scholarly journals Secondary organic aerosol formation in cloud droplets and aqueous particles (aqSOA): a review of laboratory, field and model studies

2011 ◽  
Vol 11 (8) ◽  
pp. 22301-22383 ◽  
Author(s):  
B. Ervens ◽  
B. J. Turpin ◽  
R. J. Weber
Keyword(s):  
Relative Humidity ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Secondary Organic Aerosol ◽  
Current Knowledge ◽  
Laboratory Data ◽  
Organic Aerosol ◽  
Current Data ◽  
Aerosol Formation ◽  
Model Studies

Abstract. Progress has been made over the past decade in predicting secondary organic aerosol (SOA) mass in the atmosphere using vapor pressure-driven partitioning, which implies that SOA compounds are formed in the gas phase and then partition to an organic phase (gasSOA). However, discrepancies in predicting organic aerosol oxidation state, size and product (molecular mass) distribution, relative humidity (RH) dependence, color, and vertical profile suggest that additional SOA sources and aging processes may be important. The formation of SOA in cloud and aerosol water (aqSOA) is not considered in these models even though water is an abundant medium for atmospheric chemistry and such chemistry can form dicarboxylic acids and "humic-like substances" (oligomers, high-molecular-weight compounds), i.e., compounds that do not have any gas phase sources but comprise a significant fraction of the total SOA mass. There is direct evidence from field observations and laboratory studies that organic aerosol is formed in cloud and aerosol water, contributing substantial mass to the droplet mode. This review summarizes the current knowledge on aqueous phase organic reactions and combines evidence that points to a significant role of aqSOA formation in the atmosphere. Model studies are discussed that explore the importance of aqSOA formation and suggestions for model improvements are made based on the comprehensive set of laboratory data presented here. A first comparison is made between aqSOA and gasSOA yields and mass predictions for selected conditions. These simulations suggest that aqSOA might contribute almost as much mass as gasSOA to the SOA budget, with highest contributions from biogenic VOC emissions in the presence of anthropogenic pollutants (i.e., NOx) at high relative humidity and cloudiness. Gaps in the current understanding of aqSOA processes are discussed and further studies (laboratory, field, model) are outlined to complement current data sets.

scholarly journals Secondary organic aerosol formation in cloud droplets and aqueous particles (aqSOA): a review of laboratory, field and model studies

2011 ◽  
Vol 11 (21) ◽  
pp. 11069-11102 ◽  
Author(s):  
B. Ervens ◽  
B. J. Turpin ◽  
R. J. Weber
Keyword(s):  
Relative Humidity ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Secondary Organic Aerosol ◽  
Current Knowledge ◽  
Laboratory Data ◽  
Organic Aerosol ◽  
Current Data ◽  
Aerosol Formation ◽  
Model Studies

Abstract. Progress has been made over the past decade in predicting secondary organic aerosol (SOA) mass in the atmosphere using vapor pressure-driven partitioning, which implies that SOA compounds are formed in the gas phase and then partition to an organic phase (gasSOA). However, discrepancies in predicting organic aerosol oxidation state, size and product (molecular mass) distribution, relative humidity (RH) dependence, color, and vertical profile suggest that additional SOA sources and aging processes may be important. The formation of SOA in cloud and aerosol water (aqSOA) is not considered in these models even though water is an abundant medium for atmospheric chemistry and such chemistry can form dicarboxylic acids and "humic-like substances" (oligomers, high-molecular-weight compounds), i.e. compounds that do not have any gas phase sources but comprise a significant fraction of the total SOA mass. There is direct evidence from field observations and laboratory studies that organic aerosol is formed in cloud and aerosol water, contributing substantial mass to the droplet mode. This review summarizes the current knowledge on aqueous phase organic reactions and combines evidence that points to a significant role of aqSOA formation in the atmosphere. Model studies are discussed that explore the importance of aqSOA formation and suggestions for model improvements are made based on the comprehensive set of laboratory data presented here. A first comparison is made between aqSOA and gasSOA yields and mass predictions for selected conditions. These simulations suggest that aqSOA might contribute almost as much mass as gasSOA to the SOA budget, with highest contributions from biogenic emissions of volatile organic compounds (VOC) in the presence of anthropogenic pollutants (i.e. NOx) at high relative humidity and cloudiness. Gaps in the current understanding of aqSOA processes are discussed and further studies (laboratory, field, model) are outlined to complement current data sets.

scholarly journals Kinetic modeling of secondary organic aerosol formation: effects of particle- and gas-phase reactions of semivolatile products

