The Tokyo Electric Power Company's, Fukushima Dai-ichi nuclear power plant in Fukushima-Ken (Fukushima Prefecture), Japan, was destroyed in March 2011 by a massive magnitude 9 earthquake (centred offshore to the northeast of Honshu Island) and by the subsequent historic Tsunami of March 11, 2011. Because of the nuclear meltdown, hydrogen-explosion damage to the buildings that housed the reactors, and the contamination of the cooling water from the reactor cores, large quantities of radioisotopes were emitted into the atmosphere and adjacent seawater. The Tokyo University of Marine Science and Technology has measured radioisotope levels in fishery species off Iwaki-Shi(Iwaki City), Fukushima-Ken (located south of the former nuclear power plant); these data could be used to understand the relationship between the accumulation of specific nuclides (radioisotopes) and certain species of fish, as follows: [1] It is possible to accumulate or separate specific nuclides (134Cs and 137Cs) by combining Sebastes cheni (Japanese rockfish; SHIROMEBARU) and Kareius bicoloratus (Stone flounder; ISHIGAREI), and Ditrema temmincki temmincki (Surfperch; UMITANAGO) and Cynoglossus joyneri (Red tongue sole; AKASHITA BIRAME). [2] There are differences in 134Cs and 137Cs accumulation between adult fish and fry of Paralichthys olivaceus (Bastard halibut; HIRAME). Therefore, some fish species have the ability to accumulate a specific nuclide (radioisotope). To date, ultra-centrifugation and diffusion methods have been used to accumulate specific nuclides for atomic fuel. However, if we could use the ability of some fish species to accumulate specific nuclides, we would have additional methods to concentrate nuclides.
Key Words: Nuclide, Accumulate, Fukushima, Fish.
The Tokyo Electric Power Company's, Fukushima Dai-ichi nuclear power plant (37.4212°:N, 141.0334°:E), located in Futaba-Gun (Futaba County), Fukushima-Ken (Fukushima Prefecture), Japan, was destroyed in March 2011 by a massive magnitude 9 earthquake (centred offshore to the northeast of Honshu Island) and by the subsequent historic tsunami of March 11, 2011. Because of the resulting nuclear meltdown, the hydrogen-explosion damage to the buildings that housed the reactors, and the contamination of the cooling water from the reactor cores, large quantities of radioisotopes were emitted into the atmosphere and adjacent seawater. From November 22 to 23, 2012, the Tokyo University of Marine Science and Technology independently sampled radioisotope levels in fishery species off Iwaki-Shi (Iwaki City), Fukushima-Ken, just south of the former nuclear power plant. These data included detailed measurements of individual fish such as weight, sex, length, and collection site, which can be used to better understand the accumulation of radioisotopes in fishes. This report shows new insights into the relationship between the accumulation of specific nuclides (radioisotopes) by specific fish species based on this sampling after Katsura’s report (Katsura, 2013a; Gerhard et al., 1998; Hellstrom and Brune, 1964; Kalmun, 1982; Murray, 1962; Wolfson, 1956) (Figure 1).
To sample local fish, trawl (dragnet) fishing was conducted on the November 22, 2012, off Yotsukura and Ena, Iwaki-Shi, Fukushima-Ken, Japan, in a total fishing area of 9,450 and 9,775 m2, respectively (Atkins and Warren, 1953). Gill-net fishing was conducted from November 22-23, 2012 in the same location, with a total fishing area of 28,900 and 50,141 m2 off Yotsukura and Ena, respectively (Buscaino et al., 2009). The edible portion of sampled fish was minced and placed into 100 ml plastic containers (U-8 containers). The concentration of Cs-134 and Cs-137 radioisotopes in the fish biomass were measured by IDEA Consultants Inc. (Tokyo, Japan) using a germanium semiconductor detector (Seiko EG&G Co.Model:GEM20-70) (Inazu et al., 2011; Minatani et al., 2012).
The total fish-collection area for November 22-23, 2012 as shown in Table 1 was calculated as follows (Katsura, 2013b):
9,450+28,900+9,775+50,141= 98,266 m2
Table 2 shows the following:
i) [Percentage of Total Fish Weight] = [%TFW] is the percentage that each species of fish has with respect to the total fish weight sampled.
ii) ([134Cs per Fish Species] / [Total 134Cs for All Species]) × 100
= ([134Cs] / [T134Cs]) × 100=[134Cs%]
is the percentage of 134Cs becquerel that each fish species has of the total 134Cs becquerel for all fish species (Bq is the symbol for “becquerel”, an SI derived unit of radioactivity; One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second) (Choppin et al., 2002).
iii) ([137Cs per Fish Species]/[Total 137Cs All Species]) x 100 =([137Cs]/[T137Cs])x100=[137Cs%]
is the percentage of 137Cs becquerel that each fish species has of the total 137Cs becquerel for all fish species sampled.
iv) Tables 3 and 4 show the proportion of 134Cs and 137Cs accumulated by each fish species according to their percentage of the total fish weight in descending order, as follows:
[134Cs%]/[%TFW] × 100
[137Cs%]/[%TFW] × 100
If there was a proportional relationship between the amount of 134Cs or 137Cs Bq (that is, quantity of 134Cs or 137Cs radioactive material) in sampled fish body weight regardless of species, all percentages of 134Cs or 137Cs Bq per percentage of total fish weight should be 100% (Table 5).
