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.2011年3月东京电力公司（TEPCO）福岛第一核电站事故发生后，2011年4月至6月间在大范围区域（含福岛县）种植的桂竹（*Phyllostachys reticulata* (Rupr.) K. Koch）竹笋中，铯-134（¹³⁴Cs）与铯-137（¹³⁷Cs）的放射性活度水平显著升高，最高可达3100 Bq·kg⁻¹（鲜重）。2012年采集的竹笋同样检测出较高的放射性活度水平。对2012年收获的竹笋开展放射性成像分析后发现，其放射性活度浓度从基部至顶部呈逐渐升高的梯度分布。研究人员将竹笋的笋壳与可食用内部髓部（茎秆）分别分离，并将可食用髓部沿节间从顶部至基部进行切片分段。随后分别对每一段髓部及其对应的笋壳进行放射性铯（¹³⁴Cs与¹³⁷Cs）与稳定铯（¹³³Cs）的浓度检测。检测结果显示，¹³⁴Cs与¹³⁷Cs的浓度从基部至顶部呈显著升高趋势，而¹³³Cs的浓度在髓部与笋壳中基本保持恒定，仅顶部节位的笋壳除外。研究团队推测，2012年新生竹笋中的¹³⁴Cs与¹³⁷Cs主要来自老龄竹各组织中沉积的核沉降物，而¹³³Cs则通过新生竹笋的根系从土壤中吸收转运，主要分布于根系与茎秆中。