scholarly journals Aqueous-Phase Production of Secondary Organic Aerosols from Oxidation of Dibenzothiophene (DBT)

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 151 ◽  
Author(s):  
Yu Liu ◽  
Junchen Lu ◽  
Yanfang Chen ◽  
Yue Liu ◽  
Zhaolian Ye ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Aqueous Phase ◽  
Reaction Pathway ◽  
Photochemical Reactions ◽  
Oxidation Products ◽  
Gas Phase Reactions ◽  
Photo Oxidation ◽  
Oxygenated Compounds ◽  
Direct Light ◽  
Triplet Excited States

Intermediate-volatility organic compounds (IVOCs) have been recognized as an important contributor to the secondary organic aerosol (SOA) formation via gas-phase reactions. However, it is unclear whether or not IVOCs-SOA can be produced in the aqueous phase. This work investigated aqueous oxidation of one model compound of IVOCs, dibenzothiophene (DBT). Results show that DBT can be degraded by both hydroxyl radical and the triplet excited states of organic light chromophores (3C*). Aqueous dark oxidation of DBT was also possible. SOA yields of 32% and 15% were found for hydroxyl radical (OH)-mediated photo-oxidation and dark oxidation, respectively. A continuous and significant increase of oxidation degree of SOA was observed during OH photo-oxidation, but not during the dark oxidation. Factor analyses revealed that there was a persistent production of highly oxygenated compounds from the less oxygenated species. OH-initiated photochemical reactions can also produce species with a relatively large light-absorbing ability, while such photo-enhancement due to direct light irradiation and 3C*-initiated oxidation could occur, but is much less important. In the future, studies on the second-order rate constants, molecular characterization of the oxidation products from this and other IVOCs precursors are needed to better understand the role of this reaction pathway in SOA budget, air quality and climate change.

Kinetics, Mechanism, and Secondary Organic Aerosol Yield of Aqueous Phase Photo-oxidation of α-Pinene Oxidation Products

2015 ◽  
Vol 120 (9) ◽  
pp. 1395-1407 ◽  
Author(s):  
Dana Aljawhary ◽  
Ran Zhao ◽  
Alex K.Y. Lee ◽  
Chen Wang ◽  
Jonathan P.D. Abbatt
Keyword(s):  
Aqueous Phase ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Photo Oxidation

scholarly journals Polar organic compounds in rural PM<sub>2.5</sub> aerosols from K-puszta, Hungary, during a 2003 summer field campaign: Sources and diel variations

2005 ◽  
Vol 5 (7) ◽  
pp. 1805-1814 ◽  
Author(s):  
A. C. Ion ◽  
R. Vermeylen ◽  
I. Kourtchev ◽  
J. Cafmeyer ◽  
X. Chi ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Malic Acid ◽  
Sampling Site ◽  
Photochemical Reactions ◽  
Oxidation Products ◽  
Forest Site ◽  
Supporting Evidence ◽  
Diel Pattern ◽  
Field Campaign ◽  
Photo Oxidation

Abstract. In the present study, we examined PM2.5 continental rural background aerosols, which were collected during a summer field campaign at K-puszta, Hungary (4 June-10 July 2003), a mixed coniferous/deciduous forest site characterized by intense solar radiation during summer. Emphasis was placed on polar oxygenated organic compounds that provide information on aerosol sources and source processes. The major components detected at significant atmospheric concentrations were: (a) photo-oxidation products of isoprene including the 2-methyltetrols (2-methylthreitol and 2-methylerythritol) and 2-methylglyceric acid, (b) levoglucosan, a marker for biomass burning, (c) malic acid, an intermediate in the oxidation of unsaturated fatty acids, and (d) the sugar alcohols, arabitol and mannitol, markers for fungal spores. Diel patterns with highest concentrations during day-time were observed for the 2-methyltetrols, which can be regarded as supporting evidence for their fast photochemical formation from locally emitted isoprene. In addition, a diel pattern with highest concentrations during day-time was observed for the fungal markers, suggesting that the release of fungal fragments that are associated with the PM2.5 aerosol is enhanced during that time. Furthermore, a diel pattern was also found for levoglucosan with the highest concentrations at night when wood burning may take place in the settlements around the sampling site. In contrast, malic acid did not show day/night differences but was found to follow quite closely the particulate and organic carbon mass. This is interpreted as an indication that malic acid is formed in photochemical reactions which have a much longer overall time-scale than that of isoprene photo-oxidation, and the sources of its precursors are manifold, including both anthropogenic and natural emissions. On the basis of the high concentrations found for the isoprene oxidation products during day-time, it can be concluded that rapid photo-oxidation of isoprene is an important atmospheric chemistry process that contributes to secondary organic aerosol (SOA) formation at K-puszta during summer.

