Chemical speciation models based upon the Pitzer activity coefficient equations, including the propagation of uncertainties. III. Seawater from the freezing point to 45 °C, including acid-base equilibria
Chemical speciation models based upon the Pitzer activity coefficient equations, including the propagation of uncertainties. III. Seawater from the freezing point to 45 °C, including acid-base equilibria
复制标题
基于 Pitzer 活度系数方程的化学形态模型，包括不确定性的传播。
DOI：
10.1016/j.marchem.2022.104196
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发表时间：
2023
期刊：
影响因子：
3
通讯作者：
Clegg S
中科院分区：
文献类型：
--
作者：
Clegg S
在从全球变化到环境和水质管理的各种应用中，需要对包括海水在内的自然水域中的pH、酸碱平衡和化学形态进行定量了解。在先前的一项研究(Humphreys等人，2022年)中，我们实施了一个含有人造海水离子的溶液模型，该模型基于计算活度系数的Pitzer方程，并首次包括了不确定因素的传播。这一范围被扩大(Clegg等人，2022年)，包括用于校准海水总pH标度的Tris缓冲溶液。在这里，我们应用相同的方法来开发一个包含标准参考海水离子的溶液模型，这是基于Millero和他的同事的研究。我们将模型的预测与文献数据进行了比较：溶解的二氧化碳和重碳酸盐离子的解离；硼酸的解离；相对于方解石的饱和，水的离子产物，以及海水的渗透系数。所有热力学平衡常数和Pitzer参数对计算量的方差的不确定度贡献的估计被用来确定模型的哪些元素需要改进，目的是在其实验不确定度范围内与上述性质相一致。建议进一步研究。与几个碳酸盐体系在海水中解离的数据集的比较表明，哪一个是最可靠的，并确定低盐度水域(S和lt； 10)是一个尚未准确知道碳酸氢盐解离常数的区域。目前，该模型可能最适用于直接计算任意组成的天然水中的平衡，或将海水介质中已知的离解常数调整为主要离子相对组成不同的天然水中的值。
A quantitative understanding of pH, acid-base equilibria, and chemical speciation in natural waters including seawater is needed in applications ranging from global change to environmental and water quality management. In a previous study (Humphreys et al., 2022) we implemented a model of solutions containing the ions of artificial seawater, based upon the use of the Pitzer equations for the calculation of activity coefficients and including, for the first time, the propagation of uncertainties. This was extended (Clegg et al., 2022) to include the Tris buffer solutions that are used to calibrate the seawater total pH scale. Here we apply the same methods to develop a model of solutions containing the ions of standard reference seawater, based upon studies by Millero and co-workers. We compare the predictions of the model to literature data for: the dissociation of dissolved CO2and bicarbonate ion; boric acid dissociation; saturation with respect to calcite, the ion product of water, and osmotic coefficients of seawater. Estimates of the uncertainty contributions of all thermodynamic equilibrium constants and Pitzer parameters to the variance of the calculated quantity are used to determine which elements of the model need improvement, with the aim of agreeing with properties noted above to within their experimental uncertainty. Further studies are recommended. Comparisons made with several datasets for carbonate system dissociation in seawater suggest which are the most reliable, and identify low salinity waters (S< 10) as a region for which dissociation constants of bicarbonate are not yet accurately known. At present, the model is likely to be most useful for the direct calculation of equilibria in natural waters of arbitrary composition, or for adjusting dissociation constants known for seawater media to values for natural waters in which the relative compositions of the major ions are different.