Just ten years ago, the world witnessed the Great East Japan Earthquake (GEJE), the subsequent Fukushima Daiichi nuclear power plant (FDNPP) accident and the severe impacts these had on the society and environment of eastern Japan. A wide range of research related to the nuclear accident has been conducted, with the results already released in many cases regarding the environmental impacts of the large amounts of radioactive substances emitted into the environment during that event. In addition, research is being carried out on sustainable community development, including the establishment of sustainable regional environments, reconstruction according to environmentally conscious principles and creation of disaster resilient regions. Such environmental emergency research has contributed greatly to environmental recovery in areas affected by the GEJE and nuclear accident and also to environmental emergency management for natural disasters after the GEJE. This special issue focuses on the progress in environmental emergency research after the GEJE and nuclear accident, and provides an integrated body of relevant scientific knowledge. The articles in this issue cover a wide range of studies addressing environmental emergency aspects such as post-disaster environmental impacts of pollutants, environmental recovery and management of disaster waste. Many articles have been provided by researchers of the National Institute for Environmental Studies, Japan Atomic Energy Agency, and other organizations. We are profoundly grateful for their contribution of valuable scientific knowledge and technical expertise toward environmental restoration, and strongly hope that this information will be utilized in efforts towards disaster-resilience and environmental sustainability worldwide.

Guest Editors

Toshimasa OHARA

Seiji HAYASHI

Kazuki IIJIMA

The radioactive environmental contamination that resulted from the Fukushima Daiichi nuclear power plant accident has clearly been declining during the nearly 10 years that have passed since the accident. Many studies, however, have indicated prolongation of radioactive contamination in natural ecosystems, probably arising from non-decontaminated forested areas, so a more detailed examination is needed on the environmental dynamics of bioavailable radiocesium and its transfer to ecosystems. Also, regarding the influences of radiation on organisms, the effects on wild organisms of the evacuation of humans have been more pronounced than the direct effects from radiation, especially in the Fukushima evacuation zones.

Examining the comprehensive impacts of the nuclear accidents in Fukushima on biodiversity continues to be a challenge. Data availability may be one problem. Previous studies have used hardly any ecological data from before the accidents. Furthermore, raw data from the previous studies have been not adequately released for re-analysis and integration into new analyses. To examine the current status and problems with open biodiversity data and monitoring systems related with nuclear plants, we surveyed (1) datasets registered in GBIF (the Global Biodiversity Information Facility) around the Fukushima evacuation zone (including the “difficult to return zone,” Fig. 1) and (2) monitoring sites of the Monitoring Sites 1000 Project and JaLTER (Japan Long-Term Ecological Research Network) around Japan’s nuclear power plants. The GBIF database shows that few datasets on wild organisms exist covering periods both before and after the Fukushima accident around the evacuation zone, except on birds. The present monitoring sites near the nuclear power plants are shown mainly to target wild birds and sites targeting other taxa are limited. In addition, the monitoring surveys have been highly dependent on citizen scientists. To enhance biodiversity data availability in preparation for evaluating impacts of nuclear emergencies, it would be desirable to improve monitoring systems and technologies for integrating monitoring by citizen scientists in normal times with monitoring by scientists belonging to institutes in times of emergency.

Positive and negative roles of dam reservoirs in radiocesium behavior in a river catchment were examined based on the results of comprehensive, long-term hydrological monitoring from 2013 to 2017 at Matsugabou Dam on the upstream reaches of the Uda River, which is one of the main rivers in the northern coastal region of Fukushima Prefecture. An estimation of the annual mass balance of Cs-137 associated with suspended solids (SS) in the reservoir showed that Matsugabou Dam had the effect of reducing the migration of radiocesium associated with SS from the dam reservoir catchment to the downstream reaches by more than 85% by storing SS in the reservoir bed. Moreover, proactive discharge control for preventing flood inundation in the downstream region had the ability to make this storage function perform even more effectively. On the other hand, the estimated annual mass balance of dissolved Cs-137 in the reservoir showed that the amount in the water discharged clearly tended to exceed the amount in the inflow, suggesting that substantial amounts of dissolved radiocesium were presumably produced by dissolution/elution from the stored bottom sediments in the dam reservoir. This negative role of a dam producing dissolved radiocesium may contribute to long-term contamination of freshwater ecosystems in downstream water bodies.

