11/5        Hiso

11            2369           8965       2014/10/13      Tsushima

12            378            1395       2014/10/13        Hiso

13            424            508         2011/11/9    Benten-yama

14            6346           8016       2011/10/18       Iitoi

15            1912           3169        2012/5/5        Iitoi

16           11464          17445        2012/5/1     Benten-yama

17            1383           2932        2013/6/5        Iitoi

18            360            1206       2014/10/13       Iitoi

19            513            1800        2014/11/2       Maeda

20            436            686         2014/11/2       Iitoi

21            174            436         2012/9/27    Miyuki-yama

22            1218           2506        2012/9/16        Hiso
23            1006           1271        2012/3/30    Benten-yama

24            8073          10759        2011/11/9       Iitoi

25           26734          34842        2011/11/9    Benten-yama

26           11360          14768        2011/11/9       Maeda

27            6233           7672       2011/11/10    Benten-yama

28            871            1271        2012/6/16       Ryozen

29            357            476         2011/11/9    Benten-yama
30           11466          14778        2012/7/12      Yamakiya
31            5709          12130        2012/6/15       Iitoi

32           17785          23544        2012/3/30       Iitoi

33            6519          18544        2013/6/5         Hiso
34            2584           7671       2013/11/10        Hiso
35           11500          14700       2011/10/18       Iitoi
36            3300           4900        2012/9/27       Iitoi
37            431            1338       2014/10/13       Iitoi
38            274            504         2012/7/11       Oguni

39            816            829        2011/10/18     Nimaibashi
40            111            251         2013/4/30       Oguni
41            1348           2563        2011/11/9    Benten-yama

42            1724           2550        2011/11/9    Benten-yama

43            2833           5095        2012/9/27       Oguni

44            6856          13272        2012/7/11    Benten-yama

45            845            1445        2012/7/12    Benten-yama

46            580            1007        2012/7/12    Benten-yama

47            70.1           105         2012/8/16    Benten-yama

48            699            1196        2012/8/17    Benten-yama

49            129            207         2012/6/15       Maeda

50            8206          11320        2011/11/9       Iitoi

51            354            805         2013/6/5         Sasu

52             91            250         2013/6/5       Usuishi

53            2418           3300       2011/11/10        Sasu

54            7980          18800        2012/8/17        Hiso

55            637            1490        2012/6/15        Sasu

56            2755           3487        2011/9/20       Iitoi

57            746            2387        2014/5/30      Nagadoro

58            172            230         2012/3/30    Hanami-yama

59           10800          30600        2014/5/30       Akougi

60            5450          14100        2013/7/8         Hiso

61            246            483         2012/6/15    Benten-yama

62            142            257         2012/8/17    Benten-yama

63            63.4          147.1        2013/6/5        Iitoi
64            484            1760       2014/10/13        Sasu

65            883            3289        2014/11/3       Akougi

Sample    Aerial     [sup.134]Cs/    [sup.110m]Ag/
number     dose       [sup.137]Cs     [sup.137]Cs
          (pSv/h)

1           3.5          0.94             0.70

2           2.1          0.80             0.60

3           3.2          0.74             0.67

4           4.3          0.73             0.30

5           4.3          0.47             n.d.

6           4.6          0.47             n.d.

7           4.4          0.50             n.d.

8           1.3          0.46             0.10

9           4.5          0.41            0.059

10          3.5          0.28             0.13

11          8.2          0.26            0.016

12          3.1          0.27            0.013

13          2.3          0.83             0.32

14          5.4          0.79             0.40

15          4.5          0.60             0.20

16          4.5          0.66             0.16

17          3.7          0.47            0.079

18          2.7          0.30             n.d.

19          3.1          0.29            0.048

20          2.9          0.64             n.d.

21          4.6          0.40             0.32

22          4.2          0.49            0.073
23          2.5          0.79             0.39

24          2.7          0.75             0.20

25          3.0          0.77             0.11

26          4.2          0.77             n.d.

27          2.8          0.81             n.d.

