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The aggregated transfer factor (Tag) is commonly used to represent the actual transfer of radiocesium from soil to wild edible plants, but the values have shown substantial variation since the Fukushima nuclear accident. To elucidate the factors causing this variation, we investigated the effects of spatial scale and vertical 137Cs distribution in the soil on the variation of Tag-137Cs values for one of the most severely contaminated wild edible plants, Eleutherococcus sciadophylloides Franch. et Sav. (Koshiabura). The variation in Tag-137Cs values was not reduced by direct measurement of 137Cs deposition in soil samples from the Koshiabura habitat, as a substitute for using spatially averaged airborne survey data at the administrative district scale. The 137Cs activity concentration in Koshiabura buds showed a significant positive correlation with the 137Cs inventories only in the organic horizon of soil from the Koshiabura habitat. The ratio of 137Cs inventories in the organic horizon to the total 137Cs deposition in soil exhibited substantial variation, especially in broad-leaved deciduous forests that Koshiabura primarily inhabits. This variation may be the cause of the wide range of Tag-137Cs values observed in Koshiabura buds when calculated from the total 137Cs deposition in soil. [ABSTRACT FROM AUTHOR]

Large-scale decontamination work has been carried out in the aftermath of the Fukushima Daiichi nuclear power station accident in Japan in 2011. The soil that was removed and the wastes that were generated during the decontamination will be finally disposed of outside Fukushima Prefecture by 2045. To ensure successful and socially acceptable implementation of this final disposal process, it is essential to have a good understanding of what is considered important by the public. We used a choice-based conjoint analysis in the form of a web-based questionnaire to examine the relative importance of several factors in the choice of the final disposal sites of the removed soil and incinerated ash of the wastes. The questionnaires covered four attributes and 12 levels, namely the distance between the disposal site and a person's residential area, procedural fairness (decision process), distributive fairness (direct mitigation of inequity through multiple siting locations), and the volume and radioactivity of the substances to be disposed. Responses were received from 4000 people nationwide, excluding Fukushima residents. The results showed that the respondents gave high importance to choosing sites that were far from residential areas and to the two types of fairness, especially distributive fairness. The respondents showed no preference for the volume and radioactivity. This indicates that the public cares about the fairness of the siting for the final disposal sites and feels uncomfortable with plans for a final disposal site located close to them. Distributive fairness is necessary to pursue consensus in addition to procedural fairness. [ABSTRACT FROM AUTHOR]

We obtained the aggregated transfer factor (Tag) for 10 common edible wild plant species (four perennial spermatophytes, bamboo shoot, two tree species, and three perennial pteridophytes) in northeastern Japan. Measurement of Tag was carried out in 2012–2019 and we also used publicly available data for 2012–2019: food monitoring data and total deposition data from an airborne survey. The Tag obtained from actual measurements agreed well with Tag values calculated from the publicly available data. The sampling locations were only identified at the municipal level and uncertainty of the deposition for the publicly available data, and thus Tag values showed substantial variation. The Tag of the perennial spermatophytes, including bamboo shoot, and perennial pteridophytes showed single exponential decline with effective half-lives of approximately 2 years, whereas those of tree species did not show distinct temporal change. These results imply that data since 2014 are applicable for Tag estimation for long-term potential ingestion dose in the future to the public because of the slow decline. The calculated Tag values of all species for 2014–2019 ranged from 6.1 × 10−5 to 5.2 × 10−3 m2/kg-fresh mass. The maximum Tag value was observed for the tree koshiabura (Chengiopanax sciadophylloides) and the minimum value was observed for the perennial spermatophyte giant butterbur (Petasites japonica). Tree species showed higher Tag than spermatophyte and pteridophyte perennials. [ABSTRACT FROM AUTHOR]

The spatial distribution of radiation air dose was assessed on the floor of a secondary mixed forest located 35 km northwest of the Fukushima Daiichi Nuclear Power Plant. All trees with diameter at breast height ≥5 cm were measured and mapped within two plots. Radiation air doses were measured on the forest floor at each 1-m grid point and at stem bases and were analyzed in relation to bark texture, tree strata position, and leaf phenology. Radiocesium concentration measured from soils sampled in a similar manner (2-m grid point and at stem bases) in one of the two plots showed significant correlation with the air dose rate. Air dose rate showed a highly heterogeneous spatial distribution and tended to increase toward the stem bases. This trend was distinctive in some tree functional groups, with the rate being higher in some smaller deciduous trees with smooth bark (e.g.Fraxinus lanuginosa, Acer rufinerve). The trends were indistinctive in larger canopy trees with thick, coarse bark (Quercus mongolicasubsp.crispula): in such trees, air dose rate become lower at stem bases than those in the outer range of the concentric zone in some large evergreen conifer trees (Abies firma). However, radiocesium concentration measured near tree stem bases (1 m away from the base) did not vary in relation to tree functional groups. Bark smoothness, which facilitated immediate vertical runoff of contaminated water to lower positions, may have increased air dose rates at the tree bases but would not have enhanced the heterogeneity of radiocesium concentration in the forest floor soils. [ABSTRACT FROM PUBLISHER]