Lake water, phytoplankton and zooplankton were sampled in a total of 12 quarterly surveys from August 2014 to May 2017 at a reservoir in the Fukushima nuclear disaster area, and variations in dissolved forms of 137 Cs and planktonic 137Cs were observed. Seasonal variations in dissolved 137Cs concentration becoming high in summer and low in winter were observed in the upstream, midstream and downstream areas of the reservoir, but no seasonal or site-specific differences in planktonic 137Cs concentrations or dominant species were found. The concentration factors of 137Cs for phytoplankton and zooplankton were 340 and 1,700, which were comparable to previously reported values. The amount of planktonic 137Cs in the water was less than 1.4% of the total 137Cs in the reservoir water; therefore the effect of plankton on the dynamics of 137Cs in the reservoir was minimal.

A three-year monitoring of 137Cs outflow associated with soil erosion from decontaminated and non decontaminated sites using an experimental plot was conducted in a mountainous forest of Fukushima Prefecture during the rainy season. The annual 137Cs outflow from the decontaminated site was 9–13 times larger than that of the non-decontaminated site. However, the outflow from the decontaminated site decreased from 2.55% to 0.65% corresponding with recovery of the forest floor cover. When the forest floor cover reached 60% or more, the 137Cs outflow from the decontaminated site began to show relatively minor fluctuations at a similar level to the non-decontaminated site. The decrease in the 137Cs outflow corresponding to the restoration of the forest floor cover was due to the recovery of the protective effect of the forest floor against raindrop splashes and a decrease in the ratio of soil components with relatively high 137Cs activity in the particulate matter.

A large amount of radioactive Cs was released into the environment from the Fukushima Daiichi nuclear power plant (FDNPP) following the 2011 Great East Japan Earthquake. Nine years have passed since this accident, and the radioactive Cs concentration in seabed sediments has decreased. The behavior of radioactive Cs in coastal areas, however, is complicated due to the influence of rivers, waves and so on. The Japan Atomic Energy Agency has conducted several studies at the mouth of the Ukedo River. Here, we review previous studies and evaluate the impact of the radioactive Cs supplied by rivers using a sediment trap. In this study, a mooring system consisting of a sediment trap was installed in the Ukedo River estuary near the FDNPP in 2017. The results showed 137Cs flux in winter accounting for 60% of the annual flux. This suggests that mobilization of radioactive Cs in the coastal area is primarily due to resuspension and not river discharge.

The nuclear power plant accident that occurred at the Fukushima Daiichi Nuclear Power Station operated by Tokyo Electric Power Co. in the aftermath of the Great East Japan Earthquake of 2011 resulted in radioactive contamination of a substantial portion of the surrounding area, mostly in Fukushima Prefecture. Immediately after the accident, direct contamination of crops occurred in areas where radioactive cesium falling from the atmosphere was deposited on plant leaves or branches. As the effects of direct contamination subsided over time, indirect contamination of crops, caused by absorption of radioactive cesium from the soil, became a problem. The local authorities overseeing accident control in Fukushima Prefecture decided to suspend all farming in the area, prohibiting planting of paddy fields within a 30 km radius of the Fukushima Daiichi Nuclear Power Station with soil radiocesium concentrations of more than 5,000 Bq Kg−1. Although the damage caused by the earthquake was relatively minor in Iitate Village in the Date district of Fukushima Prefecture, the influence of radioactive fallout forced all of the villagers to evacuate their homes. While decontamination of the entire region and environmental restoration by the government is in progress, the village is still confronted with various problems, including promoting public awareness of nuclear materials and disposing of radioactively contaminated waste. The author was dispatched to Iitate Village as a specialist for the Industry Promotion Section from April 2012 to the present (FY2020) to collaborate with staff of the municipal government. He partook in various activities, including negotiating with relevant government ministries, attending resident information sessions, and addressing issues of decontamination, waste disposal and agricultural business. In this paper, the process from decontamination to resuming agricultural business and progress toward environmental restoration with disposal of decontamination wastes is discussed in detail.

