A simple representation of surface active organic aerosol in cloud droplet formation

Prisle, Nønne L.; Maso, Miikka Dal; Kokkola, Harri

doi:10.5194/acp-11-4073-2011

Cited by 55 publications

(123 citation statements)

References 28 publications

(50 reference statements)

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“…The model can be used with surface tension data from bulk measurements while maintaining a thermodynamically rigorous description of the surface-to-bulk partitioning process. The developed framework is consistent with, and builds upon similar simplified treatments of the problem that were recently reported in the literature (Topping, 2010;Prisle et al, 2011;Raatikainen and Laaksonen, 2011). The resulting conceptual framework is useful for highlighting several uncertainties that hinder our ability to precisely pinpoint the role of surface tension in cloud droplet activation using current measurement and data analysis approaches.…”

Section: Introductionmentioning

confidence: 57%

A single parameter representation of hygroscopic growth and cloud condensation nucleus activity – Part 3: Including surfactant partitioning

2013

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Abstract. Atmospheric particles can serve as cloud condensation nuclei in the atmosphere. The presence of surface active compounds in the particle may affect the critical supersaturation that is required to activate a particle. Modelling surfactants in the context of Köhler theory, however, is difficult because surfactant enrichment at the surface implies that a stable radial concentration gradient must exist in the droplet. In this study, we introduce a hybrid model that accounts for partitioning between the bulk and surface phases in the context of single parameter representations of cloud condensation nucleus activity. The presented formulation incorporates analytical approximations of surfactant partitioning to yield a set of equations that maintain the conceptual and mathematical simplicity of the single parameter framework. The resulting set of equations allows users of the single parameter model to account for surfactant partitioning by applying minor modifications to already existing code.

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Section: Introductionmentioning

confidence: 57%

A single parameter representation of hygroscopic growth and cloud condensation nucleus activity – Part 3: Including surfactant partitioning

2013

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“…This is indicative of surfactants being present, as particles activating at higher supersaturations (i.e., smaller particles) tend to be more concentrated in surfactants at the critical wet diameter, resulting in a greater surface tension reduction than in particles which activate at lower supersaturations. This is applicable when surface-bulk partitioning of organics does not fully compensate for surface tension depression (32), and if surfactants are in equilibrium with the bulk and gas phase.…”

Section: Resultsmentioning

confidence: 99%

Surfactants from the gas phase may promote cloud droplet formation

Sareen

Schwier

Lathem

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

117

128

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Clouds, a key component of the climate system, form when water vapor condenses upon atmospheric particulates termed cloud condensation nuclei (CCN). Variations in CCN concentrations can profoundly impact cloud properties, with important effects on local and global climate. Organic matter constitutes a significant fraction of tropospheric aerosol mass, and can influence CCN activity by depressing surface tension, contributing solute, and influencing droplet activation kinetics by forming a barrier to water uptake. We present direct evidence that two ubiquitous atmospheric trace gases, methylglyoxal (MG) and acetaldehyde, known to be surface-active, can enhance aerosol CCN activity upon uptake. This effect is demonstrated by exposing acidified ammonium sulfate particles to 250 parts per billion (ppb) or 8 ppb gas-phase MG and/or acetaldehyde in an aerosol reaction chamber for up to 5 h. For the more atmospherically relevant experiments, i.e., the 8-ppb organic precursor concentrations, significant enhancements in CCN activity, up to 7.5% reduction in critical dry diameter for activation, are observed over a timescale of hours, without any detectable limitation in activation kinetics. This reduction in critical diameter enhances the apparent particle hygroscopicity up to 26%, which for ambient aerosol would lead to cloud droplet number concentration increases of 8-10% on average. The observed enhancements exceed what would be expected based on Köhler theory and bulk properties. Therefore, the effect may be attributed to the adsorption of MG and acetaldehyde to the gas-aerosol interface, leading to surface tension depression of the aerosol. We conclude that gas-phase surfactants may enhance CCN activity in the atmosphere.atmospheric chemistry | VOCs | indirect effect T he reactive uptake of volatile organic compounds (VOCs) by wet aerosols is a potentially important source of organic matter (OM) (1-3). The α-dicarbonyl species glyoxal and methylglyoxal (MG), along with acetaldehyde and other carbonylcontaining species, belong to this class; they are absorbed by wet aerosol particles (or cloud droplets) and undergo aqueous phase reactions to form low-volatility secondary organic aerosol (SOA) (2, 4-6). The impacts of these processes on aerosol cloud condensation nuclei (CCN) activity and cloud droplet formation are highly uncertain at this time. Few studies have focused on the impact of SOA generated in the aqueous phase on aerosol CCN activity (7-9). It was recently shown that the formation of SOA via the condensation of low-volatility VOC oxidation products, which are generally less hygroscopic than deliquescent inorganic salts, can affect the CCN activity of the seed aerosol (10-15). SOA generated through aqueous-phase chemistry is likely to be highly oxygenated and surface-active, hence making it strongly CCN-active (6,16,17). Some of the VOC precursors themselves, including MG and acetaldehyde, are also surface-active (6,16,17).We studied the changes in the CCN activity of acidified ammonium sulfate seed aerosol...

