Uptake of Radiocesium by Plants

Abstract

Radiocesium transfer to plants immediately after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident was investigated by collecting soil and newly emerged leaf samples between May 2011 and November 2012 from 20 sites in the Fukushima Prefecture. Autoradiograph images indicated that woody plants tend to accumulate radiocesium in their newly emerged leaves than herbaceous plants due to translocation-deposited radiocesium on old stems and/or leaves. Radiocesium uptake by plants was evaluated by ratios of the radiocesium concentration in plant to that in soil (concentration ratio, CR). Although the CR values decreased in 2012, CR values of woody plants remain high compared to that of herbaceous plants. Exchangeable137Cs rates in soil (extraction rate) were measured at five sites, and these rates decreased at four sites in 2012 and depended on environmental conditions and soil type. Both CR values and extraction rates decreased in 2012; however, CR values reflected the changes in not only extraction rates but also characteristics of each species. Amaranthaceae, Chenopodiaceae, and Polygonaceae, which had been identified as Cs accumulators, presented no clear137Cs accumulation ability. In 2012, the perennial plant Houttuynia cordata and deciduous trees Chengiopanax sciadophylloides and Acer crataegifolium displayed high CR values, indicating that these species are137Cs accumulators.