[1D15-20] Environmental Radioacitivty and Monitoring 3

[1D15] Investigation on distribution of radioactive substances in Fukushima

(11)Spatial variation in the transport and deposition of radiocesium through the tree canopy via branchflow and stemflow

*Zul Hilmi Saidin¹, Yuichi Onda¹, Hiroaki Kato¹, Momo Kurihara¹, Slim Mtibaa ¹, Kazuki Nanko², Delphis F. Levia³ (1. Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, Japan, 2. Department of Disaster Prevention, Meteorology and Hydrology, Forestry and Forest Products Research Institute, Tsukuba, Japan, 3. Departments of Geography, University of Delaware, Newark, Delaware, USA)

Keywords:Leachable radiocesium, Stable isotopes, Branchflow, Stemflow, Cedar stand, Oak stand, Bark water storage capacity

This study seeks to better understand the spatial variation in the transport and deposition of radiocesium through the tree canopy via branchflow and stemflow in the aftermath of the Fukushima Dai-ichi Nuclear Power Plant accident. Working in both a coniferous forest (Cryptomeria japonica, young Japanese cedar stands) and a mixed deciduous broadleaved forest (Quercus serrata, Japanese oak stands), we investigated the fate of radiocesium transported by branchflow from upper and lower portions of canopy and deposited by stemflow at trunk basal area. The results showed leachable radiocesium was greater for branchflow that received washoff from the dead foliage than the branchflow receiving radiocesium inputs from mixed and younger foliage. For the tree trunk, radiocesium leached more in stemflow from the lower part as compared to the upper part, possibly due to the increased residence time of stemflow on the lower reaches of the trunk. Further work should examine the effect of bark water capacity and its relationship with the ¹³⁷Cs vertical distribution and isotopic composition of each tree stands.