Reconciliation of measurements of hygroscopic growth and critical supersaturation of aerosol particles in central Germany

Irwin, M.; Good, Nicholas; Crosier, Jonathan; McFiggans, G.

doi:10.5194/acp-10-11737-2010

Cited by 67 publications

(97 citation statements)

References 49 publications

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“…Measurements of the hygroscopic growth of atmospheric aerosols in both subsaturated and supersaturated conditions have demonstrated discontinuities in water-uptake behavior below and above water saturation Irwin et al, 2010Irwin et al, , 2011Dusek et al, 2011;Ovadnevaite et al, 2011;Hersey et al, 2013). Specifically, for a given population of aerosols, previous studies have observed low degrees of hygroscopic growth below water saturation but high CCN activity.…”

Section: Introductionmentioning

confidence: 99%

Discontinuities in hygroscopic growth below and above water saturation for laboratory surrogates of oligomers in organic atmospheric aerosols

et al. 2016

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Abstract. Discontinuities in apparent hygroscopicity below and above water saturation have been observed for organic and mixed organic-inorganic aerosol particles in both laboratory studies and in the ambient atmosphere. However, uncertainty remains regarding the factors that contribute to observations of low hygroscopic growth below water saturation but enhanced cloud condensation nuclei (CCN) activity for a given aerosol population. Utilizing laboratory surrogates for oligomers in atmospheric aerosols, we explore the extent to which such discontinuities are influenced by organic component molecular mass and viscosity, non-ideal thermodynamic interactions between aerosol components, and the combination of these factors. Measurements of hygroscopic growth under subsaturated conditions and the CCN activity of aerosols comprised of polyethylene glycol (PEG) with average molecular masses ranging from 200 to 10 000 g mol −1 and mixtures of PEG with ammonium sulfate (AS) were conducted. Experimental results are compared to calculations of hygroscopic growth at thermodynamic equilibrium conducted with the Aerosol Inorganic Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) model, and the potential influence of kinetic limitations on observed water uptake was further explored through estimations of water diffusivity in the PEG oligomers. Particle-phase behavior, including the prevalence of liquid-liquid phase separation (LLPS), was also modeled with AIOMFAC. Under subsaturated relative humidity (RH) conditions, we observed little variability in hygroscopic growth across PEG systems with different molecular masses; however, an increase in CCN activity with increasing PEG molecular mass was observed. This effect is most pronounced for PEG-AS mixtures, and, in fact, an enhancement in CCN activity was observed for the PEG10000-AS mixture as compared to pure AS, as evidenced by a 15 % reduction in critical activation diameter at a supersaturation of 0.8 %. We also observed a marked increase in apparent hygroscopicity for mixtures of higher molecular mass PEG and AS under supersaturated conditions as compared to subsaturated hygroscopic growth. AIOMFAC-based predictions and estimations of water diffusivity in PEG suggest that such discontinuities in apparent hygroscopicity above and below water saturation can be attributed, at least in part, to differences in the sensitivity of water uptake behavior to surface tension effects. There is no evidence that kinetic limitations to water uptake due to the presence of viscous aerosol components influenced hygroscopic growth. For the systems that display an enhancement in apparent hygroscopicity above water saturation, LLPS is predicted to persist to high RH. This indicates a miscibilityPublished by Copernicus Publications on behalf of the European Geosciences Union. 12768 N. Hodas et al.: Discontinuities in the hygroscopicity of oligomers gap and is likely to influence bulk-to-surface partitioning of PEG at high RH, impacting droplet surface tension and CCN activity....

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Section: Introductionmentioning

confidence: 99%

Discontinuities in hygroscopic growth below and above water saturation for laboratory surrogates of oligomers in organic atmospheric aerosols

et al. 2016

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“…Other studies, however, have either implicitly or explicitly reported significant discrepancies between κ chem and κ app (e.g. Moore et al, 2008;Engelhart et al, 2008;King et al, 2009;Wex et al, 2009;Good et al, 2010a;Irwin et al, 2010;Padro et al, 2010). This discrepancy has been attributed to a combination of several effects, including gradual dissolution of sparingly soluble compounds at high relative humidity Petters et al, 2009b), highly non-ideal solution behaviour (Prenni et al, 2007;Petters et al, 2009b), measurement uncertainties related to HTDMA operation including residence time and other unresolved sources of disagreements between instruments of similar design (Sjogren et al, 2007;Good et al, 2010b), and unaccounted surface tension effects when applying Eq.…”

