Connecting the solubility and CCN activation of complex organic aerosols: a theoretical study using solubility distributions
We present a theoretical study investigating the cloud activation of multicomponent organic particles. We modeled these complex mixtures using solubility distributions (analogous to volatility distributions in the VBS, i.e., volatility basis set, approach), describing the mixture as a set of surroga...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/15/6305/2015/acp-15-6305-2015.pdf |
| _version_ | 1818309702242533376 |
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| author | I. Riipinen N. Rastak S. N. Pandis |
| author_facet | I. Riipinen N. Rastak S. N. Pandis |
| author_sort | I. Riipinen |
| collection | DOAJ |
| description | We present a theoretical study investigating the cloud activation of
multicomponent organic particles. We modeled these complex mixtures using
solubility distributions (analogous to volatility distributions in the VBS,
i.e., volatility basis set, approach), describing the mixture as a set of
surrogate compounds with varying water solubilities in a given range. We
conducted Köhler theory calculations for 144 different mixtures with
varying solubility range, number of components, assumption about the organic
mixture thermodynamics and the shape of the solubility distribution, yielding
approximately 6000 unique cloud condensation nucleus (CCN)-activation points.
The results from these comprehensive calculations were compared to three
simplifying assumptions about organic aerosol solubility: (1) complete
dissolution at the point of activation; (2) combining the aerosol solubility
with the molar mass and density into a single effective hygroscopicity
parameter κ; and (3) assuming a fixed water-soluble fraction
ϵ<sub>eff</sub>. The complete dissolution was able to reproduce
the activation points with a reasonable accuracy only when the majority
(70–80%) of the material was dissolved at the point of activation. The
single-parameter representations of complex mixture solubility were confirmed
to be powerful semi-empirical tools for representing the CCN activation of
organic aerosol, predicting the activation diameter within 10% in most
of the studied supersaturations. Depending mostly on the condensed-phase
interactions between the organic molecules, material with solubilities larger
than about 0.1–100 g L<sup>−1</sup> could be treated as soluble in the CCN
activation process over atmospherically relevant particle dry diameters and
supersaturations. Our results indicate that understanding the details of the
solubility distribution in the range of 0.1–100 g L<sup>−1</sup> is thus
critical for capturing the CCN activation, while resolution outside this
solubility range will probably not add much information except in some
special cases. The connections of these results to the previous observations
of the CCN activation and the molecular properties of complex organic mixture
aerosols are discussed. The presented results help unravel the mechanistic
reasons behind observations of hygroscopic growth and CCN activation of
atmospheric secondary organic aerosol (SOA) particles. The proposed
solubility distribution framework is a promising tool for modeling the
interlinkages between atmospheric aging, volatility and water uptake of
atmospheric organic aerosol. |
| first_indexed | 2024-12-13T07:34:22Z |
| format | Article |
| id | doaj.art-c9f68e529ae74e37b4d37e4667b601cf |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-13T07:34:22Z |
| publishDate | 2015-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-c9f68e529ae74e37b4d37e4667b601cf2022-12-21T23:55:07ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242015-06-0115116305632210.5194/acp-15-6305-2015Connecting the solubility and CCN activation of complex organic aerosols: a theoretical study using solubility distributionsI. Riipinen0N. Rastak1S. N. Pandis2Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, SwedenDepartment of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, SwedenCenter of Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USAWe present a theoretical study investigating the cloud activation of multicomponent organic particles. We modeled these complex mixtures using solubility distributions (analogous to volatility distributions in the VBS, i.e., volatility basis set, approach), describing the mixture as a set of surrogate compounds with varying water solubilities in a given range. We conducted Köhler theory calculations for 144 different mixtures with varying solubility range, number of components, assumption about the organic mixture thermodynamics and the shape of the solubility distribution, yielding approximately 6000 unique cloud condensation nucleus (CCN)-activation points. The results from these comprehensive calculations were compared to three simplifying assumptions about organic aerosol solubility: (1) complete dissolution at the point of activation; (2) combining the aerosol solubility with the molar mass and density into a single effective hygroscopicity parameter κ; and (3) assuming a fixed water-soluble fraction ϵ<sub>eff</sub>. The complete dissolution was able to reproduce the activation points with a reasonable accuracy only when the majority (70–80%) of the material was dissolved at the point of activation. The single-parameter representations of complex mixture solubility were confirmed to be powerful semi-empirical tools for representing the CCN activation of organic aerosol, predicting the activation diameter within 10% in most of the studied supersaturations. Depending mostly on the condensed-phase interactions between the organic molecules, material with solubilities larger than about 0.1–100 g L<sup>−1</sup> could be treated as soluble in the CCN activation process over atmospherically relevant particle dry diameters and supersaturations. Our results indicate that understanding the details of the solubility distribution in the range of 0.1–100 g L<sup>−1</sup> is thus critical for capturing the CCN activation, while resolution outside this solubility range will probably not add much information except in some special cases. The connections of these results to the previous observations of the CCN activation and the molecular properties of complex organic mixture aerosols are discussed. The presented results help unravel the mechanistic reasons behind observations of hygroscopic growth and CCN activation of atmospheric secondary organic aerosol (SOA) particles. The proposed solubility distribution framework is a promising tool for modeling the interlinkages between atmospheric aging, volatility and water uptake of atmospheric organic aerosol.http://www.atmos-chem-phys.net/15/6305/2015/acp-15-6305-2015.pdf |
| spellingShingle | I. Riipinen N. Rastak S. N. Pandis Connecting the solubility and CCN activation of complex organic aerosols: a theoretical study using solubility distributions Atmospheric Chemistry and Physics |
| title | Connecting the solubility and CCN activation of complex organic aerosols: a theoretical study using solubility distributions |
| title_full | Connecting the solubility and CCN activation of complex organic aerosols: a theoretical study using solubility distributions |
| title_fullStr | Connecting the solubility and CCN activation of complex organic aerosols: a theoretical study using solubility distributions |
| title_full_unstemmed | Connecting the solubility and CCN activation of complex organic aerosols: a theoretical study using solubility distributions |
| title_short | Connecting the solubility and CCN activation of complex organic aerosols: a theoretical study using solubility distributions |
| title_sort | connecting the solubility and ccn activation of complex organic aerosols a theoretical study using solubility distributions |
| url | http://www.atmos-chem-phys.net/15/6305/2015/acp-15-6305-2015.pdf |
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