Radiocesium concentrations in invertebrates and their environmental media at two distances from the Fukushima Dai-ichi Nuclear Power Plant during 3–6 years after the 2011 accident
2020
Iwasa, Mitsuhiro | Nakaya, Fumiya | Kabeya, Hideyuki | Sato, Kosuke | Ishikawa, Shin'ichirō | Takahashi, Teppei
Activity concentrations of the radioactive cesium (¹³⁴Cs and ¹³⁷Cs) were investigated in invertebrates at two sites of moderately high and higher air radiation dose rates, 14 km and 11 km distances, respectively, from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) from 2013 to 2016. At a14-km point, the ¹³⁴⁺¹³⁷Cs concentrations of soils in coniferous and broadleaf forests increased from 2013 to 2014, and thereafter declined until 2016. The ¹³⁴⁺¹³⁷Cs concentrations of the phytophagous beetle Anomala cuprea (Hope) rapidly decreased by 76.1% from 2013 to 2014, reflecting reduction in those of broadleaves. The ¹³⁴⁺¹³⁷Cs concentration levels of the carnivorous beetle Dolichus halensis (Schaller) showed a relatively low levels. The ¹³⁷Cs concentrations of the necrophagous beetle Eusilpha japonica (Motshulsky) and coprophagous beetle Onthophagus lenzii (Harold) remained constant without reduction from 2013 to 2016. Average ¹³⁴⁺¹³⁷Cs concentrations throughout four years were the highest in the geophagous crustacean (Armadillidium vulgare Latreille), followed by necrophagous beetle and coprophagus beetle. The ¹³⁴⁺¹³⁷Cs concentrations in earthworms with gut contents were significantly correlated with those in soils at each habitat from 2014 to 2015 at a14-km point, and the concentration levels at an 11-km point in 2015 were remarkably high (898 kBq kg⁻¹). Transfer factors (TFs) in earthworms ranged from 1.02 to 2.66 at a 14-km point and 0.66 to 5.0 at an11-km point. The transfer and chronological changes of radiocesium in invertebrates were discussed in relation to food habits through trophic levels in woodlands and pasturelands.
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