We have developed a Pitzer model in the Na–K–Ca–Mg–Cl–SO₄ system valid from 298.15 to <200 K up to saturated salt concentrations, which builds upon our previous low temperature model in the Na–K–Ca–Mg–Cl system. This model includes new experimental heat capacities in Na₂SO₄, K₂SO₄ and MgSO₄ solutions measured using differential scanning calorimetry, as well as comprehensive heat capacities of crystalline phases, enthalpies of solution, activity coefficients, and solubilities from literature sources. The model improves over previous sulfate models because it accurately represents the thermodynamic properties of MgSO₄ and its mixtures and more accurately represents gypsum and anhydrite equilibria in mixed salt solutions, in addition to accurate representations of many other salt systems. The model also includes temperature-dependent parameters for a number of new phases, such as variably hydrated Mg-sulfates, Na-sulfates, and polyhalite. This model is applicable to Cl–SO₄-rich brines on Earth that typically evolve during evaporative or freezing modification of seawater, as well as Cl–SO₄-rich planetary solutions.

中文翻译：

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Na–K–Ca–Mg–Cl–SO ₄系统的低温水热力学模型，其中包含在Na ₂ SO ₄，K ₂ SO ₄和MgSO ₄溶液中的新实验热容量

我们在Na–K–Ca–Mg–Cl–SO ₄系统中开发了一个Pitzer模型，该模型的有效范围为298.15至<200 K，直至饱和盐浓度，该模型建立在我们先前在Na–K–Ca–Ca2 +中的低温模型的基础上Mg–Cl系统。该模型包括使用差示扫描量热法测量的在Na ₂ SO ₄，K ₂ SO ₄和MgSO ₄溶液中的新实验热容量，以及晶相的综合热容量，溶液的焓，活度系数和文献来源的溶解度。该模型比以前的硫酸盐模型有所改进，因为它可以准确表示MgSO ₄的热力学性质。以及其混合物，更准确地表示混合盐溶液中的石膏和硬石膏平衡，以及许多其他盐体系的准确表示。该模型还包括许多新相的温度相关参数，例如可变水合的硫酸镁，硫酸钠和多卤石。该模型适用于地球上富含Cl–SO _4的盐水，这些盐水通常在海水的蒸发或冷冻改性过程中演化，以及富含Cl–SO _4的行星溶液。