scholarly journals The sensitivity of secondary organic aerosol component partitioning to the predictions of component properties – Part 1: A systematic evaluation of some available estimation techniques

2010 ◽  
Vol 10 (21) ◽  
pp. 10255-10272 ◽  
Author(s):  
G. McFiggans ◽  
D. O. Topping ◽  
M. H. Barley
Keyword(s):  
Molar Mass ◽  
Estimation Method ◽  
Organic Aerosol ◽  
Systematic Evaluation ◽  
Complex Behaviour ◽  
Organic Mixture ◽  
Number Of Components ◽  
Activity Coefficient Model ◽  
Highly Sensitive ◽  
Volatile Organic

Abstract. A large number of calculations of the absorptive partitioning of organic compounds have been made using a number of methods to predict the component vapour pressures, p0, and activity coefficients, γi, required in the calculations. The sensitivities of the predictions in terms of the condensed component masses, volatility, O:C ratio, molar mass and functionality distributions to the choice of p0 and γi models and to the number of components to represent the organic mixture have been systematically compared. The condensed component mass was found to be highly sensitive to the vapour pressure model, and less sensitive to both the activity coefficient model and the number of components used to represent the mixture although the sensitivity to the change in property estimation method increased substantially with increased simplification in the treatment of the organic mixture. This was a general finding and was also clearly evident in terms of the predicted component functionality, O:C ratio, molar mass and volatility distributions of the condensed organic components. Within the limitations of the study, this clearly demonstrates the requirement for more accurate representation of the p0 and γi of the semi-volatile organic proxy components used in simplified models as the degree of simplification increases. This presents an interesting paradox, since such reduction in complexity necessarily leads to divergence from the complex behaviour of real multicomponent atmospheric aerosol.

scholarly journals The sensitivity of secondary organic aerosol component partitioning to the predictions of component properties – Part 1: A systematic evaluation of some available estimation techniques

2010 ◽  
Vol 10 (6) ◽  
pp. 15379-15415 ◽  
Author(s):  
G. McFiggans ◽  
D. O. Topping ◽  
M. H. Barley
Keyword(s):  
Molar Mass ◽  
Estimation Method ◽  
Organic Aerosol ◽  
Systematic Evaluation ◽  
Complex Behaviour ◽  
Organic Mixture ◽  
Number Of Components ◽  
Activity Coefficient Model ◽  
Highly Sensitive ◽  
Volatile Organic

Abstract. A large number of calculations of the absorptive partitioning of organic compounds have been made using a number of methods to predict the component vapour pressures, p0, and activity coefficients, γi, required in the calculations. The sensitivities of the predictions in terms of the condensed component masses, volatility, O:C ratio, molar mass and functionality distributions to the choice of p0 and γi models and to the number of components to represent the organic mixture have been systematically compared. The condensed component mass was found to be highly sensitive to the vapour pressure model, and less sensitive to both the activity coefficient model and the number of components used to represent the mixture although the sensitivity to the change in property estimation method increased substantially with increased simplification in the treatment of the organic mixture. This was a general finding and was also clearly evident in terms of the predicted component functionality, O:C ratio, molar mass and volatility distributions of the condensed organic components. Within the limitations of the study, this clearly demonstrates the requirement for more accurate representation of the p0 and γi of the semi-volatile organic proxy components used in simplified models as the degree of simplification increases. This presents an interesting paradox, since such reduction in complexity necessarily leads to divergence from the complex behaviour of real multicomponent atmospheric aerosol.

scholarly journals Sensitivities of the absorptive partitioning model of secondary organic aerosol formation to the inclusion of water

2008 ◽  
Vol 8 (6) ◽  
pp. 20311-20348 ◽  
Author(s):  
M. Barley ◽  
D. O. Topping ◽  
G. McFiggans ◽  
M. E. Jenkin
Keyword(s):  
Relative Humidity ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Organic Component ◽  
Condensed Phases ◽  
Aerosol Formation ◽  
Ambient Relative Humidity ◽  
Highly Sensitive ◽  
Volatile Organic ◽  
Secondary Organic Aerosol Formation

Abstract. Depending on the assumptions about the participation of water in absorptive partitioning, the prediction of the distribution of semi-volatile organic component between the gaseous and condensed phases is shown to be highly sensitive to the ambient relative humidity and the formulation of the partitioning model used. Further sensitivities to the assumed pre-existing particulate loading and to parameterised organic component non-ideality are explored and shown to contribute significantly to the variation in predicted secondary organic particulate loading.

scholarly journals Explicit modelling of SOA formation from α-pinene photooxidation: sensitivity to vapour pressure estimation

