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Hygroscopic properties of aminium sulfate aerosols

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)4369-4385
Number of pages17
JournalAtmospheric Chemistry and Physics
DateAccepted/In press - 9 Mar 2017
DatePublished (current) - 31 Mar 2017


Alkylaminium sulfates originate from the neutralisation reaction between short-chained amines and sulfuric acid and have been detected in atmospheric aerosol particles. Their physicochemical behaviour is less well characterised than their inorganic equivalent, ammonium sulfate, even though they play a role in atmospheric processes such as the nucleation and growth of new particles and cloud droplet formation. In this work, a comparative evaporation kinetics experimental technique using a cylindrical electrodynamic balance is applied to determine the hygroscopic properties of six short-chained alkylaminium sulfates, specifically mono-, di-, and tri-methylaminium sulfate and mono-, di-, and tri-ethyl aminium sulfate. This approach allows for the retrieval of a water-activity-dependent growth curve in less than 10 s, avoiding the uncertainties that can arise from the volatilisation of semi-volatile components. Measurements are made on particles > 5 µm in radius, avoiding the need to correct equilibrium measurements for droplet-surface curvature with assumed values of the droplet-surface tension. Variations in equilibrium solution droplet composition with varying water activity are reported over the range 0.5 to > 0.98, along with accurate parameterisations of solution density and refractive index. The uncertainties in water activities associated with the hygroscopicity measurements are typically < ±0.2 % at water activities > 0.9 and  ∼  ±1 % below 0.9, with maximum uncertainties in diameter growth factors of ±0.7 %. Comparison with previously reported measurements show deviation across the entire water activity range.

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    Rights statement: This is the final published version of the article (version of record). It first appeared online via European Geosciences Union (EGU) at DOI:10.5194/acp-17-4369-2017. Please refer to any applicable terms of use of the publisher.

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    Licence: CC BY


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