Description
Knowledge of surface tension is central to accurate predictions of cloud droplet activation and nucleation. However, limited attention has been given to the value of surface tension for ubiquitous inorganic electrolyte solutions under atmospheric conditions, where instances of supersaturation or supercooling are present. In this work, a semi-empirical model for calculating surface tension of atmospherically relevant inorganic aqueous solutions has been developed, based on solution mixing and solute-structure formation properties. The resultant surface tension model for the inorganic electrolytes will be integrated with a study of aerosol density that has just been completed as part of our project, and then incorporated into the Extended Aerosol Inorganics Model and made available on the web (Clegg and Wexler, Wexler and Clegg 2002).
The electrolytes studied are HCl, HNO3, H2SO4, NaCl, NaNO3, Na2SO4, NaHSO4, Na2CO3, NaHCO3, NaOH, NH4Cl, NH4NO3, (NH4)2SO4, NH4HCO3, NH4OH, KCl, KNO3, K2SO4, K2CO3, KHCO3, KOH, CaCl2, Ca(NO3)2, CaSO4, MgCl2, Mg(NO3)2, and MgSO4. With over 2000 experimental surface tension values from the literature for single salt solutions, the average error between the model and experimental surface tension is < 1%. Model parameters for > 10 mixed electrolyte solutions were also determined, with an average error near 1.5 %.
Unlike other models, this model extrapolates smoothly to temperatures as low as 150 K over the entire concentration range from infinitely dilute to the theoretical supercooled melt. Additionally, theoretical molten surface tension properties extrapolated to low temperatures for salts with no experimental molten data have been estimated by relating known molten salt surface tension properties to properties such as ion valency, melting temperature, salt molar volume and ion radius.
Clegg, SL, and AS Wexler. Extended Aerosol Inorganics Model (E-AIM). http://www.aim.env.uea.ac.uk/aim/aim.php.
Wexler, AS, and SL Clegg. 2002. “Atmospheric aerosol models for systems including the ions H+, NH4+, Na+, SO42−, NO3−, Cl−, Br− and H2O.” Journal of Geophysical Research, 107, D14.
