Dataset Information

Dispersion of radiocesium-contaminated bottom sediment caused by heavy rainfall in Joso City, Japan.

ABSTRACT: A large-scale heavy rainfall disaster occurred in Joso City, Japan, in September 2015, and one third of the city area (40 km2) was flooded by the Kinu River. Artificial radionuclides such as 134Cs and 137Cs were known to have accumulated in the river bottom sediment after their release in the 2011 Fukushima Dai-ichi Nuclear Power Plant accident. It was thought that these radionuclides might have been dispersed by the rainfall disaster. A car-borne survey of absorbed dose rate in air had been made by the authors in Joso City in August 2015. Then, the present study made a second car-borne survey in October 2015, to evaluate changes in the rate after the rainfall disaster. The absorbed dose rate in air and the standard deviation (range) measured in the flooded areas of Joso City after the disaster were 68 ± 9 nGy h-1 (39-98 nGy h-1), which was 10% higher than the rate before it. Additionally, higher dose rates (> 60 nGy h-1) were observed for the flooded areas after the disaster; furthermore, up to 886 Bq kg-1 of activity concentration from 134Cs and 137Cs was observed in these flooded areas, and this was 11 times higher than the activity concentration before the disaster. These results suggested the dispersion of artificial radionuclides accumulated in the bottom sediment of the Kinu River after the Fukushima Daiichi Nuclear Power Plant accident occurred by the heavy rainfall disaster.

SUBMITTER: Inoue K

PROVIDER: S-EPMC5325223 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Dispersion of radiocesium-contaminated bottom sediment caused by heavy rainfall in Joso City, Japan.

Inoue Kazumasa K Arai Moeko M Fukushi Masahiro M

PloS one 20170224 2

A large-scale heavy rainfall disaster occurred in Joso City, Japan, in September 2015, and one third of the city area (40 km2) was flooded by the Kinu River. Artificial radionuclides such as 134Cs and 137Cs were known to have accumulated in the river bottom sediment after their release in the 2011 Fukushima Dai-ichi Nuclear Power Plant accident. It was thought that these radionuclides might have been dispersed by the rainfall disaster. A car-borne survey of absorbed dose rate in air had been mad ...[more]

PMID: 28234986

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Project description:Coal bottom ash (CBA) was modified on the basis of the engineering problems of low resource utilization of CBA and difficulty in treating HMS through alkali activation to synthesize geopolymers and solidify heavy metal-contaminated soil (HMS). The optimal values of geopolymers were selected through response surface methodology. Their mineral compositions, microstructure, and binding energy were determined through X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy tests, respectively. The stress-strain curve, the leaching concentration and fraction of heavy metals, and the solidifying mechanism for remolded soil were determined through unconfined compressive strength, leaching toxicity, sequential chemical extraction, and infrared (IR) spectroscopy tests, respectively. Based on these experiments, the following conclusions were presented. The optimum ratios of CBA-based geopolymers were n(Si) : n(Al) = 2.666, n(Na) : n(Al) = 0.687, and n(water) : n(binder) = 2.422. The X-ray curves of the geopolymers were obvious hump-like protuberances at diffraction angles of 20-35° and had a dense amorphous structure on the surface. The maximum binding energies of Si 2p and Al 2p decreased to 101.03 and 72.89 eV, respectively. A 3D network polymerized because of strong geopolymerization. The maximum axial stress of the remolded soil was 104.91% higher than that of the undisturbed soil, and the leaching concentration decreased by more than 45.88%. The leaching toxicity met the requirements of standard GB 5085.3-2007. The proportion of the acid-extractable fraction of heavy metals in the remolded soil decreased, whereas the proportion of residual fraction increased. The stretching vibration of Si-O-Si (Al) and the bending vibration of Si-O-Si appeared in the IR spectrum. The soil particles were completely encapsulated by a hardened geopolymer structure, thereby forming a multilayer space-skeleton barrier structure that could greatly improve the mechanical properties.

Dataset Information

Dispersion of radiocesium-contaminated bottom sediment caused by heavy rainfall in Joso City, Japan.

Publications

Dispersion of radiocesium-contaminated bottom sediment caused by heavy rainfall in Joso City, Japan.

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