Hygroscopic properties and cloud condensation nuclei activation of limonene-derived organosulfates and their mixtures with ammonium sulfate

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http://hdl.handle.net/10138/161726

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Hansen , A M K , Hong , J , Raatikainen , T , Kristensen , K , Ylisirnio , A , Virtanen , A , Petäjä , T , Glasius , M & Prisle , N L 2015 , ' Hygroscopic properties and cloud condensation nuclei activation of limonene-derived organosulfates and their mixtures with ammonium sulfate ' , Atmospheric Chemistry and Physics , vol. 15 , no. 24 , pp. 14071-14089 . https://doi.org/10.5194/acp-15-14071-2015

Title: Hygroscopic properties and cloud condensation nuclei activation of limonene-derived organosulfates and their mixtures with ammonium sulfate
Author: Hansen, A. M. K.; Hong, J.; Raatikainen, T.; Kristensen, K.; Ylisirnio, A.; Virtanen, A.; Petäjä, T.; Glasius, M.; Prisle, N. L.
Contributor: University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
Date: 2015
Language: eng
Number of pages: 19
Belongs to series: Atmospheric Chemistry and Physics
ISSN: 1680-7316
URI: http://hdl.handle.net/10138/161726
Abstract: Organosulfates have been observed as constituents of atmospheric aerosols in a wide range of environments; however their hygroscopic properties remain uncharacterised. Here, limonene-derived organosulfates with a molecular weight of 250 Da (L-OS 250) were synthesised and used for simultaneous measurements with a hygroscopicity tandem differential mobility analyser (H-TDMA) and a cloud condensation nuclei counter (CCNC) to determine the hygroscopicity parameter, kappa, for pure L-OS 250 and mixtures of L-OS 250 with ammonium sulfate (AS) over a wide range of humidity conditions. The kappa values derived from measurements with H-TDMA decreased with increasing particle dry diameter for all chemical compositions investigated, indicating that kappa H-TDMA depends on particle diameter and/or surface effects; however, it is not clear if this trend is statistically significant. For pure L-OS 250, kappa was found to increase with increasing relative humidity, indicating dilution/solubility effects to be significant. Discrepancies in kappa between the sub-and supersaturated measurements were observed for LOS 250, whereas kappa of AS and mixed L-OS 250/AS were similar. This discrepancy was primarily ascribed to limited dissolution of L-OS 250 at subsaturated conditions. In general, hygroscopic growth factor, critical particle diameter and kappa for the mixed L-OS 250/AS particles converged towards the values of pure AS for mixtures with >= 20% w/w AS. Surface tension measurements of bulk aqueous L-OS 250/AS solutions showed that L-OS 250 was indeed surface active, as expected from its molecular structure, decreasing the surface tension of solutions with 24% from the pure water value at a L-OS 250 concentration of 0.0025 mol L-1. Based on these surface tension measurements, we present the first concentration-dependent parametrisation of surface tension for aqueous L-OS 250, which was implemented to different process-level models of L-OS 250 hygroscopicity and CCN activation. The values of kappa obtained from the measurements were compared with kappa calculated applying the volume additive Zdanovskii-Stokes-Robinson mixing rule, as well as kappa modelled from equilibrium Kohler theory with different assumptions regarding L-OS 250 bulk-to-surface partitioning and aqueous droplet surface tension. This study is to our knowledge the first to investigate the hygroscopic properties and surface activity of L-OS 250; hence it is an important first step towards understanding the atmospheric impact of organosulfates.
Subject: SECONDARY ORGANIC AEROSOL
BOREAL FOREST ENVIRONMENT
HUMIC-LIKE SUBSTANCES
DROPLET ACTIVATION
ATMOSPHERIC AEROSOL
SURFACE-TENSION
CCN ACTIVITY
PARTICLE HYGROSCOPICITY
SUBMICROMETER AEROSOL
CHEMICAL-COMPOSITION
114 Physical sciences
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