Elemental composition and oxidation of chamber organic aerosol

Abstract. Recently, graphical representations of aerosol mass spectrometer (AMS) spectra and elemental composition have been developed to explain the oxidative and aging processes of secondary organic aerosol (SOA). It has been shown previously that oxygenated organic aerosol (OOA) components from ambient and laboratory data fall within a triangular region in the f44 vs. f43 space, where f44 and f43 are the ratios of the organic signal at m/z 44 and 43 to the total organic signal, respectively; we refer to this model as the "triangle plot." Alternatively, the Van Krevelen diagram has been used to describe the evolution of functional groups in SOA. In this study we investigate the variability of SOA formed in chamber experiments from twelve different precursors in both "triangle plot" and Van Krevelen domains. Spectral and elemental data from the high-resolution Aerodyne aerosol mass spectrometer are compared to offline species identification analysis and FTIR filter analysis to better understand the changes in functional and elemental composition inherent in SOA formation and aging. We find that SOA formed under high- and low-NOx conditions occupy similar areas in the "triangle plot" and Van Krevelen diagram and that SOA generated from already oxidized precursors starts higher on the "triangle plot." As SOA ages, it migrates toward the top of the triangle, suggesting higher organic acid content and decreased mass spectral variability. The most oxidized SOA come from the photooxidation of methoxyphenol precursors which yielded SOA O/C ratios near unity. α-pinene ozonolysis and naphthalene photooxidation SOA systems have had the highest degree of mass closure in previous chemical characterization studies and also show the best agreement between AMS elemental composition measurements and elemental composition of identified species. In general, compared to their respective unsaturated SOA precursors, the elemental composition of chamber SOA follows a slope shallower than −1 on the Van Krevelen diagram. From the spectra of SOA studied here, we are able to reproduce the triangular region originally constructed with ambient OOA components with chamber aerosol showing that SOA becomes more chemically similar as it ages. Ambient data in the middle of the triangle represent the ensemble average of many different SOA precursors, ages, and oxidative processes.

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Elemental composition and oxidation of chamber organic aerosol

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-8827-2011 ◽

2011 ◽

Vol 11 (17) ◽

pp. 8827-8845 ◽

Cited By ~ 145

Author(s):

P. S. Chhabra ◽

N. L. Ng ◽

M. R. Canagaratna ◽

A. L. Corrigan ◽

L. M. Russell ◽

...

Keyword(s):

Elemental Composition ◽

Mass Spectrometer ◽

Graphical Representation ◽

Laboratory Data ◽

Chemical Characterization ◽

Organic Aerosol ◽

Aerosol Mass Spectrometer ◽

Aerosol Mass ◽

Triangular Region ◽

Van Krevelen Diagram

Abstract. Recently, graphical representations of aerosol mass spectrometer (AMS) spectra and elemental composition have been developed to explain the oxidative and aging processes of secondary organic aerosol (SOA). It has been shown previously that oxygenated organic aerosol (OOA) components from ambient and laboratory data fall within a triangular region in the f44 vs. f43 space, where f44 and f43 are the ratios of the organic signal at m/z 44 and 43 to the total organic signal in AMS spectra, respectively; we refer to this graphical representation as the "triangle plot." Alternatively, the Van Krevelen diagram has been used to describe the evolution of functional groups in SOA. In this study we investigate the variability of SOA formed in chamber experiments from twelve different precursors in both "triangle plot" and Van Krevelen domains. Spectral and elemental data from the high-resolution Aerodyne aerosol mass spectrometer are compared to offline species identification analysis and FTIR filter analysis to better understand the changes in functional and elemental composition inherent in SOA formation and aging. We find that SOA formed under high- and low-NOx conditions occupy similar areas in the "triangle plot" and Van Krevelen diagram and that SOA generated from already oxidized precursors allows for the exploration of areas higher on the "triangle plot" not easily accessible with non-oxidized precursors. As SOA ages, it migrates toward the top of the triangle along a path largely dependent on the precursor identity, which suggests increasing organic acid content and decreasing mass spectral variability. The most oxidized SOA come from the photooxidation of methoxyphenol precursors which yielded SOA O/C ratios near unity. α-pinene ozonolysis and naphthalene photooxidation SOA systems have had the highest degree of mass closure in previous chemical characterization studies and also show the best agreement between AMS elemental composition measurements and elemental composition of identified species within the uncertainty of the AMS elemental analysis. In general, compared to their respective unsaturated SOA precursors, the elemental composition of chamber SOA follows a slope shallower than −1 on the Van Krevelen diagram, which is indicative of oxidation of the precursor without substantial losss of hydrogen, likely due to the unsaturated nature of the precursors. From the spectra of SOA studied here, we are able to reproduce the triangular region originally constructed with ambient OOA compents with chamber aerosol showing that SOA becomes more chemically similar as it ages. Ambient data in the middle of the triangle represent the ensemble average of many different SOA precursors, ages, and oxidative processes.