28          2.1          0.69             0.25

29          3.8          0.75            0.044
30          5.1          0.78             0.21
31          5.5          0.47            0.035

32          4.5          0.76            0.0087

33          3.5          0.35            0.0029
34          3.7          0.34            0.010
35          5.1          0.78             n.d.
36          4.5          0.67             n.d.
37          2.7          0.32             n.d.
38          2.2          0.54            0.036

39          3.5          0.98            0.031
40          2.3          0.44             n.d.
41          2.2          0.53            0.025

42          2.0          0.68            0.227

43          3.4          0.56            0.032

44          3.3          0.52            0.018

45          1.4          0.58             n.d.

46          1.3          0.58             n.d.

47          1.2          0.67             n.d.

48          1.5          0.58             n.d.

49          4.0          0.62             n.d.

50          4.5          0.72            0.024

51          1.2          0.44             n.d.

52          2.1          0.36             n.d.

53          2.5          0.73             n.d.

54          4.5          0.42            0.045

55          2.5          0.43             0.12

56          5.2          0.79             0.17

57          6.2          0.31            0.034

58          1.8          0.75             0.70

59          8.0          0.35            0.0060

60          5.5          0.39            0.047

61          1.0          0.51            0.021

62          1.2          0.55             0.18

63          3.0          0.43             n.d.
64          0.8          0.28             n.d.

65          6.9          0.27             0.13

([double dagger]) : measured without desiccation and
expressed as Bq/kgFW. n.d.: not detected, not determined.

Table 3b. Decay corrected data of Table 3a. All data of Table 3a was
corrected following physical half-life of each nuclide to the date
Mar. 15, 2011

Sample    Faunal species                                     Bq/kgDW
number
                                           [sup.110m]Ag    [sup.134]Cs

1         Nephila clavata (silk spider)          * 1640           1293
2         Nephila clavata (silk spider)          * 1559           1286
3         Nephila clavata (silk spider)          * 3754           2163
4         Nephila clavata (silk spider)          * 1074           1360
5         Nephila clavata (silk spider)            n.d.           1524
6         Nephila clavata (silk spider)            n.d.           1011
7         Nephila clavata (silk spider)            n.d.            878
8         Nephila clavata (silk spider)             986           1618
9         Nephila clavata (silk spider)            n.d.            878
10        Nephila clavata (silk spider)             495            259
11        Nephila clavata (silk spider)         ** 5167           7852
12        Nephila clavata (silk spider)             677           1253
13        Araneus ventricosus (Onigumo)             344            544
14        Atypus karschi (ground spider)        ** 6811           8142
15        Atypus karschi (ground spider)         * 1955           2800
16        Atypus karschi (ground spider)        ** 9852          17261
17        Atypus karschi (ground spider)         * 2089           2863
18        Atypus karschi (ground spider)           n.d.           1193
19        Atypus karschi (ground spider)         * 3832           1800
20        Atypus karschi (ground spider)           n.d.           1630
21        Argiope amoena (Koganegumo)            * 1260            360
22        Spider (Unknown)                       * 1639           2523
23        Doricus herensis (Seaka x              * 1469           1447
            gomimushi)
24        Armadillidium vulgare (pill           ** 5482          11097
            bug)
25        Armadillidium vulgare (pill          ** 13998          40812
            bug)
26        Aphaenogaster famelica (ant)             n.d.          14942
27        Aphaenogaster famelica (ant)             n.d.           9214
28        Aphaenogaster famelica (ant)           * 1234           1366
29        Oligochaeta (earthworm)                    46            464
30        Euhadra (snail: Maimai)              ** 14504          19084
31        Bufo japonicas (frog:                  * 5517          13341
            Hikigaeru)
32        Rana rugosa (frog:                        650          26026
            Tsuchigaeru)
33        Frog (unknown)                            778          15878
34        Frog (unknown)                         * 1095           6294
35        Lacertidae (lizard)                      n.d.          13949
36        Lacertidae (lizard)                      n.d.           5507
37        Lacertidae (lizard)                      n.d.           1429
38        Elaphe climacophora                      85.8            458
            (snake) ([double dagger])
39        Patanga japonica (locust)                57.6           1066
40        Patanga japonica (locust)                n.d.            236
41        Diestrammena apicalis                     382           2424
            (Kamadouma)
42        Thereuonema tuberculata                * 3329           3080
            (millipede: Geji)
43        Meghimatium bilineatum                    932           5029
            (slug) ([double dagger])
44        Meghimatium bilineatum                 * 1130          11570
            (slug) ([double dagger])
45        Allomylina dichotoma                     n.d.           1413
            (female beetle)
46        Allomylina dichotoma                     n.d.            970
            (male beetle)
47        Cerambycidae (longicorn)                 n.d.            117
48        Graptopsaltria nigrofuscata              n.d.           1503
            (Aburazemi)
49        Pentatoma japonica (Kamemushi)           n.d.            236
50        Vespa mandarinia (hornet:                 649          10933
            Suzumebachi)
51        Apis cerana japonica Rad                 n.d.            789
            (honeybee)
52        Rhopalocera (butterfly:                  n.d.            206
            Unknown)
53        Rhopalocera (butterfly:                  n.d.           4324
            Monshirocyo)
54        Anotogaster sieboldii                 ** 8177          16979
            (dragonfly)
55        Sympetrum croceolum                       849           1065
            (dragonfly)
56        Sympetrum frequens                     * 3465           4899
            (dragonfly)
57        Palaemon paucidens                     * 2688           2375
            (river shrimp)
58        Geothelphusa dehaani                      970            311
            (crab: Sawagani)
59        Geothelphusa dehaani                     4625          31384
            (crab: Sawagani)
60        Geothelphusa dehaani                 ** 11039          13825
            (crab: Sawagani)
61        Bellamya quadrata histrica               58.8            439
            (Tanishi)
62        Cybister japonicus (Gengoro)              274            255
63        tadpole ([double dagger])                n.d.            135
64        Cynops pyrrhogaster (newt:               n.d.            484
            Akaharaimori)
65        Epimorpha (centipede: Mukade)        ** 18782           3099

