Effect of litter removal five years after the Fukushima accident on Cs uptake by Japanese cedar.

Removal of litter-associated Cs from the forest floor (litter removal) can reduce the Cs uptake by plants; however, the proposed effective period for litter removal was 1-2 years after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. This is because the Cs in forest soil migrates rapidly from the litter to surface mineral soil layers in Japanese forests, and thus the effectiveness of litter removal will quickly become limited. However, it is unknown whether this approach can be applied to forests whose vertical migration of Cs in the forest soil is relatively slow.

Difference of ecological half-life and transfer coefficient in aquatic invertebrates between high and low radiocesium contaminated streams.

The Fukushima accident emitted radioactive substances into the environment, contaminating litter, algae, sand substrate, aquatic invertebrates, and fish in freshwater streams. Because these substances have substantial effects on stream ecology over many years, it is necessary to clarify the diffusion and decay mechanisms of radiocesium. The transfer coefficient differed among aquatic invertebrate groups, likely due to the differences in habitat.

Temporal changes in the spatial patterns of air dose rate from 2012 to 2016 at forest floors in Fukushima, Japan.

This study investigates temporal changes in the distribution of air dose rates at forest floors from 2012 to 2016 by measuring air dose rates at a height of 10 cm. The study was conducted at four different topography forest sites in Fukushima Prefecture, Japan. At each forest site, the air dose rate was found to have decreased by 7%-22% over time from 2012 to 2016 owing to the movement of radiocesium from organic layers to mineral soil layers in the forest site.

Assessment of vertical radiocesium transfer in soil via roots.

Several years after the Fukushima Daiichi Nuclear Power Plant accident, the surface mineral soil layer is believed to be the main reservoir of radiocesium (Cs) in forest ecosystems in Japan. Dissolved Cs combines with clay minerals in the soil, and hence, it is not expected to easily infiltrate over time. However, previous studies have indicated that Cs derived from the older global fallout migrated deeper than that of the Chernobyl accident, and this cannot be explained by only the dissolved Cs vertical migration in the soil.

Characteristics of initial deposition and behavior of radiocesium in forest ecosystems of different locations and species affected by the Fukushima Daiichi Nuclear Power Plant accident.

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, information about stand-level spatial patterns of radiocesium initially deposited in the surrounding forests was essential for predicting the future dynamics of radiocesium and suggesting a management plan for contaminated forests. In the first summer (approximately 6 months after the accident), we separately estimated the amounts of radiocesium ((134)Cs and (137)Cs; Bq m(-2)) in the major components (trees, organic layers, and soils) in forests of three sites with different contamination levels. For a Japanese cedar (Cryptomeria japonica) forest studied at each of the three sites, the radiocesium concentration greatly differed among the components, with the needle and organic layer having the highest concentrations.

Changes in radiocesium concentrations in epigeic earthworms in relation to the organic layer 2.5 years after the 2011 Fukushima Dai-ichi Nuclear Power Plant accident.

We reported previously that radiocesium ((137)Cs) concentrations in earthworms increased with those in litter and/or soil in Fukushima Prefecture forests 0.5 y after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. This study provides further results for 1.

Growth and transpiration of Japanese cedar (Cryptomeria japonica) and Hinoki cypress (Chamaecyparis obtusa) seedlings in response to soil water content.

To investigate the effects of soil water content on growth and transpiration of Japanese cedar (Cryptomeria japonica D. Don) and Hinoki cypress (Chamaecyparis obtusa (Siebold et Zucc.) Endl.