Section: Introductionmentioning

confidence: 99%

“…This discrepancy has been attributed to a combination of several effects, including gradual dissolution of sparingly soluble compounds at high relative humidity Petters et al, 2009b), highly non-ideal solution behaviour (Prenni et al, 2007;Petters et al, 2009b), measurement uncertainties related to HTDMA operation including residence time and other unresolved sources of disagreements between instruments of similar design (Sjogren et al, 2007;Good et al, 2010b), and unaccounted surface tension effects when applying Eq. (1) to derive κ app (Moore et al, 2008;Engelhart et al, 2008;King et al, 2009;Wex et al, 2009;Good et al, 2010a;Irwin et al, 2010;Padro et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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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“…Such a protocol should minimise sampling artefacts of condensation and evaporation. Discrepancies between online measurements of composition and hygroscopic growth when particles contain substantial amounts of semi-volatile material show that correction for this fraction are required , and the equilibration of semi-volatile material will likely contribute to discrepancies between measurements of chemical composition, sub-saturated hygroscopic growth and droplet activation in the laboratory (Good et al, 2010c) and atmosphere (Irwin et al, 2010).…”

Section: Precursormentioning

confidence: 99%

Water uptake is independent of the inferred composition of secondary aerosols derived from multiple biogenic VOCs

et al. 2013

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Abstract. We demonstrate that the water uptake properties derived from sub-and super-saturated measurements of chamber-generated biogenic secondary organic aerosol (SOA) particles are independent of their degree of oxidation, determined using both online and offline methods. SOA particles are formed from the photooxidation of five structurally different biogenic VOCs, representing a broad range of emitted species and their corresponding range of chemical reactivity: α-pinene, β-caryophyllene, limonene, myrcene and linalool. The fractional contribution of mass fragment 44 to the total organic signal (f 44 ) is used to characterise the extent of oxidation of the formed SOA as measured online by an aerosol mass spectrometer. Results illustrate that the values of f 44 are dependent on the precursor, the extent of photochemical ageing as well as on the initial experimental conditions. SOA generated from a single biogenic precursor should therefore not be used as a general proxy for biogenic SOA. Similarly, the generated SOA particles exhibit a range of hygroscopic properties, depending on the precursor, its initial mixing ratio and photochemical ageing. The activation behaviour of the formed SOA particles show no temporal trends with photochemical ageing. The average κ values derived from the HTDMA and CCNc are generally found to cover the same range for each precursor under two different initial mixing ratio conditions. A positive correlation is observed between the hygroscopicity of particles of a single size and f 44 for α-pinene, β-caryophyllene, linalool and myrcene, but not for limonene SOA. The investigation of the generality of this relationship reveals that α-pinene, limonene, linalool and myrcene are all able to generate particles with similar hygroscopicity (κ HTDMA ∼ 0.1) despite f 44 exhibiting a relatively wide range of values (∼ 4 to 11 %). Similarly, κ CCN is found to be independent of f 44 . The same findings are also true when sub-and super-saturated water uptake properties of SOA are compared to the averaged carbon oxidation state (OS C ) determined using an offline method. These findings do not necessarily suggest that water uptake and chemical composition are not related. Instead, they suggest that either f 44 and OS C do not represent the main dominant composition-related factors controlling water uptake of SOA particles, or they may emphasise the possible impact of semi-volatile compounds on limiting the ability of current state-of-the-art techniques to determine the chemical composition and water uptake properties of aerosol particles.

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Reconciliation of measurements of hygroscopic growth and critical supersaturation of aerosol particles in central Germany

Cited by 67 publications

References 49 publications

Discontinuities in hygroscopic growth below and above water saturation for laboratory surrogates of oligomers in organic atmospheric aerosols

Discontinuities in hygroscopic growth below and above water saturation for laboratory surrogates of oligomers in organic atmospheric aerosols

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

Water uptake is independent of the inferred composition of secondary aerosols derived from multiple biogenic VOCs

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