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Complexity of Measuring and Representing the Hygroscopicity of Mixed Component Aerosol

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Complexity of Measuring and Representing the Hygroscopicity of Mixed Component Aerosol. / Marsh, Aleks; Rovelli, Grazia; Miles, Rachael; Reid, Jonathan.

In: Journal of Physical Chemistry A, Vol. 123, No. 8, 28.02.2019, p. 1648-1660.

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Marsh, Aleks ; Rovelli, Grazia ; Miles, Rachael ; Reid, Jonathan. / Complexity of Measuring and Representing the Hygroscopicity of Mixed Component Aerosol. In: Journal of Physical Chemistry A. 2019 ; Vol. 123, No. 8. pp. 1648-1660.

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@article{8b4852ca6eaf4edeaa690903077f2f93,
title = "Complexity of Measuring and Representing the Hygroscopicity of Mixed Component Aerosol",
abstract = "The validation of approaches to predict the hygroscopicity of complex mixtures of organic components in aerosol is important for understanding the hygroscopic response of organic aerosol in the atmosphere. We report new measurements of the hygroscopicity of mixtures of dicarboxylic acids and amino acids using a comparative kinetic electrodynamic balance (CK-EDB) approach, inferring the equilibrium water content of the aerosol from close to a saturation relative humidity (100 {\%}) down to 80 {\%}. We show that the solution densities and refractive indices of the mixtures can be estimated with an accuracy of better than ±2 {\%} using the molar refractive index mixing rule and densities and refractive indices for the individual binary organic-aqueous solutions. Further, we show that the often-used mass, volume and mole-weighted mixing rules to estimate the hygroscopicity parameter  can over-estimate the hygroscopic parameter by a factor of as much as 3, highlighting the need to understand the specific non-ideal interactions that may arise synergistically in mixtures and cannot be represented by simple models. Indeed, in some extreme cases the hygroscopicity of a multicomponent mixture can be very close to that for the least hygroscopic component. For mixtures of similar components for which no additional synergistic interactions need be considered, the hygroscopicity of the mixed component aerosol can be estimated with high accuracy from the hygroscopic response of the binary aqueous-organic aerosol. In conclusion, we suggest that the hygroscopicity of multicomponent organic aerosol can be highly non-additive and that simple correlations of hygroscopicity with composition may often misrepresent the level of complexity essential to interpret aerosol hygroscopicity.",
author = "Aleks Marsh and Grazia Rovelli and Rachael Miles and Jonathan Reid",
year = "2019",
month = "2",
day = "28",
doi = "10.1021/acs.jpca.8b11623",
language = "English",
volume = "123",
pages = "1648--1660",
journal = "Journal of Physical Chemistry A",
issn = "1089-5639",
publisher = "American Chemical Society",
number = "8",

}

RIS - suitable for import to EndNote

TY - JOUR

T1 - Complexity of Measuring and Representing the Hygroscopicity of Mixed Component Aerosol

AU - Marsh, Aleks

AU - Rovelli, Grazia

AU - Miles, Rachael

AU - Reid, Jonathan

PY - 2019/2/28

Y1 - 2019/2/28

N2 - The validation of approaches to predict the hygroscopicity of complex mixtures of organic components in aerosol is important for understanding the hygroscopic response of organic aerosol in the atmosphere. We report new measurements of the hygroscopicity of mixtures of dicarboxylic acids and amino acids using a comparative kinetic electrodynamic balance (CK-EDB) approach, inferring the equilibrium water content of the aerosol from close to a saturation relative humidity (100 %) down to 80 %. We show that the solution densities and refractive indices of the mixtures can be estimated with an accuracy of better than ±2 % using the molar refractive index mixing rule and densities and refractive indices for the individual binary organic-aqueous solutions. Further, we show that the often-used mass, volume and mole-weighted mixing rules to estimate the hygroscopicity parameter  can over-estimate the hygroscopic parameter by a factor of as much as 3, highlighting the need to understand the specific non-ideal interactions that may arise synergistically in mixtures and cannot be represented by simple models. Indeed, in some extreme cases the hygroscopicity of a multicomponent mixture can be very close to that for the least hygroscopic component. For mixtures of similar components for which no additional synergistic interactions need be considered, the hygroscopicity of the mixed component aerosol can be estimated with high accuracy from the hygroscopic response of the binary aqueous-organic aerosol. In conclusion, we suggest that the hygroscopicity of multicomponent organic aerosol can be highly non-additive and that simple correlations of hygroscopicity with composition may often misrepresent the level of complexity essential to interpret aerosol hygroscopicity.

AB - The validation of approaches to predict the hygroscopicity of complex mixtures of organic components in aerosol is important for understanding the hygroscopic response of organic aerosol in the atmosphere. We report new measurements of the hygroscopicity of mixtures of dicarboxylic acids and amino acids using a comparative kinetic electrodynamic balance (CK-EDB) approach, inferring the equilibrium water content of the aerosol from close to a saturation relative humidity (100 %) down to 80 %. We show that the solution densities and refractive indices of the mixtures can be estimated with an accuracy of better than ±2 % using the molar refractive index mixing rule and densities and refractive indices for the individual binary organic-aqueous solutions. Further, we show that the often-used mass, volume and mole-weighted mixing rules to estimate the hygroscopicity parameter  can over-estimate the hygroscopic parameter by a factor of as much as 3, highlighting the need to understand the specific non-ideal interactions that may arise synergistically in mixtures and cannot be represented by simple models. Indeed, in some extreme cases the hygroscopicity of a multicomponent mixture can be very close to that for the least hygroscopic component. For mixtures of similar components for which no additional synergistic interactions need be considered, the hygroscopicity of the mixed component aerosol can be estimated with high accuracy from the hygroscopic response of the binary aqueous-organic aerosol. In conclusion, we suggest that the hygroscopicity of multicomponent organic aerosol can be highly non-additive and that simple correlations of hygroscopicity with composition may often misrepresent the level of complexity essential to interpret aerosol hygroscopicity.

U2 - 10.1021/acs.jpca.8b11623

DO - 10.1021/acs.jpca.8b11623

M3 - Article

VL - 123

SP - 1648

EP - 1660

JO - Journal of Physical Chemistry A

T2 - Journal of Physical Chemistry A

JF - Journal of Physical Chemistry A

SN - 1089-5639

IS - 8

ER -