A single parameter representation of hygroscopic growth and cloud condensation nucleus activity

Abstract. The ability of a particle to serve as a cloud condensation nucleus in the atmosphere is determined by its size, hygroscopicity and its solubility in water. Usually size and hygroscopicity alone are sufficient to predict CCN activity. Single parameter representations for hygroscopicity have been shown to model successfully complex, multicomponent particles types. Under the assumption of either complete solubility, or complete insolubility of a component, it is not necessary to explicitly include that components solubility into the single parameter framework. This is not the case if sparingly soluble particles are present. In this work we explicitly account for solubility by modifying the single parameter equations. We demonstrate that sensitivity to the actual value of solubility emerges only in the narrow regime of 1×10−1–5×10−3, where the solubility values are expressed as volume of solute per unit volume of water present in a saturated solution. Since only a few pure compounds fall inside this sparingly soluble envelope and those only make up a small fraction of the total organic fraction most organic species in the atmospheric aerosol can be adequately modeled assuming they are either infinitely soluble in water or completely insoluble .

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A single parameter representation of hygroscopic growth and cloud condensation nucleus activity – Part 2: Including solubility

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-6273-2008 ◽

2008 ◽

Vol 8 (20) ◽

pp. 6273-6279 ◽

Cited By ~ 132

Author(s):

M. D. Petters ◽

S. M. Kreidenweis

Keyword(s):

Unit Volume ◽

Condensation Nucleus ◽

Single Parameter ◽

Saturated Solution ◽

Cloud Condensation Nucleus ◽

Hygroscopic Growth ◽

Solubility In Water ◽

Parameter Representation ◽

Model Complex ◽

Ccn Activity

Abstract. The ability of a particle to serve as a cloud condensation nucleus in the atmosphere is determined by its size, hygroscopicity and its solubility in water. Usually size and hygroscopicity alone are sufficient to predict CCN activity. Single parameter representations for hygroscopicity have been shown to successfully model complex, multicomponent particles types. Under the assumption of either complete solubility, or complete insolubility of a component, it is not necessary to explicitly include that component's solubility into the single parameter framework. This is not the case if sparingly soluble materials are present. In this work we explicitly account for solubility by modifying the single parameter equations. We demonstrate that sensitivity to the actual value of solubility emerges only in the regime of 2×10−1–5×10−4, where the solubility values are expressed as volume of solute per unit volume of water present in a saturated solution. Compounds that do not fall inside this sparingly soluble envelope can be adequately modeled assuming they are either infinitely soluble in water or completely insoluble.

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

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-22687-2012 ◽

2012 ◽

Vol 12 (9) ◽

pp. 22687-22712 ◽

Cited By ~ 1

Author(s):

M. D. Petters ◽

S. M. Kreidenweis

Keyword(s):

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Condensation Nucleus ◽

Single Parameter ◽

Cloud Condensation Nucleus ◽

Extended Model ◽

Hygroscopic Growth ◽

Analytical Approximations ◽

Critical Supersaturation ◽

Kohler Theory

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 the analytical approximations introduced by Raatikainen and Laaksonen 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. We apply this extended model to discuss several uncertainties that hinder our ability to precisely pinpoint the role of surface tension in cloud droplet activation with current measurement and data analysis approaches.

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-1081-2013 ◽

2013 ◽

Vol 13 (2) ◽

pp. 1081-1091 ◽

Cited By ~ 57

Author(s):

M. D. Petters ◽

S. M. Kreidenweis

Keyword(s):

Cloud Condensation Nuclei ◽

Condensation Nucleus ◽

Single Parameter ◽

Cloud Condensation Nucleus ◽

Hygroscopic Growth ◽

Analytical Approximations ◽

Critical Supersaturation ◽

Kohler Theory ◽

Surface Active ◽

Surface Active Compounds

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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Relating particle hygroscopicity and CCN activity to chemical composition during the HCCT-2010 field campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-7983-2013 ◽

2013 ◽

Vol 13 (16) ◽

pp. 7983-7996 ◽

Cited By ~ 65

Author(s):

Z. J. Wu ◽

L. Poulain ◽

S. Henning ◽

K. Dieckmann ◽

W. Birmili ◽

...

