Sato Hikaru, Gusyev Maksym, Veremenko Dmytro, Laptev Gennady, Shibasaki Naoaki, Onda Yuichi, Zheleznyak Mark, Kirieiev Serhii, Nanba Kenji
Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan.
Institute of Environmental Radioactivity, Fukushima University, Fukushima, Japan.
Sci Total Environ. 2023 May 10;872:161997. doi: 10.1016/j.scitotenv.2023.161997. Epub 2023 Feb 2.
In the vicinity of the Chornobyl Nuclear Power Plant (ChNPP), the cooling pond (CP) was an artificially maintained reservoir with water levels regulated to 7 m above the Pripyat River until May 2014, when its pumps stopped operating, resulting in a natural drawdown. To investigate the surface-groundwater system before and after the drawdown, we evaluated the spatial and temporal changes in Sr and Cs radionuclide concentrations and groundwater levels in the shallow unconfined aquifer near the ChNPP from 2010 to 2019. Additionally, we compared water levels and Sr concentrations in Azbuchin Lake, wetlands inside the CP, and the Pripyat River. Using three-year averages before (2011-2013) and after (2017-2019) the drawdown period, we found that Sr concentrations significantly increased up to 10 kBq/m in the Pripyat River floodplain, north of ChNPP, exceeding the WHO drinking water guideline of 10 kBq/m. In contrast Cs concentrations ranged consistently between 10 and 100 Bq/m. The groundwater levels decreased over 50 cm at approximately 65 % of shallow monitoring wells and up to 6 m near the CP. The Sr concentration increases in some wells at the Pripyat River floodplain were associated with decreased dilution rates from the CP due to the reduced CP leakage, causing changes in groundwater flow direction and decreases in groundwater velocity. From the new finding of this study that the drawdown increased Sr concentrations near the floodplain, we estimated the Sr flux and contribution to the Pripyat River and the Sr contribution did not change significantly after the drawdown. However, radionuclides may accumulate more at the floodplain in the future; therefore, additional monitoring is required to verify Sr transport from areas of elevated concentrations and its impact on groundwater in the aquifer.
在切尔诺贝利核电站（ChNPP）附近，冷却池（CP）是一个人工维护的蓄水池，直到2014年5月，其水位一直被调节至比普里皮亚季河高7米，之后其水泵停止运行，导致水位自然下降。为了调查水位下降前后的地表水 - 地下水系统，我们评估了2010年至2019年期间ChNPP附近浅层无压含水层中锶（Sr）和铯（Cs）放射性核素浓度以及地下水位的时空变化。此外，我们比较了阿兹布钦湖、冷却池内湿地以及普里皮亚季河的水位和Sr浓度。利用水位下降期之前（2011 - 2013年）和之后（2017 - 2019年）的三年平均值，我们发现ChNPP以北普里皮亚季河泛滥平原中的Sr浓度显著增加至10 kBq/m，超过了世界卫生组织10 kBq/m的饮用水指导标准。相比之下，Cs浓度一直介于10至100 Bq/m之间。约65%的浅层监测井地下水位下降超过50厘米，冷却池附近下降高达6米。普里皮亚季河泛滥平原一些井中Sr浓度的增加与冷却池渗漏减少导致的冷却池稀释率降低有关，这导致地下水流向改变和地下水流速降低。根据本研究的新发现，即水位下降增加了泛滥平原附近的Sr浓度，我们估算了Sr通量及其对普里皮亚季河的贡献，水位下降后Sr贡献没有显著变化。然而，放射性核素未来可能会在泛滥平原积累更多；因此，需要额外监测以核实高浓度区域的Sr迁移及其对含水层地下水的影响。
