scholarly journals The sensitivity of secondary organic aerosol (SOA) component partitioning to the predictions of component properties – Part 3: Investigation of condensed compounds generated by a near-explicit model of VOC oxidation

2011 ◽  
Vol 11 (24) ◽  
pp. 13145-13159 ◽  
Author(s):  
M. H. Barley ◽  
D. Topping ◽  
D. Lowe ◽  
S. Utembe ◽  
G. McFiggans
Keyword(s):  
Activity Coefficients ◽  
Vapour Pressure ◽  
Molar Mass ◽  
Emission Scenario ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Estimation Methods ◽  
Explicit Model ◽  
Voc Emission ◽  
Aerosol Properties

Abstract. Calculations of the absorptive partitioning of secondary organic aerosol components were carried out using a number of methods to estimate vapour pressure and non-ideality. The sensitivity of predicted condensed component masses, volatility, O:C ratio, molar mass and functionality distribution to the choice of estimation methods was investigated in mixtures of around 2700 compounds generated by a near explicit mechanism of atmospheric VOC degradation. The sensitivities in terms of all metrics were comparable to those previously reported (using 10 000 semi-randomly generated compounds). In addition, the change in predicted aerosol properties and composition with changing VOC emission scenario was investigated showing key dependencies on relative anthropogenic and biogenic contributions. Finally, the contribution of non-ideality to the changing distribution of condensed components was explored in terms of the shift in effective volatility by virtue of component activity coefficients, clearly demonstrating both enhancement and reduction of component masses associated with negative and positive deviations from ideality.

scholarly journals The sensitivity of secondary organic aerosol (SOA) component partitioning to the predictions of component properties – Part 3: Investigation of condensed compounds generated by a near-explicit model of VOC oxidation

2011 ◽  
Vol 11 (7) ◽  
pp. 21055-21090 ◽  
Author(s):  
M. H. Barley ◽  
D. Topping ◽  
D. Lowe ◽  
S. Utembe ◽  
G. McFiggans
Keyword(s):  
Activity Coefficients ◽  
Vapour Pressure ◽  
Molar Mass ◽  
Emission Scenario ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Estimation Methods ◽  
Explicit Model ◽  
Voc Emission ◽  
Aerosol Properties

Abstract. Calculations of the absorptive partitioning of secondary organic aerosol components were carried out using a number of methods to estimate vapour pressure and non-ideality. The sensitivity of predicted condensed component masses, volatility, O:C ratio, molar mass and functionality distribution to the choice of estimation methods was investigated in mixtures of around 2700 compounds generated by a near explicit mechanism of atmospheric VOC degradation. The sensitivities in terms of all metrics were comparable to those previously reported (using 10 000 semi-randomly generated compounds). In addition, the change in predicted aerosol properties and composition with changing VOC emission scenario was investigated showing key dependencies on relative anthropogenic and biogenic contributions. Finally, the contribution of non-ideality to the changing distribution of condensed components was explored in terms of the shift in effective volatility by virtue of component activity coefficients, clearly demonstrating both enhancement and reduction of component masses associated with negative and positive deviations from ideality.

scholarly journals Novel methods for predicting gas–particle partitioning during the formation of secondary organic aerosol

2014 ◽  
Vol 14 (23) ◽  
pp. 13189-13204 ◽  
Author(s):  
F. Wania ◽  
Y. D. Lei ◽  
C. Wang ◽  
J. P. D. Abbatt ◽  
K.-U. Goss
Keyword(s):  
Functional Groups ◽  
Vapour Pressure ◽  
Secondary Organic Aerosol ◽  
Prediction Method ◽  
Organic Aerosol ◽  
Estimation Methods ◽  
Minor Effect ◽  
Normal Alkanes ◽  
Sorption Data ◽  
Order Of Magnitude

