1. Concentrations and biological half-life of radioactive cesium in epigeic earthworms after the Fukushima Dai-ichi Nuclear Power Plant accident
- Author
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Sota Tanaka, Tarô Adati, Shuko Takahashi, Keiko Fujiwara, and Tomoyuki Takahashi
- Subjects
Health, Toxicology and Mutagenesis ,chemistry.chemical_element ,010501 environmental sciences ,01 natural sciences ,Animal science ,Japan ,Radiation Monitoring ,Animals ,Fukushima Nuclear Accident ,Soil Pollutants, Radioactive ,Environmental Chemistry ,Oligochaeta ,Waste Management and Disposal ,0105 earth and related environmental sciences ,biology ,Chemistry ,04 agricultural and veterinary sciences ,General Medicine ,biology.organism_classification ,Pollution ,Radioactivity ,Cesium Radioisotopes ,Megascolecidae ,Caesium ,040103 agronomy & agriculture ,Litter ,0401 agriculture, forestry, and fisheries ,Biological half-life ,Epigeal ,Half-Life - Abstract
To understand the long-term behavior of radiocesium in the biological processes of a forest ecosystem, its concentration in Japanese epigeic earthworms (Megascolecidae), litter, and soil, and the ambient dose equivalent rates, were investigated after the Fukushima Dai-ichi Nuclear Power Plant accident. The metabolism of radiocesium in the earthworms was also investigated in the laboratory, and its biological half-life (Tb) was estimated. The concentration of ¹³⁷Cs in the habitat soil and litter changed from 2014 to 2016, with levels in the litter going from 44.9 Bq/g dw (in 2014) to 45.3 Bq/g dw (2015) and 10.7 Bq/g dw (2016); in soil, these values were 9.79 Bq/g dw, 7.14 Bq/g dw and 18.0 Bq/g dw, respectively. By contrast, no significant changes were observed in the concentrations in the earthworms, which were 4.87 Bq/g fw, 5.30 Bq/g fw and 4.67 Bq/g fw in 2014, 2015, and 2016, respectively. The ambient dose equivalent rates at the sampling site declined significantly over these three years, going from 2.15 μSv/h to 1.68 μSv/h and 1.35 μSv/h, mostly corresponding to physical decay of radiocesium. The majority (95%) of the ¹³⁷Cs in the earthworms, observed via autoradiography, was concentrated primarily in the intestine. The clearance of ¹³⁷Cs from the earthworms was described by dual exponential functions: the half-life in the rapid loss due to gut clearance was 0.10 days and a second slower loss due to physiological clearance was 27.4 days.
- Published
- 2018