New insights into secondary organic aerosol from nitrate oxidation of isoprene in the atmospheric simulation chamber SAPHIR

2020 ◽  
Author(s):  
Juliane L. Fry ◽  
Bellamy Brownwood ◽  
Thorsten Hohaus ◽  
Avtandil Turdziladze ◽  
Philip Carlsson ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Organic Nitrate ◽  
Nitrate Radical ◽  
Peroxy Radicals ◽  
Radical Reactivity ◽  
No3 Radical ◽  
Chemical Conditions ◽  
Seed Aerosol ◽  
Simulation Chamber

<p>Experiments at a set of atmospherically relevant conditions were performed in the atmospheric simulation chamber SAPHIR, investigating the oxidation of isoprene by the nitrate radical (NO3). A comprehensive set of instruments detected trace gases, radicals, aerosol properties and hydroxyl (OH) and NO3 radical reactivity. The chemical conditions in the chamber were varied to change the fate of the peroxy radicals (RO2) formed after the reaction between NO3 and isoprene, and seed aerosol of varying composition was added to initiate gas/aerosol partitioning. This presentation discusses observed gas/aerosol partitioning of the major organic nitrate products and summarizes the observations of secondary organic aerosol yield.</p>

New insights into the gas-phase oxidation of isoprene by the nitrate radical from experiments in the atmospheric simulation chamber SAPHIR

2020 ◽  
Author(s):  
Philip Carlsson ◽  
Patrick Dewald ◽  
Justin Shenolikar ◽  
Nils Friedrich ◽  
John Crowley ◽  
...  
Keyword(s):  
Chemical Mechanism ◽  
Organic Nitrate ◽  
Nitrate Radical ◽  
Peroxy Radicals ◽  
Night Time ◽  
Alkyl Nitrates ◽  
Model Calculations ◽  
Alkyl Nitrate ◽  
Chemical Conditions ◽  
Simulation Chamber

<p>Experiments at a set of atmospherically relevant conditions were performed in the simulation chamber SAPHIR, investigating the oxidation of isoprene by the nitrate radical (NO<sub>3</sub>)<sub>.</sub> An extremely comprehensive set of instruments detected trace gases, radicals, aerosol properties and hydroxyl (OH) and NO<sub>3</sub> radical reactivity. The chemical conditions in the chamber were varied to change the fate of the peroxy radicals (RO<sub>2</sub>) formed after the reaction between NO<sub>3</sub> and isoprene from either mainly recombining with other RO<sub>2</sub> or mainly reacting with hydroperoxyl radicals (HO<sub>2</sub>). These major atmospheric pathways for RO<sub>2</sub> radicals lead to the formation of organic nitrate compounds which then have different atmospheric fates. The experimental concentration profiles are compared to box model calculations using both the current Master Chemical Mechanism (MCM) as well as recently available literature data alongside new quantum chemical calculations. The discussion here focusses on the resulting RO<sub>2</sub> distribution and deviations in the predictions of early products and total alkyl nitrate yields for the different chemical conditions. Preliminary results for instance show too high night time losses of alkyl nitrates due to ozonolysis in the current MCM.<span> </span></p>

scholarly journals Impact of NO<sub>x</sub> on secondary organic aerosol (SOA) formation from <i>α</i>-pinene and <i>β</i>-pinene photo-oxidation: the role of highly oxygenated organic nitrates

2020 ◽  
Author(s):  
Iida Pullinen ◽  
Sebastian Schmitt ◽  
Sungah Kang ◽  
Mehrnaz Sarrafzadeh ◽  
Patrick Schlag ◽  
...  
Keyword(s):  
Gas Phase ◽  
Functional Groups ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Peroxy Radicals ◽  
Photo Oxidation ◽  
Mass Formation