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“…Many organic compounds found in ambient organic aerosol lower the surface tension at the solution-air interface (Tuckermann and Cammenga, 2004;Tuckerman, 2007). However, several studies have demonstrated via experiment and theory that surfactant partitioning between the bulk solution and the Gibbs surface phase greatly diminishes the effect one would predict by applying macroscopic surface tensions in Köhler theory (Li et al, 1998;Rood and Williams, 2001;Sorjamaa et al, 2004;Prisle et al, 2011). Neglecting to account for reduced surface tension and using water activity to estimate CCN activity results in an underestimate of κ by ∼ 30 % for the strong surfactant sodium dodecyl sulfate (Petters and Kreidenweis, 2013).…”

Section: Model Assumptions and Limitationsmentioning

confidence: 99%

Prediction of cloud condensation nuclei activity for organic compounds using functional group contribution methods

2016

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Abstract.A wealth of recent laboratory and field experiments demonstrate that organic aerosol composition evolves with time in the atmosphere, leading to changes in the influence of the organic fraction to cloud condensation nuclei (CCN) spectra. There is a need for tools that can realistically represent the evolution of CCN activity to better predict indirect effects of organic aerosol on clouds and climate. This work describes a model to predict the CCN activity of organic compounds from functional group composition. Following previous methods in the literature, we test the ability of semi-empirical group contribution methods in Köh-ler theory to predict the effective hygroscopicity parameter, kappa. However, in our approach we also account for liquidliquid phase boundaries to simulate phase-limited activation behavior. Model evaluation against a selected database of published laboratory measurements demonstrates that kappa can be predicted within a factor of 2. Simulation of homologous series is used to identify the relative effectiveness of different functional groups in increasing the CCN activity of weakly functionalized organic compounds. Hydroxyl, carboxyl, aldehyde, hydroperoxide, carbonyl, and ether moieties promote CCN activity while methylene and nitrate moieties inhibit CCN activity. The model can be incorporated into scale-bridging test beds such as the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) to evaluate the evolution of kappa for a complex mix of organic compounds and to develop suitable parameterizations of CCN evolution for larger-scale models.

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A simple representation of surface active organic aerosol in cloud droplet formation

Cited by 55 publications

References 28 publications

A single parameter representation of hygroscopic growth and cloud condensation nucleus activity – Part 3: Including surfactant partitioning

A single parameter representation of hygroscopic growth and cloud condensation nucleus activity – Part 3: Including surfactant partitioning

Surfactants from the gas phase may promote cloud droplet formation

Prediction of cloud condensation nuclei activity for organic compounds using functional group contribution methods

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