The percentage that each species of fish has with respect to the total fish sampled = [%TFW]; (134Cs per Fish Species) [becquerel]/[kg] = [134Cs]; ([134Cs per Fish Species]/[Total 134Cs for All Species])x100 [%] = [134Cs%]; (137Cs per Fish Species) [becquerel]/[kg] = [137Cs]; ([137Cs per Fish Species]/[Total 134Cs for All Species])x100 [%] = [137Cs%].
However, these percentages vary depending on fish species from 0 to 242.855% for 134Cs and from 0 to 231.9655554% for 137Cs.
The values of [134Cs%] / [%TFW] × 100 and [137Cs%] / [%TFW] × 100 for the following species are 0%: Acanthopagrus schlegeli (Japanese black seabream; KURODAI), Clupea pallasii Vakenciennes (Pacific herring; NISHIN), Engraulis japonica (Japanese anchovy; KATAKUCHI IWASHI), Lepidotrigla microptena Gunther (Gurnard, Sea-robin; KANAGASHIRA), Liparis tanakai (English Name: Not-Available=N/A; KUSAUO), Mustelus manazo (Starspotted smooth hound; HOSHI-ZAME), Oncorhynchus keta (Chum salmon, Salmon; SAKE), Oplegnathus punctatus (Spotted Knifejaw; ISHIGAKIDAI), Pagrus major (Red seabream; MADAI (SEIGYO)), P. major (fry) (Redseabream (Fry); MADAI (CHIGYO)), Paralichthys olivaceus (fry) (Bastard halibut (Fry); HIRAME (CHIGYO)), Platycephalus sp. (Flathead; MAGOCHI), Platycephalus sp. (fry) (Flathead (Fry); MAGOCHI (CHIGYO)), Takifugu poecilonotus (Pufferfish; Name: KOMON FUGU), Takifugu snyderi (Globefish, Blowfish, Puffer; SHOUSAI FUGU), Takifugu stictonotus (Globefish, Blowfish, Puffer; GOMA FUGU), Trachurus japonicas (Japanese jack mackerel. Japanese horse mackerel, Japanese scad; MAAJI) and Zeus faber Linnaeus (John dory; MATOU DAI). These findings indicate that these fish species do not have the ability to accumulate 134Cs and 137Cs radioisotopes. In other words, these species eliminate 134Cs and 137Cs radioisotopes from their bodies.
iv) Tables 3 and 4 show the differences in the 134Cs and 137Cs accumulation ratio depending on fish species; some species accumulate more 134Cs whereas other species accumulate more 137Cs.
Thus, the order values of ([134Cs%] / [%TFW]) × 100% and ([137Cs%] / [%TFW]) × 100% are reversed. In detail, it has the following features.
a) The order value of ([137Cs%] / [%TFW]) × 100% of Sebastes cheni (Japanese rockfish, Japanese sea perch; SHIRO MEBARU) is higher than that of Kareius bicoloratus (Stone flounder; ISHIGAREI). However, the order value of ([134Cs%] / [%TFW]) × 100% of Kareius bicoloratus is higher than that of Sebastes cheni. Therefore, it may be possible to use Sebastes cheni and Kareius bicoloratus for the separation or accumulation of nuclide 134CS and 137Cs. Sebastes cheni shows ((231.965554-231.6548179) / 231.6548179) × 100=0.13413755 Weight% higher accumulation than Kareius bicoloratus for 137Cs.
However, Kareius bicoloratus shows ((242.85505-241.14706) / 241.14706) × 100=0.708277347 Weight% higher accumulation than Sebastes cheni for 134Cs.