Keyword(s):

Chemical Composition ◽

Cloud Condensation Nuclei ◽

Condensation Nucleus ◽

Sampling Period ◽

Cloud Condensation Nucleus ◽

Mountain Range ◽

Mixing Rule ◽

Hygroscopic Growth ◽

Parameter Values ◽

Ccn Activity

Abstract. Particle hygroscopic growth at 90% RH (relative humidity), cloud condensation nuclei (CCN) activity, and size-resolved chemical composition were concurrently measured in the Thüringer Wald mid-level mountain range in central Germany in the fall of 2010. The median hygroscopicity parameter values, κ, of 50, 75, 100, 150, 200, and 250 nm particles derived from hygroscopicity measurements are respectively 0.14, 0.14, 0.17, 0.21, 0.24, and 0.28 during the sampling period. The closure between HTDMA (Hygroscopicity Tandem Differential Mobility Analyzers)-measured (κHTDMA) and chemical composition-derived (κchem) hygroscopicity parameters was performed based on the Zdanovskii–Stokes–Robinson (ZSR) mixing rule. Using size-averaged chemical composition, the κ values are substantially overpredicted (30 and 40% for 150 and 100 nm particles). Introducing size-resolved chemical composition substantially improved closure. We found that the evaporation of NH4NO3, which may happen in a HTDMA system, could lead to a discrepancy in predicted and measured particle hygroscopic growth. The hygroscopic parameter of the organic fraction, κorg, is positively correlated with the O : C ratio (κorg = 0.19 × (O : C) − 0.03). Such correlation is helpful to define the κorg value in the closure study. κ derived from CCN measurement was around 30% (varied with particle diameters) higher than that determined from particle hygroscopic growth measurements (here, hydrophilic mode is considered only). This difference might be explained by the surface tension effects, solution non-ideality, gas-particle partitioning of semivolatile compounds, and the partial solubility of constituents or non-dissolved particle matter. Therefore, extrapolating from HTDMA data to properties at the point of activation should be done with great care. Finally, closure study between CCNc (cloud condensation nucleus counter)-measured (κCCN) and chemical composition (κCCN, chem) was performed using CCNc-derived κ values for individual components. The results show that the κCCN can be well predicted using particle size-resolved chemical composition and the ZSR mixing rule.

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Hygroscopic growth and droplet activation of soot particles: uncoated, succinic or sulfuric acid coated

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-4525-2012 ◽

2012 ◽

Vol 12 (10) ◽

pp. 4525-4537 ◽

Cited By ~ 41

Author(s):

S. Henning ◽

M. Ziese ◽

A. Kiselev ◽

H. Saathoff ◽

O. Möhler ◽

...

Keyword(s):

Sulfuric Acid ◽

Succinic Acid ◽

Condensation Nucleus ◽

Cloud Condensation Nucleus ◽

Hygroscopic Growth ◽

Reaction Products ◽

Carrier Gas ◽

Soot Particles ◽

Polycyclic Aromatic ◽

Droplet Activation

Abstract. The hygroscopic growth and droplet activation of uncoated soot particles and such coated with succinic acid and sulfuric acid were investigated during the IN-11 campaign at the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) facility. A GFG-1000 soot generator applying either nitrogen or argon as carrier gas and a miniCAST soot generator were utilized to generate soot particles. Different organic carbon (OC) to black carbon (BC) ratios were adjusted for the CAST-soot by varying the fuel to air ratio. The hygroscopic growth was investigated by means of the mobile Leipzig Aerosol Cloud Interaction Simulator (LACIS-mobile) and two different Hygroscopicity Tandem Differential Mobility Analyzers (HTDMA, VHTDMA). Two Cloud Condensation Nucleus Counter (CCNC) were applied to measure the activation of the particles. For the untreated soot particles neither hygroscopic growth nor activation was observed at a supersaturation of 1%, with exception of a partial activation of GFG-soot generated with argon as carrier gas. Coatings of succinic acid lead to a detectable hygroscopic growth of GFG-soot and enhanced the activated fraction of GFG- (carrier gas: argon) and CAST-soot, whereas no hygroscopic growth of the coated CAST-soot was found. Sulfuric acid coatings led to an OC-content dependent hygroscopic growth of CAST-soot. Such a dependence was not observed for activation measurements. Coating with sulfuric acid decreased the amount of Polycyclic Aromatic Hydrocarbons (PAH), which were detected by AMS-measurements in the CAST-soot, and increased the amount of substances with lower molecular weight than the initial PAHs. We assume that these reaction products increased the hygroscopicity of the coated particles in addition to the coating substance itself.