2007 ◽  
Vol 7 (15) ◽  
pp. 4135-4147 ◽  
Author(s):  
A. W. H. Chan ◽  
J. H. Kroll ◽  
N. L. Ng ◽  
J. H. Seinfeld
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Laboratory Data ◽  
Organic Aerosol ◽  
Formation Mechanisms ◽  
Hydrocarbon Oxidation ◽  
Phase Reaction ◽  
Particle Phase ◽  
Aerosol Formation ◽  
Kinetics Of

Abstract. The distinguishing mechanism of formation of secondary organic aerosol (SOA) is the partitioning of semivolatile hydrocarbon oxidation products between the gas and aerosol phases. While SOA formation is typically described in terms of partitioning only, the rate of formation and ultimate yield of SOA can also depend on the kinetics of both gas- and aerosol-phase processes. We present a general equilibrium/kinetic model of SOA formation that provides a framework for evaluating the extent to which the controlling mechanisms of SOA formation can be inferred from laboratory chamber data. With this model we examine the effect on SOA formation of gas-phase oxidation of first-generation products to either more or less volatile species, of particle-phase reaction (both first- and second-order kinetics), of the rate of parent hydrocarbon oxidation, and of the extent of reaction of the parent hydrocarbon. The effect of pre-existing organic aerosol mass on SOA yield, an issue of direct relevance to the translation of laboratory data to atmospheric applications, is examined. The importance of direct chemical measurements of gas- and particle-phase species is underscored in identifying SOA formation mechanisms.

scholarly journals Kinetic modeling of Secondary Organic Aerosol formation: effects of particle- and gas-phase reactions of semivolatile products

2007 ◽  
Vol 7 (3) ◽  
pp. 7051-7085 ◽  
Author(s):  
A. W. H. Chan ◽  
J. H. Kroll ◽  
N. L. Ng ◽  
J. H. Seinfeld
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Laboratory Data ◽  
Organic Aerosol ◽  
Formation Mechanisms ◽  
Hydrocarbon Oxidation ◽  
Phase Reaction ◽  
Particle Phase ◽  
Aerosol Formation ◽  
Kinetics Of

Abstract. The distinguishing mechanism of formation of secondary organic aerosol (SOA) is the partitioning of semivolatile hydrocarbon oxidation products between the gas and aerosol phases. While SOA formation is typically described in terms of partitioning only, the rate of formation and ultimate yield of SOA can also depend on the kinetics of both gas- and aerosol-phase processes. We present a general equilibrium/kinetic model of SOA formation that provides a framework for evaluating the extent to which the controlling mechanisms of SOA formation can be inferred from laboratory chamber data. With this model we examine the effect on SOA formation of gas-phase oxidation of first-generation products to either more or less volatile species, of particle-phase reaction (both first- and second-order kinetics), of the rate of parent hydrocarbon oxidation, and of the extent of reaction of the parent hydrocarbon. The effect of pre-existing organic aerosol mass on SOA yield, an issue of direct relevance to the translation of laboratory data to atmospheric applications, is examined. The importance of direct chemical measurements of gas- and particle-phase species is underscored in identifying SOA formation mechanisms.

scholarly journals Modeling organic aerosols in a megacity: comparison of simple and complex representations of the volatility basis set approach

2010 ◽  
Vol 10 (12) ◽  
pp. 30205-30277 ◽  
Author(s):  
M. Shrivastava ◽  
J. Fast ◽  
R. Easter ◽  
W. I. Gustafson ◽  
R. A. Zaveri ◽  
...  
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Computational Cost ◽  
Organic Aerosols ◽  
Field Measurements ◽  
Organic Aerosol ◽  
Basis Set ◽  
Aerosol Formation ◽  
Secondary Organic Aerosol Formation ◽  
The City

Abstract. The Weather Research and Forecasting model coupled with chemistry (WRF-Chem) is modified to include a volatility basis set (VBS) treatment of secondary organic aerosol formation. The VBS approach, coupled with SAPRC-99 gas-phase chemistry mechanism, is used to model gas-particle partitioning and multiple generations of gas-phase oxidation of organic vapors. In addition to the detailed 9-species VBS, a simplified mechanism using 2 volatility species (2-species VBS) is developed and tested for similarity to the 9-species VBS in terms of both mass and oxygen-to-carbon ratios of organic aerosols in the atmosphere. WRF-Chem results are evaluated against field measurements of organic aerosols collected during the MILAGRO 2006 campaign in the vicinity of Mexico City. The simplified 2-species mechanism reduces the computational cost by a factor of 2 as compared to 9-species VBS. Both ground site and aircraft measurements suggest that the 9-species and 2-species VBS predictions of total organic aerosol mass as well as individual organic aerosol components including primary, secondary, and biomass burning are comparable in magnitude. In addition, oxygen-to-carbon ratio predictions from both approaches agree within 25%, providing evidence that the 2-species VBS is well suited to represent the complex evolution of organic aerosols. Model sensitivity to amount of anthropogenic semi-volatile and intermediate volatility (S/IVOC) precursor emissions is also examined by doubling the default emissions. Both the emission cases significantly under-predict primary organic aerosols in the city center and along aircraft flight transects. Secondary organic aerosols are predicted reasonably well along flight tracks surrounding the city, but are consistently over-predicted downwind of the city. Also, oxygen-to-carbon ratio predictions are significantly improved compared to prior studies by adding 15% oxygen mass per generation of oxidation; however, all modeling cases still under-predict these ratios downwind as compared to measurements, suggesting a need to further improve chemistry parameterizations of secondary organic aerosol formation.

