scholarly journals A curved multi-component aerosol hygroscopicity model framework: Part 2 – Including organic compounds

2005 ◽  
Vol 5 (5) ◽  
pp. 1223-1242 ◽  
Author(s):  
D. O. Topping ◽  
G. B. McFiggans ◽  
H. Coe
Keyword(s):  
Surface Tension ◽  
Atmospheric Aerosols ◽  
Dynamic Balance ◽  
Laboratory Data ◽  
Dicarboxylic Acids ◽  
Companion Paper ◽  
Particulate Material ◽  
Dry Density ◽  
Model Framework ◽  
Organic Systems

Abstract. This paper describes the inclusion of organic particulate material within the Aerosol Diameter Dependent Equilibrium Model (ADDEM) framework described in the companion paper applied to inorganic aerosol components. The performance of ADDEM is analysed in terms of its capability to reproduce the behaviour of various organic and mixed inorganic/organic systems using recently published bulk data. Within the modelling architecture already described two separate thermodynamic models are coupled in an additive approach and combined with a method for solving the Kohler equation in order to develop a tool for predicting the water content associated with an aerosol of known inorganic/organic composition and dry size. For development of the organic module, the widely used group contribution method UNIFAC is employed to explicitly deal with the non-ideality in solution. The UNIFAC predictions for components of atmospheric importance were improved considerably by using revised interaction parameters derived from electro-dynamic balance studies. Using such parameters, the model was found to adequately describe mixed systems including 5–6 dicarboxylic acids, down to low relative humidity conditions. By comparison with electrodynamic balance data, it was also found that the model was capable of capturing the behaviour of aqueous aerosols containing Suwannee River Fulvic acid, a structure previously used to represent the functionality of complex oxidised macromolecules often found in atmospheric aerosols. The additive approach for modelling mixed inorganic/organic systems worked well for a variety of mixtures. As expected, deviations between model predictions and measurements increase with increasing concentration. Available surface tension models, used in evaluating the Kelvin term, were found to reproduce measured data with varying success. Deviations from experimental data increased with increased organic compound complexity. For components only slightly soluble in water, significant deviations from measured surface tension depression behaviour were predicted with both model formalisms tested. A Sensitivity analysis showed that such variation is likely to lead to predicted growth factors within the measurement uncertainty for growth factor taken in the sub-saturated regime. Greater sensitivity was found for the value of dry density used in the assumed form of the dried out aerosol. Comparison with a coupled thermodynamic approach showed that assumed values for interactions parameters may lead to erroneous results where a simple additive approach may provide more accurate results. However, where available, the use of coupled thermodynamics can better reproduce measured behaviour. Further work (and laboratory data) is required to assess whether this difference lies within the experimental uncertainty of observed hygroscopic behaviour for a variety of systems.

scholarly journals A curved multi-component aerosol hygroscopicity model framework: 2 – Including organics

2004 ◽  
Vol 4 (6) ◽  
pp. 8677-8726 ◽  
Author(s):  
D. O. Topping ◽  
G. B. McFiggans ◽  
H. Coe
Keyword(s):  
Surface Tension ◽  
Dynamic Balance ◽  
Laboratory Data ◽  
Dicarboxylic Acids ◽  
Companion Paper ◽  
Particulate Material ◽  
Measured Data ◽  
Dry Density ◽  
Model Framework ◽  
Organic Systems

