Aiichiro Fujinaga

Methodology for Setting Risk‐Based Concentrations of Contaminants in Soil and Groundwater and Application to a Model Contaminated Site

In Japan, environmental standards for contaminants in groundwater and in leachate from soil are set with the assumption that they are used for drinking water over a human lifetime. Where there is neither a well nor groundwater used for drinking, the standard is thus too severe. Therefore, remediation based on these standards incurs excessive effort and cost. In contrast, the environmental-assessment procedure used in the United States and the Netherlands considers the site conditions (land use, existing wells, etc.); however, a risk assessment is required for each site. Therefore, this study proposes a new framework for judging contamination in Japan by considering the merits of the environmental standards used and a method for risk assessment. The framework involves setting risk-based concentrations that are attainable remediation goals for contaminants in soil and groundwater. The framework was then applied to a model contaminated site for risk management, and the results are discussed regarding the effectiveness and applicability of the new methodology.

Volume Reduction of Municipal Solid Wastes Contaminated with Radioactive Cesium by Ferrocyanide Coprecipitation Technique

Municipal solid wastes (MSW) with elevated concentrations of radioactive cesium (rad-Cs hereafter) have been generated in some areas of Japan in the aftermath of the Fukushima Daiichi Nuclear Power Plant (F1 hereafter) accident. Both recycling and final disposal of the contaminated MSW have become a difficult problem in the affected areas, resulting in accumulation of treated residues in the treatment facilities.

Extractability and Chemical Forms of Radioactive Cesium in Designated Wastes Investigated in an On-Site Test

In the aftermath of the 2011 accident at Fukushima Daiichi Nuclear Power Plant (F1 hereafter), municipal solid waste (MSW) contaminated with radioactive cesium (rad-Cs hereafter) has been generated in 12 prefectures in Japan. The Japanese Minister of Environment classified MSW that contained rad-Cs in the concentration more than 8,000 Bq/kg as “designated (solid) waste (DSW hereafter), and prescribed the collection, storage and transportation procedures. When MSW containing rad-Cs was incinerated, rad-Cs was concentrated in fly ash, and the ash often fell into the category of DSW. We have investigated a technique that can reduce the volume of the rad-Cs-contaminated fly-ash by extracting rad-Cs with aqueous solvents such as water and oxalic acid and concentrating rad-Cs in a small amount of hexacyanoferrate (or ferrocyanide, designated as Fer hereafter) precipitate. Since DSW could not be transported to the outside laboratory, we have conducted on-site tests at places where DSW were generated to investigate the applicability of the extraction – precipitation technique.

Risk Evaluation for Remediation Techniques to Metal-Contaminated Soils

In Japan, environmental standards for contaminants in groundwater and in leachate from soil are set with the assumption that they are used for drinking water over a human lifetime. Where there is neither a well nor groundwater used for drinking, the standard is thus too severe. Therefore, remediation based on these standards incurs excessive effort and cost. In contrast, the environmental assessment procedure used in the USA and the Netherlands considers the site conditions (land use, existing wells, etc.); however, a risk assessment is required for each site. This chapter shows a framework for validating contamination by considering the merits of the environmental standards used and a method for risk assessment. The framework involves setting risk-based concentrations (RBCs), which are attainable remediation goals for contaminants in soil and groundwater. The framework was then applied to a model contaminated site for risk management. RBCs of Cr(VI) in a contaminated site were set according to the site conditions. The RBCs of Cr(VI) with/without drinking water in residential area are calculated. Second, an experiment for contaminated soil was introduced by using column equipment. The equipment was designed by applying water permeability test. And then, variation of concentration of the contaminant was simulated using an advection-diffusion model. Simulation by the mathematical model is also useful for monitored natural attenuation or in situ treatment, because the simulation can estimate clean-up time at the contaminated site. Even though the estimated clean-up time is not exact time, the cost of in situ treatment is not expensive. And then land owners can choose the in situ treatment.

Risk Assessment of the Intake of Foods and Soil With the Radionuclides and the Air Radiation Dose After the Fukushima Nuclear Disaster

The exposure routes by which the dispersion of radionuclides from the accident at theFukushima atomic power plant were estimated, and the risk was evaluated based on theoverall exposure routes, which include the ingestion of food, ingestion and inhalation ofsoil, and external air dose. This study shows that the air dose from this disaster shouldbe less than 0.2lSv/h to control the radiation dose with the consumption of food beingless than 1 mSv/yr. However, to maintain the lifetime dose under 100 mSv, several mSv/yr is sufficient, considering radioactive decay and dilution by advection and diffusion.[DOI: 10.1115/1.4026811]