scholarly journals Development of aroCACM/MPMPO 1.0: a model to simulate secondary organic aerosol from aromatic precursors in regional models

2016 ◽  
Vol 9 (6) ◽  
pp. 2143-2151 ◽  
Author(s):  
Matthew L. Dawson ◽  
Jialu Xu ◽  
Robert J. Griffin ◽  
Donald Dabdub
Keyword(s):  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Urban Areas ◽  
Secondary Organic Aerosol ◽  
Three Dimensional ◽  
Organic Aerosol ◽  
Phase Partitioning ◽  
California Institute Of Technology ◽  
Institute Of Technology ◽  
Three Dimensional Models

Abstract. The atmospheric oxidation of aromatic compounds is an important source of secondary organic aerosol (SOA) in urban areas. The oxidation of aromatics depends strongly on the levels of nitrogen oxides (NOx). However, details of the mechanisms by which oxidation occurs have only recently been elucidated. Xu et al. (2015) developed an updated version of the gas-phase Caltech Atmospheric Chemistry Mechanism (CACM) designed to simulate toluene and m-xylene oxidation in chamber experiments over a range of NOx conditions. The output from such a mechanism can be used in thermodynamic predictions of gas–particle partitioning leading to SOA. The current work reports the development of a model for SOA formation that combines the gas-phase mechanism of Xu et al. (2015) with an updated lumped SOA-partitioning scheme (Model to Predict the Multi-phase Partitioning of Organics, MPMPO) that allows partitioning to multiple aerosol phases and that is designed for use in larger-scale three-dimensional models. The resulting model is termed aroCACM/MPMPO 1.0. The model is integrated into the University of California, Irvine – California Institute of Technology (UCI-CIT) Airshed Model, which simulates the South Coast Air Basin (SoCAB) of California. Simulations using 2012 emissions indicate that “low-NOx” pathways to SOA formation from aromatic oxidation play an important role, even in regions that typically exhibit high-NOx concentrations.

scholarly journals Mapping gas-phase organic reactivity and concomitant secondary organic aerosol formation: chemometric dimension reduction techniques for the deconvolution of complex atmospheric data sets

2015 ◽  
Vol 15 (14) ◽  
pp. 8077-8100 ◽  
Author(s):  
K. P. Wyche ◽  
P. S. Monks ◽  
K. L. Smallbone ◽  
J. F. Hamilton ◽  
M. R. Alfarra ◽  
...  
Keyword(s):  
Phase Composition ◽  
Dimension Reduction ◽  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Chemical Mechanism ◽  
Particle Phase ◽  
Aerosol Formation ◽  
Holistic View

Abstract. Highly non-linear dynamical systems, such as those found in atmospheric chemistry, necessitate hierarchical approaches to both experiment and modelling in order to ultimately identify and achieve fundamental process-understanding in the full open system. Atmospheric simulation chambers comprise an intermediate in complexity, between a classical laboratory experiment and the full, ambient system. As such, they can generate large volumes of difficult-to-interpret data. Here we describe and implement a chemometric dimension reduction methodology for the deconvolution and interpretation of complex gas- and particle-phase composition spectra. The methodology comprises principal component analysis (PCA), hierarchical cluster analysis (HCA) and positive least-squares discriminant analysis (PLS-DA). These methods are, for the first time, applied to simultaneous gas- and particle-phase composition data obtained from a comprehensive series of environmental simulation chamber experiments focused on biogenic volatile organic compound (BVOC) photooxidation and associated secondary organic aerosol (SOA) formation. We primarily investigated the biogenic SOA precursors isoprene, α-pinene, limonene, myrcene, linalool and β-caryophyllene. The chemometric analysis is used to classify the oxidation systems and resultant SOA according to the controlling chemistry and the products formed. Results show that "model" biogenic oxidative systems can be successfully separated and classified according to their oxidation products. Furthermore, a holistic view of results obtained across both the gas- and particle-phases shows the different SOA formation chemistry, initiating in the gas-phase, proceeding to govern the differences between the various BVOC SOA compositions. The results obtained are used to describe the particle composition in the context of the oxidised gas-phase matrix. An extension of the technique, which incorporates into the statistical models data from anthropogenic (i.e. toluene) oxidation and "more realistic" plant mesocosm systems, demonstrates that such an ensemble of chemometric mapping has the potential to be used for the classification of more complex spectra of unknown origin. More specifically, the addition of mesocosm data from fig and birch tree experiments shows that isoprene and monoterpene emitting sources, respectively, can be mapped onto the statistical model structure and their positional vectors can provide insight into their biological sources and controlling oxidative chemistry. The potential to extend the methodology to the analysis of ambient air is discussed using results obtained from a zero-dimensional box model incorporating mechanistic data obtained from the Master Chemical Mechanism (MCMv3.2). Such an extension to analysing ambient air would prove a powerful asset in assisting with the identification of SOA sources and the elucidation of the underlying chemical mechanisms involved.

