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

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

10.5194/gmd-2015-227 ◽

2016 ◽

Author(s):

M. L. Dawson ◽

J. Xu ◽

R. J. Griffin ◽

D. Dabdub

Keyword(s):

Gas Phase ◽

Atmospheric Chemistry ◽

Urban Areas ◽

Secondary Organic Aerosol ◽

Three Dimensional ◽

Organic Aerosol ◽

California Institute Of Technology ◽

Institute Of Technology ◽

Three Dimensional Models ◽

South Coast Air Basin

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 are only recently being 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 (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.

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Gas-phase kinetics modifies the CCN activity of a biogenic SOA

Physical Chemistry Chemical Physics ◽

10.1039/c8cp00075a ◽

2018 ◽

Vol 20 (9) ◽

pp. 6591-6597

Author(s):

A. E. Vizenor ◽

A. A. Asa-Awuku

Keyword(s):

Particle Size ◽

Thermodynamic Properties ◽

Gas Phase ◽

Secondary Organic Aerosol ◽

Cloud Condensation Nuclei ◽

Organic Aerosol ◽

Aerosol Composition ◽

Phase Partitioning ◽

Gas Phase Kinetics ◽

Ccn Activity

Cloud condensation nuclei (CCN) activity and the hygroscopicity of secondary organic aerosol (SOA) depends on the particle size and composition, explicitly, the thermodynamic properties of the aerosol solute and subsequent interactions with water. The gas-to-aerosol phase partitioning is critical for aerosol composition and thus gas-phase vapors and kinetics can play an important role in the CCN activity of SOA.

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Characterization of Organosulfates in Secondary Organic Aerosol Derived from the Photooxidation of Long-Chain Alkanes

10.5194/acp-2016-20 ◽

2016 ◽

Cited By ~ 1

Author(s):

M. Riva ◽

T. Da Silva Barbosa ◽

Y.-H. Lin ◽

E. A. Stone ◽

A. Gold ◽

...

Keyword(s):

Gas Phase ◽

Urban Areas ◽

Secondary Organic Aerosol ◽

Field Studies ◽

Organic Aerosol ◽

Ultra Performance Liquid Chromatography ◽

Urban Aerosol ◽

Flight Mass Spectrometry ◽

Phase Oxidation ◽

Gas Phase Oxidation

Abstract. We report the formation of aliphatic organosulfates (OSs) in secondary organic aerosol (SOA) from the photooxidation of C10 – C12 alkanes. The results complement those from our laboratories reporting the formation of OSs and sulfonates from gas-phase oxidation of polycyclic aromatic hydrocarbons (PAHs). Both studies strongly support formation of OSs from gas-phase oxidation of anthropogenic precursors, hypothesized on the basis of recent field studies in which aromatic and aliphatic OSs were detected in fine aerosol collected from several major urban locations. In this study, dodecane, cyclodecane and decalin, considered to be important SOA precursors in urban areas, were photochemically oxidized in an outdoor smog chamber in the presence of either non-acidified or acidified ammonium sulfate seed aerosol. Effects of chemical structure, acidity and relative humidity on OS formation were examined. Aerosols collected from all experiments were characterized by ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of flight mass spectrometry (UPLC/ESI-HR-QTOFMS). Most of the OSs identified could be explained by formation of gaseous epoxide precursors with subsequent acid-catalyzed reactive uptake onto sulfate aerosol. The OSs identified here were also observed and quantified in fine urban aerosol samples collected in Lahore, Pakistan, and Pasadena, USA. Many of the OSs identified from the photooxidation of decalin and cyclodecane are isobars of known monoterpene organosulfates, and thus care must be taken in the analysis of alkane-derived organosulfates in urban aerosol.

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-11069-2011 ◽

2011 ◽

Vol 11 (21) ◽

pp. 11069-11102 ◽

Cited By ~ 730

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.

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Reducing secondary organic aerosol formation from gasoline vehicle exhaust

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1620911114 ◽

2017 ◽

Vol 114 (27) ◽

pp. 6984-6989 ◽

Cited By ~ 47

Author(s):

Yunliang Zhao ◽

Rawad Saleh ◽

Georges Saliba ◽

Albert A. Presto ◽

Timothy D. Gordon ◽

...

