Cesium is an element that belongs to the same group as K, and is known to show similar behaviour to that of K in plants. In this study, we conducted a serial leaching test for 120 h to compare the leaching characteristics of dissolved ¹³⁷Cs and K in forest litter, obtained from Japanese cedar and deciduous broadleaf forests located 40 km from the site of the 2011 Fukushima Dai-ichi nuclear power plant accident. The litter was collected in 2018 and was divided into three groups according to the decomposition level. The cumulative leachable fraction of ¹³⁷Cs at 120 h ranged from 0.3% to 3.3%, suggesting that most of the ¹³⁷Cs in the litter was hardly leachable in water. The leachable fraction of ¹³⁷Cs generally decreased with the decomposition level of the litter, implying that the easily leachable ¹³⁷Cs eluted into the water during the first stage of decomposition. Meanwhile, the cumulative leachable fraction of K at 120 h was approximately 10 times greater than that of ¹³⁷Cs and ranged from 22.7% to 54.8%. The leaching speeds of ¹³⁷Cs and K decreased suddenly with elapsed time regardless of the tree species, decomposition degree, or element. Our findings contribute to the long-term understanding of the ¹³⁷Cs cycle in forest ecosystems.

铯是与K属于同一族的元素，已知在植物中与K具有相似的行为。在这项研究中，我们进行了120小时的连续浸出试验，以比较森林凋落物中溶解的¹³⁷ Cs和K的浸出特性，这些凋落物是从距离2011年福岛第一核电站所在地40公里的日本雪松和落叶阔叶林中获得的发电厂事故。垃圾收集于2018年，根据分解水平分为三类。120 h时¹³⁷ Cs的累积可浸出率在0.3％至3.3％范围内，表明垫料中的¹³⁷ Cs大部分在水中几乎不可浸出。¹³⁷的可浸出部分Cs通常随垃圾的分解水平而降低，这意味着在分解的第一阶段，易于浸出的¹³⁷ Cs溶入水中。同时，钾在120 h的累积可浸出率约为¹³⁷ Cs的10倍，范围为22.7％至54.8％。¹³⁷ Cs和K的浸出速度随时间的流逝而突然降低，与树木的种类，分解程度或元素无关。我们的发现有助于对森林生态系统中¹³⁷ Cs循环的长期了解。