scholarly journals Modeling organic aerosols in a megacity: comparison of simple and complex representations of the volatility basis set approach

2011 ◽  
Vol 11 (13) ◽  
pp. 6639-6662 ◽  
Author(s):  
M. Shrivastava ◽  
J. Fast ◽  
R. Easter ◽  
W. I. Gustafson ◽  
R. A. Zaveri ◽  
...  
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Computational Cost ◽  
Organic Aerosols ◽  
Field Measurements ◽  
Organic Aerosol ◽  
Basis Set ◽  
Aerosol Formation ◽  
Secondary Organic Aerosol Formation ◽  
The City

Abstract. The Weather Research and Forecasting model coupled with chemistry (WRF-Chem) is modified to include a volatility basis set (VBS) treatment of secondary organic aerosol formation. The VBS approach, coupled with SAPRC-99 gas-phase chemistry mechanism, is used to model gas-particle partitioning and multiple generations of gas-phase oxidation of organic vapors. In addition to the detailed 9-species VBS, a simplified mechanism using 2 volatility species (2-species VBS) is developed and tested for similarity to the 9-species VBS in terms of both mass and oxygen-to-carbon ratios of organic aerosols in the atmosphere. WRF-Chem results are evaluated against field measurements of organic aerosols collected during the MILAGRO 2006 campaign in the vicinity of Mexico City. The simplified 2-species mechanism reduces the computational cost by a factor of 2 as compared to 9-species VBS. Both ground site and aircraft measurements suggest that the 9-species and 2-species VBS predictions of total organic aerosol mass as well as individual organic aerosol components including primary, secondary, and biomass burning are comparable in magnitude. In addition, oxygen-to-carbon ratio predictions from both approaches agree within 25 %, providing evidence that the 2-species VBS is well suited to represent the complex evolution of organic aerosols. Model sensitivity to amount of anthropogenic semi-volatile and intermediate volatility (S/IVOC) precursor emissions is also examined by doubling the default emissions. Both the emission cases significantly under-predict primary organic aerosols in the city center and along aircraft flight transects. Secondary organic aerosols are predicted reasonably well along flight tracks surrounding the city, but are consistently over-predicted downwind of the city. Also, oxygen-to-carbon ratio predictions are significantly improved compared to prior studies by adding 15 % oxygen mass per generation of oxidation; however, all modeling cases still under-predict these ratios downwind as compared to measurements, suggesting a need to further improve chemistry parameterizations of secondary organic aerosol formation.

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 Secondary organic aerosol formation from photooxidation of naphthalene and alkylnaphthalenes: implications for oxidation of intermediate volatility organic compounds (IVOCs)

2009 ◽  
Vol 9 (1) ◽  
pp. 1873-1905
Author(s):  
A. W. H. Chan ◽  
K. E. Kautzman ◽  
P. S. Chhabra ◽  
J. D. Surratt ◽  
M. N. Chan ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Gas Phase ◽  
Aromatic Hydrocarbons ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Aerosol Formation ◽  
Atmospheric Models ◽  
Gas Phase Reactions ◽  
Aerosol Mass ◽  
Polycyclic Aromatic

Abstract. Current atmospheric models do not include secondary organic aerosol (SOA) production from gas-phase reactions of polycyclic aromatic hydrocarbons (PAHs). Recent studies have shown that primary semivolatile emissions, previously assumed to be inert, undergo oxidation in the gas phase, leading to SOA formation. This opens the possibility that low-volatility gas-phase precursors are a potentially large source of SOA. In this work, SOA formation from gas-phase photooxidation of naphthalene, 1-methylnaphthalene (1-MN), 2-methylnaphthalene (2-MN), and 1,2-dimethylnaphthalene (1,2-DMN) is studied in the Caltech dual 28-m3 chambers. Under high-NOx conditions and aerosol mass loadings between 10 and 40 μg m

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