Therefore, it may be possible to use Sebastes cheni and Kareius bicoloratus for the accumulation or separation for specific nuclides 134Cs and 137Cs.
b) The order value of ([137Cs%] / [%TFW]) × 100%of Ditrema temminkii (Surfperch; Japanese Name: UMITANAGO) is higher than that of Cynoglossus joyneri (Red tongue sole; AKASHITA BIRAME) (Figure 4) and the order value of: ([134Cs%] / [%TFW]) x 100% of Cynoglossus joyneri is higher than that of Ditrema temminkii. Therefore, it may be possible to use Ditrema temminkii and Cynoglossus joyneri for the separation or accumulation of nuclide 134CS and 137Cs. Ditrema temminkii shows ((24.2530309-24.19868403) / 24.19868403) × 100=0.224719079 Weight% higher accumulation than Cynoglossus joyneri for 137Cs. However, Cynoglossus joyneri shows ((26.340432-23.248701) / 23.278701) × 100=13.29851074 Weight%higher accumulation than Ditrema temminkii for 134Cs. Therefore, it may be possible to use Ditrema temminkii and Cynoglossus joyneri for the accumulation orseparation of specific nuclides 134Cs and 137Cs.
v) Additionally, Tables 3 and 4 show accumulation ratio differences between adult fish and fry of the same species.
a) Pagrus major (Adult Fish) (Red seabream (Adult Fish); MADAI (SEIGYO)), Pagrus major (Fry) (Red seabream (Fry); MADAI (CHIGYO)), Platycephalus sp. (Adult Fish) (Flathead (Adult Fish); MAGOCHI (SEIGYO)) and Platycephalus sp.(fry) (Flathead (Fry); MAGOCHI (CHIGYO)) do not have the ability to accumulate both 134Cs and 137Cs. Additionally, there do not appear to be any differences between adult fish and fry for the accumulation 134Cs and 137Cs.
b) Paralichthys olivaceus (Adult Fish) (Bastard halibut (Adult Fish); HIRAME (SEIGYO)) has the ability to accumulate both134Cs and 137Cs; however, Paralichthys olivaceus (Fry) (Bastard halibut (Fry); HIRAME (CHIGYO)) does not have ability to accumulate both 134Cs and 137Cs. There are differences between adult fish and fry of Paralichthys olivaceus for the accumulation of 134Cs and 137Cs.
vi) It is currently known that specific fish species have the ability to accumulate specific elements, ions and molecules (Thompson et al., 1972). However, the accumulation of specific radioisotopes had not been reported until this and Katsura’s research article (Katsura, 2013a). The disaster at Fukushima on March 11, 2011 provides the opportunity to gain new insight into the accumulation of specific radioisotopes by fishes. We must discover the theoretical reasons for these phenomena in order to use fishes as new methods for atomic fuel production and clean-up of specific radioisotope contamination.
1) This finding indicates that the following fishes do not have the ability to accumulate the 134Cs and 137Cs radioisotopes: Acanthopagrus schlegeli (Japanese black seabream; KURODAI), Clupea pallasii Vakenciennes (Pacific herring; NISHIN), Engraulis japonica (Japanese anchovy; KATAKUCHI IWASHI), Lepidotrigla microptena Gunther (Gurnard, Sea-robin; KANAGASHIRA), Liparis tanakai (English Name: Not Available=N/A; KUSAUO), Mustelus manazo (Starspotted smooth hound; HOSHIZAME), Oncorhynchus keta (Chum salmon, Salmon; SAKE), Oplegnathus punctatus (Spotted Knifejaw; ISHIGAKI DAI), Pagrus major (Red seabream; MADAI), Pagrus major (Fry) (Red seabream (Fry); MADAI (CHIGYO)), Paralichthys olivaceus (Fry) (Bastard halibut (Fry); HIRAME (CHIGYO)), Platycephalus sp. (Flathead; MAGOCHI), Platycephalus sp. (fry) (Flathead (Fry); MAGOCHI (CHIGYO)), Takifugu poecilonotus (Pufferfish; KOMON-FUGU), Takifugu snyderi (Globefish, Blowfish, Puffer; SHOUSAI-FUGU), Takifugu stictonotus (Globefish, Blowfish, Puffer; GOMA-FUGU), Trachurus-japonicas (Japanese jack mackerel. Japanese horse mackerel, Japanese scad; MAAJI) and Zeus faber Linnaeus (John-dory; MATOUDAI). Several fish species are able to eliminate 134Cs and 137Cs radioisotopes.
2) It is possible to accumulate or separate specific radioisotopes (134Cs or 137Cs) by combining the following fish species: Sebastes cheni (Japanese rockfish, Japanese sea perch; SHIRO-MEBARU) (Figure 2) and Kareius bicoloratus (Stone flounder; ISHIGAREI) (Figure 3); and Ditrema temminkii (Surfperch; UMITANAGO) (Figure 5) and Cynoglossus joyneri (Red tongue sole; AKASHITA BIRAME) (Figure 4).
3) Neither Pagrus major (Red seabream; MADAI) nor Platycephalus sp. (Flathead; MAGOCHI) adult fish and fry accumulated 134Cs and 137Cs. There were differences in the accumulation of 134Cs and 137Cs between adult fish and fry of Paralichthys olivaceus (Bastard halibut; HIRAME).
4) Physical methods such as ultra-centrifugation and diffusion have been used to obtain high concentrations of nuclides (e.g., 235 U). This study suggests that physical methods are not required to accumulate high concentrations of specific radioisotopes.
