Radioactive cesium distribution in bamboo [<i>Phyllostachys reticulata</i> (Rupr) K. Koch] shoots after the TEPCO Fukushima Daiichi Nuclear Power Plant disaster

Radioactivity levels of cesium (Cs)-134 and ¹³⁷Cs in bamboo [<i>Phyllostachys reticulata</i> (Rupr) K. Koch] sprouts grown from April to June 2011 over a wide area (including Fukushima Prefecture) were elevated (max. 3100 Bq kg⁻¹ fresh weight) after the Tokyo Electric Power Company, Inc. (TEPCO) Fukushima Daiichi Nuclear Power Plant disaster in March 2011. Bamboo sprouts in 2012 also contained high radioactivity levels. Radioactivity imaging analysis of bamboo sprouts harvested in 2012 showed increasing concentration gradients of radioactivity from the lower parts to the top of the sprouts. The peels were individually separated from the sprouts, and the inner edible part (trunk) was cross-sectioned at the internodal sections from the top to the lower parts. Each segmented trunk and its corresponding peel were analyzed for radioactive cesium (¹³⁴Cs and ¹³⁷Cs) and stable cesium (¹³³Cs). The concentrations of ¹³⁴Cs and ¹³⁷Cs showed significant increases from the lower part to the top, whereas ¹³³Cs showed an almost constant value in the trunk and peel except in the peel of the top node. We speculated that ¹³⁴Cs and ¹³⁷Cs in newly emerging bamboo sprouts in 2012 were translocated mainly from various plant tissues (where the fallout was layered on the bamboo tissues) in older bamboo, while ¹³³Cs was translocated from the soil through the roots of the new bamboo sprouts and was present in the roots and stems.