Properties of aqueous (NH{sub 4}){sub 2}SO{sub 4} as a function of temperature and to high supersaturation, within a generalised multicomponent thermodynamic model
- Univ. of East Anglia, Norwich (United Kingdom)
- Hong Kong Univ. of Sciences and Technology, Clear Water Bay (Hong Kong); and others
Ammonium sulphate is an important component of aqueous atmospheric aerosols in both remote and urban regions. At low relative humidity, aerosols can readily supersaturate with respect to dissolved salts before crystallisation occurs. Calculations of the behaviour of aqueous atmospheric aerosols therefore require a knowledge of the properties of supersaturated solutions, including mixtures, over a range of temperature. Ideally, this should be integrated within a self-consistent thermodynamic model in order to predict the properties of multicomponent aerosols for different compositions, temperature and relative humidities. Here we present new measurements, using an electrodynamic balance, of water activities of supersaturated aqueous (NH{sub 4}){sub 2}SO{sub 4} from 278.15 to 313.15 K. The results are combined with literature data for activities, thermal properties and aqueous solubilities to yield functions enabling the calculation of osmotic and activity coefficients of aqueous (NH{sub 4}){sub 2}SO{sub 4}, and saturation with respect to solid phases ice and (NH{sub 4}){sub 2}SO{sub 4}(cr), from 0 to {approximately}25 mol kg{sup -1} and from <273.15 K to about 373 K. The results are used to extend the parameterisation of the Pitzer, Simonson and Clegg activity coefficient model (e.g., Clegg and Brimlecombe, 1995ab) for (NH{sub 4}){sub 2}SO{sub 4}-h{sub 2}O interactions. The model is least well constrained at temperatures greater than about 323.15 K and high (supersaturated) concentrations. This is because boiling point elevations, used to derive partial molar heat capacities, extend only to about 8 mol kg{sup -1}. The present study is an important step in the generalisation of the model (already parameterised for systems HC1-HNO{sub 3}-H{sub 2}SO{sub 4}-H{sub 2}O [as f (T)], and (NH{sub 4}){sub 2}SO{sub 4}-H{sub 2}O [at 298.15 K]) for aqueous mixtures including dissolved (NH{sub 4}){sub 2}SO{sub 4}.
- OSTI ID:
- 166558
- Report Number(s):
- CONF-9510126-; TRN: 95:008181-0049
- Resource Relation:
- Conference: Annual meeting of the American Association for Aerosol Research, Pittsburgh, PA (United States), 9-13 Oct 1995; Other Information: PBD: 1995; Related Information: Is Part Of American Association for Aerosol Research (AAAR) `95; PB: 464 p.
- Country of Publication:
- United States
- Language:
- English
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