Linking heterogeneous distribution of radiocaesium in soils and pond sediments in the Fukushima Daiichi exclusion zone to mobility and potential bioavailability

Estela Reinoso-Maset*, Justin Brown, Marit N. Pettersen, Frits Steenhuisen, Abednego Tetteh, Toshihiro Wada, Thomas G. Hinton, Brit Salbu, Ole Christian Lind

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

During the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011 significant amounts of radiocaesium were released into the atmosphere from the reactor units 1, 2 and 3. This caused a non-uniform deposition, in composition and direction, of 134Cs and 137Cs in the near field (<30 km) from the reactors. In this work, we elucidate the influence of speciation, including radioactive particles, on mobility and potential bioavailability of radiocaesium in soils and sediments from sites located in different directions and distances from the FDNPP. Samples collected in September 2016 were characterized and subjected to sequential chemical extractions and simulated gastrointestinal fluid leaching, and the 137Cs and 134Cs activities were determined in bulk, grain-size and extracted fractions. The results show that radiocaesium was mainly irreversibly bound and in an inert form. Combined, the two forms contained >90% of the activity present in soils and ~84% in sediments. Digital autoradiography revealed that the inert fraction was predominantly associated with heterogeneities, an indication of radioactive particles. The frequency of heterogeneities was correlated with 137Cs activity concentrations, and both were in agreement with the ambient equivalent air doses measured in situ during sampling. Moreover, in situ gamma spectrometry measurements were used in the InSiCal software tool to derive 134Cs and 137Cs surface contamination. Soil activity concentrations and contamination density estimations, decay-corrected to the day of the FDNPP accident, resulted in 134Cs/137Cs ratios that match the reported release and deposition plumes from the reactor units. Overall, these results demonstrate the persistence of the particle contamination in the Fukushima near field and highlight the importance of including radioactive particles in environmental impact assessments.

Original languageEnglish
Article number106080
Pages (from-to)1-11
Number of pages12
JournalJournal of Environmental Radioactivity
Volume211
Early online date31-Oct-2019
DOIs
Publication statusPublished - Jan-2020

Keywords

  • Extractions
  • Fukushima
  • Radioactive particles
  • Radiocaesium
  • NUCLEAR-POWER-PLANT;
  • CS-BEARING MICROPARTICLES;
  • RADIOACTIVE PARTICLES;
  • SIZE DISTRIBUTION
  • DEPTH PROFILES
  • ENVIRONMENT
  • CESIUM
  • DISCOVERY
  • BEHAVIOR
  • URANIUM

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