Sample
number                   [sup.110m]Ag
          [sup.137]Cs    [sup.137]Cs

1                1072    ([dagger]) 1.5
2                1201    ([dagger]) 1.3
3                2144    ([dagger]) 1.8
4                1370           0.78
5                1709           n.d.
6                1130           n.d.
7                1129           n.d.
8                2237           0.44
9                1129           n.d.
10                409           +1.2
11               9734           0.53
12               1515           0.45
13                517           0.67
14               8154           0.84
15               3253           0.61
16          (#) 17942           0.55
17               3082           0.68
18               1309           n.d.
19               1960            2.0
20                784           n.d.
21                458           +2.8
22               2634           0.62
23               1303           +1.1
24          (#) 10997           0.50
25          (#) 35869           0.39
26          (#) 15049           n.d.
27               7831           n.d.
28               1311           0.94
29                485          0.095
30          (#) 15304           0.95
31          (#) 12858           0.43
32          (#) 24957          0.026
33          (#) 19713          0.039
34               8155           0.13
35          (#) 14926           n.d.
36               5320           n.d.
37               1452           n.d.
38                522           0.16
39                844          0.068
40                264           n.d.
41               2668           0.14
42               2654    ([dagger]) 1.3
43               5300           0.18
44          (#) 13758          0.082
45               1497           n.d.
46               1043           n.d.
47                109           n.d.
48               1239           n.d.
49                216           n.d.
50          (#) 11545          0.056
51                851           n.d.
52                264           n.d.
53               3434           n.d.
54          (#) 19774           0.41
55               1543           0.55
56               3628           0.96
57               2585    ([dagger]) 1.0
58                240    ([dagger]) 4.0
59              32926           0.14
60          (#) 15084           0.73
61                503           0.12
62                268           *1.0
63                155           n.d.
64               1760           n.d.
65               3595    ([dagger])  5.2

*: 1000-5000 [sup.110m]Ag Bq/kg. **: >5000 [sup.110m]Ag Bq/kg.
(#) : >10000 [sup.137]Cs Bq/kg. ([dagger]) : >1.0 of [sup.110m]Ag/
[sup.137]Cs. ([double dagger]): expressed as Bq/kgFW. n.d.:
not detected, not determined.