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Elemental analysis of chamber organic aerosol using an aerodyne high-resolution aerosol mass spectrometer

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-4111-2010 ◽

2010 ◽

Vol 10 (9) ◽

pp. 4111-4131 ◽

Cited By ~ 132

Author(s):

P. S. Chhabra ◽

R. C. Flagan ◽

J. H. Seinfeld

Keyword(s):

High Resolution ◽

Elemental Composition ◽

Mass Spectrometer ◽

Organic Aerosol ◽

Uptake System ◽

Aerosol Mass Spectrometer ◽

Aerosol Mass ◽

Single Ring ◽

Spectrometer Data ◽

Ambient Measurements

Abstract. The elemental composition of laboratory chamber secondary organic aerosol (SOA) from glyoxal uptake, α-pinene ozonolysis, isoprene photooxidation, single-ring aromatic photooxidation, and naphthalene photooxidation is evaluated using Aerodyne high-resolution time-of-flight mass spectrometer data. SOA O/C ratios range from 1.13 for glyoxal uptake experiments to 0.30–0.43 for α-pinene ozonolysis. The elemental composition of α-pinene and naphthalene SOA is also confirmed by offline mass spectrometry. The fraction of organic signal at m/z 44 is generally a good measure of SOA oxygenation for α-pinene/O3, isoprene/high-NOx, and naphthalene SOA systems. The agreement between measured and estimated O/C ratios tends to get closer as the fraction of organic signal at m/z 44 increases. This is in contrast to the glyoxal uptake system, in which m/z 44 substantially underpredicts O/C. Although chamber SOA has generally been considered less oxygenated than ambient SOA, single-ring aromatic- and naphthalene-derived SOA can reach O/C ratios upward of 0.7, well within the range of ambient PMF component OOA, though still not as high as some ambient measurements. The spectra of aromatic and isoprene-high-NOx SOA resemble that of OOA, but the spectrum of glyoxal uptake does not resemble that of any ambient organic aerosol PMF component.

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Mixing state of carbonaceous aerosol in an urban environment: single particle characterization using the soot particle aerosol mass spectrometer (SP-AMS)

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-1823-2015 ◽

2015 ◽

Vol 15 (4) ◽

pp. 1823-1841 ◽

Cited By ~ 52

Author(s):

A. K. Y. Lee ◽

M. D. Willis ◽

R. M. Healy ◽

T. B. Onasch ◽

J. P. D. Abbatt

Keyword(s):

