Ten-year trends in vertical distribution of radiocesium in Fukushima forest soils, Japan.

To elucidate interannual changes in the vertical distribution of Cs in forest ecosystems contaminated by the Fukushima Dai-ichi Nuclear Power Plant accident, we investigated Cs inventories in forest soils (both organic and mineral soil horizons) at 10 sampling plots with different Cs deposition levels and dominant species for up to 10 years after the accident. We examined the temporal variation of the Cs inventories by depth with exponential regression models (assuming that the transition and partitioning of Cs are still active) and exponential offset regression models (assuming a shift to a stable Cs distribution, defined as the "quasi-equilibrium steady-state" in the Chernobyl accident). In the organic horizon, the Cs inventories were exponentially decreasing, and it might take more time to converge in the quasi-equilibrium steady-state at most plots.

Dynamics of radiocaesium within forests in Fukushima-results and analysis of a model inter-comparison.

Forests cover approximately 70% of the area contaminated by the Fukushima Daiichi Nuclear Power Plant accident in 2011. Following this severe contamination event, radiocaesium (Cs) is anticipated to circulate within these forest ecosystems for several decades. Since the accident, a number of models have been constructed to evaluate the past and future dynamics of Cs in these forests.

Estimation of the rate of Cs root uptake into stemwood of Japanese cedar using an isotopic approach.

Japanese cedar (Cryptomeria japonica) is the main timber species in Japan. The prediction of the temporal changes in the Cs concentration in the stemwood of Japanese cedar after the Fukushima nuclear accident is essential for optimizing forest management in contaminated areas. However, it is difficult to estimate the respective contributions of root and foliar uptake to Cs accumulation in stemwood from simple field measurements, especially in trees that contain the residue of initially-deposited Cs.

Chemical sequential extraction of O horizon samples from Fukushima forests: Assessment for degradability and radiocesium retention capacity of organic matters.

To investigate how radiocesium (Cs) is retained in the O horizon via interactions with organic matter, we collected O horizon samples in Japanese cedar (Cryptomeria japonica) and konara oak (Quercus serrata) forest sites in Fukushima during the 8 years following the Fukushima Dai-ichi Nuclear Power Plant accident. To assess degradability and Cs retention capacity of organic matter, we conducted chemical sequential extraction with organic solvent and sulfuric acid, collecting the following fractions: organic solvent extractives (Fraction 1), acid-soluble carbohydrates (Fraction 3), and acid-insoluble residue (Fraction 4). In all samples, across sampling years and sites, Cs content in Fractions 1, 3, and 4, as a proportion of the total Cs content, was 0.