The solubility of oxygen in water and saline solutions

Oxygen is one of the key reaction partners for many redox reactions also in the context of nuclear waste disposal. Its solubility influences radionuclides’ behavior, corrosion processes and even microbial activity. Therefore, a reliable calculation of the solubility of molecular oxygen in aqueous solutions is relevant for the safety assessment.
In the available geochemical speciation and reactive transport programs, these data are handled very differently. In some data files for such codes the hypothetical equilibrium between dissolved oxygen and water is used to balance redox reactions. Equilibrium constants are given in “temperature grids” for up to 573.15 K. In other cases, temperature functions for the solubility of gaseous oxygen in water are given, without any reference to a valid temperature range.
In some cases, these data were also used in the context of modeling equilibria in high-saline solutions using the Pitzer formalism. This raised the question about the experimental foundation of equilibrium constants given in such data files and their validity for the solubility of molecular oxygen in saline solutions.
For this article a thorough literature review was conducted with respect to the solubility of molecular oxygen in saline solutions. From these primary experimental data Pitzer coefficients were derived. An internally consistent set of thermodynamic data for dissolved oxygen is presented, along with statements about its validity in terms of temperature and, as far as Pitzer coefficients are concerned, of solution composition.