A new value for the stable oxygen isotope fractionation between dissolved sulfate ion and water
A new value for the stable oxygen isotope fractionation between dissolved sulfate ion and water
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DOI：
10.1016/j.gca.2009.10.034
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发表时间：
2010-02
影响因子：
5
通讯作者：
R. Zeebe
中科院分区：
文献类型：
--
作者：
R. Zeebe
尽管溶解的硫酸根离子（SO42-）和H2O（下文[化学式：见正文]）之间的稳定氧同位素分馏具有物理化学和生物地球化学意义，但迄今为止尚未建立实验值。主要原因是SO42-和H2O之间的非催化氧交换极其缓慢，在室温下需要大约105年。由于缺乏更好的方法，过去根据理论“气相”计算和对在 >75°C 温度下获得的实际属于硫酸氢盐 (HSO4-)–H2O 系统的实验室结果进行外推，假设 25°C 时的值为 16‰ 和 31‰。在这里，我使用新颖的量子化学计算，该计算考虑了详细的溶质与水的相互作用，以确定 25°C 时的 [公式：参见文本] 23‰ 的新值。硫酸氢根离子的相应计算结果与观测结果一致。新的理论值表明，反映微生物硫酸盐还原过程中硫酸盐与环境水之间氧同位素平衡的沉积物[式：见正文]-数据与SO42-与水之间的非生物平衡一致。
Although the stable oxygen isotope fractionation between dissolved sulfate ion (SO42-) and H2O (hereafter [Formula: see text] ) is of physico-chemical and biogeochemical significance, no experimental value has been established until present. The primary reason being that uncatalyzed oxygen exchange between SO42-and H2O is extremely slow, taking ∼105years at room temperature. For lack of a better approach, values of 16‰ and 31‰ at 25°C have been assumed in the past, based on theoretical ‘gas-phase’ calculations and extrapolation of laboratory results obtained at temperatures >75°C that actually pertain to the bisulfate (HSO4-)–H2O system. Here I use novel quantum-chemistry calculations, which take into account detailed solute–water interactions to establish a new value for [Formula: see text] of 23‰ at 25°C. The results of the corresponding calculations for the bisulfate ion are in agreement with observations. The new theoretical values show that sediment [Formula: see text] -data, which reflect oxygen isotope equilibration between sulfate and ambient water during microbial sulfate reduction, are consistent with the abiotic equilibrium between SO42-and water.