Abstract. The formation of organic nitrates (ON) in the gas phase and their impact on mass formation of Secondary Organic Aerosol (SOA) was investigated in a laboratory study for α-pinene and β-pinene photo-oxidation. Focus was the elucidation of those mechanisms that cause the often observed suppression of SOA mass formation by NOx, and therein the role of highly oxygenated multifunctional molecules (HOM). We observed that with increasing NOx (a) the portion of HOM organic nitrates (HOM-ON) increased, (b) the fraction of accretion products (HOM-ACC) decreased and (c) HOM-ACC contained on average smaller carbon numbers. Specifically, we investigated HOM organic nitrates (HOM-ON), arising from the termination reactions of HOM peroxy radicals with NOx, and HOM permutation products (HOM-PP), such as ketones, alcohols or hydroperoxides, formed by other termination reactions. Effective uptake coefficients γeff of HOM on particles were determined. HOM with more than 6 O-atoms efficiently condensed on particles (γeff > 0.5 in average) and for HOM containing more than 8 O-atoms, every collision led to loss. There was no systematic difference in γeff for HOM-ON and HOM-PP arising from the same HOM peroxy radicals. This similarity is attributed to the multifunctional character of the HOM: as functional groups in HOM arising from the same precursor HOM peroxy radical are identical, vapor pressures should not strongly depend on the character the final termination group. As a consequence, the suppressing effect of NOx on SOA formation cannot be simply explained by replacement of terminal functional groups by organic nitrate groups. The fraction of organic bound nitrate (OrgNO3) stored in gas-phase HOM-ON appeared to be substantially higher than the fraction of particulate OrgNO3 observed by aerosol mass spectrometry. This result suggests losses of OrgNO3 for organic nitrates in particles, probably due to hydrolysis of OrgNO3 that releases HNO3 into the gas phase but leaves behind the organic rest in the particulate phase. However, the loss of HNO3 alone, could not explain the observed suppressing effect of NOx on particle mass formation from α-pinene and β-pinene. We therefore attributed most of the reduction in SOA mass yields with increasing NOx to the significant suppression of gas-phase HOM-ACC which have high molecular mass and are potentially important for SOA mass formation at low NOx conditions.

scholarly journals Secondary organic aerosol formation from <i>m</i>-xylene, toluene, and benzene

2007 ◽  
Vol 7 (14) ◽  
pp. 3909-3922 ◽  
Author(s):  
N. L. Ng ◽  
J. H. Kroll ◽  
A. W. H. Chan ◽  
P. S. Chhabra ◽  
R. C. Flagan ◽  
...  
Keyword(s):  
Oxidation Rate ◽  
Secondary Organic Aerosol ◽  
Peroxy Radical ◽  
Organic Aerosol ◽  
Rate Effect ◽  
Peroxy Radicals ◽  
Aerosol Formation ◽  
Yield Curves ◽  
Secondary Organic Aerosol Formation ◽  
Seed Aerosol

Abstract. Secondary organic aerosol (SOA) formation from the photooxidation of m-xylene, toluene, and benzene is investigated in the Caltech environmental chambers. Experiments are performed under two limiting NOx conditions; under high-NOx conditions the peroxy radicals (RO2) react only with NO, while under low-NOx conditions they react only with HO2. For all three aromatics studied (m-xylene, toluene, and benzene), the SOA yields (defined as the ratio of the mass of organic aerosol formed to the mass of parent hydrocarbon reacted) under low-NOx conditions substantially exceed those under high-NOx conditions, suggesting the importance of peroxy radical chemistry in SOA formation. Under low-NOx conditions, the SOA yields for m-xylene, toluene, and benzene are constant (36%, 30%, and 37%, respectively), indicating that the SOA formed is effectively nonvolatile under the range of Mo(>10 μg m−3) studied. Under high-NOx conditions, aerosol growth occurs essentially immediately, even when NO concentration is high. The SOA yield curves exhibit behavior similar to that observed by Odum et al. (1996, 1997a, b), although the values are somewhat higher than in the earlier study. The yields measured under high-NOx conditions are higher than previous measurements, suggesting a "rate effect" in SOA formation, in which SOA yields are higher when the oxidation rate is faster. Experiments carried out in the presence of acidic seed aerosol reveal no change of SOA yields from the aromatics as compared with those using neutral seed aerosol.

scholarly journals Impact of NO<sub><i>x</i></sub> on secondary organic aerosol (SOA) formation from <i>α</i>-pinene and <i>β</i>-pinene photooxidation: the role of highly oxygenated organic nitrates

2020 ◽  
Vol 20 (17) ◽  
pp. 10125-10147
Author(s):  
Iida Pullinen ◽  
Sebastian Schmitt ◽  
Sungah Kang ◽  
Mehrnaz Sarrafzadeh ◽  
Patrick Schlag ◽  
...  
Keyword(s):  
Gas Phase ◽  
Functional Groups ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Peroxy Radicals ◽  
Particulate Phase ◽  
Mass Formation