scholarly journals Polar organic compounds in rural PM<sub>2.5</sub> aerosols from K-puszta, Hungary, during a 2003 summer field campaign: sources and diurnal variations

2005 ◽  
Vol 5 (2) ◽  
pp. 1863-1889 ◽  
Author(s):  
A. C. Ion ◽  
R. Vermeylen ◽  
I. Kourtchev ◽  
J. Cafmeyer ◽  
X. Chi ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Malic Acid ◽  
Photochemical Reactions ◽  
Oxidation Products ◽  
Forest Site ◽  
Diurnal Pattern ◽  
Field Campaign ◽  
Photo Oxidation ◽  
Isoprene Oxidation ◽  
Isoprene Oxidation Products

Abstract. In the present study, we examined PM2.5 continental rural background aerosols, which were collected during a summer field campaign at K-puszta, Hungary (4 June–10 July 2003), a mixed coniferous/deciduous forest site characterized by intense solar radiation during summer. Emphasis was placed on polar oxygenated organic compounds that provide information on aerosol sources and source processes. Analysis was performed using gas chromatography/mass spectrometry (GC/MS) after suitable sample workup consisting of extraction with methanol and derivatisation into trimethylsilyl (TMS) derivatives. The major components detected at significant atmospheric concentrations were: (a) photo-oxidation products of isoprene including the 2-methyltetrols (2-methylthreitol and 2-methylerythritol) and 2-methylglyceric acid, (b) levoglucosan, a marker for biomass burning, (c) malic acid, an end-oxidation product of unsaturated fatty acids, and (d) the sugar alcohols, arabitol and mannitol, markers for fungal spores. Diurnal patterns with highest concentrations during day-time were observed for the isoprene oxidation products, i.e., the 2-methyltetrols and 2-methylglyceric acid, which can be regarded as supporting evidence for their fast photochemical formation from their locally emitted precursor. In addition, a diurnal pattern with highest concentrations during day-time was observed for the fungal markers, arabitol and mannitol, suggesting that the release of fungal fragments that are associated with the PM2.5 aerosol is enhanced during that time. Furthermore, a diurnal pattern was also found for levoglucosan with the highest concentrations at night when wood burning may take place in the settlements around the sampling site. In contrast, malic acid did not show day/night differences but was found to follow quite closely the particulate and organic carbon mass. This is interpreted as an indication that malic acid is formed in photochemical reactions which have a much longer overall time-scale than that of isoprene photo-oxidation, and the sources of its precursors are manifold, including both anthropogenic and natural emissions. On the basis of the high concentrations found for the isoprene oxidation products, i.e., the 2-methyltetrols (28.5 ng m-3) and 2-methylglyceric acid (7.6 ng m-3), it can be concluded that rapid photo-oxidation of isoprene is an important atmospheric chemistry process that contributes to secondary organic aerosol (SOA) formation at K-puszta during summer.

scholarly journals Insights into secondary organic aerosol formed via aqueous-phase reactions of phenolic compounds based on high resolution mass spectrometry

2010 ◽  
Vol 10 (2) ◽  
pp. 2915-2943 ◽  
Author(s):  
Y. Sun ◽  
Q. Zhang ◽  
C. Anastasio ◽  
J. Sun
Keyword(s):  
Phenolic Compounds ◽  
High Resolution ◽  
Aromatic Ring ◽  
Aqueous Phase ◽  
Secondary Organic Aerosol ◽  
High Resolution Mass Spectrometry ◽  
Organic Aerosol ◽  
Photochemical Reactions ◽  
Oxidation Products ◽  
Formation Mechanisms