Abstract. Several methods have been presented in the literature to predict an organic chemical's equilibrium partitioning between the water insoluble organic matter (WIOM) component of aerosol and the gas phase, Ki,WIOM, as a function of temperature. They include (i) polyparameter linear free energy relationships calibrated with empirical aerosol sorption data, as well as (ii) the solvation models implemented in SPARC and (iii) the quantum-chemical software COSMOtherm, which predict solvation equilibria from molecular structure alone. We demonstrate that these methods can be used to predict Ki,WIOM for large numbers of individual molecules implicated in secondary organic aerosol (SOA) formation, including those with multiple functional groups. Although very different in their theoretical foundations, these methods give remarkably consistent results for the products of the reaction of normal alkanes with OH, i.e. their partition coefficients Ki,WIOM generally agree within one order of magnitude over a range of more than ten orders of magnitude. This level of agreement is much better than that achieved by different vapour pressure estimation methods that are more commonly used in the SOA community. Also, in contrast to the agreement between vapour pressure estimates, the agreement between the Ki,WIOM estimates does not deteriorate with increasing number of functional groups. Furthermore, these partitioning coefficients Ki,WIOM predicted SOA mass yields in agreement with those measured in chamber experiments of the oxidation of normal alkanes. If a Ki,WIOM prediction method was based on one or more surrogate molecules representing the solvation properties of the mixed OM phase of SOA, the choice of those molecule(s) was found to have a relatively minor effect on the predicted Ki,WIOM, as long as the molecule(s) are not very polar. This suggests that a single surrogate molecule, such as 1-octanol or a hypothetical SOA structure proposed by Kalberer et al. (2004), may often be sufficient to represent the WIOM component of the SOA phase, greatly simplifying the prediction. The presented methods could substitute for vapour-pressure-based methods in studies such as the explicit modelling of SOA formation from single precursor molecules in chamber experiments.

scholarly journals Novel methods for predicting gas-particle partitioning during the formation of secondary organic aerosol

2014 ◽  
Vol 14 (15) ◽  
pp. 21341-21385 ◽  
Author(s):  
F. Wania ◽  
Y. D. Lei ◽  
C. Wang ◽  
J. P. D. Abbatt ◽  
K.-U. Goss
Keyword(s):  
Functional Groups ◽  
Vapour Pressure ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Basis Sets ◽  
Estimation Methods ◽  
Minor Effect ◽  
Normal Alkanes ◽  
Sorption Data ◽  
Better Than

Abstract. Several methods have been presented in the literature to predict an organic chemical's equilibrium partitioning between the water insoluble organic matter (WIOM) component of aerosol and the gas phase, Ki, WIOM as a function of temperature. They include (i) polyparameter linear free energy relationships calibrated with empirical aerosol sorption data, as well as (ii) the solvation models implemented in SPARC and (iii) the quantum-chemical software Cosmotherm, which predict solvation equilibria from molecular structure alone. We demonstrate that these methods can be used to predict Ki, WIOM for large numbers of individual molecules implicated in secondary organic aerosol (SOA) formation, including those with multiple functional groups. Although very different in their theoretical foundations, these methods give remarkably consistent results for the products of the reaction of normal alkanes with OH, i.e. their partition coefficients Ki, WIOM generally agree within one order of magnitude over a range of more than ten orders of magnitude. This level of agreement is much better than that achieved by different vapour pressure estimation methods that are more commonly used in the SOA community. Also, in contrast to the agreement between vapour pressure estimates, that between the Ki, WIOM estimates does not deteriorate with increasing number of functional groups. Furthermore, these partitioning coefficients Ki, WIOM are found to predict the SOA mass yield in chamber experiments of the oxidation of normal alkanes as good or better than a vapour pressure based method. If a Ki, WIOM prediction method was based on one or more surrogate molecules representing the solvation properties of the mixed OM phase of SOA, the choice of those molecule(s) was found to have a relatively minor effect on the predicted Ki, WIOM, as long as the molecule(s) are not very polar. This suggests that a single surrogate molecule, such as 1-octanol or a hypothetical SOA structure proposed by Kalberer et al. (2004), may often be sufficient to represent the WIOM component of the SOA phase, greatly simplifying the prediction. The presented methods could substitute for vapour pressure based methods in studies such as the explicit modeling of SOA formation from single precursor molecules in chamber experiments or the assignment of SOA-forming molecules to volatility basis sets.

scholarly journals Estimating fusion properties for functionalised acids

2011 ◽  
Vol 11 (16) ◽  
pp. 8385-8394 ◽  
Author(s):  
S. Compernolle ◽  
K. Ceulemans ◽  
J.-F. Müller
Keyword(s):  
Vapour Pressure ◽  
Estimation Error ◽  
Estimation Method ◽  
Organic Aerosol ◽  
Estimation Methods ◽  
Fusion Temperature ◽  
Subcooled Liquid ◽  
Fusion Data ◽  
Simple Estimation ◽  
Data Estimation

