Fig. 3.

Autoradiography of trees in the forest [1,2]: (A) pine tree (Pinus dinsiflora) and (B) sugi (Cryptomeria japonica). The height of the sugi and pine tree were 23.2 m and 22.2 m, respectively. Wood disks were harvested from 1.3 m, 4.0 m, 7.0 m, 10 m, 13 m, 16 m and 19 m above the surface of the soil, and an autoradiograph of each disk was taken by an imaging plate: (a) autoradiograph and (b) photograph. The radioactivity of the wood disks was high at the surface of the bark in both trees. In the case of sugi (B), a large amount of radioactive Cs was transferred into the heartwood, especially higher in the tree. However, in the case of the pine tree (A), most of the radioactive cesium was found to be at the surface of the trunk (S. Masumori, T. Tange et al.).