Cluster Analysis ◽

Urban Environment ◽

Mass Spectrometer ◽

Single Particle ◽

Soot Particle ◽

Organic Aerosol ◽

Mixing State ◽

Aerosol Mass Spectrometer ◽

Mass Spectral ◽

Aerosol Mass

Abstract. Understanding the impact of atmospheric black carbon (BC)-containing particles on human health and radiative forcing requires knowledge of the mixing state of BC, including the characteristics of the materials with which it is internally mixed. In this study, we examine the mixing state of refractory BC (rBC) and other aerosol components in an urban environment (downtown Toronto) utilizing the Aerodyne soot particle aerosol mass spectrometer equipped with a light scattering module (LS-SP-AMS). k-means cluster analysis was used to classify single particle mass spectra into chemically distinct groups. One resultant particle class is dominated by rBC mass spectral signals (C1&plus; to C5&plus;) while the organic signals fall into a few major particle classes identified as hydrocarbon-like organic aerosol (HOA), oxygenated organic aerosol (OOA), and cooking emission organic aerosol (COA). A gradual mixing is observed with small rBC particles only thinly coated by HOA (~ 28% by mass on average), while over 90% of the HOA-rich particles did not contain detectable amounts of rBC. Most of the particles classified into other inorganic and organic particle classes were not significantly associated with rBC. The single particle results also suggest that HOA and COA emitted from anthropogenic sources were likely major contributors to organic-rich particles with vacuum aerodynamic diameter (dva) ranging from ~ 200 to 400 nm. The similar temporal profiles and mass spectral features of the organic classes identified by cluster analysis and the factors from a positive matrix factorization (PMF) analysis of the ensemble aerosol data set validate the interpretation of the PMF results.

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Single particle characterization using the soot particle aerosol mass spectrometer (SP-AMS)

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-15323-2014 ◽

2014 ◽

Vol 14 (10) ◽

pp. 15323-15361 ◽

Cited By ~ 3

Author(s):

A. K. Y. Lee ◽

M. D. Willis ◽

R. M. Healy ◽

T. B. Onasch ◽

J. P. D. Abbatt

Keyword(s):

Mass Spectrometer ◽

Single Particle ◽

Soot Particle ◽

Organic Aerosol ◽

Anthropogenic Sources ◽

Mixing State ◽

Aerosol Mass Spectrometer ◽

Mass Spectral ◽

Aerosol Mass ◽

The Impact

Abstract. Understanding the impact of atmospheric black carbon (BC) containing particles on human health and radiative forcing requires knowledge of the mixing state of BC, including the characteristics of the materials with which it is internally mixed. In this study, we demonstrate for the first time the capabilities of the Aerodyne Soot-Particle Aerosol Mass Spectrometer equipped with a light scattering module (LS-SP-AMS) to examine the mixing state of refractory BC (rBC) and other aerosol components in an urban environment (downtown Toronto). K-means clustering analysis was used to classify single particle mass spectra into chemically distinct groups. One resultant cluster is dominated by rBC mass spectral signals (C1+ to C5+) while the organic signals fall into a few major clusters, identified as hydrocarbon-like organic aerosol (HOA), oxygenated organic aerosol (OOA), and cooking emission organic aerosol (COA). A nearly external mixing is observed with small BC particles only thinly coated by HOA (∼28% by mass on average), while over 90% of the HOA-rich particles did not contain detectable amounts of rBC. Most of the particles classified into other inorganic and organic clusters were not significantly associated with BC. The single particle results also suggest that HOA and COA emitted from anthropogenic sources were likely major contributors to organic-rich particles with low to mid-range aerodynamic diameter (dva). The similar temporal profiles and mass spectral features of the organic clusters and the factors from a positive matrix factorization (PMF) analysis of the ensemble aerosol dataset validate the conventional interpretation of the PMF results.

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Elemental analysis of chamber organic aerosol using an aerodyne high-resolution aerosol mass spectrometer

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-27485-2009 ◽

2009 ◽

Vol 9 (6) ◽

pp. 27485-27542 ◽

Cited By ~ 1

Author(s):

P. S. Chhabra ◽

R. C. Flagan ◽

J. H. Seinfeld

Keyword(s):

