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Experimental determination of the temperature dependence of water activities for a selection of aqueous organic solutions

Ganbavale, G. and Marcolli, C. and Krieger, U. K. and Zuend, A. and Stratmann, Greta and Peter, T. (2014) Experimental determination of the temperature dependence of water activities for a selection of aqueous organic solutions. Atmospheric Chemistry and Physics, pp. 9993-10012. Copernicus Publications. DOI: 10.5194/acp-14-9993-2014 ISSN 1680-7316

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Official URL: http://www.atmos-chem-phys.net/14/9993/2014/acp-14-9993-2014.html

Abstract

This work presents experimental data of the temperature dependence of water activity in aqueous organic solutions relevant for tropospheric conditions (200–273 K). Water activity (aw) at low temperatures (T) is a crucial parameter for predicting homogeneous ice nucleation. We investigated temperature-dependent water activities, ice freezing and melting temperatures of solutions, and vapour pressures of a selection of atmospherically relevant aqueous organic systems. To measure aw over a wide composition range and with a focus on low temperatures, we use various aw measurement techniques and instruments: a dew point water activity meter, an electrodynamic balance (EDB), differential scanning calorimetry (DSC), and a setup to measure the total gas phase pressure at equilibrium over aqueous solutions. Water activity measurements were performed for aqueous multicomponent and multifunctional organic mixtures containing the functional groups typically found in atmospheric organic aerosols, such as hydroxyl, carboxyl, ketone, ether, ester, and aromatic groups. The aqueous organic systems studied at several fixed compositions over a considerable temperature range differ significantly in their temperature dependence. Aqueous organic systems of 1,4-butanediol and methoxyacetic acid show a moderate decrease in aw with decreasing temperature. The aqueous M5 system (a multicomponent system containing five different dicarboxylic acids) and aqueous 2-(2-ethoxyethoxy)ethanol solutions both show a strong increase of water activity with decreasing temperature at high solute concentrations for T < 270 K and T < 260 K, respectively. These measurements show that the temperature trend of aw can be reversed at low temperatures and that linear extrapolations of high-temperature data may lead to erroneous predictions. To avoid this, experimentally determined aw at low temperature are needed to improve thermodynamic models towards lower temperatures and for improved predictions of the ice nucleation ability of organic–water systems.

Item URL in elib:https://elib.dlr.de/90730/
Document Type:Article
Title:Experimental determination of the temperature dependence of water activities for a selection of aqueous organic solutions
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Ganbavale, G.IAC, ETH ZürichUNSPECIFIED
Marcolli, C.IAC, ETH ZurichUNSPECIFIED
Krieger, U. K.IAC, ETH ZurichUNSPECIFIED
Zuend, A.McGill University, MontrealUNSPECIFIED
Stratmann, GretaDLR, IPAUNSPECIFIED
Peter, T.ETH, Zürich, CHUNSPECIFIED
Date:2014
Journal or Publication Title:Atmospheric Chemistry and Physics
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
DOI :10.5194/acp-14-9993-2014
Page Range:pp. 9993-10012
Publisher:Copernicus Publications
ISSN:1680-7316
Status:Published
Keywords:water activity, aqueous organic solutions, troposphere, homogeneous ice nucleation
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Erdbeobachtung
DLR - Research theme (Project):R - Vorhaben Atmosphären- und Klimaforschung
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics
Deposited By: Stratmann, Greta
Deposited On:25 Sep 2014 13:57
Last Modified:02 May 2019 14:04

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