First study of Np-237 in Chinese soils: Source, distribution and mobility in comparison with plutonium isotopes
First study of Np-237 in Chinese soils: Source, distribution and mobility in comparison with plutonium isotopes
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中国土壤中 Np-237 的首次研究：来源、分布和迁移性与钚同位素的比较
DOI：
10.1016/j.chemosphere.2020.126683
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发表时间：
2020
期刊：
影响因子：
8.8
通讯作者：
Bu Wenting
中科院分区：
文献类型：
--
作者：
Ni Youyi;Guo Qiuju;Huang Zhaoya;Zheng Jian;Li Sixuan;Huang Wenna;Bu Wenting
本文研究了237 Np和239 + 240 Pu在中国秦山和田湾核电站附近（<5 km）土壤中的分布和迁移规律，这是首次对全球放射性核素237 Np在中国土壤中的分布和迁移规律进行专门研究。表层土壤237 Np和239 + 240 Pu浓度具有较大的空间不均匀性。秦山核电厂附近表层土壤中239 + 240 Pu的浓度为4.783mBq/g，为我国土壤中迄今为止的最高值。秦山和田湾两个土样的239 + 240 Pu储量分别为128.8 Bq/m2和121.0 Bq/m2，而237 Np储量分别为0.039 Bq/m2和0.035 Bq/m2。土壤中240 Pu/239 Pu的原子比表明，全球沉降物是这些地区Pu的主要来源。然而，环境土壤中的非同位素237 Np/239 Pu原子比不是来源识别的敏感指标。在此基础上，利用对流-弥散方程（CDE）模型对237 Np和239 + 240 Pu在秦山核电站土芯中的迁移行为进行了初步研究。237 Np的表观弥散系数（2.82 ± 2.06 cm ~ 2/y）比239 + 240 Pu的表观弥散系数（0.57 ± 0.16 cm ~ 2/y）高5倍，说明237 Np在秦山土壤中的迁移能力比Pu同位素强。随着迁移时间的延长，237 Np和239 + 240 Pu在土壤中的浓度分布将逐渐趋于均匀，这主要是由于分散效应的影响。
In this study, the distribution and migration of237Np and239+240Pu in soils in the vicinity (<5 km) of Qinshan and Tianwan Nuclear Power Plants in China were studied, which is the first specific study of global fallout237Np in Chinese soils. The237Np and239+240Pu concentrations in surface soils showed large spatial inhomogeneity. A remarkable239+240Pu concentration (4.783 mBq/g) was observed in a surface soil near Qinshan NPP and stands for the ever reported highest value in the Chinese soils. The inventories of239+240Pu in two Qinshan and Tianwan soil cores were estimated to be 128.8 Bq/m2and 121.0 Bq/m2, respectively; while the237Np inventories were 0.039 Bq/m2and 0.035 Bq/m2at these sites, respectively. The240Pu/239Pu atomic ratios in these soils indicated that the global fallout is the main source of Pu in these regions. However, the non-isotopic237Np/239Pu atomic ratio in environmental soil is not a sensitive indicator for source identification. Furthermore, we conducted pilot study on the migration behaviors of237Np and239+240Pu in soil core at Qinshan site with the Convection-Dispersion Equation (CDE) model. The obtained apparent dispersion coefficients of237Np (2.82 ± 2.06 cm2/y) was 5 times higher than that of239+240Pu (0.57 ± 0.16 cm2/y), proving that237Np has stronger migration ability than Pu isotopes in the Qinshan soil. Finally, we predicted that with the increase of migration time, both237Np and239+240Pu concentration in the soil will gradually become more evenly distributed among different soil layers due to the dominant dispersion effects.