Institute of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181, Japan.
Oriental Consultants, Sumitomo Fudosan Nishi Shinjuku Bldg. No. 6, 3-12-1 Honmachi, Shibuya-ku, Tokyo 151-0071, Japan.
Sci Total Environ. 2014 May 15;481:252-9. doi: 10.1016/j.scitotenv.2014.01.129. Epub 2014 Mar 4.
There is concern that radiocesium deposited in the environment after the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 will migrate to paddy fields through hydrological pathways and cause serious and long-lasting damage to the agricultural activities. This study was conducted in the Towa region of Nihonmatsu in the northern part of Fukushima Prefecture, Japan, (1) to quantify (137)Cs in stream water used to irrigate paddy fields by separating the dissolved and particulate components in water samples and then fractionating the particulate components bonded in different ways using a sequential extraction procedure, and (2) to determine the amounts of radiocesium newly added to paddy fields in irrigation water relative to the amounts of radiocesium already present in the fields from the deposition of atmospheric fallout immediately after the FDNPP accident. Three catchments were studied, and the (137)Cs activity concentrations in stream water samples were 79-198 mBq L(-1) under stable runoff conditions and 702-13,400 Bq L(-1) under storm runoff conditions. The residual fraction (F4, considered to be non-bioavailable) was dominant, accounting for 59.5-82.6% of the total (137)Cs activity under stable runoff conditions and 69.4-95.1% under storm runoff conditions. The (137)Cs newly added to paddy fields in irrigation water only contributed 0.03-0.05% of the amount already present in the soil (201-348 kBq m(-2)). This indicates that the (137)Cs inflow load in irrigation water is negligible compared with that already in the soil. However, the contribution from the potentially bioavailable fractions (F1+F2+F3) was one order of magnitude larger, accounting for 0.20-0.59%. The increase in the dissolved and soluble radiocesium fraction (F1) was especially large (3.0% to infinity), suggesting that radiocesium migration in irrigation water is increasing the accumulation of radiocesium in rice.
人们担心，2011 年 3 月福岛第一核电站（FDNPP）事故后沉积在环境中的放射性铯会通过水文途径迁移到稻田，并对农业活动造成严重和持久的破坏。本研究在日本福岛县北部的女川地区的户田进行，（1）通过分离水样中的溶解和颗粒成分，定量分析用于灌溉稻田的溪流水中的（137）Cs，并使用顺序提取程序对以不同方式结合的颗粒成分进行分级，（2）确定与 FDNPP 事故后大气沉降立即沉积在田间的放射性铯相比，灌溉水中新添加到稻田的放射性铯的量。研究了三个集水区，在稳定径流条件下，溪流水中（137）Cs 活度浓度为 79-198 mBq L（-1），在暴雨径流条件下为 702-13400 Bq L（-1）。残留部分（F4，被认为是不可生物利用的）占主导地位，在稳定径流条件下占总（137）Cs 活度的 59.5-82.6%，在暴雨径流条件下占 69.4-95.1%。灌溉水中新添加到稻田的（137）Cs 仅占土壤中现有（137）Cs 量的 0.03-0.05%（201-348 kBq m（-2））。这表明与土壤中已有的（137）Cs 相比，灌溉水中（137）Cs 的流入负荷可以忽略不计。然而，潜在可生物利用部分（F1+F2+F3）的贡献要大一个数量级，占 0.20-0.59%。溶解和可溶性放射性铯部分（F1）的增加尤其大（3.0%到无穷大），表明灌溉水中放射性铯的迁移正在增加水稻中放射性铯的积累。
