Atmospheric Gas-Aerosol Equilibrium: IV. Thermodynamics of Carbonates

Abstract

Data and correlations for incorporating carbonate and bicarbonate salts into a gas/aerosol equilibrium model are developed. The species considered include CO₂(g), CO₂(aq), HCO₃⁻, CO₂²⁻, NH₂CO₂⁻, Na₂CO₃(s), NaHCO₃(s), K₂CO₃ (s), KHCO₃(s), CaCO₃(s), MgCO₃(s), NH₄HCO₃(s), and NH₂COONH₄(s). Three activity coefficient estimation methods (Bromley, K-M, and Pitzer) are examined. Necessary parameters for these three methods are obtained. It is found that, in general, the Pitzer method performs better than the other two, and is selected as the multicomponent activity coefficient estimation method of choice. Water activity correlations for binary carbonate solutions are obtained by polynomial fitting of available data. Deliquescence points for the important atmospheric carbonate salts and their temperature dependence are given.