The chemical states of heavy metals and radioactive Cs were estimated in fly ash sampled at Fukushima prefecture, Japan. Estimating the speciation of incinerator fly ash is important to ensure an appropriate and efficient management of fly ash generated from disaster-related waste. In this study, fly ash collected at a waste incineration facility in Fukushima prefecture was treated using a sequential extraction test. The test results indicated that the solubility behavior of radioactive Cs was similar to that of NaCl and KCl, and approximately 60% of radioactive Cs was included as watersoluble chloride compounds in the fly ash sample. Most heavy metals eluted in three fractions, in the extraction steps for carbonate-bound, free oxide, and bound to organic matter species. The chemical states of elements in the three non-watersoluble fractions and residue showed minimal elution into the environment. Therefore, most heavy metals in the fly ash exhibited minimal elution into the environment.

Radioactive Cs derived from the Fukushima Daiichi Nuclear Power Plant accident was detected in soils sampled at Kawasaki, Japan. Radioactive Cs adsorbed on soil is hard to be removed. Fixed-point observation of radioactive Cs concentration was performed on two observation sites of Meiji University. The soil samples were also analyzed for the distribution of radioactive Cs concentration and chemical form. 10 years after the accident, the activity concentration of radioactive Cs in soil samples at the Ikuta Campus of Meiji University ranged from 127 to 448 Bq kg−1. The sequential extraction method results indicated that most radioactive Cs in the surface soil exists in a poorly soluble form.

The TEPCO Fukushima Daiichi Nuclear Power Plant accident that occurred in March 2011 resulted in the release of radioactive caesium into the environment. The radioactive caesium has been detected in the Tama River watershed. Previous investigations have shown that the concentration of radioactive caesium in sediment was relatively high in the Nogawa River. In this study, the relationship between the concentration of radioactive caesium in the sediment and the sediment characteristics was investigated. We found that 137Cs concentration in the tributary sediment has difficulty migrating downstream, while exhibiting a strong correlation with the amount of organic matter and a correlation with the clay, silt layer. Based on the results, we inferred that 137Cs is deposited together with the organic matter and clay, silt layer in the sediment and migrates at a slower pace than that in the mainstem.

The insoluble treatment of radioactive cesium in municipal solid waste incineration (MSWI) fly ash by soil-mixed geopolymer solidification using Akadama soil, which contained abundant amounts of SiO2 and Al2O3, as an activated filler was investigated. The elution rate of radioactive cesium from the geopolymer solidified substance mixed MSWI fly ash and Akadama soil was suppressed to 0.55%, compared to 69.6% for raw MSWI fly ash, using the Japanese No. 13 leaching test. Almost all radioactive cesium in MSWI fly ash was insolubilized by mixing it with Akadama soil, which showed ability as an active filler and adsorption potential for radioactive cesium. A tank leaching test was applied to confirm the long-term stability of the geopolymer solidified substance. The geopolymer solidified substance showed stability in contact with pure water and on ultraviolet radiation. The geopolymer solidifying method using Akadama soil is effective as an insolubilization treatment of radioactive cesium in MSWI fly ash. This method could be applied to other waste materials.