AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Modelling the Water Uptake and Solubilities of Aminium Sulphate Salts
SIMON CLEGG, Chong Qiu, Renyi Zhang, University of California, Davis; University of East Anglia
Abstract Number: 34 Working Group: Aerosol Chemistry
Abstract Volumetric growth factors of five aminium sulphate salts have recently been measured as a function of relative humidity (RH) by Zhang and co-workers (Environ. Sci. Technol. 2011, 46, 4474-4480). Using new data for solubilities and solution densities we have modeled the growth factors based upon the RH / concentration relationship (on a mole of water per mole of salt basis) of aqueous (NH$_4)$_2SO$_4, on the assumption that aminium ions in aqueous solution will have similar interactions with water and other ions to those of NH$_4$^+. This is consistent with the observed behaviour of solutions of a number of aminium nitrates, for which water activities and solute activity coefficients are close to those of NH$_4NO$_3. Calculations were carried out using the Extended Aerosol Inorganics Model (E-AIM, http://www.aim.env.uea.ac.uk/aim/aim.php). Modelled growth factors agree very well with the data, although some trends in water uptake with aminium ion size are evident at low RH (high concentration). Measured solubilities have been used to obtain equilibrium solubility products that can be entered in E-AIM to predict properties of aerosol particles containing NaCl, acid ammonium sulphate and nitrate, and amines which will be neutralized to aminium ions in the same way as ammonia to NH$_4$^+.