High Resolution ◽

Elemental Composition ◽

Mass Spectrometer ◽

Organic Aerosol ◽

Resolution Time ◽

Aerosol Mass Spectrometer ◽

Aerosol Mass ◽

Single Ring ◽

Spectrometer Data ◽

Ambient Measurements

Abstract. The elemental composition of laboratory chamber secondary organic aerosol (SOA) from glyoxal uptake, α-pinene ozonolysis, isoprene photooxidation, single-ring aromatic photooxidation, and naphthalene photooxidation is evaluated using Aerodyne high-resolution time-of-flight mass spectrometer data. SOA O/C ratios ranged from 1.13 for glyoxal to 0.30–0.43 for α-pinene ozonolysis. The elemental composition of α-pinene and naphthalene SOA was also confirmed by offline mass spectrometry. The fraction of organic signal at m/z 44 is generally a good measure of SOA oxygenation for all systems except for glyoxal uptake, in which m/z 44 substantially underpredicts O/C. Although chamber SOA has generally been considered less oxygenated than ambient SOA, single-ring aromatic- and naphthalene-derived SOA can reach O/C ratios upward of 0.7, well within the range of OOA, though still not as high as some ambient measurements. The spectra of aromatic- and isoprene-high-NOx SOA resemble that of OOA, but the spectrum of glyoxal uptake does not resemble that of any PMF component.

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Organic aerosol components observed in Northern Hemispheric datasets from Aerosol Mass Spectrometry

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-4625-2010 ◽

2010 ◽

Vol 10 (10) ◽

pp. 4625-4641 ◽

Cited By ~ 677

Author(s):

N. L. Ng ◽

M. R. Canagaratna ◽

Q. Zhang ◽

J. L. Jimenez ◽

J. Tian ◽

...

Keyword(s):

Mass Spectrum ◽

Organic Aerosol ◽

Total Signal ◽

Mass Spectral ◽

Aerosol Mass ◽

Aerosol Mass Spectrometry ◽

Wide Range ◽

Triangular Region ◽

Photochemical Aging ◽

Spectral Diagnostic

Abstract. In this study we compile and present results from the factor analysis of 43 Aerosol Mass Spectrometer (AMS) datasets (27 of the datasets are reanalyzed in this work). The components from all sites, when taken together, provide a holistic overview of Northern Hemisphere organic aerosol (OA) and its evolution in the atmosphere. At most sites, the OA can be separated into oxygenated OA (OOA), hydrocarbon-like OA (HOA), and sometimes other components such as biomass burning OA (BBOA). We focus on the OOA components in this work. In many analyses, the OOA can be further deconvolved into low-volatility OOA (LV-OOA) and semi-volatile OOA (SV-OOA). Differences in the mass spectra of these components are characterized in terms of the two main ions m/z 44 (CO2+) and m/z 43 (mostly C2H3O+), which are used to develop a new mass spectral diagnostic for following the aging of OA components in the atmosphere. The LV-OOA component spectra have higher f44 (ratio of m/z 44 to total signal in the component mass spectrum) and lower f43 (ratio of m/z 43 to total signal in the component mass spectrum) than SV-OOA. A wide range of f44 and O:C ratios are observed for both LV-OOA (0.17±0.04, 0.73±0.14) and SV-OOA (0.07±0.04, 0.35±0.14) components, reflecting the fact that there is a continuum of OOA properties in ambient aerosol. The OOA components (OOA, LV-OOA, and SV-OOA) from all sites cluster within a well-defined triangular region in the f44 vs. f43 space, which can be used as a standardized means for comparing and characterizing any OOA components (laboratory or ambient) observed with the AMS. Examination of the OOA components in this triangular space indicates that OOA component spectra become increasingly similar to each other and to fulvic acid and HULIS sample spectra as f44 (a surrogate for O:C and an indicator of photochemical aging) increases. This indicates that ambient OA converges towards highly aged LV-OOA with atmospheric oxidation. The common features of the transformation between SV-OOA and LV-OOA at multiple sites potentially enable a simplified description of the oxidation of OA in the atmosphere. Comparison of laboratory SOA data with ambient OOA indicates that laboratory SOA are more similar to SV-OOA and rarely become as oxidized as ambient LV-OOA, likely due to the higher loadings employed in the experiments and/or limited oxidant exposure in most chamber experiments.

