[1I01-07] Environmental Dynamics 1

[1I03] Investigation on distribution of radioactive substances in Fukushima

(3) The Cs-137 vertical distribution in soil and tree roots in cedar forest in Fukushima Prefecture

*Satoshi Iguchi¹, Junko Takahashi ¹, Yuichi Onda¹, Hiroaki Kato¹ (1. Univ. of Tsukuba)

Keywords:forest soil, tree root, Cs-137, soil vartical distribution

Cs-137 from the Fukushima Daiichi Nuclear Power Station accident has moved downward over time in forest soil. However, there are many unclear points about the downward movement mechanism. In this study we clarify the Cs-137 concentration and inventry in soil and tree roots up to the deep soil layer (0-80 cm depth) , in order to evaluate the contribution of tree roots to the downward migration of Cs-137 in soil,. At the cedar forest site in Fukushima prefecture, the soil samples depth of 0-80 cm were collected each 5 cm using a scraper plate (30 cm x 15 cm). After that, tree root samples were collected at the same site. The Cs-137 concentration were measured using a Ge semiconductor detector. As the results, the concentration of Cs-137 in the soil decreased exponentially toward the deeper layers. On the other hunds the Cs-137 concentration in the roots decreased to a depth of 0-15 cm, but at a depth of 15 cm or deeper the concentration became almost the same value. In addition, the concentration ratio of roots/soil increased in the deeper layers, This trend may suggest that the contribution of roots to the soil downward migration of Cs-137 increased in the deeper layers.