DISSOLVED-OXYGEN CONCENTRATIONS IN HYPERSALINE WATERS

Henry's law constants (k(o)) and equilibrium concentrations (C(o triple-overdot)* of dissolved oxygen (DO) at 1 atm were measured in NaCl solutions of concentration (S) up to approximately 260 parts per thousand and at temperatures (T) between 273 and 308K. An equation of the form ln C(o)* = a0 + a1/T + a2ln T + a3T + a4T2 + S(a5 + a6T + a7T2) + a8S2 was found to predict DO values to within the experimental uncertainty. An equation of the same form satisfactorily described the variation of ln k(o) over the same temperature and concentration ranges. In order to develop these equations it was also necessary to develop ones to describe the variation of density and vapor pressure of NaCl solutions with T and S. The equations can be used to generate tables of oxygen solubility values that can be used for hypersaline waters dominated by NaCl. Theoretically, DO values based on NaCl can be corrected for the presence of other ionic salts in natural waters. At present this correction is limited by the availability of DO data for these subdominant electrolytes.