Keyword(s):

Los Angeles ◽

Atmospheric Chemistry ◽

Urban Areas ◽

Secondary Organic Aerosol ◽

Organic Aerosol ◽

Peroxy Radicals ◽

Oxides Of Nitrogen ◽

Aerosol Formation ◽

Vehicle Exhaust ◽

Gasoline Vehicles

On-road gasoline vehicles are a major source of secondary organic aerosol (SOA) in urban areas. We investigated SOA formation by oxidizing dilute, ambient-level exhaust concentrations from a fleet of on-road gasoline vehicles in a smog chamber. We measured less SOA formation from newer vehicles meeting more stringent emissions standards. This suggests that the natural replacement of older vehicles with newer ones that meet more stringent emissions standards should reduce SOA levels in urban environments. However, SOA production depends on both precursor concentrations (emissions) and atmospheric chemistry (SOA yields). We found a strongly nonlinear relationship between SOA formation and the ratio of nonmethane organic gas to oxides of nitrogen (NOx) (NMOG:NOx), which affects the fate of peroxy radicals. For example, changing the NMOG:NOxfrom 4 to 10 ppbC/ppbNOxincreased the SOA yield from dilute gasoline vehicle exhaust by a factor of 8. We investigated the implications of this relationship for the Los Angeles area. Although organic gas emissions from gasoline vehicles in Los Angeles are expected to fall by almost 80% over the next two decades, we predict no reduction in SOA production from these emissions due to the effects of rising NMOG:NOxon SOA yields. This highlights the importance of integrated emission control policies for NOxand organic gases.

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

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-22301-2011 ◽

2011 ◽

Vol 11 (8) ◽

pp. 22301-22383 ◽

Cited By ~ 12

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.

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Multi-generational oxidation model to simulate secondary organic aerosol in a 3-D air quality model

Geoscientific Model Development ◽

10.5194/gmd-8-2553-2015 ◽

2015 ◽

Vol 8 (8) ◽

pp. 2553-2567 ◽

Cited By ~ 21

Author(s):

S. H. Jathar ◽

C. D. Cappa ◽

A. S. Wexler ◽

J. H. Seinfeld ◽

M. J. Kleeman

Keyword(s):

Air Quality ◽

Secondary Organic Aerosol ◽

Organic Aerosol ◽

Eastern United States ◽

Air Quality Model ◽

Quality Model ◽

Organic Vapors ◽

California Institute Of Technology ◽

Oxidation Model ◽

Institute Of Technology

Abstract. Multi-generational gas-phase oxidation of organic vapors can influence the abundance, composition and properties of secondary organic aerosol (SOA). Only recently have SOA models been developed that explicitly represent multi-generational SOA formation. In this work, we integrated the statistical oxidation model (SOM) into SAPRC-11 to simulate the multi-generational oxidation and gas/particle partitioning of SOA in the regional UCD/CIT (University of California, Davis/California Institute of Technology) air quality model. In the SOM, evolution of organic vapors by reaction with the hydroxyl radical is defined by (1) the number of oxygen atoms added per reaction, (2) the decrease in volatility upon addition of an oxygen atom and (3) the probability that a given reaction leads to fragmentation of the organic molecule. These SOM parameter values were fit to laboratory smog chamber data for each precursor/compound class. SOM was installed in the UCD/CIT model, which simulated air quality over 2-week periods in the South Coast Air Basin of California and the eastern United States. For the regions and episodes tested, the two-product SOA model and SOM produce similar SOA concentrations but a modestly different SOA chemical composition. Predictions of the oxygen-to-carbon ratio qualitatively agree with those measured globally using aerosol mass spectrometers. Overall, the implementation of the SOM in a 3-D model provides a comprehensive framework to simulate the atmospheric evolution of organic aerosol.

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Chemical characterization of organosulfates in secondary organic aerosol derived from the photooxidation of alkanes

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-11001-2016 ◽

2016 ◽

Vol 16 (17) ◽

pp. 11001-11018 ◽

Cited By ~ 45

Author(s):

Matthieu Riva ◽

Thais Da Silva Barbosa ◽

Ying-Hsuan Lin ◽

Elizabeth A. Stone ◽

Avram Gold ◽

...

Keyword(s):

Gas Phase ◽

Urban Areas ◽

Secondary Organic Aerosol ◽

Chemical Characterization ◽

Organic Aerosol ◽

Ultra Performance Liquid Chromatography ◽

Heterogeneous Reactions ◽

Urban Aerosol ◽

Phase Oxidation ◽

Gas Phase Oxidation

Abstract. We report the formation of aliphatic organosulfates (OSs) in secondary organic aerosol (SOA) from the photooxidation of C10–C12 alkanes. The results complement those from our laboratories reporting the formation of OSs and sulfonates from gas-phase oxidation of polycyclic aromatic hydrocarbons (PAHs). Both studies strongly support the formation of OSs from the gas-phase oxidation of anthropogenic precursors, as hypothesized on the basis of recent field studies in which aromatic and aliphatic OSs were detected in fine aerosol collected from several major urban locations. In this study, dodecane, cyclodecane and decalin, considered to be important SOA precursors in urban areas, were photochemically oxidized in an outdoor smog chamber in the presence of either non-acidified or acidified ammonium sulfate seed aerosol. Effects of acidity and relative humidity on OS formation were examined. Aerosols collected from all experiments were characterized by ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-QTOFMS). Most of the OSs identified could be explained by formation of gaseous epoxide precursors with subsequent acid-catalyzed reactive uptake onto sulfate aerosol and/or heterogeneous reactions of hydroperoxides. The OSs identified here were also observed and quantified in fine urban aerosol samples collected in Lahore, Pakistan, and Pasadena, CA, USA. Several OSs identified from the photooxidation of decalin and cyclodecane are isobars of known monoterpene organosulfates, and thus care must be taken in the analysis of alkane-derived organosulfates in urban aerosol.