Abstract. This paper describes the inclusion of organic particulate material within the Aerosol Diameter Dependent Equilibrium Model (ADDEM) framework described in the companion paper applied to inorganic aerosol components. The performance of ADDEM is analysed in terms of its capability to reproduce the behaviour of various organic and mixed inorganic/organic systems using recently published bulk data. Within the modelling architecture already described two separate thermodynamic models are coupled in an additive approach and combined with a method for solving the Köhler equation in order to develop a tool for predicting the water content associated with an aerosol of known inorganic/organic composition and dry size. For development of the organic module, the widely used group contribution method UNIFAC is employed to explicitly deal with the non-ideality in solution. The UNIFAC predictions for components of atmospheric importance were improved considerably by using revised interaction parameters derived from electro-dynamic balance studies. Using such parameters, the model was found to adequately describe mixed systems including 5–6 dicarboxylic acids, down to low relative humidity conditions. The additive approach for modelling mixed inorganic/organic systems worked well for a variety of mixtures. As expected, deviations between predicted and measured data increase with increasing concentration. Available surface tension models, used in evaluating the Kelvin term, were found to reproduce measured data with varying success. Deviations from experimental data increased with increased organic compound complexity. For components only slightly soluble in water, significant deviations from measured surface tension depression behaviour were predicted with both model formalisms tested. A Sensitivity analysis showed that such variation is likely to lead to predicted growth factors within the measurement uncertainty for growth factor taken in the sub-saturated regime. Greater sensitivity was found for the value of dry density used in the assumed form of the dried out aerosol. Comparison with a coupled thermodynamic approach showed that assumed values for interactions parameters may lead to erroneous results where a simple additive approach may provide more accurate results. However, where available, the use of coupled thermodynamics can better reproduce measured behaviour. Further work (and laboratory data) is required to assess whether this difference lies within the experimental uncertainty of observed hygroscopic behaviour for a variety of systems.

scholarly journals A curved multi-component aerosol hygroscopicity model framework: 1 – Inorganics

2004 ◽  
Vol 4 (6) ◽  
pp. 8627-8676 ◽  
Author(s):  
D. O. Topping ◽  
G. B. McFiggans ◽  
H. Coe
Keyword(s):  
Surface Tension ◽  
Companion Paper ◽  
Dry Density ◽  
Model Framework ◽  
Aerosol Model ◽  
Modelling Framework ◽  
Systematic Uncertainties ◽  
Model Aerosol ◽  
Theoretical Predictions ◽  
Models Comparison

Abstract. A thermodynamic modelling framework to predict the equilibrium behaviour of mixed inorganic salt aerosols is developed, and then coupled with a technique for finding a solution to the Köhler equation in order to create a diameter dependent hygroscopic aerosol model (Aerosol Diameter Dependent Equilibrium Model – ADDEM). The model described here provides a robust and accurate inorganic basis using a mole fraction based activity coefficient model and adjusted energies of formation for treating solid precipitation. The model framework can accommodate organic components, though this added complexity is considered in a companion paper, whereas this paper describes the development of the modelling architecture to be used and predictions of an inorganic model alone. The modelling framework has been developed to flexibly use a combination of mixing rules and other potentially more accurate techniques where available to calculate the water content. Comparisons with other state-of-the-art general equilibrium models and experimental data are presented and show excellent agreement. The Kelvin effect can be considered in this scheme using a variety of surface tension models. Comparison of predicted diameter dependent phenomena, such as the increased relative humidity for onset of deliquescence with decreasing diameter, with another diameter dependent model is very good despite the different approach used. The model is subject to various sensitivities. For the inorganic systems studied here, the model is sensitive to choice of surface tension scheme used, which decreases for larger aerosol. Large sensitivities are found for the value of dry density used. It is thus likely that the history of the aerosol studied in a hygroscopic tandem differential mobility analyser (HTDMA), specifically the nature of the drying process that will influence the final crystalline form, will create systematic uncertainties upon comparisons with theoretical predictions. However, the magnitudes of all of the above sensitivities are potentially less than those introduced when using a semi ideal growth factor analogue for certain conditions.

scholarly journals A curved multi-component aerosol hygroscopicity model framework: Part 1 – Inorganic compounds

2005 ◽  
Vol 5 (5) ◽  
pp. 1205-1222 ◽  
Author(s):  
D. O. Topping ◽  
G. B. McFiggans ◽  
H. Coe
Keyword(s):  
Surface Tension ◽  
Inorganic Compounds ◽  
Companion Paper ◽  
Dry Density ◽  
Model Framework ◽  
Aerosol Model ◽  
Modelling Framework ◽  
Systematic Uncertainties ◽  
Model Aerosol ◽  
Models Comparison