Abstract. The formation of organic nitrates (ONs) in the gas phase and their impact on mass formation of secondary organic aerosol (SOA) was investigated in a laboratory study for α-pinene and β-pinene photooxidation. Focus was the elucidation of those mechanisms that cause the often observed suppression of SOA mass formation by NOx, and therein the role of highly oxygenated multifunctional molecules (HOMs). We observed that with increasing NOx concentration (a) the portion of HOM organic nitrates (HOM-ONs) increased, (b) the fraction of accretion products (HOM-ACCs) decreased, and (c) HOM-ACCs contained on average smaller carbon numbers. Specifically, we investigated HOM organic nitrates (HOM-ONs), arising from the termination reactions of HOM peroxy radicals with NOx, and HOM permutation products (HOM-PPs), such as ketones, alcohols, or hydroperoxides, formed by other termination reactions. Effective uptake coefficients γeff of HOMs on particles were determined. HOMs with more than six O atoms efficiently condensed on particles (γeff>0.5 on average), and for HOMs containing more than eight O atoms, every collision led to loss. There was no systematic difference in γeff for HOM-ONs and HOM-PPs arising from the same HOM peroxy radicals. This similarity is attributed to the multifunctional character of the HOMs: as functional groups in HOMs arising from the same precursor HOM peroxy radical are identical, vapor pressures should not strongly depend on the character of the final termination group. As a consequence, the suppressing effect of NOx on SOA formation cannot be simply explained by replacement of terminal functional groups by organic nitrate groups. According to their γeff all HOM-ONs with more than six O atoms will contribute to organic bound nitrate (OrgNO3) in the particulate phase. However, the fraction of OrgNO3 stored in condensable HOMs with molecular masses > 230 Da appeared to be substantially higher than the fraction of particulate OrgNO3 observed by aerosol mass spectrometry. This result suggests losses of OrgNO3 for organic nitrates in particles, probably due to hydrolysis of OrgNO3 that releases HNO3 into the gas phase but leaves behind the organic rest in the particulate phase. However, the loss of HNO3 alone could not explain the observed suppressing effect of NOx on particle mass formation from α-pinene and β-pinene. Instead we can attribute most of the reduction in SOA mass yields with increasing NOx to the significant suppression of gas phase HOM-ACCs, which have high molecular mass and are potentially important for SOA mass formation at low-NOx conditions.

scholarly journals Nitrate radical oxidation of <i>γ</i>-terpinene: hydroxy nitrate, total organic nitrate, and secondary organic aerosol yields

2017 ◽  
Vol 17 (14) ◽  
pp. 8635-8650 ◽  
Author(s):  
Jonathan H. Slade ◽  
Chloé de Perre ◽  
Linda Lee ◽  
Paul B. Shepson
Keyword(s):  
Secondary Organic Aerosol ◽  
Mixed Forest ◽  
Organic Aerosol ◽  
High Reactivity ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Nitrate Radical ◽  
Particle Phase ◽  
Forest Environment ◽  
Radical Oxidation

Abstract. Polyolefinic monoterpenes represent a potentially important but understudied source of organic nitrates (ONs) and secondary organic aerosol (SOA) following oxidation due to their high reactivity and propensity for multi-stage chemistry. Recent modeling work suggests that the oxidation of polyolefinic γ-terpinene can be the dominant source of nighttime ON in a mixed forest environment. However, the ON yields, aerosol partitioning behavior, and SOA yields from γ-terpinene oxidation by the nitrate radical (NO3), an important nighttime oxidant, have not been determined experimentally. In this work, we present a comprehensive experimental investigation of the total (gas + particle) ON, hydroxy nitrate, and SOA yields following γ-terpinene oxidation by NO3. Under dry conditions, the hydroxy nitrate yield  =  4(+1/−3) %, total ON yield  =  14(+3/−2) %, and SOA yield  ≤  10 % under atmospherically relevant particle mass loadings, similar to those for α-pinene + NO3. Using a chemical box model, we show that the measured concentrations of NO2 and γ-terpinene hydroxy nitrates can be reliably simulated from α-pinene + NO3 chemistry. This suggests that NO3 addition to either of the two internal double bonds of γ-terpinene primarily decomposes forming a relatively volatile keto-aldehyde, reconciling the small SOA yield observed here and for other internal olefinic terpenes. Based on aerosol partitioning analysis and identification of speciated particle-phase ON applying high-resolution liquid chromatography–mass spectrometry, we estimate that a significant fraction of the particle-phase ON has the hydroxy nitrate moiety. This work greatly contributes to our understanding of ON and SOA formation from polyolefin monoterpene oxidation, which could be important in the northern continental US and the Midwest, where polyolefinic monoterpene emissions are greatest.