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Secondary organic aerosol formation from reaction of tertiary amines with nitrate radical

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-16585-2008 ◽

2008 ◽

Vol 8 (4) ◽

pp. 16585-16608 ◽

Cited By ~ 6

Author(s):

M. E. Erupe ◽

D. J. Price ◽

P. J. Silva ◽

Q. G. J. Malloy ◽

L. Qi ◽

...

Keyword(s):

Mass Spectrometer ◽

Secondary Organic Aerosol ◽

Organic Aerosol ◽

Nitrate Radical ◽

Tertiary Amines ◽

Aerosol Formation ◽

Night Time ◽

Aerosol Mass Spectrometer ◽

Aerosol Mass ◽

Secondary Organic Aerosol Formation

Abstract. Secondary organic aerosol formation from the reaction of tertiary amines with nitrate radical was investigated in an indoor environmental chamber. Particle chemistry was monitored using a high resolution aerosol mass spectrometer while gas-phase species were detected using a proton transfer reaction mass spectrometer. Trimethylamine, triethylamine and tributylamine were studied. Results indicate that tributylamine forms the most aerosol mass followed by trimethylamine and triethylamine respectively. Spectra from the aerosol mass spectrometer indicate the formation of complex non-salt aerosol products. We propose a reaction mechanism that proceeds via abstraction of a proton by nitrate radical followed by RO2 chemistry. Rearrangement of the aminyl alkoxy radical through hydrogen shift leads to the formation of hydroxylated amides, which explain most of the higher mass ions in the mass spectra. These experiments show that oxidation of tertiary amines by nitrate radical may be an important night-time source of secondary organic aerosol.

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Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-11807-2015 ◽

2015 ◽

Vol 15 (20) ◽

pp. 11807-11833 ◽

Cited By ~ 121

Author(s):

W. W. Hu ◽

P. Campuzano-Jost ◽

B. B. Palm ◽

D. A. Day ◽

A. M. Ortega ◽

...

Keyword(s):

Mass Spectrometer ◽

Secondary Organic Aerosol ◽

Transport Model ◽

Organic Aerosol ◽

Oxidation Products ◽

Chemical Transport Model ◽

Aerosol Mass Spectrometer ◽

Aerosol Mass ◽

Multiple Field

Abstract. Substantial amounts of secondary organic aerosol (SOA) can be formed from isoprene epoxydiols (IEPOX), which are oxidation products of isoprene mainly under low-NO conditions. Total IEPOX-SOA, which may include SOA formed from other parallel isoprene oxidation pathways, was quantified by applying positive matrix factorization (PMF) to aerosol mass spectrometer (AMS) measurements. The IEPOX-SOA fractions of organic aerosol (OA) in multiple field studies across several continents are summarized here and show consistent patterns with the concentration of gas-phase IEPOX simulated by the GEOS-Chem chemical transport model. During the Southern Oxidant and Aerosol Study (SOAS), 78 % of PMF-resolved IEPOX-SOA is accounted by the measured IEPOX-SOA molecular tracers (2-methyltetrols, C5-Triols, and IEPOX-derived organosulfate and its dimers), making it the highest level of molecular identification of an ambient SOA component to our knowledge. An enhanced signal at C5H6O+ (m/z 82) is found in PMF-resolved IEPOX-SOA spectra. To investigate the suitability of this ion as a tracer for IEPOX-SOA, we examine fC5H6O (fC5H6O= C5H6O+/OA) across multiple field, chamber, and source data sets. A background of ~ 1.7 ± 0.1 ‰ (‰ = parts per thousand) is observed in studies strongly influenced by urban, biomass-burning, and other anthropogenic primary organic aerosol (POA). Higher background values of 3.1 ± 0.6 ‰ are found in studies strongly influenced by monoterpene emissions. The average laboratory monoterpene SOA value (5.5 ± 2.0 ‰) is 4 times lower than the average for IEPOX-SOA (22 ± 7 ‰), which leaves some room to separate both contributions to OA. Locations strongly influenced by isoprene emissions under low-NO levels had higher fC5H6O (~ 6.5 ± 2.2 ‰ on average) than other sites, consistent with the expected IEPOX-SOA formation in those studies. fC5H6O in IEPOX-SOA is always elevated (12–40 ‰) but varies substantially between locations, which is shown to reflect large variations in its detailed molecular composition. The low fC5H6O (< 3 ‰) reported in non-IEPOX-derived isoprene-SOA from chamber studies indicates that this tracer ion is specifically enhanced from IEPOX-SOA, and is not a tracer for all SOA from isoprene. We introduce a graphical diagnostic to study the presence and aging of IEPOX-SOA as a triangle plot of fCO2 vs. fC5H6O. Finally, we develop a simplified method to estimate ambient IEPOX-SOA mass concentrations, which is shown to perform well compared to the full PMF method. The uncertainty of the tracer method is up to a factor of ~ 2, if the fC5H6O of the local IEPOX-SOA is not available. When only unit mass-resolution data are available, as with the aerosol chemical speciation monitor (ACSM), all methods may perform less well because of increased interferences from other ions at m/z 82. This study clarifies the strengths and limitations of the different AMS methods for detection of IEPOX-SOA and will enable improved characterization of this OA component.

