放射性セシウム沈着量の異なる林分から採取した スギの葉と材のセシウム，ルビジウム，カリウム含有量

スギにおけるセシウム（Cs）の経根吸収と樹体内での動態を明らかにするために，福島県の４つのスギ林分（川内，上川内，大玉，只見）から伐倒したスギ成木について，葉と材の安定セシウム（１３３Cs），ルビジウム（Rb），カリウム（K）含有量を測定した。４つの林分の放射性Cs沈着量は異なり，川内＞上川内＞大玉＞只見である。１３３Cs，Rb，K含有量は，旧葉より当年葉で高く，辺材より心材で高かった。また，小さい個体は大きい個体よりも１３３Cs，Rb，K含有量が低い傾向がみられた。これらの結果から，スギは心材にCsを蓄積する性質があり，成長の旺盛な個体ほど蓄積しやすいことが示された。旧葉の１３３Cs含有量と心材および辺材の１３３Cs含有量には比例関係がみられたことから，葉の１３３Cs含有量から材の１３３Cs含有量を推定することが可能だと考えられた。葉と材の１３３Cs含有量は調査林分によって異なり，只見と上川内は，川内と大玉に比べて葉と材の１３３Cs含有量が高く，また表層土壌の交換性K含有量はやや低かった。土壌の交換性１３３Cs含有量は只見で高かった。土壌の交換性K，１３３Cs含有量が，１３３Csの経根吸収と樹体内の動態に影響していると考えられた。

Junko Nagakura, Hisashi Abe, Chunhua Zhang, Tsutomu Takano and Masamichi Takahashi：Cesium, rubidium and potassium content in the needles and wood of Japanese cedar trees harvested from the sites of different radiocesium deposition levels 58:51―59, 2016.

To elucidate uptake via the roots and the dynamics of cesium (Cs) in Japanese cedar (Cryptomeria japonica D. Don), we measured the stable cesium (133Cs), rubidium (Rb), and potassium (K) content in the needles and wood of Japanese cedar harvested from four sites: 1) Kawauchi; 2) Kamikawauchi; 3) Otama; and 4) Tadami in Fukushima Prefecture, Japan. The levels of deposition of radiocesium were different among sites. The contents of 133Cs, Rb, and K were higher in current needles and heartwood than in old needles and sapwood, respectively. In addition, 133Cs, Rb, and K content tended to be lower in the small than in the large trees. This result suggests that Cs would be accumulated in heartwood, particularly in mature trees. Proportional relationships were observed between 133Cs in old needles and heartwoods as well as sapwoods. Therefore, 133Cs in wood may be estimated from 133Cs in needles. 133Cs in needles and wood varied among sites, with higher levels observed in Tadami and Kamikawauchi. Exchangeable K in surface soil was slightly lower in Tadami and Kamikawauchi than in Kawauchi and Otama. Soil exchangeable 133Cs was the highest in Tadami. The 133Cs uptake via roots and the dynamics of 133Cs in Japanese cedar may be affected by soil exchangeable K and 133Cs.