Thermodynamic prediction of the water activity, ammonium-nitrate dissociation, constant density, and refractive index for the aqueous ammonium-nitrate/ammonium-sulfate system at 25°C

Stelson, A.W.; Seinfeld, J.H.

Atmospheric Environment 16(10): 2507-2514


The thermodynamic properties, water activity, density and refractive index of NH4NO3-(NH4)2SO4-H2O aerosols were estimated from binary solution data and existing mixing rules. Particle growth was predictable from the particle composition, the NH4-NO3-(NH4)2SO4-H2O phase diagram and the water activity calculation technique of C. L. Kusik and H.P. Meissner. Good agreement between the theoretical predictions and the experimental measurements of I. N. Tang, J. Thudium, and H. H. Emons and W. Hahn was shown. The effect of (NH4)2SO4 on the relative humidity dependence of the NH4NO3 Kd was evaluated.