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Hygroscopic growth and droplet activation of soot particles: uncoated, succinic or sulfuric acid coated

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-28445-2011 ◽

2011 ◽

Vol 11 (10) ◽

pp. 28445-28475 ◽

Cited By ~ 1

Author(s):

S. Henning ◽

M. Ziese ◽

A. Kiselev ◽

H. Saathoff ◽

O. Möhler ◽

...

Keyword(s):

Sulfuric Acid ◽

Succinic Acid ◽

Condensation Nucleus ◽

Cloud Condensation Nucleus ◽

Hygroscopic Growth ◽

Reaction Products ◽

Carrier Gas ◽

Soot Particles ◽

Polycyclic Aromatic ◽

Droplet Activation

Abstract. The hygroscopic growth and droplet activation of uncoated soot particles and such coated with succinic acid and sulfuric acid were investigated during the IN-11 campaign at the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) facility. A GFG-1000 soot generator applying nitrogen, respectively argon as carrier gas and a miniCAST soot generator were utilized to generate soot particles. Different organic carbon (OC) to black carbon (BC) ratios were adjusted for the CAST-soot by varying the fuel to air ratio. The hygroscopic growth was investigated by means of the mobile Leipzig Aerosol Cloud Interaction Simulator (LACIS-mobile) and two different Hygroscopicity Tandem Differential Mobility Analyzers (HTDMA, VHTDMA). Two Cloud Condensation Nucleus Counter (CCNC) were applied to measure the activation of the particles. For the untreated soot particles neither hygroscopic growth nor activation was observed, with exception of a partial activation of GFG-soot generated with argon as carrier gas. Coatings of succinic acid lead to a detectable hygroscopic growth of GFG-soot and enhanced the activated fraction of GFG- (carrier gas: argon) and CAST-soot, whereas no hygroscopic growth of the coated CAST-soot was found. Sulfuric acid coatings lead to an OC-content dependent hygroscopic growth of CAST-soot. Such a dependence was not observed for activation measurements. Coating with sulfuric acid decreased the amount of Polycyclic Aromatic Hydrocarbons (PAH), which were detected by AMS-measurements in the CAST-soot, and increased the amount of substances with lower molecular weight than the initial PAHs. We assume, that these reaction products increased the hygroscopicity of the coated particles in addition to the coating substance itself.

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Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol: Part 1 – Evidence from measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-3987-2009 ◽

2009 ◽

Vol 9 (12) ◽

pp. 3987-3997 ◽

Cited By ~ 148

Author(s):

H. Wex ◽

M. D. Petters ◽

C. M. Carrico ◽

E. Hallbauer ◽

A. Massling ◽

...

Keyword(s):

Pure Water ◽

Condensation Nucleus ◽

Organic Aerosol ◽

Cloud Condensation Nucleus ◽

Hygroscopic Growth ◽

The Past ◽

Particle Activation ◽

Closing The Gap ◽

Scattering Signal ◽

Made In

Abstract. Secondary Organic Aerosols (SOA) studied in previous laboratory experiments generally showed only slight hygroscopic growth, but a much better activity as a CCN (Cloud Condensation Nucleus) than indicated by the hygroscopic growth. This discrepancy was examined at LACIS (Leipzig Aerosol Cloud Interaction Simulator), using a portable generator that produced SOA particles from the ozonolysis of α-pinene, and adding butanol or butanol and water vapor during some of the experiments. The light scattering signal of dry SOA-particles was measured by the LACIS optical particle spectrometer and was used to derive a refractive index for SOA of 1.45. LACIS also measured the hygroscopic growth of SOA particles up to 99.6% relative humidity (RH), and a CCN counter was used to measure the particle activation. SOA-particles were CCN active with critical diameters of e.g. 100 nm and 55 nm at super-saturations of 0.4% and 1.1%, respectively. But only slight hygroscopic growth with hygroscopic growth factors ≤1.05 was observed at RH<98% RH. At RH>98%, the hygroscopic growth increased stronger than would be expected if a constant hygroscopicity parameter for the particle/droplet solution was assumed. An increase of the hygroscopicity parameter by a factor of 4–6 was observed in the RH-range from below 90% to 99.6%, and this increase continued for increasingly diluted particle solutions for activating particles. This explains an observation already made in the past: that the relation between critical super-saturation and dry diameter for activation is steeper than what would be expected for a constant value of the hygroscopicity. Combining measurements of hygroscopic growth and activation, it was found that the surface tension that has to be assumed to interpret the measurements consistently is greater than 55 mN/m, possibly close to that of pure water, depending on the different SOA-types produced, and therefore only in part accounts for the discrepancy between hygroscopic growth and CCN activity observed for SOA particles in the past.