Abstract. A thermodynamic modelling framework to predict the equilibrium behaviour of mixed inorganic salt aerosols is developed, and then coupled with a technique for finding a solution to the Kohler equation in order to create a diameter dependent hygroscopic aerosol model (Aerosol Diameter Dependent Equilibrium Model – ADDEM). The model described here provides a robust and accurate inorganic basis using a mole fraction based activity coefficient model and adjusted energies of formation for treating solid precipitation. The model framework can accommodate organic components, though this added complexity is considered in a companion paper, this paper describes the development of the modelling architecture to be used and predictions of an inorganic model alone. The modelling framework has been developed to flexibly use a combination of mixing rules and other potentially more accurate techniques where available to calculate the water content. Comparisons with other state-of-the-art general equilibrium models and experimental data are presented and show excellent agreement. The Kelvin effect can be considered in this scheme using a variety of surface tension models. Comparison of predicted diameter dependent phenomena, such as the increased relative humidity for onset of deliquescence with decreasing diameter, with another diameter dependent model is very good despite the different approach used. The model is subject to various sensitivities. For the inorganic systems studied here, the model is sensitive to choice of surface tension scheme used, which decreases for larger aerosol. Large sensitivities are found for the value of dry density used. It is thus likely that the history of the aerosol studied in a hygroscopic tandem differential mobility analyser (HTDMA), specifically the nature of the drying process that will influence the final crystalline form, will create systematic uncertainties upon comparisons with theoretical predictions. However, the magnitudes of all of the above sensitivities are potentially less than those introduced when using a semi ideal growth factor analogue for certain conditions.

scholarly journals Average molecular weight of surfactants in aerosols

2007 ◽  
Vol 7 (5) ◽  
pp. 13805-13838 ◽  
Author(s):  
M. T. Latif ◽  
P. Brimblecombe
Keyword(s):  
Molecular Weight ◽  
Surface Tension ◽  
Atmospheric Aerosols ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Weight Fraction ◽  
Ozone Exposure ◽  
Before And After ◽  
Fine Mode ◽  
Active Substances

Abstract. Surfactants in atmospheric aerosols determined as methylene blue active substances (MBAS) and ethyl violet active substances (EVAS). The MBAS and EVAS concentrations can be correlated with surface tension as determined by pendant drop analysis. The effect of surface tension was more clearly indicated in fine mode aerosol extracts. The concentration of MBAS and EVAS was determined before and after ultrafiltration analysis using AMICON centrifuge tubes that define a 5000 Da (5 K Da) nominal molecular weight fraction. Overall, MBAS and to a greater extent EVAS predominates in fraction with molecular weight below 5 K Da. In case of aerosols collected in Malaysia the higher molecular fractions tended to be a more predominant. The MBAS and EVAS are correlated with yellow to brown colours in aerosol extracts. Further experiments showed possible sources of surfactants (e.g. petrol soot, diesel soot) in atmospheric aerosols to yield material having molecular size below 5 K Da except for humic acid. The concentration of surfactants from these sources increased after ozone exposure and for humic acids it also general included smaller molecular weight surfactants.

scholarly journals Dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls in atmospheric aerosols from Mt. Fuji, Japan: Implication for primary emission versus secondary formation

2019 ◽  
Vol 221 ◽  
pp. 58-71 ◽  
Author(s):  
Bhagawati Kunwar ◽  
Kimitaka Kawamura ◽  
Shintaro Fujiwara ◽  
Pingqing Fu ◽  
Yuzo Miyazaki ◽  
...  
Keyword(s):  
Atmospheric Aerosols ◽  
Dicarboxylic Acids ◽  
Secondary Formation ◽  
Oxocarboxylic Acids

scholarly journals Modeling the surface tension of complex, reactive organic–inorganic mixtures

2013 ◽  
Vol 13 (21) ◽  
pp. 10721-10732 ◽  
Author(s):  
A. N. Schwier ◽  
G. A. Viglione ◽  
Z. Li ◽  
V. Faye McNeill
Keyword(s):  
Surface Tension ◽  
Organic Compounds ◽  
Atmospheric Aerosols ◽  
Goodness Of Fit ◽  
Cloud Droplet ◽  
Aqueous Mixtures ◽  
Surface Tension Data ◽  
Inorganic Systems ◽  
Experimental Surface ◽  
Using Data

