Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-1051
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
14 Dec 2016
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
Influence of Organic Compound Functionality on Aerosol Hygroscopicity: Dicarboxylic Acids, Alkyl-Substituents, Sugars and Amino Acids
Aleksandra Marsh1, Rachael E. H. Miles1, Grazia Rovelli1, Alexander G. Cowling1, Lucy Nandy2, Cari S. Dutcher2, and Jonathan P. Reid1 1School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK
2Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455, USA
Abstract. Hygroscopic data for 36 organic compounds including amino acids, organic acids, alcohols and sugars is determined using a Comparative Kinetics Electrodynamic Balance (CK-EDB). The CK-EDB employs an electric field to trap charged aqueous droplets in a temperature and relative humidity (RH) controlled chamber. The dual micro dispenser set up allows for sequential trapping of probe and sample droplets for accurate determination of droplet water activities from 0.45 to > 0.99. Here, we validate and benchmark the CK-EDB for the homologous series of straight chain dicarboxylic acids (oxalic – pimelic) with measurements in better agreement with UNIversal quasichemical Functional group Activity Coefficients (UNIFAC) predictions than the original data used to parametrise UNIFAC. Further, a series of increasingly complex organic compounds, with subtle changes to molecular structure and branching, are used to rigorously assess the accuracy of predictions by UNIFAC, which does not explicitly account for molecular structure. We show that the changes in hygroscopicity that result from increased branching and chain length are poorly represented by UNIFAC, with UNIFAC under-predicting hygroscopicity. Similarly, amino acid hygroscopicity is under-predicted by UNIFAC predictions, a consequence of the original data used in the parametrisation of the molecular subgroups. New hygroscopicity data are also reported for a selection of alcohols and sugars.

Citation: Marsh, A., Miles, R. E. H., Rovelli, G., Cowling, A. G., Nandy, L., Dutcher, C. S., and Reid, J. P.: Influence of Organic Compound Functionality on Aerosol Hygroscopicity: Dicarboxylic Acids, Alkyl-Substituents, Sugars and Amino Acids, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1051, in review, 2016.
Aleksandra Marsh et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version      Supplement - Supplement
 
RC1: 'Review of Marsh et al.', Andreas Zuend, 18 Jan 2017 Printer-friendly Version Supplement 
AC1: 'Reply to Referee #1', Jonathan Reid, 16 Mar 2017 Printer-friendly Version Supplement 
 
RC2: 'see attached', Anonymous Referee #2, 13 Feb 2017 Printer-friendly Version Supplement 
AC2: 'Response to Anonymous Referee #2', Jonathan Reid, 16 Mar 2017 Printer-friendly Version Supplement 
Aleksandra Marsh et al.
Aleksandra Marsh et al.

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Short summary
The response of aerosol particles to changes in relative humidity (RH) is dependent on the hygroscopicity of the constituent chemical components. We present accurate measurements of the hygroscopic response of aerosols over a wide range in RH extending up to the saturation RH. The chemical compounds studied include dicarboxylic acids, amino acids, sugars and polyols. These data provide a comprehensive source of data to help improve functional group activity models of aerosol hygroscopicity.
The response of aerosol particles to changes in relative humidity (RH) is dependent on the...
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