The Distribution of ¹³⁷Cs Concentration in the Coppiced Trees of 10-year-old Konara Oak (Querucus serrata) Growned after the Fukushima Dai-ichi Nuclear Power Plant Accident

Abstract

The ¹³⁷Cs contamination of the ground part of Quercus serrata, used as mushroom logs, was investigated, 10 years after coppicing in February 2011 just before the Fukushima nuclear accident. In May 2021, nine sprouting coppiced trees were felled from the three stumps in a deciduous broad-leaved forest in Fukushima Prefecture. Stem, branch, and leaf samples were collected, and the ¹³⁷Cs concentrations in each parts and the ¹³⁷Cs stock in the stems and the thicker branches were measured. As a result, the concentration of ¹³⁷Cs in the branch tips and leaves was significantly higher than compared to the thicker branches and the trunk, and there was a significant variation in concentration. The differences in ¹³⁷Cs concentration between the thicker branches and the trunk and was small. It was suggested that there was a relatively stable distribution of ¹³⁷Cs concentration in the vertical direction in the coppiced trees, except for the leaves and the branch tips. Moreover, the concentration of the stem showed a positive correlation with the leaves and the branches classified by the diameter, especially in the thicker branches. Furthermore, because collecting thicker branches is easier and their concentration variability is lower, compared to leaves or branch tips, it was more suitable to use thicker branches for estimating trunk concentrations for use of mushroom logs.