Abstract. Recent work has shown that aqueous-phase reactions of phenolic compounds – phenol (C6H6O), guaiacol (C7H8O2), and syringol (C8H10O3) – can form secondary organic aerosol (SOA) at high yields. Here we examine the chemical characteristics of this SOA and its formation mechanisms using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-AMS), an Ion Chromatograph (IC), and a Total Organic Carbon (TOC) analyzer. The phenolic SOA are highly oxygenated with oxygen-to-carbon (O/C) ratios in the range of 0.80–1.06 and carbon oxidation states (=2×O/C–H/C) between −0.14 and +0.47. The organic mass-to-carbon (OM/OC) ratios determined by the HR-AMS (=2.21–2.55) agree well with values determined based on the SOA mass measured gravimetrically and the OC mass from the TOC analyzer. Both the O/C and OM/OC ratios of the phenolic SOA are similar to the values observed for ambient low-volatility oxygenated/secondary OA (LV-OOA). Oxalate is a minor, but ubiquitous, component of the SOA formed from all three phenolic precursors, accounting for 1.4–5.2% of the SOA mass, with generally higher yields in experiments with H2O2 added as an ·OH source compared to without. The AMS spectra show evidence for the formation of syringol and guaiacol dimers and higher oligomers via C–C and C–O coupling of phenoxyl radicals, which are formed through oxidation pathways such as abstraction of the phenolic hydrogen atom or ·OH addition to the aromatic ring. This latter pathway leads to hydroxylation of the aromatic ring, which is one mechanism that increases the degree of oxidation of the SOA products. Compared to direct photochemical reactions of the phenols, ·OH-initiated reactions favor the formation of smaller oxidation products but less dimers or higher oligomers. Two unique and prominent ions in the syringol and guaiacol SOA spectra, m/z 306 (C16H18O6+) and m/z 246 (C14H14O4+), respectively, are observed in ambient aerosols significantly influenced by wood combustion and fog processing. Our results indicate that cloud and fog processing of phenolic compounds, especially in areas with active biomass burning, might represent an important pathway for the formation of low-volatility and highly oxygenated organic species, which would remain in particle phase after fog/cloud evaporation and affect the hygroscopicity and radiative impacts of ambient OA.

scholarly journals Insights into secondary organic aerosol formed via aqueous-phase reactions of phenolic compounds based on high resolution mass spectrometry

2010 ◽  
Vol 10 (10) ◽  
pp. 4809-4822 ◽  
Author(s):  
Y. L. Sun ◽  
Q. Zhang ◽  
C. Anastasio ◽  
J. Sun
Keyword(s):  
Phenolic Compounds ◽  
High Resolution ◽  
Aromatic Ring ◽  
Aqueous Phase ◽  
Secondary Organic Aerosol ◽  
High Resolution Mass Spectrometry ◽  
Organic Aerosol ◽  
Photochemical Reactions ◽  
Oxidation Products ◽  
Formation Mechanisms

Abstract. Recent work has shown that aqueous-phase reactions of phenolic compounds – phenol (C6H6O), guaiacol (C7H8O2), and syringol (C8H10O3) – can form secondary organic aerosol (SOA) at high yields. Here we examine the chemical characteristics of this SOA and its formation mechanisms using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-AMS), an Ion Chromatography system (IC), and a Total Organic Carbon (TOC) analyzer. The phenolic SOA are highly oxygenated with oxygen-to-carbon (O/C) ratios in the range of 0.80–1.06 and carbon oxidation states (=2×O/C-H/C) between −0.14 and +0.47. The organic mass-to-carbon (OM/OC) ratios determined by the HR-AMS (=2.21–2.55) agree well with values determined based on the SOA mass measured gravimetrically and the OC mass from the TOC analyzer. Both the O/C and OM/OC ratios of the phenolic SOA are similar to the values observed for ambient low-volatility oxygenated/secondary OA (LV-OOA). Oxalate is a minor, but ubiquitous, component of the SOA formed from all three phenolic precursors, accounting for 1.4−5.2% of the SOA mass, with generally higher yields in experiments with H2O2 added as an OH source compared to without. The AMS spectra show evidence for the formation of syringol and guaiacol dimers and higher oligomers via C-C and C-O coupling of phenoxyl radicals, which are formed through oxidation pathways such as abstraction of the phenolic hydrogen atom or OH addition to the aromatic ring. This latter pathway leads to hydroxylation of the aromatic ring, which is one mechanism that increases the degree of oxidation of the SOA products. Compared to direct photochemical reactions of the phenols, OH-initiated reactions favor the formation of smaller oxidation products but less dimers or higher oligomers. Two unique and prominent ions in the syringol and guaiacol SOA spectra, m/z 306 (C16H18O6+) and m/z 246 (C14H14O4+), respectively, are observed in ambient aerosols significantly influenced by wood combustion and fog processing. Our results indicate that cloud and fog processing of phenolic compounds, especially in areas with active biomass burning, might represent an important pathway for the formation of low-volatility and highly oxygenated organic species, which would remain in the particle phase after fog/cloud evaporation and affect the chemical and optical properties of atmospheric particles.

scholarly journals Deliquescence, efflorescence, and phase miscibility of mixed particles of ammonium sulfate and isoprene-derived secondary organic material

2012 ◽  
Vol 12 (4) ◽  
pp. 9903-9943 ◽  
Author(s):  
M. L. Smith ◽  
A. K. Bertram ◽  
S. T. Martin
Keyword(s):  
Liquid Phase ◽  
Relative Humidity ◽  
Ammonium Sulfate ◽  
Organic Material ◽  
Important Variable ◽  
Oxidation Products ◽  
Liquid Separation ◽  
Inorganic Particles ◽  
Photo Oxidation ◽  
Hygroscopic Properties