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Atmospheric Chemistry and Physics ◽

10.5194/acp-7-1961-2007 ◽

2007 ◽

Vol 7 (8) ◽

pp. 1961-1971 ◽

Cited By ~ 1424

Author(s):

M. D. Petters ◽

S. M. Kreidenweis

Keyword(s):

Compositional Data ◽

Cloud Condensation Nuclei ◽

Condensation Nucleus ◽

Atmospheric Particulate Matter ◽

Cloud Condensation Nucleus ◽

Hygroscopic Growth ◽

Activation Data ◽

Surface Active ◽

Surface Active Compounds ◽

Ccn Activity

Abstract. We present a method to describe the relationship between particle dry diameter and cloud condensation nuclei (CCN) activity using a single hygroscopicity parameter κ. Values of the hygroscopicity parameter are between 0.5 and 1.4 for highly-CCN-active salts such as sodium chloride, between 0.01 and 0.5 for slightly to very hygroscopic organic species, and 0 for nonhygroscopic components. Observations indicate that atmospheric particulate matter is typically characterized by 0.1<κ<0.9. If compositional data are available and if the hygroscopicity parameter of each component is known, a multicomponent hygroscopicity parameter can be computed by weighting component hygroscopicity parameters by their volume fractions in the mixture. In the absence of information on chemical composition, experimental data for complex, multicomponent particles can be fitted to obtain the hygroscopicity parameter. The hygroscopicity parameter can thus also be used to conveniently model the CCN activity of atmospheric particles, including those containing insoluble components. We confirm the applicability of the hygroscopicity parameter and its mixing rule by applying it to published hygroscopic diameter growth factor and CCN-activation data for single- and multi-component particles containing varying amounts of inorganic, organic and surface active compounds. We suggest that κ may be fit to CCN data assuming σs/a=0.072 J m−2 and present a table of κ derived for this value and T=298.15 K. The predicted hygroscopicities for mixtures that contain the surfactant fulvic acid agree within uncertainties with the measured values. It thus appears that this approach is adequate for predicting CCN activity of mixed particles containing surface active materials, but the generality of this assumption requires further verification.

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A single parameter representation of hygroscopic growth and cloud condensation nucleus activity

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-8435-2006 ◽

2006 ◽

Vol 6 (5) ◽

pp. 8435-8456 ◽

Cited By ~ 8

Author(s):

M. D. Petters ◽

S. M. Kreidenweis

Keyword(s):

Compositional Data ◽

Cloud Condensation Nuclei ◽

Particle Diameter ◽

Condensation Nucleus ◽

Cloud Condensation Nucleus ◽

Hygroscopic Growth ◽

General Applicability ◽

Activation Data ◽

Parameter Values ◽

Ccn Activity

Abstract. We present a method to describe the relationship between dry particle diameter and cloud condensation nuclei (CCN) activity using a single hygroscopicity parameter. Values of the hygroscopicity parameter are between 0.5 and 2 for highly-CCN-active salts such as sodium chloride, between 0.01 and 0.5 for slightly to very hygroscopic organic species, and 0 for nonhygroscopic components. If compositional data are available and if the hygroscopicity parameter of each component is known, a multicomponent hygroscopicity parameter can be computed by weighting component hygroscopicity parameters by their volume fractions in the mixture. In the absence of information on chemical composition, experimental data for complex, multicomponent particles can be fitted to obtain the hygroscopicity parameter. The hygroscopicity parameter can thus also be used to conveniently model the CCN activity of atmospheric particles, including those containing insoluble components. We confirm the general applicability of the hygroscopicity parameter and its mixing rule by applying it to published hygroscopic diameter growth factor and CCN-activation data for single- and multi-component particles.

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