Mass balance calculations and hydrodynamics of groundwater flow suggest that the solutes in brines of the coastal sabkha aquifer from the Emirate of Abu Dhabi are derived largely from ascending geologic brines into the sabkha from the underlying formations. Solute interpretation for the ascending brine model (ABM) was based on two independent but secondary lines of evidence (solute ratios and solute fluxes). In the current study, direct primary evidence for this ABM was provided through analyses of δ⁸¹Br, δ³⁷Cl, and ⁸⁷Sr/⁸⁶Sr. Different solute histories of geologic brine and sea water provide an “isotopic fingerprint” that can uniquely distinguish between the two possible sources. Samples from the coastal sabkha aquifer of Abu Dhabi were determined to have a mean δ⁸¹Br of 1.17‰ that is statistically equal, at the 95% confidence level, to the mean of 1.11‰ observed in the underlying geologic brine and statistically different than sea water. Similarly, the δ³⁷Cl in sabkha brine has a mean of 0.25‰ and is statistically equal to a mean of 0.21‰ in the underlying geologic brines at the 95% confidence level and statistically different from sea water. Also, dissolved strontium isotope data are consistent with the ABM and even with the complex set of processes in the sabkha, the variance in strontium isotope results is similar to the geologic brine. These observations provide primary direct evidence consistent that the major source of these solutes (and presumably others in the aquifer) is from discharging geologic brines, not from adjacent sea water.

中文翻译：

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同位素富集的地质成因 δ81Br 和 δ37Cl：上升盐水模型的主要证据

地下水流的质量平衡计算和流体动力学表明，阿布扎比酋长国沿海 sabkha 含水层盐水中的溶质主要来自从下伏地层上升到 sabkha 的地质盐水。上升盐水模型 (ABM) 的溶质解释基于两个独立但次要的证据线（溶质比和溶质通量）。在目前的研究中，通过对 δ ⁸¹ Br、δ ³⁷ Cl 和⁸⁷ Sr/ ^{86 的}分析提供了这种 ABM 的直接主要证据Sr. 地质卤水和海水的不同溶质历史提供了一种“同位素指纹”，可以唯一地区分两种可能的来源。来自阿布扎比沿海 sabkha 含水层的样本被确定具有1.17‰的平均 δ ⁸¹ Br，在 95% 的置信水平下，这在统计上等于在底层地质盐水中观察到的 1.11‰ 的平均值，并且在统计上不同于海水水。同样，δ ³⁷sabkha 盐水中的 Cl 平均值为 0.25‰，在 95% 置信水平下统计上等于底层地质盐水中的平均值 0.21‰，并且在统计上与海水不同。此外，溶解锶同位素数据与 ABM 一致，即使与 sabkha 中的复杂过程集，锶同位素结果的差异与地质卤水相似。这些观察提供了一致的主要直接证据，即这些溶质（以及含水层中的其他溶质）的主要来源来自排放地质盐水，而不是来自邻近的海水。