Table 4. [sup.110m]Ag/[sup.137]Cs radioactivity ratio in the feces
of some of the studied faunal species and the radioactivity
concentration ratio for their feces vs. soil. All data are
calculated after decay correction to the date Mar. 15, 2011

                                  Radioactivity (Bq/kg)
Feces secreted
from fauna         [sup.110m]Ag    [sup.134]Cs    [sup.137]Cs

earthworm (1)           536           163000         267000
earthworm (2)          n.d.           569000         593000
Atypus karschi         n.d.           271000         337000
lizard                 17700          58300          77100
Seaka gomimushi        1460           20900          23500
dragonfly              2510            4230           5420
locust                 n.d.            4480           4840

                                                Radioactivity ratio
                                                   feces/soil
Feces secreted     [sup.110m]Ag   Sampling
from fauna         [sup.137]Cs    date          [sup.110m]Ag

earthworm (1)         0.0020       2013/2/22         15
earthworm (2)          n.d.       2011/10/18        n.d.
Atypus karschi         n.d.       2011/10/18        n.d.
lizard                 0.23       2011/10/18         746
Seaka gomimushi       0.062       2011/11/30         45
dragonfly              0.46        2011/11/9         101
locust                 n.d.        2011/11/9        n.d.

                       Radioactivity ratio
                          feces/soil

Feces secreted
from fauna         [sup.134]Cs    [sup.137]Cs

earthworm (1)          9.0             13
earthworm (2)           15             18
Atypus karschi          17             19
lizard                 4.0            4.3
Seaka gomimushi        0.79           1.3
dragonfly              0.27           0.30
locust                 0.17           0.17

n.d.: not detected, not determined. Earthworm (2), Atypus karschi
and lizard correspond to no. 29, no. 14 and no. 35 in Table 3,
respectively. Other specimens are different from those listed in
Table 3.

Table 5. Concentration of radionuclides in Atypus karschi during
the 3.5 years after the NPP disaster. Sampling was carried out
on Oct. 18, 2011, May 5, 2012, June 5, 2013, and Oct. 13, 2014
that correspond to the sample nos. 14, 15, 17 and 18 in Table 3a,
respectively, at the fixed observation site in Iitoi. Parentheses
indicate the calculated data based on the assumption that the
radioactivity in the samples collected on the first sampling date
(Oct. 18, 2011) decayed following the physical half-life of each
radionuclide

Date of sampling                 Radionuclides (Bq/kg)

                    [sup.110m]Ag    [sup.134]Cs    [sup.137]Cs

2011/10/18          3211            6346           8016
2012/5/5            618 (1859)      1912 (5294)    3169 (7916)
2013/6/5            232 (742)       1383 (3909)    2932 (7754)
2014/10/13          0 (144)         360 (2184)     1206 (7469)

Table 6. Concentration of soil radioactivity and the [sup.110m]Ag/
[sup.137]Cs ratio. All data was corrected following physical
half-life of each nuclide to the date Mar. 15, 2011

      Soils                Radioactivity (Bq/kg) in soils

                     [sup.110m]Ag    [sup.134]Cs    [sup.137]Cs

1     Oguni               56            32000          33400
2     Hanami-yama         42            25600          26500
3     Benten-yama         22            12900          13800
4     Tsushima           238           105900         108000
5     Iitoi               41            17200          18100
6     Nimaibashi          43            29100          30300
7     Hiso                37            18200          21300

      [sup.110m]Ag
      [sup.137]Cs

1        0.0017
2        0.0016
3        0.0016
4        0.0022
5        0.0023
6        0.0014
7        0.0017
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Author:Nakanishi, Hiromi; Mori, Atsushi; Takeda, Kouki; Tanaka, Houdo; Kobayashi, Natsuko; Tanoi, Keitaro;
Publication:Japan Academy Proceedings Series B: Physical and Biological Sciences
Article Type:Report
Geographic Code:9JAPA
Date:Apr 1, 2015
Words:8518
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