Radiocesium accumulation properties of Chengiopanax sciadophylloides.

Abstract Through the assessments of radioactive contamination after the Fukushima Dai-ichi Nuclear Power Plant (F1NPP) accident, it has been reported that some sprouts of Chengiopanax sciadophylloides (Franch. et Sav.) at the site contained radiocesium ( 134 , 137 Cs) at higher concentrations than the other plants. To assess the phytoremediation properties of C. sciadophylloides for 137 Cs decontamination, we aimed to quantify the 137 Cs accumulation in C. sciadophylloides . We measured the 137 Cs concentrations in various organs of C . sciadophylloides collected from the forest in the town of Kawamata, Fukushima prefecture, together with the concentrations of other elements [potassium (K), rubidium, 133 Cs, calcium, strontium, and manganese] present. In addition, we compared the foliar concentrations of these elements in C . sciadophylloides with those in four different deciduous tree species. The mean of foliar 137 Cs concentration in C . sciadophylloides was 28.1 kBq kg −1 DW, one order of magnitude higher than that found in the other species. The 137 Cs concentrations were in the order of leaves > bark > wood. The wood of the treetop, leaf scars, and roots contained higher amounts of 137 Cs than that of the trunk. From the distribution of 137 Cs in C . sciadophylloides , we confirmed that 137 Cs tends to accumulate in the young growing parts. The difference in the distribution of 137 Cs and 133 Cs indicated that surface uptake of 137 Cs occurs. A significant correlation between K and 137 Cs concentrations in each organ was found, which suggested that 137 Cs in the plant body is transferred through the same pathway as K. On the other hand, there was no correlation between foliar K and 137 Cs concentrations, implying that the uptake ratio of K to 137 Cs was different for each individual. To determine the factors driving specific 137 Cs accumulation and/or the variability of the ratio between K and 137 Cs, the distribution of 137 Cs and the root in soil, the difference of the expression of transporter, and the existence of mycorrhizal fungi should be considered. However, further research is required.