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129I in a sediment core offshore Fukushima: Distribution, source and its implication
Yukun Fan1, Xiaolin Hou2, Miho Fukuda3
1Xi'an AMS Center, SKLLQG, Shaanxi Key Laboratory of AMS Technology and Application, Institute of Earth Environment, CAS, Xi'an, 710061, China.
Chemosphere
|March 29, 2020
Summary
Iodine-129 from the Fukushima Daiichi Nuclear Power Plant accident significantly impacted marine sediments near Japan. Sediment core analysis revealed elevated iodine-129 levels, indicating its transfer and incorporation into offshore shallow sediments.
Area of Science:
- Environmental Science
- Nuclear Chemistry
- Marine Geology
Background:
- The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released significant amounts of Iodine-129 (129I) into the environment.
- While 129I has been studied in seawater, atmospheric, and terrestrial environments, its presence and behavior in marine sediments near FDNPP remain less understood.
- Marine sediments act as a crucial archive for understanding radionuclide deposition and transport.
Purpose of the Study:
- To investigate the distribution and concentration of Iodine-129 (129I) in a marine sediment core collected near the FDNPP.
- To compare the 129I levels in sediments with pre- and post-accident seawater data.
- To analyze the environmental behavior of 129I in sediments relative to 137Cs, considering sediment grain size distribution.
Main Methods:
- Collection and analysis of a marine sediment core from the vicinity of FDNPP.
- Measurement of 129I/127I atomic ratios within the sediment core.
- Comparison of 129I concentrations with historical seawater data and co-existing radionuclides like 137Cs.
- Analysis of sediment grain size distribution to understand radionuclide association.
Main Results:
- Sediment core analysis showed 129I/127I atomic ratios significantly higher (2 orders of magnitude) than pre-accident seawater levels.
- The observed 129I/127I ratios in sediments were comparable to post-accident seawater and sediment samples from offshore Fukushima.
- Peak concentrations of iodine isotopes were detected at a deeper sediment layer compared to radiocesium (137Cs).
- Radiocesium (137Cs) distribution correlated with fine-grained sediments, suggesting strong association, while 129I exhibited different depth distribution.
Conclusions:
- The FDNPP accident led to substantial transfer and incorporation of 129I into shallow marine sediments offshore Fukushima.
- The distinct depth profiles of 129I and 137Cs indicate different environmental behaviors and affinities within marine sediments.
- Marine sediment cores provide valuable insights into the long-term fate and transport of radionuclides released from nuclear accidents.
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