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Single-particle measurements of bouncing particles and in situ collection efficiency from an airborne aerosol mass spectrometer (AMS) with light-scattering detection

Atmospheric Measurement Techniques ◽

10.5194/amt-10-3801-2017 ◽

2017 ◽

Vol 10 (10) ◽

pp. 3801-3820 ◽

Cited By ~ 6

Author(s):

Jin Liao ◽

Charles A. Brock ◽

Daniel M. Murphy ◽

Donna T. Sueper ◽

André Welti ◽

...

Keyword(s):

Light Scattering ◽

Mass Spectrometer ◽

Single Particle ◽

Total Mass ◽

Mass Spectra ◽

Collection Efficiency ◽

Aerosol Mass Spectrometer ◽

Mass Spectral ◽

Aerosol Mass ◽

Spectral Signal

Abstract. A light-scattering module was coupled to an airborne, compact time-of-flight aerosol mass spectrometer (LS-AMS) to investigate collection efficiency (CE) while obtaining nonrefractory aerosol chemical composition measurements during the Southeast Nexus (SENEX) campaign. In this instrument, particles scatter light from an internal laser beam and trigger saving individual particle mass spectra. Nearly all of the single-particle data with mass spectra that were triggered by scattered light signals were from particles larger than ∼ 280 nm in vacuum aerodynamic diameter. Over 33 000 particles are characterized as either prompt (27 %), delayed (15 %), or null (58 %), according to the time and intensity of their total mass spectral signals. The particle mass from single-particle spectra is proportional to that derived from the light-scattering diameter (dva-LS) but not to that from the particle time-of-flight (PToF) diameter (dva-MS) from the time of the maximum mass spectral signal. The total mass spectral signal from delayed particles was about 80 % of that from prompt ones for the same dva-LS. Both field and laboratory data indicate that the relative intensities of various ions in the prompt spectra show more fragmentation compared to the delayed spectra. The particles with a delayed mass spectral signal likely bounced off the vaporizer and vaporized later on another surface within the confines of the ionization source. Because delayed particles are detected by the mass spectrometer later than expected from their dva-LS size, they can affect the interpretation of particle size (PToF) mass distributions, especially at larger sizes. The CE, measured by the average number or mass fractions of particles optically detected that had measurable mass spectra, varied significantly (0.2–0.9) in different air masses. The measured CE agreed well with a previous parameterization when CE > 0.5 for acidic particles but was sometimes lower than the minimum parameterized CE of 0.5.

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