Abstract. Multicomponent organic aerosol (OA) is likely to be liquid, or partially liquid. Hence, to describe the partitioning of these components, their liquid vapour pressure is desired. Functionalised acids (e.g. diacids) can be a significant part of OA. But often measurements are available only for solid state vapour pressure, which can differ by orders of magnitude from their liquid counterparts. To convert such a sublimation pressure to a subcooled liquid vapour pressure, fusion properties (two out of these three quantities: fusion enthalpy, fusion entropy, fusion temperature) are required. Unfortunately, experimental knowledge of fusion properties is sometimes missing in part or completely, hence an estimation method is required. Several fusion data estimation methods are tested here against experimental data of functionalised acids, and a simple estimation method is developed, specifically for this family of compounds, with a significantly smaller estimation error than the literature methods.

scholarly journals The critical assessment of vapour pressure estimation methods for use in modelling the formation of atmospheric organic aerosol

2010 ◽  
Vol 10 (2) ◽  
pp. 749-767 ◽  
Author(s):  
M. H. Barley ◽  
G. McFiggans
Keyword(s):  
Vapour Pressure ◽  
Organic Aerosol ◽  
Critical Assessment ◽  
Estimation Methods ◽  
Atmospheric Conditions ◽  
Group Contribution Method ◽  
Pressure Data ◽  
Multifunctional Compounds ◽  
Stringent Test ◽  
Selection Of

Abstract. A selection of models for estimating vapour pressures have been tested against experimental data for a set of compounds selected for their particular relevance to the formation of atmospheric aerosol by gas-liquid partitioning. The experimental vapour pressure data (all <100 Pa) of 45 multifunctional compounds provide a stringent test of the estimation techniques, with a recent complex group contribution method providing the best overall results. The effect of errors in vapour pressures upon the formation of organic aerosol by gas-liquid partitioning in an atmospherically relevant example is also investigated. The mass of organic aerosol formed under typical atmospheric conditions was found to be very sensitive to the variation in vapour pressure values typically present when comparing estimation methods.

scholarly journals The critical assessment of vapour pressure estimation methods for use in modelling the formation of atmospheric organic aerosol

2009 ◽  
Vol 9 (5) ◽  
pp. 18375-18416 ◽  
Author(s):  
M. H. Barley ◽  
G. McFiggans
Keyword(s):  
Vapour Pressure ◽  
Organic Aerosol ◽  
Critical Assessment ◽  
Estimation Methods ◽  
Atmospheric Conditions ◽  
Group Contribution Method ◽  
Pressure Data ◽  
Multifunctional Compounds ◽  
Stringent Test ◽  
Selection Of

Abstract. A selection of models for estimating vapour pressures have been tested against experimental data for a set of compounds selected for their particular relevance to the formation of atmospheric aerosol by gas-liquid partitioning. The experimental vapour pressure data (all <100 Pa) of 45 multifunctional compounds provide a stringent test of the estimation techniques, with a recent complex group contribution method providing the best overall results. The effect of errors in vapour pressures upon the formation of organic aerosol by gas-liquid partitioning in an atmospherically relevant example is also investigated. The mass of organic aerosol formed under typical atmospheric conditions was found to be very sensitive to the variation in vapour pressure values typically present when comparing estimation methods.

scholarly journals The Secondary Organic Aerosol Processor (SOAP v1.0) model: a unified model with different ranges of complexity based on the molecular surrogate approach

2014 ◽  
Vol 7 (1) ◽  
pp. 379-429 ◽  
Author(s):  
F. Couvidat ◽  
K. Sartelet
Keyword(s):  
Phase Separation ◽  
Gas Phase ◽  
Organic Compounds ◽  
Aqueous Phase ◽  
Activity Coefficients ◽  
Organic Phase ◽  
Secondary Organic Aerosol ◽  
Computing Time ◽  
Organic Aerosol ◽  
Dynamic Representation

Abstract. The Secondary Organic Aerosol Processor (SOAP v1.0) model is presented. This model is designed to be modular with different user options depending on the computing time and the complexity required by the user. This model is based on the molecular surrogate approach, in which each surrogate compound is associated with a molecular structure to estimate some properties and parameters (hygroscopicity, absorption on the aqueous phase of particles, activity coefficients, phase separation). Each surrogate can be hydrophilic (condenses only on the aqueous phase of particles), hydrophobic (condenses only on the organic phase of particles) or both (condenses on both the aqueous and the organic phases of particles). Activity coefficients are computed with the UNIFAC thermodynamic model for short-range interactions and with the AIOMFAC parameterization for medium and long-range interactions between electrolytes and organic compounds. Phase separation is determined by Gibbs energy minimization. The user can choose between an equilibrium and a dynamic representation of the organic aerosol. In the equilibrium representation, compounds in the particle phase are assumed to be at equilibrium with the gas phase. However, recent studies show that the organic aerosol (OA) is not at equilibrium with the gas phase because the organic phase could be semi-solid (very viscous liquid phase). The condensation or evaporation of organic compounds could then be limited by the diffusion in the organic phase due to the high viscosity. A dynamic representation of secondary organic aerosols (SOA) is used with OA divided into layers, the first layer at the center of the particle (slowly reaches equilibrium) and the final layer near the interface with the gas phase (quickly reaches equilibrium).

