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

2007 ◽  
Vol 7 (8) ◽  
pp. 1961-1971 ◽  
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.

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

2006 ◽  
Vol 6 (5) ◽  
pp. 8435-8456 ◽  
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.

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

2013 ◽  
Vol 13 (2) ◽  
pp. 1081-1091 ◽  
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.

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

2013 ◽  
Vol 13 (16) ◽  
pp. 7983-7996 ◽  
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.

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

2008 ◽  
Vol 8 (20) ◽  
pp. 6273-6279 ◽  
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.

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

2012 ◽  
Vol 12 (9) ◽  
pp. 22687-22712 ◽  
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.

scholarly journals Widening the gap between measurement and modelling of secondary organic aerosol properties?

2010 ◽  
Vol 10 (6) ◽  
pp. 2577-2593 ◽  
Author(s):  
N. Good ◽  
D. O. Topping ◽  
J. Duplissy ◽  
M. Gysel ◽  
N. K. Meyer ◽  
...  
Keyword(s):  
Surface Tension ◽  
Water Activity ◽  
Condensation Nucleus ◽  
Organic Aerosol ◽  
Solute Concentration ◽  
Complex Model ◽  
Cloud Condensation Nucleus ◽  
Saturated Water ◽  
Cloud Activation ◽  
Ccn Activity

Abstract. The link between measured sub-saturated hygroscopicity and cloud activation potential of secondary organic aerosol particles produced by the chamber photo-oxidation of α-pinene in the presence or absence of ammonium sulphate seed aerosol was investigated using two models of varying complexity. A simple single hygroscopicity parameter model and a more complex model (incorporating surface effects) were used to assess the detail required to predict the cloud condensation nucleus (CCN) activity from the sub-saturated water uptake. Sub-saturated water uptake measured by three hygroscopicity tandem differential mobility analyser (HTDMA) instruments was used to determine the water activity for use in the models. The predicted CCN activity was compared to the measured CCN activation potential using a continuous flow CCN counter. Reconciliation using the more complex model formulation with measured cloud activation could be achieved widely different assumed surface tension behavior of the growing droplet; this was entirely determined by the instrument used as the source of water activity data. This unreliable derivation of the water activity as a function of solute concentration from sub-saturated hygroscopicity data indicates a limitation in the use of such data in predicting cloud condensation nucleus behavior of particles with a significant organic fraction. Similarly, the ability of the simpler single parameter model to predict cloud activation behaviour was dependent on the instrument used to measure sub-saturated hygroscopicity and the relative humidity used to provide the model input. However, agreement was observed for inorganic salt solution particles, which were measured by all instruments in agreement with theory. The difference in HTDMA data from validated and extensively used instruments means that it cannot be stated with certainty the detail required to predict the CCN activity from sub-saturated hygroscopicity. In order to narrow the gap between measurements of hygroscopic growth and CCN activity the processes involved must be understood and the instrumentation extensively quality assured. It is impossible to say from the results presented here due to the differences in HTDMA data whether: i) Surface tension suppression occurs ii) Bulk to surface partitioning is important iii) The water activity coefficient changes significantly as a function of the solute concentration.

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

2016 ◽  
Author(s):  
Natasha Hodas ◽  
Andreas Zuend ◽  
Katherine Schilling ◽  
Thomas Berkemeier ◽  
Manabu Shiraiwa ◽  
...  
Keyword(s):  
Molecular Mass ◽  
Water Uptake ◽  
Atmospheric Aerosols ◽  
Water Saturation ◽  
Cloud Condensation Nuclei ◽  
Ambient Atmosphere ◽  
Hygroscopic Growth ◽  
Water Diffusivity ◽  
Molecular Masses ◽  
Ccn Activity

Abstract. Organic oligomers and other organic high molecular mass compounds are potential sources of viscous atmospheric aerosol components, which may inhibit the mass transport of water and introduce kinetic limitations to water uptake. This, in turn, impacts aerosol optical properties and the efficiency with which these particles serve as cloud condensation nuclei (CCN). To investigate the influence of particle viscosity on water-uptake behavior, measurements of hygroscopic growth under subsaturated relative humidity (RH) conditions and of the CCN activity of laboratory surrogates for oligomers in atmospheric aerosols were conducted with the Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe and a CCN counter, respectively. In order to explore variability in water-uptake behavior across aerosol systems with differing viscosities, experiments were conducted for particles comprised of polyethylene glycol (PEG) with average molecular masses of 200, 1,000, and 10,000 g/mol, as well as mixtures of these PEG oligomers with ammonium sulfate (AS). Experimental results were compared with 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 to observed water uptake was further explored through estimations of water diffusivity in the PEG oligomers. Under subsaturated 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 latter finding is attributed to an increase in the efficiency of PEG as a surfactant with increasing molecular mass. This effect is most pronounced for PEG-AS mixtures, and a modest enhancement in CCN activity was observed for the PEG10,000-AS mixture as compared to pure AS, as evidenced by a 8 % reduction in critical activation diameter at a supersaturation of 0.6 %. The supplementation of experimental observations with the AIOMFAC-based model results and estimations of water diffusivity in PEG suggests that apparent discontinuities in hygroscopicity above and below water saturation can be attributed, at least in part, to a combination of RH-dependent differences in the sensitivity of water uptake behavior to non-ideal interactions and to surface tension effects. There was no evidence that kinetic limitations to water uptake due to the presence of viscous aerosol components influenced hygroscopic growth. This work provides insight into the factors likely to be contributing to discontinuities in aerosol water-uptake behavior below and above water saturation (e.g., low hygroscopic growth at subsaturated RHs, but enhanced CCN activity for a given aerosol population) that have been observed previously in the ambient atmosphere.

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

2012 ◽  
Vol 12 (10) ◽  
pp. 4525-4537 ◽  
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.

scholarly journals Thermodynamic properties and cloud droplet activation of a series of oxo-acids

2010 ◽  
Vol 10 (13) ◽  
pp. 5873-5890 ◽  
Author(s):  
M. Frosch ◽  
A. A. Zardini ◽  
S. M. Platt ◽  
L. Müller ◽  
M.-C. Reinnig ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Thermodynamic Properties ◽  
Vapor Pressure ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Dicarboxylic Acids ◽  
Atmospheric Particulate Matter ◽  
Flow Tube ◽  
Order Of Magnitude ◽  
Ccn Activity

Abstract. We have investigated the thermodynamic properties of four aliphatic oxo-dicarboyxlic acids identified or thought to be present in atmospheric particulate matter: oxosuccinic acid, 2-oxoglutaric acid, 3-oxoglutaric acid, and 4-oxopimelic acid. The compounds were characterized in terms of their cloud condensation nuclei (CCN) activity, vapor pressure, density, and tendency to decarboxylate in aqueous solution. We deployed a variety of experimental techniques and instruments: a CCN counter, a Tandem Differential Mobililty Analyzer (TDMA) coupled with a laminar flow-tube, and liquid chromatography/mass spectrometry (LC/MS). The presence of the oxo functional group in the α-position causes the vapor pressure of the compounds to diminish by an order of magnitude with respect to the parent dicarboxylic acid, while the CCN activity is similar or increased. Dicarboxylic acids with an oxo-group in the β-position decarboxylate in aqueous solution. We studied the effects of this process on our measurements and findings.

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