A Consistent Set of Pitzer Interaction Parameters for NO₃^– Ions in the Senary Aqueous Oceanic System at 25 °C: The Zdanovskii Approach

A consistent set of binary and ternary interaction Pitzer parameters for the description of the chemical thermodynamics of nitrate solutions and their interactions with salts of the oceanic system Na+-K+-Mg2+-Ca2+-Cl–-SO42–-H2O at 25 °C was developed on the basis of a comprehensive compilation of reported binary and ternary isopiestic data. The extended Zdanovskii rule was applied to supply an additional isopiestic data set at high ionic strengths until near saturation concentrations or when experimental data were unavailable. The validation of the prediction power of the calculated set of coefficients, compatible with ubiquitous thermochemical codes, was validated by their capability of reproducing most solubility lines in ternary systems. Large discrepancies between experimental and calculated solubility data found in some systems were corrected by the introduction of an auxiliary association reaction, easily integrable into geochemical software, accounting for the formation of ion clusters with two cations or two anions.