scholarly journals The SOA/VOC/NO<sub>x</sub> system: an explicit model of secondary organic aerosol formation

2007 ◽  
Vol 7 (21) ◽  
pp. 5599-5610 ◽  
Author(s):  
M. Camredon ◽  
B. Aumont ◽  
J. Lee-Taylor ◽  
S. Madronich
Keyword(s):  
Gas Phase ◽  
First Principles ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Current Understanding ◽  
Aerosol Formation ◽  
Explicit Model ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Atmospherically Relevant

Abstract. Our current understanding of secondary organic aerosol (SOA) formation is limited by our knowledge of gaseous secondary organics involved in gas/particle partitioning. The objective of this study is to explore (i) the potential for products of multiple oxidation steps contributing to SOA, and (ii) the evolution of the SOA/VOC/NOx system. We developed an explicit model based on the coupling of detailed gas-phase oxidation schemes with a thermodynamic condensation module. Such a model allows prediction of SOA mass and speciation on the basis of first principles. The SOA/VOC/NOx system is studied for the oxidation of 1-octene under atmospherically relevant concentrations. In this study, gaseous oxidation of octene is simulated to lead to SOA formation. Contributors to SOA formation are shown to be formed via multiple oxidation steps of the parent hydrocarbon. The behaviour of the SOA/VOC/NOx system simulated using the explicit model agrees with general tendencies observed during laboratory chamber experiments. This explicit modelling of SOA formation appears as a useful exploratory tool to (i) support interpretations of SOA formation observed in laboratory chamber experiments, (ii) give some insights on SOA formation under atmospherically relevant conditions and (iii) investigate implications for the regional/global lifetimes of the SOA.

scholarly journals The Secondary Organic Aerosol Processor (SOAP v1.0) model: a unified model with different ranges of complexity based on the molecular surrogate approach

2015 ◽  
Vol 8 (4) ◽  
pp. 1111-1138 ◽  
Author(s):  
F. Couvidat ◽  
K. Sartelet
Keyword(s):  
Phase Separation ◽  
Gas Phase ◽  
Organic Compounds ◽  
Aqueous Phase ◽  
Activity Coefficients ◽  
Secondary Organic Aerosol ◽  
Organic Aerosols ◽  
Organic Aerosol ◽  
Processing Unit ◽  
Dynamic Representation

Abstract. In this paper the Secondary Organic Aerosol Processor (SOAP v1.0) model is presented. This model determines the partitioning of organic compounds between the gas and particle phases. It is designed to be modular with different user options depending on the computation time and the complexity required by the user. This model is based on the molecular surrogate approach, in which each surrogate compound is associated with a molecular structure to estimate some properties and parameters (hygroscopicity, absorption into the aqueous phase of particles, activity coefficients and phase separation). Each surrogate can be hydrophilic (condenses only into the aqueous phase of particles), hydrophobic (condenses only into the organic phases of particles) or both (condenses into both the aqueous and the organic phases of particles). Activity coefficients are computed with the UNIFAC (UNIversal Functional group Activity Coefficient; Fredenslund et al., 1975) thermodynamic model for short-range interactions and with the Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) parameterization for medium- and long-range interactions between electrolytes and organic compounds. Phase separation is determined by Gibbs energy minimization. The user can choose between an equilibrium representation and a dynamic representation of organic aerosols (OAs). In the equilibrium representation, compounds in the particle phase are assumed to be at equilibrium with the gas phase. However, recent studies show that the organic aerosol is not at equilibrium with the gas phase because the organic phases could be semi-solid (very viscous liquid phase). The condensation–evaporation of organic compounds could then be limited by the diffusion in the organic phases due to the high viscosity. An implicit dynamic representation of secondary organic aerosols (SOAs) is available in SOAP with OAs divided into layers, the first layer being at the center of the particle (slowly reaches equilibrium) and the final layer being near the interface with the gas phase (quickly reaches equilibrium). Although this dynamic implicit representation is a simplified approach to model condensation–evaporation with a low number of layers and short CPU (central processing unit) time, it shows good agreements with an explicit representation of condensation–evaporation (no significant differences after a few hours of condensation).

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