Isotopic fractionation during ion filtration; I, Theory
Isotopic fractionation during ion filtration; I, Theory
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DOI：
10.1016/0016-7037(87)90079-2
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发表时间：
1987-03
影响因子：
5
通讯作者：
F. Phillips;H. Bentley
中科院分区：
文献类型：
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作者：
F. Phillips;H. Bentley
在实验室中观察到水溶液通过半渗透粘土圆盘流动过程中H、O和Cl同位素的分馏。在深沉积盆地中观察到的这些元素的同位素丰度趋势归因于类似的现象。然而，负责这种同位素分馏的机制尚未确定。我们建议，分馏的O和H同位素的水分子的结果从增加的活动的重同位素物种在膜溶液中，因为高的阳离子浓度在膜孔隙流体中增加hydration sphere分馏效应。因此，重的同位素物质会从膜中扩散出去，从而在膜后聚集。基于这一理论的预测令人满意地模拟了实验室和现场观测。我们提出，氯同位素的分馏是35Cl −和37Cl −离子迁移率差异的结果。膜上的负电荷以略微不同的速度排斥同位素物质，从而使更易流动的35 Cl −在膜后富集。从这个理论计算的预测比较以及与实验室和现场数据。
Fractionation of the isotopes of H, O, and Cl during flow of aqueous solutions through semipermeable clay discs has been observed in the laboratory. The observed isotopic abundance trends of these elements in deep sedimentary basins have been attributed to similar phenomena. However, the mechanism responsible for such isotopic fractionation has not been identified. We propose that the fractionation of O and H isotopes in the water molecule results from increased activity of the heavy isotopic species in the membrane solution because high cation concentrations in the membrane pore fluid increase hydrationsphere fractionation effects. The heavy isotopic species thus diffuse away from the membrane and therefore are concentrated behind it. Predictions based on this theory satisfactorily model both laboratory and field observations.We propose that the fractionation of chlorine isotopes is a result of differences in the ionic mobility of35Cl−and37Cl−. Negative charges on the membrane repel the isotopic species at slightly different velocities against the uniform advective motion of the bulk water and thus the more mobile35Cl−is enriched behind the membrane. Predictions calculated from this theory compare well with laboratory and field data.