After the Fukushima Daiichi nuclear power plant accident, a large region of northeastern Japan was contaminated by radio-Cs (r-Cs). Contaminated soil and incineration ashes are generated through decontamination processes and daily human activities, respectively. To reduce the volume of such substances, several kinds of pyroprocessing techniques have been developed. R-Cs is thought to be trapped within aluminosilicates. With the addition of Ca to these compounds, alkali metals may be readily removed. Next, Cl is added and the alkali metals are volatilized in the order of Cs > K > Na. On the basis of this estimation, the highest Ca content is expected to produce the best conditions for the removal of Cs. Calcium silicate and aluminate with the highest Ca concentration are found in Portland cement. To understand the mechanism of Cs volatilization, the effect of the Ca/(Si+Al) ratio on the ratio of Cs remaining is introduced on the basis of data from the literature. A high-efficiency Cs removal process in cement is also investigated using a small scale rotary furnace for real contaminated soil and ashes, and by pilot-scale experiments with model soil. Additionally, through detailed experiments using pollucite — a cesium aluminosilicate — Cs removal behaviors were found to correspond to phase change, depending on the Ca/Si and Cl/Cs ratios. At high Ca/Si ratios, even without adding Cl, a significant amount of Cs could be removed. Potassium existing in or added to the initially contaminated samples facilitated Cs removal such that Cs was reduced to an undetectable level even without the addition of Cl.

At present, reducing the volume of decontamination wastes/soils is an indispensable task in Japan because to secure final disposal sites with vast capacity is considered difficult. One promising option is thermal treatment to separate radioactive cesium (Cs) from wastes/soils. This, however, generates Cs concentrates in which Cs is thought to have high solubility. From a long-term viewpoint on ensuring safety, the solubility of Cs itself in the concentrates should be reduced even though it will be stored in containers. In this study, insolubilization of Cs by co-heating with potassium feldspar (hereafter, K-feldspar) was investigated. This process can insolubilize almost 100% of Cs when only Cs carbonate and K-feldspar are co heated. However, concentrates in actuality consist mainly of fly ash and contain various elements. Thus the objective of this study was to elucidate the influence of the presence of fly ash. In particular, elements that inhibit Cs capture were focused on. Various co-heating experiments on mixtures of CsCl, K-feldspar, fly ash and alkali metal compounds were conducted. As a result, the following findings were obtained: 1) the efficiency of Cs insolubilization decreased in the presence of fly ash, 2) Ca in fly ash inhibited Cs insolubilization. Notably, when Ca was in chloride form, this inhibition was at a maximum, 3) converting in fly ash to CaCO3 by use of Na2 CO3 , improved the efficiency of Cs insolubilization. When the ratio of CaCl2 fly ash to K-feldspar was increased, however, the efficiency showed a gradual decrease.

The durability of the covering sheets used for storage of decontamination soil and waste at temporary storage sites (TSSs) in Fukushima Prefecture was investigated. In this study, we investigated durability from three viewpoints, accelerated UV exposure tests, comparisons among several municipal TSSs, and material aging. The results indicated that the water resistance of gas-permeable/waterproof sheets (GWSs) used for more than two years at TSSs was much lower than its standard value in many cases, which means the possibility of rainwater intrusion to storage containers holding decontamination soil. On the other hand, the tensile strength and water resistance of the geomembrane used at TSSs remained above the standard values. The results of accelerated UV exposure tests showed no significant damage observable in the microstructure of the microporous membranes of GWSs, even after accelerated UV exposure equivalent to 10 years of outdoor use. On the other hand, sunlight exposure for more than two years at TSSs caused significant damage among GWSs to the microporous membrane and its water resistance. The aging of GWSs at TSSs might be stimulated not only by UV radiation and moisture but also by other factors not considered in the accelerated UV exposure tests.

The degradation of forest ecosystems due to depopulation, aging and economic depression of industries in rural areas, has been extensively discussed, while at the same time, increased demand for renewable energy from woody biomass has resulted in much attention to forestry and rural areas. This study provides an overview of regional circulation in a small woody biomass energy system in a typical Japanese rural area, Mishima Town, Fukushima Prefecture. To resolve the problem of forest degradation, two issues (energy and forests) in the study area are focused on and discussed in light of the national-level background. We have derived two constraints (circulation radius and feasible size) and conducted four research activities (focused respectively on forest resources, production, energy infrastructure and the social system and scenarios) for local revitalization. To address implementation of an energy system, Mishima Town established a council that has working groups strongly related to our research activities. Finally, it can be stressed that the goal of our project is identical to the concept of "regional circular and ecological spheres" (regional CESs).

