Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan.
Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan.
J Environ Radioact. 2021 Nov;238-239:106725. doi: 10.1016/j.jenvrad.2021.106725. Epub 2021 Aug 27.
The Fukushima Dai-ichi Nuclear Power Plant accident caused serious Cs contamination in mountainous forest areas. To understand the spatial variation in soil Cs inventory in complex mountainous topography and the influencing factors, a whole-area investigation of Cs deposition in a broad-leaved forest catchment of a mountain stream was conducted using grid sampling. Across the catchment, organic and surface mineral soil layers were collected at 42 locations in 2013 and 6 locations in 2015. Cesium-137 deposition on the forest floor exhibited high spatial heterogeneity and altitude-dependent distribution over the catchment. The Cs retention ratio in the organic layer, determined as the inventory in the organic layer divided by the soil (organic and mineral soil layers) inventory, ranged from 6% to 82% in 2013, and the coefficient of variation was 0.6. The Cs retention ratios had positive correlations with the material inventory in the organic layer and the elevation. The Cs retention ratios in the organic layer were less than 20% in 2015, even at the locations where the retention ratio was higher than 55% in 2013. Although there was spatial variation in the migration speed, Cs migration from the organic layer to mineral soil was almost completed within 4 y of the deposition, suggesting a decrease in Cs circulation within the forest ecosystem. This study also examined a relationship between the Cs inventory and the air dose rate to assess the potential of using the air dose rate to estimate soil Cs inventory. Soil Cs inventories and air dose rates were highly positively correlated, indicating that measurement of air dose rate can provide an easier and quicker alternative to measurement of soil Cs inventory in forest ecosystems.
福岛第一核电站事故导致山区森林地区遭受严重的 Cs 污染。为了了解复杂山地地形中土壤 Cs 储量的空间变化及其影响因素，采用网格采样对山区溪流阔叶林区的 Cs 沉降进行了全区域调查。在整个流域范围内，于 2013 年在 42 个地点和 2015 年在 6 个地点采集了有机层和表层矿质土壤层。森林地表的 Cs-137 沉降具有很高的空间异质性和随海拔分布的特征。有机层中 Cs 的保留率（有机层中 Cs 的含量与土壤（有机层和矿质土壤层）中 Cs 的含量之比）在 2013 年的范围为 6%至 82%，变异系数为 0.6。Cs 的保留率与有机层中的物质含量和海拔呈正相关。2015 年有机层中 Cs 的保留率小于 20%，即使在 2013 年保留率高于 55%的地点也是如此。尽管迁移速度存在空间差异，但 Cs 从有机层向矿质土壤的迁移在沉降后 4 年内几乎完成，这表明森林生态系统中 Cs 的循环减少。本研究还研究了 Cs 储量与空气剂量率之间的关系，以评估利用空气剂量率来估计土壤 Cs 储量的潜力。土壤 Cs 储量和空气剂量率高度正相关，表明测量空气剂量率可以为测量森林生态系统中的土壤 Cs 储量提供一种更简单、更快捷的替代方法。
