ABSTRACT

The purpose of this study is to estimate the contribution of water-derived ¹³⁷Cs in the total activity of ¹³⁷Cs in brown rice collected from Minamisoma, Fukushima. Three different methods used for the estimation were: 1) the concentration ratio of ¹³⁷Cs from water to brown rice (CR_{–water–rice}), 2) mass balance ratio of the total activity of ¹³⁷Cs from water to brown rice (MB_{–water–rice}), and 3) the ratio of ¹³⁷Cs/¹³³Cs. To obtain water-to-brown rice transfer parameters (CR_{–water–rice} and MB_{–water–rice}), rice plants were grown in pots filled with soil collected from Minamisoma, Fukushima and irrigated with three types of water (tap water free of ¹³⁷Cs containing 0.39 mg L⁻¹ K⁺, tap water free of ¹³⁷Cs containing 1.0 mg L⁻¹ K⁺, and tap water containing 5.6 Bq L^{−1 137}Cs and 1.0 mg L⁻¹ K⁺). The activity concentrations of ¹³⁷Cs in irrigation water, soils, and brown rice collected from Minamisoma, Fukushima were 0.032 Bq L⁻¹, 1.04, and 0.0012 Bq g⁻¹ dry wt, respectively. Water-derived ¹³⁷Cs in brown rice only accounted for 1.9% estimated from the CR_{–water–rice} parameter. It was 2.8% if estimated with the MB_{–water–rice} parameter. The ratio of ¹³⁷Cs/¹³³Cs in brown rice was 0.00162 Bq ng⁻¹, similar to that in the exchangeable fraction of soils (0.00173 ± 0.00007 Bq ng⁻¹, n = 3). Thus, the contribution of ¹³⁷Cs from irrigation water to brown rice was negligible. The results estimated by three different methods were in good agreement. Therefore, these methods will be useful tools for assessing the contribution of water-derived ¹³⁷Cs in the total activity of ¹³⁷Cs in brown rice collected from Minamisoma, Fukushima. The estimation using ¹³⁷Cs/¹³³Cs ratio can also be applicable for rice in other regions.

摘要

本研究的目的是估计水源性¹³⁷ Cs 在福岛南相马县采集的糙米中¹³⁷ Cs总活性中的贡献。用于估计的三种不同方法是：1) ¹³⁷ Cs 从水到糙米的浓度比 (CR – water _-rice )，2)从水到糙米的¹³⁷ Cs总活性的质量平衡比(MB _{–水-大米}）和 3）¹³⁷ Cs/ ¹³³ Cs 的比值。获得水到糙米的转移参数（CR _{- 水 - 大米}和 MB _{- 水 - 大米})，将水稻种植在装满从福岛南相马收集的土壤的盆中，并用三种水灌溉（不含¹³⁷ Cs 的自来水含有 0.39 mg L ^-1 K ^{+ ，不含137} Cs 的自来水含有 1.0 mg L ^{- 1} K ^{+和含有 5.6 Bq L -1 137} Cs 和 1.0 mg L ^-1 K ⁺的自来水）。从福岛南相马县采集的灌溉水、土壤和糙米中¹³⁷ Cs的活度浓度分别为 0.032 Bq L ^-1、1.04 和 0.0012 Bq g ^-1干重。水性¹³⁷糙米中的 Cs 仅占 CR _-water-rice参数估计的 1.9%。如果使用 MB _{–water–rice}参数估计，则为 2.8%。糙米中¹³⁷ Cs/ ¹³³ Cs的比率为 0.00162 Bq ng ^-1，与土壤可交换部分的比率相似（0.00173 ± 0.00007 Bq ng ^-1，n = 3）。因此，灌溉水中的¹³⁷ Cs 对糙米的贡献可以忽略不计。三种不同方法估计的结果吻合较好。因此，这些方法将成为评估水衍生¹³⁷ Cs 在 137 总活度中^{的贡献的有用工具。}从福岛南相马采集的糙米中的 Cs。使用¹³⁷ Cs/ ¹³³ Cs 比率的估算也适用于其他地区的水稻。