The present study was aimed at investigating urban reconstruction development in Shinchi Town, which is located on the northeastern coastal edge of Fukushima Prefecture. Shinchi Town experienced major damage from the Great East Japan Earthquake in 2011. Thereafter, an environmentally friendly community energy supply system was planned and introduced as a core project for reconstruction of the town. The National Institute for Environmental Studies, Japan, provided academic support for designing and planning of systems, determining energy conservation and CO2 emission reduction, and feasibility studies. As a part of the project, a community-based energy organization, named Shinchi Smart Energy, was newly established near the town’s rebuilt railway station. This organization supplies electric power and heat energy in the area undergoing redevelopment around the station. Shinchi Smart Energy employs a cogeneration system that uses waste heat from electricity generation for heating and hot water provision and an absorption chiller (Genelink), which uses waste heat to chill water for air conditioning, enabling high-efficiency energy management. Evaluation of the project reveals that it is being properly operated at this stage, although the facilities on the demand side have not been fully completed since the arrival of COVID-19 and the resulting socioeconomic impacts. Future studies will focus on furthering the introduction of renewable energy and expanding the area receiving the power supply in Shinchi Town, as well as spreading the knowledge gained from this town to other areas.

This study evaluated the energy-saving effects of electricity consumption monitoring and energy-saving campaigns in Shinchi Town, Fukushima, Japan, where a community energy management system was introduced as part of recovery efforts after the Great East Japan Earthquake of 2011. First, a longitudinal evaluation through all six energy-saving campaigns conducted since 2014 illustrates that the first campaign showed the highest energy-saving effect, indicating the energy-saving potential brought by visualization of one’s own energy consumption by home energy management systems (HEMS). Declining trends in energy saving were observed over time. In addition, the correlations between the effects of energy-saving campaigns and trends in longer-term electricity use were noted to be minimal, indicating that the effects of energy-saving campaigns did not continue beyond the campaign period. It appears, however, that electricity consumption rates were restrained during each campaign implementation period. The fact that repeated appeals for energy savings were met with responses by the study target each time provides good prospects for demand-response processes that incorporate consideration of renewable energy usage.

The nuclear accident at Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Station resulted in evacuation orders being issued for the surrounding municipalities. These have been lifted one by one, and people have begun to return to their hometowns. When considering the reconstruction and long-term development of these areas, population recovery is the most fundamental factor. In this study, I analyze the demographics of these areas, including how the inhabitants’ return is proceeding, from multiple statistical sources. The results show that out-migration according to official registration has returned to its previous trend again since 2013, that progress in evacuees’ return after the lifting of the evacuation order varies from region to region, and that the proportion of women of reproduction age is low among residents in the areas where the evacuation orders have been lifted.

We investigated the design and operation of distributed energy systems for the central area of Mishima Town in the Oku-Aizu area of Fukushima Prefecture. These systems were tailored to the characteristics of the region. Although we found that the deployment of an energy system utilizing forest biomass resources was desirable from the perspectives of CO2 emissions and economic circulation based on local natural resources, the cost of energy was relatively high. Based on these results and related information, we considered the processes required for implementing energy systems utilizing forest biomass resources. Our results show that to create sustainable communities based on renewable energy in rural areas with low population density, it is important to integrate energy system development with community development from a medium- to long term perspective.

We surveyed and analyzed the current status of household energy consumption and use of firewood and other wood biomass in the town of Mishima, Fukushima Prefecture for the purpose of building a supply chain model for forest resource use in mountainous regions. The number of questionnaires returned was 341, with a response rate of 48.6%. The survey results revealed that approximately 9% of households were using wood biomass combustion devices. Annual firewood consumption per household was 3 m3, and over 90% of the raw logs used were procured inside the town. The difference in the ages of the houses of firewood users and non-users suggests that building structure may have influenced this result.

