Absorption and translocation of cesium through Konara oak (Quercus serrata) bark

ABSTRACT

Bark–wood translocation has been suggested as an important route for the contamination of trees via radiocesium in the initial stage of deposition. In this study, we investigated the cesium absorption through bark of mature Konara oak (Quercus serrata). Stable Cs (¹³³Cs) was applied onto the bark at 1.2 m, and then after 8 weeks, the ¹³³Cs concentration was determined in the outer bark, inner bark, sapwood, and heartwood of stem disks at several heights, as well as in the current-year leaves and branches from the tree tops. At the height of 1.2 m, the ¹³³Cs concentration was significant higher in the sapwood of the treated trees than in those of the control trees. However, no difference was found in the ¹³³Cs concentration in the heartwood of the treated and control trees not only in the wood above and below 1.2 m but also at 1.2 m. There was no significant difference in the ¹³³Cs concentration of the current-year leaves and branches of the treated and control trees. Our results suggest that Cs absorption through bark may occur even in the dormant period of tree and the absorption is probably independent of cambial activities.

KEYWORDS:

• Absorption
• bark
• cesium
• radiocesium
• Quercus serrata

Highlights

• Cs can enter the wood through the bark of Konara oaks in dormant season.

• The bark-derived Cs was translocated radially to the sapwood but not to the heartwood.

• The vertical translocation of bark-derived Cs was negligible in dormant season.

Acknowledgments

This research was financially supported by the Japan Atomic Energy Agency and Grant-in-Aid for Scientific Research [Grant Numbers 24110007 and 24380078]. We would like to thank our many collaborators for their assistance in the fieldwork in Fukushima.

Conflict of interest

The authors declare that they have no conflict of interest.

Additional information

Funding

This research was financially supported by the Japan Atomic Energy Agency and Grant-in-Aid for Scientific Research [Grant Numbers [24110007] and [24380078].