2011 ◽  
Vol 11 (3) ◽  
pp. 10121-10158 ◽  
Author(s):  
R. Valorso ◽  
B. Aumont ◽  
M. Camredon ◽  
T. Raventos-Duran ◽  
C. Mouchel-Vallon ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Vapour Pressure ◽  
Estimation Method ◽  
Organic Aerosol ◽  
Reaction Scheme ◽  
Oxidation Products ◽  
Organic Species ◽  
Structure Activity ◽  
Volatile Organic ◽  
Kinetics Of

Abstract. The sensitivity of the formation of secondary organic aerosol (SOA) to the estimated vapour pressures of the condensable oxidation products is explored. A highly detailed reaction scheme was generated for α-pinene photooxidation using the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A). Vapour pressures (Pvap) were estimated with three commonly used structure activity relationships. The values of Pvap were compared for the set of secondary species generated by GECKO-A to describe α-pinene oxidation. Discrepancies in the predicted vapour pressures were found to increase with the number of functional groups borne by the species. For semi-volatile organic compounds (i.e. organic species of interest for SOA formation), differences in the predicted Pvap range between a factor of 5 to 200 in average. The simulated SOA concentrations were compared to SOA observations in the Caltech chamber during three experiments performed under a range of NOx conditions. While the model captures the qualitative features of SOA formation for the chamber experiments, SOA concentrations are systematically overestimated. For the conditions simulated, the modelled SOA speciation appears to be rather insensitive to the Pvap estimation method.

scholarly journals Relative-humidity-dependent organic aerosol thermodynamics via an efficient reduced-complexity model

2019 ◽  
Vol 19 (21) ◽  
pp. 13383-13407 ◽  
Author(s):  
Kyle Gorkowski ◽  
Thomas C. Preston ◽  
Andreas Zuend
Keyword(s):  
Relative Humidity ◽  
Molar Mass ◽  
Cloud Condensation Nuclei ◽  
Organic Aerosol ◽  
Basis Set ◽  
Aqueous Mixtures ◽  
Organic Mixture ◽  
Organic Mixtures ◽  
Wide Range ◽  
Reduced Complexity

Abstract. Water plays an essential role in aerosol chemistry, gas–particle partitioning, and particle viscosity, but it is typically omitted in thermodynamic models describing the mixing within organic aerosol phases and the partitioning of semivolatile organics. In this study, we introduce the Binary Activity Thermodynamics (BAT) model, a water-sensitive reduced-complexity model treating the nonideal mixing of water and organics. The BAT model can process different levels of physicochemical mixture information enabling its application in the thermodynamic aerosol treatment within chemical transport models, the evaluation of humidity effects in environmental chamber studies, and the analysis of field observations. It is capable of using organic structure information including O:C, H:C, molar mass, and vapor pressure, which can be derived from identified compounds or estimated from bulk aerosol properties. A key feature of the BAT model is predicting the extent of liquid–liquid phase separation occurring within aqueous mixtures containing hydrophobic organics. This is crucial to simulating the abrupt change in water uptake behavior of moderately hygroscopic organics at high relative humidity, which is essential for capturing the correct behavior of organic aerosols serving as cloud condensation nuclei. For gas–particle partitioning predictions, we complement a volatility basis set (VBS) approach with the BAT model to account for nonideality and liquid–liquid equilibrium effects. To improve the computational efficiency of this approach, we trained two neural networks; the first for the prediction of aerosol water content at given relative humidity, and the second for the partitioning of semivolatile components. The integrated VBS + BAT model is benchmarked against high-fidelity molecular-level gas–particle equilibrium calculations based on the AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficient) model. Organic aerosol systems derived from α-pinene or isoprene oxidation are used for comparison. Predicted organic mass concentrations agree within less than a 5 % error in the isoprene case, which is a significant improvement over a traditional VBS implementation. In the case of the α-pinene system, the error is less than 2 % up to a relative humidity of 94 %, with larger errors past that point. The goal of the BAT model is to represent the bulk O:C and molar mass dependencies of a wide range of water–organic mixtures to a reasonable degree of accuracy. In this context, we discuss that the reduced-complexity effort may be poor at representing a specific binary water–organic mixture perfectly. However, the averaging effects of our reduced-complexity model become more representative when the mixture diversity increases in terms of organic functionality and number of components.

scholarly journals RH-dependent organic aerosol thermodynamics via an efficient reduced-complexity model

2019 ◽  
Author(s):  
Kyle Gorkowski ◽  
Thomas C. Preston ◽  
Andreas Zuend
Keyword(s):  
Relative Humidity ◽  
Molar Mass ◽  
Cloud Condensation Nuclei ◽  
Organic Aerosol ◽  
Basis Set ◽  
Organic Mixture ◽  
Alpha Pinene ◽  
Ideal Mixing ◽  
Wide Range ◽  
Reduced Complexity