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Global impact of monocyclic aromatics on tropospheric composition

10.5194/acp-2017-928 ◽

2017 ◽

Cited By ~ 1

Author(s):

David Cabrera-Perez ◽

Domenico Taraborrelli ◽

Jos Lelieveld ◽

Thorsten Hoffmann ◽

Andrea Pozzer

Keyword(s):

Gas Phase ◽

Atmospheric Chemistry ◽

Aromatic Compounds ◽

Urban Areas ◽

General Circulation ◽

Organic Aerosol ◽

Global Scale ◽

Chemical Mechanism ◽

Aerosol Formation ◽

Mixing Ratios

Abstract. Aromatic compounds are reactive species influencing ozone formation, OH concentrations and organic aerosol formation. An assessment of their impacts on the gas-phase composition at a global scale has been performed using a general circulation atmospheric-chemistry model. Globally, we found a small annual average net decrease (less than 3 %) in global OH, ozone, and NOx mixing ratios when aromatic compounds are included in the chemical mechanism. This inclusion of aromatics also results in CO mixing ratio increases, which cause a general decrease in OH concentrations. The largest changes are found in glyoxal and NO3, with increases in the atmospheric burden of 10 % and 6 %, respectively. Regionally, significant differences were found particularly in high NOx regime areas, with an increase of up to 4 % in O3 mixing ratios and 8 % in OH concentrations. NO3 increased by more than 30 % in several regions of the northern hemisphere, and glyoxal increased up to 40 % in Europe and Asia. Large increases in formaldehyde were found in urban areas. Although the relative impact of aromatics at the global scale is limited, at a regional level they are important in atmospheric chemistry.

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Volatility of secondary organic aerosol during OH radical induced ageing

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-11055-2011 ◽

2011 ◽

Vol 11 (21) ◽

pp. 11055-11067 ◽

Cited By ~ 57

Author(s):

K. Salo ◽

M. Hallquist ◽

Å. M. Jonsson ◽

H. Saathoff ◽

K.-H. Naumann ◽

...

Keyword(s):

Gas Phase ◽

Organic Aerosol ◽

Oh Radical ◽

High Concentration ◽

Volatile Material ◽

Phase Oxidation ◽

Gas Phase Oxidation ◽

Institute Of Technology ◽

Set Up ◽

Pinic Acid

Abstract. The aim of this study was to investigate oxidation of SOA formed from ozonolysis of α-pinene and limonene by hydroxyl radicals. This paper focuses on changes of particle volatility, using a Volatility Tandem DMA (VTDMA) set-up, in order to explain and elucidate the mechanism behind atmospheric ageing of the organic aerosol. The experiments were conducted at the AIDA chamber facility of Karlsruhe Institute of Technology (KIT) in Karlsruhe and at the SAPHIR chamber of Forchungzentrum Jülich (FZJ) in Jülich. A fresh SOA was produced from ozonolysis of α-pinene or limonene and then aged by enhanced OH exposure. As an OH radical source in the AIDA-chamber the ozonolysis of tetramethylethylene (TME) was used while in the SAPHIR-chamber the OH was produced by natural light photochemistry. A general feature is that SOA produced from ozonolysis of α-pinene and limonene initially was rather volatile and becomes less volatile with time in the ozonolysis part of the experiment. Inducing OH chemistry or adding a new portion of precursors made the SOA more volatile due to addition of new semi-volatile material to the aged aerosol. The effect of OH chemistry was less pronounced in high concentration and low temperature experiments when lower relative amounts of semi-volatile material were available in the gas phase. Conclusions drawn from the changes in volatility were confirmed by comparison with the measured and modelled chemical composition of the aerosol phase. Three quantified products from the α-pinene oxidation; pinonic acid, pinic acid and methylbutanetricarboxylic acid (MBTCA) were used to probe the processes influencing aerosol volatility. A major conclusion from the work is that the OH induced ageing can be attributed to gas phase oxidation of products produced in the primary SOA formation process and that there was no indication on significant bulk or surface reactions. The presented results, thus, strongly emphasise the importance of gas phase oxidation of semi- or intermediate-volatile organic compounds (SVOC and IVOC) for atmospheric aerosol ageing.

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