Abstract. The hygroscopic phase transitions of ammonium sulfate mixed with isoprene-derived secondary organic material were investigated in aerosol experiments. The organic material was produced by isoprene photo-oxidation at 40% relative humidity. The low volatility fraction of the photo-oxidation products condensed onto ammonium sulfate particles. The particle-phase organic material had oxygen-to-carbon ratios of 0.67 to 0.74 for mass concentrations of 20 to 30 μg m−3. The deliquescence, efflorescence, and phase miscibility of the mixed particles were investigated using a dual arm tandem differential mobility analyzer. The isoprene photo-oxidation products induced deviations in behavior relative to pure ammonium sulfate. Compared to an efflorescence relative humidity (ERH) of 30 to 35% for pure ammonium sulfate, efflorescence was eliminated for mixed aqueous particles having organic volume fractions ε of approximately 0.6 and greater. Compared to a deliquescence relative humidity (DRH) of 80% for pure ammonium sulfate, the DRH steadily decreased for increasing ε, approaching a DRH of 40% for ε of 0.9. Parameterizations of the DRH(ε) and ERH(ε) curves were as follows: DRH(ε)= Σ i ci,d xi valid for 0 ≤ ε ≤ 0.86 and ERH(ε)= Σ i ci,e xi valid for 0 ≤ ε ≤ 0.55 for the coefficients c0,d= 80.67, c0,e = 28.35, c1,d= −11.45, c1,e = −13.66, c2,d = 0, c2,e = 0, c3,d = 57.99, c3,e = −83.80, c4,d = −106.80, and c4,d = 0. The molecular description that is thermodynamically implied by these strongly sloped DRH(ε) and ERH(ε) curves is that the organic isoprene photo-oxidation products, the inorganic ammonium sulfate, and water form a miscible liquid phase even at low relative humidity. This phase miscibility is in contrast to the liquid-liquid separation that occurs for some other types of secondary organic material. These differences in liquid-liquid separation are consistent with a prediction recently presented in the literature that the bifurcation between liquid-liquid phase separation versus mixing depends on the oxygen-to-carbon ratio of the organic material. The conclusions are that the influence of secondary organic material on the hygroscopic properties of ammonium sulfate varies with organic composition and that the degree of oxygenation of the organic material, which is a measurable characteristic of complex organic materials, is an important variable influencing the hygroscopic properties of mixed organic-inorganic particles.

scholarly journals Rapid formation of isoprene photo-oxidation products observed in Amazonia

2009 ◽  
Vol 9 (3) ◽  
pp. 13629-13653 ◽  
Author(s):  
T. Karl ◽  
A. Guenther ◽  
A. Turnipseed ◽  
P. Artaxo ◽  
S. Martin
Keyword(s):  
Atmospheric Chemistry ◽  
Global Climate ◽  
Oxidative Capacity ◽  
Oxidation Products ◽  
Lower Atmosphere ◽  
Peroxy Radicals ◽  
Aerosol Formation ◽  
Photo Oxidation ◽  
Voc Oxidation ◽  
Rapid Formation

Abstract. Isoprene represents the single most important reactive hydrocarbon for atmospheric chemistry in the tropical atmosphere. It plays a central role in global and regional atmospheric chemistry and possible climate feedbacks. Photo-oxidation of primary hydrocarbons (e.g. isoprene) leads to the formation of oxygenated VOCs (OVOCs). The evolution of these intermediates affects the oxidative capacity of the atmosphere (by reacting with OH) and can contribute to secondary aerosol formation, a poorly understood process. An accurate and quantitative understanding of VOC oxidation processes is needed for model simulations of regional air quality and global climate. Based on field measurements conducted during the Amazonian aerosol characterization experiment (AMAZE-08) we show that the production of certain OVOCs (e.g. hydroxyacetone) from isoprene photo-oxidation in the lower atmosphere is significantly underpredicted by standard chemistry schemes. A recently suggested novel pathway for isoprene peroxy radicals could explain the observed discrepancy and reconcile the rapid formation of these VOCs. Furthermore, if generalized our observations suggest that prompt photochemical formation of OVOCs and other uncertainties in VOC oxidation schemes could result in substantial underestimates of modelled OH reactivity that could explain a major fraction of the missing OH sink over forests which has previously been attributed to a missing source of primary biogenic VOCs.

Photochemical reactions in the tropospheric aqueous phase and on particulate matter

2006 ◽  
Author(s):  
Davide Vione ◽  
Valter Maurino ◽  
Claudio Minero ◽  
Ezio Pelizzetti ◽  
Mark A. J. Harrison ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Aqueous Phase ◽  
Photochemical Reactions
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