Abstract. Water plays an essential role in aerosol chemistry, gas-particle partitioning, and particle viscosity, but it is typically omitted in thermodynamic models describing the mixing within organic aerosol phases and the partitioning of semivolatile organics. In this study, we introduce the Binary Activity Thermodynamics (BAT) model, a water-sensitive, reduced-complexity model treating the non-ideal mixing of water and organics. The BAT model can process different levels of physicochemical mixture information enabling its application in the thermodynamic aerosol treatment within chemical transport models, the evaluation of humidity effects in environmental chamber studies, and the analysis of field observations. It is capable of using organic structure information including O:C, H:C, molar mass, and vapor pressure, which can be derived from identified compounds or estimated from bulk aerosol properties. A key feature of the BAT model is predicting the extent of liquid-liquid phase separation occurring within aqueous mixtures containing hydrophobic organics. This is crucial to simulating the abrupt change in water uptake behavior of moderately hygroscopic organics at high relative humidity, which is essential for capturing the correct behavior of organic aerosols serving as cloud condensation nuclei. For gas-particle partitioning predictions, we complement a Volatility Basis Set (VBS) approach with the BAT model to account for non-ideality and liquid-liquid equilibrium effects. To improve the computational efficiency of this approach, we trained two neural networks; the first for the prediction of aerosol water content at given relative humidity, and the second for the partitioning of semivolatile components. The integrated VBS + BAT model is benchmarked against high-fidelity molecular-level gas-particle equilibrium calculations based on the AIOMFAC model. Organic aerosol systems derived from alpha-pinene or isoprene oxidation are used for comparison. Predicted organic mass concentrations agree within less than a 5 % error in the isoprene case, which is a significant improvement over a traditional VBS implementation. In the case of the alpha-pinene system, the error is less than 2 % up to a relative humidity of 94 %, with larger errors past that point. The goal of the BAT model is to represent the bulk O:C and molar mass dependencies of a wide range of water-organic mixtures to a reasonable degree of accuracy. In this context, we discuss that the reduced-complexity effort may be poor at representing a specific binary water-organic mixture perfectly. However, the averaging effects of our reduced-complexity model become more representative when the mixture diversity increases in terms of organic functionality and number of components.

scholarly journals Explicit modelling of SOA formation from α-pinene photooxidation: sensitivity to vapour pressure estimation

2011 ◽  
Vol 11 (14) ◽  
pp. 6895-6910 ◽  
Author(s):  
R. Valorso ◽  
B. Aumont ◽  
M. Camredon ◽  
T. Raventos-Duran ◽  
C. Mouchel-Vallon ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Vapour Pressure ◽  
Estimation Method ◽  
Organic Aerosol ◽  
Reaction Scheme ◽  
Oxidation Products ◽  
Organic Species ◽  
Structure Activity ◽  
Volatile Organic ◽  
Kinetics Of

Abstract. The sensitivity of the formation of secondary organic aerosol (SOA) to the estimated vapour pressures of the condensable oxidation products is explored. A highly detailed reaction scheme was generated for α-pinene photooxidation using the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A). Vapour pressures (Pvap) were estimated with three commonly used structure activity relationships. The values of Pvap were compared for the set of secondary species generated by GECKO-A to describe α-pinene oxidation. Discrepancies in the predicted vapour pressures were found to increase with the number of functional groups borne by the species. For semi-volatile organic compounds (i.e. organic species of interest for SOA formation), differences in the predicted Pvap range between a factor of 5 to 200 on average. The simulated SOA concentrations were compared to SOA observations in the Caltech chamber during three experiments performed under a range of NOx conditions. While the model captures the qualitative features of SOA formation for the chamber experiments, SOA concentrations are systematically overestimated. For the conditions simulated, the modelled SOA speciation appears to be rather insensitive to the Pvap estimation method.

scholarly journals Sensitivities of the absorptive partitioning model of secondary organic aerosol formation to the inclusion of water

2009 ◽  
Vol 9 (9) ◽  
pp. 2919-2932 ◽  
Author(s):  
M. Barley ◽  
D. O. Topping ◽  
M. E. Jenkin ◽  
G. McFiggans
Keyword(s):  
Relative Humidity ◽  
Condensed Phase ◽  
Individual Component ◽  
Molar Mass ◽  
Organic Aerosol ◽  
Specific Form ◽  
The Other ◽  
Aerosol Formation ◽  
Ambient Relative Humidity ◽  
Volatile Organic