Abstract. Atmospheric aerosols can contain thousands of organic compounds which impact aerosol surface tension, affecting aerosol properties such as heterogeneous reactivity, ice nucleation, and cloud droplet formation. We present new experimental data for the surface tension of complex, reactive organic–inorganic aqueous mixtures mimicking tropospheric aerosols. Each solution contained 2–6 organic compounds, including methylglyoxal, glyoxal, formaldehyde, acetaldehyde, oxalic acid, succinic acid, leucine, alanine, glycine, and serine, with and without ammonium sulfate. We test two semi-empirical surface tension models and find that most reactive, complex, aqueous organic mixtures which do not contain salt are well described by a weighted Szyszkowski–Langmuir (S-L) model which was first presented by Henning et al. (2005). Two approaches for modeling the effects of salt were tested: (1) the Tuckermann approach (an extension of the Henning model with an additional explicit salt term), and (2) a new implicit method proposed here which employs experimental surface tension data obtained for each organic species in the presence of salt used with the Henning model. We recommend the use of method (2) for surface tension modeling of aerosol systems because the Henning model (using data obtained from organic–inorganic systems) and Tuckermann approach provide similar modeling results and goodness-of-fit (χ2) values, yet the Henning model is a simpler and more physical approach to modeling the effects of salt, requiring less empirically determined parameters.

scholarly journals Surface tensions of multi-component mixed inorganic/organic aqueous systems of atmospheric significance: measurements, model predictions and importance for cloud activation predictions

2007 ◽  
Vol 7 (9) ◽  
pp. 2371-2398 ◽  
Author(s):  
D. O. Topping ◽  
G. B. McFiggans ◽  
G. Kiss ◽  
Z. Varga ◽  
M. C. Facchini ◽  
...  
Keyword(s):  
Surface Tension ◽  
Binary Data ◽  
Pure Water ◽  
Higher Order ◽  
Model Parameters ◽  
Surface Tensions ◽  
Organic System ◽  
Organic Components ◽  
Organic Systems ◽  
Surface Partitioning

Abstract. In order to predict the physical properties of aerosol particles, it is necessary to adequately capture the behaviour of the ubiquitous complex organic components. One of the key properties which may affect this behaviour is the contribution of the organic components to the surface tension of aqueous particles in the moist atmosphere. Whilst the qualitative effect of organic compounds on solution surface tensions has been widely reported, our quantitative understanding on mixed organic and mixed inorganic/organic systems is limited. Furthermore, it is unclear whether models that exist in the literature can reproduce the surface tension variability for binary and higher order multi-component organic and mixed inorganic/organic systems of atmospheric significance. The current study aims to resolve both issues to some extent. Surface tensions of single and multiple solute aqueous solutions were measured and compared with predictions from a number of model treatments. On comparison with binary organic systems, two predictive models found in the literature provided a range of values resulting from sensitivity to calculations of pure component surface tensions. Results indicate that a fitted model can capture the variability of the measured data very well, producing the lowest average percentage deviation for all compounds studied. The performance of the other models varies with compound and choice of model parameters. The behaviour of ternary mixed inorganic/organic systems was unreliably captured by using a predictive scheme and this was dependent on the composition of the solutes present. For more atmospherically representative higher order systems, entirely predictive schemes performed poorly. It was found that use of the binary data in a relatively simple mixing rule, or modification of an existing thermodynamic model with parameters derived from binary data, was able to accurately capture the surface tension variation with concentration. Thus, it would appear that in order to model multi-component surface tensions involving compounds used in this study one requires the use of appropriate binary data. However, results indicate that the use of theoretical frameworks which contain parameters derived from binary data may predict unphysical behaviour when taken beyond the concentration ranges used to fit such parameters. The effect of deviations between predicted and measured surface tensions on predicted critical saturation ratios was quantified, by incorporating the surface tension models into an existing thermodynamic framework whilst firstly neglecting bulk to surface partitioning. Critical saturation ratios as a function of dry size for all of the multi-component systems were computed and it was found that deviations between predictions increased with decreasing particle dry size. As expected, use of the surface tension of pure water, rather than calculate the influence of the solutes explicitly, led to a consistently higher value of the critical saturation ratio indicating that neglect of the compositional effects will lead to significant differences in predicted activation behaviour even at large particle dry sizes. Following this two case studies were used to study the possible effect of bulk to surface partitioning on critical saturation ratios. By employing various assumptions it was possible to perform calculations not only for a binary system but also for a mixed organic system. In both cases this effect lead to a significant increase in the predicted critical supersaturation ratio compared to the above treatment. Further analysis of this effect will form the focus of future work.

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