The aim of this study is to explore the influence of community governance on the determination and implementation of decontamination policies in local communities, focusing on Miharu Town and Koriyama City in the Naka-dori region of Fukushima Prefecture. This study is based on fieldwork undertaken in Miharu Town and Koriyama City. Data were gathered from local documents and interviews. Interviews were conducted with the municipal administrations and neighbourhood associations in charge of post-accident decontamination policies. The results showed that the procedures and contents of the resulting decontamination policies were formulated on the basis of organizational cooperation among municipal administrations and neighbourhood associations in both municipalities. Immediately after the accident, neighbourhood associations participated in the process of determining the decontamination policies of these two municipalities. Networks comprising several neighbourhood associations tackled decontamination in educational facilities and along school routes. In some districts, neighbourhood associations participated in decisions on location and management of temporary storage yards for waste generated by decontamination work. In addition to these institutional factors, land-use-related factors in the spaces used in daily life influenced the procedures and contents of the decontamination policies. These defined the differences between methods of establishing temporary storage yards in Miharu Town and Koriyama City. Our findings suggest that the relationship between community governance and land use deserves more attention in this case, as in the case of other environment problems.

Despite its significance in achieving sustainability in an era of frequent disasters, environmental emergency management (EEM) is a field that has not attracted enough attention from policy makers. This article provides an overview of and outlook for EEM studies at the National Institute for Environmental Studies (NIES). For this, a framework is presented for EEM based on recent international literature, and representative works undertaken by NIES are presented in line with this framework to examine research gaps and outlook. Our analysis shows good coverage of research topics aimed at enhancing understanding of the impact of environmental emergencies and advancing both pre- and post-disaster actions for disaster waste management (DWM). Some research gaps are also identified: namely, research on post-disaster assessment of environmental impacts and decision making under emergency circumstances, research on responses and recovery actions against impacts from hazardous substances released in the course of natural hazard events, and research collaboration within the EEM discipline and between natural hazard experts (especially regarding physical countermeasures).

Various harmful substances have been released into the environment due to increased occurrences of chemical accidents. However, only a limited number of the cases have been analyzed from the perspective of health and environmental risks to the general environment. In this study, we conducted questionnaire and interview surveys with site operators to collect information related to substance release processes and responses to them in past accidents. In addition, we extracted factors relevant to the emergency responses to the accidents and systematically analyzed the release processes.

This paper aims to clarify appropriate disaster waste management behaviors by citizens based on an understanding of frequently experienced problems in past disaster waste management cases. We also discuss methods and strategies to promote citizens’ behaviors based on examples in disaster risk reduction fields. From our results, we have identified three problems that have often occurred in past disaster waste treatment: generation of large amounts of mixed disaster waste, creation of unauthorized temporary storage sites, and insufficient support for clean-up. In municipalities where large open spaces for temporary storage sites for disaster waste are difficult to find, residents also have to establish and operate the community’s storage sites in cooperation with other residents. To promote these behaviors among citizens, there are three key factors: preparedness by municipalities for disaster waste management, citizens’ understanding and motivation, and the existence of community networks. Based on examples of public involvement in the disaster risk reduction field, participatory training and planning involving citizens is effective at promoting their understanding and proper behaviors for disaster waste management. We propose three strategies to implement participatory methods and promote appropriate disaster waste management behavior by citizens. Firstly, seizing existing opportunities such as disaster drills would be a promising approach to communicating with residents and implementing participatory methods. Secondly, it would be important to identify citizen groups active in disaster risk reduction or waste management activities and collaborate with them. Thirdly, leveraging experience with disasters would be an effective way to promote disaster waste management because citizens’ awareness of disaster waste issues is enhanced after disasters.

Climate change is already showing its influence in natural disasters and is likely to exacerbate natural disasters in the future. Given these circumstances, the results of and experience in research on disasters and the environment should facilitate the creation of a sustainable, disaster-resilient society. In this regard, systematic consideration of the knowledge gained from environmental emergency research conducted since the Great East Japan Earthquake would help establish a new research field based on disaster-related environmental research of the past. Here, we propose a conceptual framework for expanding the scope of environmental emergency research towards disaster-resilience and environmental sustainability.