Abstract. The predicted distribution of semi-volatile organic components between the gaseous and condensed phase as a function of ambient relative humidity and the specific form of the partitioning model used has been investigated. A mole fraction based model, modified so as not to use molar mass in the calculation, was found to predict identical RH dependence of component partitioning to that predicted by the conventional mass-based partitioning model which uses a molar mass averaged according to the number of moles in the condensed phase. A recently reported third version of the partitioning model using individual component molar masses was shown to give significantly different results to the other two models. Further sensitivities to an assumed pre-existing particulate loading and to parameterised organic component non-ideality are explored and shown to contribute significantly to the variation in predicted secondary organic particulate loading.

A Three-Dimensional Tetraphenylethylene-Based Fluorescence Covalent Organic Framework for Molecular Recognition

2020 ◽  
Author(s):  
Junxia Ren ◽  
Yaozu Liu ◽  
Xin Zhu ◽  
Yangyang Pan ◽  
Yujie Wang ◽  
...  
Keyword(s):  
Molecular Recognition ◽  
Fluorescence Probe ◽  
Three Dimensional ◽  
Hazardous Substances ◽  
Covalent Organic Framework ◽  
Highly Sensitive ◽  
Volatile Organic ◽  
Polycyclic Aromatic ◽  
Better Than ◽  
Organic Framework

<p><a></a><a></a><a></a><a></a><a></a><a></a><a></a><a>The development of highly-sensitive recognition of </a><a></a><a></a><a></a><a></a><a>hazardous </a>chemicals, such as volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs), is of significant importance because of their widespread social concerns related to environment and human health. Here, we report a three-dimensional (3D) covalent organic framework (COF, termed JUC-555) bearing tetraphenylethylene (TPE) side chains as an aggregation-induced emission (AIE) fluorescence probe for sensitive molecular recognition.<a></a><a> </a>Due to the rotational restriction of TPE rotors in highly interpenetrated framework after inclusion of dimethylformamide (DMF), JUC-555 shows impressive AIE-based strong fluorescence. Meanwhile, owing to the large pore size (11.4 Å) and suitable intermolecular distance of aligned TPE (7.2 Å) in JUC-555, the obtained material demonstrates an excellent performance in the molecular recognition of hazardous chemicals, e.g., nitroaromatic explosives, PAHs, and even thiophene compounds, via a fluorescent quenching mechanism. The quenching constant (<i>K</i><sub>SV</sub>) is two orders of magnitude better than those of other fluorescence-based porous materials reported to date. This research thus opens 3D functionalized COFs as a promising identification tool for environmentally hazardous substances.</p>

scholarly journals Aging of atmospheric aerosols and the role of iron in catalyzing brown carbon formation

2021 ◽  
Author(s):  
Hind A. A. Al-Abadleh
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Atmospheric Aerosols ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Atmospheric Oxidation ◽  
Carbon Formation ◽  
Brown Carbon ◽  
Volatile Organic

Extensive research has been done on the processes that lead to the formation of secondary organic aerosol (SOA) including atmospheric oxidation of volatile organic compounds (VOCs) from biogenic and anthropogenic...

scholarly journals On the limit to resolution and information on basal properties obtainable from surface data on ice streams

2008 ◽  
Vol 2 (2) ◽  
pp. 167-178 ◽  
Author(s):  
G. H. Gudmundsson ◽  
M. Raymond
Keyword(s):  
Flow Line ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Surface Flow ◽  
Ice Thickness ◽  
Ice Streams ◽  
Statistical Estimates ◽  
Surface Data ◽  
Highly Sensitive ◽  
Surface Measurements

Abstract. An optimal estimation method for simultaneously determining both basal slipperiness and basal topography from variations in surface flow velocity and topography along a flow line on ice streams and ice sheets is presented. We use Bayesian inference to update prior statistical estimates for basal topography and slipperiness using surface measurements along a flow line. Our main focus here is on how errors and spacing of surface data affect estimates of basal quantities and on possibly aliasing/mixing between basal slipperiness and basal topography. We find that the effects of spatial variations in basal topography and basal slipperiness on surface data can be accurately separated from each other, and mixing in retrieval does not pose a serious problem. For realistic surface data errors and density, small-amplitude perturbations in basal slipperiness can only be resolved for wavelengths larger than about 50 times the mean ice thickness. Bedrock topography is well resolved down to horizontal scale equal to about one ice thickness. Estimates of basal slipperiness are not significantly improved by accurate prior estimates of basal topography. However, retrieval of basal slipperiness is found to be highly sensitive to unmodelled errors in basal topography.

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