scholarly journals Characterization of organic nitrate constituents of secondary organic aerosol (SOA) from nitrate-radical-initiated oxidation of limonene using high-resolution chemical ionization mass spectrometry

2018 ◽  
Vol 18 (8) ◽  
pp. 5467-5481 ◽  
Author(s):  
Cameron Faxon ◽  
Julia Hammes ◽  
Michael Le Breton ◽  
Ravi Kant Pathak ◽  
Mattias Hallquist
Keyword(s):  
High Resolution ◽  
Chemical Ionization ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Formation Mechanisms ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Ionization Mass ◽  
Nitrate Radical ◽  
Particle Phase

Abstract. The gas-phase nitrate radical (NO3⚫) initiated oxidation of limonene can produce organic nitrate species with varying physical properties. Low-volatility products can contribute to secondary organic aerosol (SOA) formation and organic nitrates may serve as a NOx reservoir, which could be especially important in regions with high biogenic emissions. This work presents the measurement results from flow reactor studies on the reaction of NO3⚫ with limonene using a High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS) combined with a Filter Inlet for Gases and AEROsols (FIGAERO). Major condensed-phase species were compared to those in the Master Chemical Mechanism (MCM) limonene mechanism, and many non-listed species were identified. The volatility properties of the most prevalent organic nitrates in the produced SOA were determined. Analysis of multiple experiments resulted in the identification of several dominant species (including C10H15NO6, C10H17NO6, C8H11NO6, C10H17NO7, and C9H13NO7) that occurred in the SOA under all conditions considered. Additionally, the formation of dimers was consistently observed and these species resided almost completely in the particle phase. The identities of these species are discussed, and formation mechanisms are proposed. Cluster analysis of the desorption temperatures corresponding to the analyzed particle-phase species yielded at least five distinct groupings based on a combination of molecular weight and desorption profile. Overall, the results indicate that the oxidation of limonene by NO3⚫ produces a complex mixture of highly oxygenated monomer and dimer products that contribute to SOA formation.

scholarly journals Secondary Organic Aerosol Formation from Camphene Oxidation: Measurements and Modeling

2021 ◽  
Author(s):  
Qi Li ◽  
Jia Jiang ◽  
Isaac Afreh ◽  
Kelley C. Barsanti ◽  
David R. Cocker III
Keyword(s):  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Basis Set ◽  
Peroxy Radicals ◽  
Aerosol Formation ◽  
Box Models ◽  
Pollution Research ◽  
Chemical Conditions ◽  
Chamber Studies ◽  
The University

Abstract. While camphene is one of the dominant monoterpenes measured in biogenic and biomass burning emission samples, oxidation of camphene has not been well-studied in environmental chambers and very little is known about its potential to form secondary organic aerosol (SOA). The lack of chamber-derived SOA data for camphene may lead to significant uncertainties in predictions of SOA from oxidation of monoterpenes using existing parameterizations when camphene is a significant contributor to total monoterpenes. Therefore, to advance the understanding of camphene oxidation and SOA formation, and to improve representation of camphene in air quality models, a series of experiments were performed in the University of California Riverside environmental chamber to explore camphene SOA yields and properties across a range of chemical conditions at atmospherically relevant OH concentrations. The experimental results were compared with modeling simulations obtained using two chemically detailed box models, Statewide Air Pollution Research Center (SAPRC) and Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A). SOA parameterizations were derived from the chamber data using both the two-product and volatility basis set (VBS) approaches. Experiments performed with added nitrogen oxides (NOx) resulted in higher SOA yields (up to 64 %) than experiments performed without added NOx (up to 28 %). In addition, camphene SOA yields increased with SOA mass (Mo) at lower mass loadings, but a threshold was reached at higher mass loadings in which the SOA yields no longer increased with Mo. SAPRC modeling of the chamber studies suggested that the higher SOA yields at higher initial NOx levels were primarily due to higher production of peroxy radicals (RO2) and the generation of highly oxygenated organic molecules (HOMs) formed through unimolecular RO2 reactions. SAPRC predicted that in the presence of NOx, camphene RO2 reacts with NO and the resultant RO2 undergo hydrogen (H)-shift isomerization reactions; as has been documented previously, such reactions rapidly add oxygen and lead to products with very low volatility (i.e., HOMs). The end products formed in the presence of NOx have significantly lower volatilities, and higher O : C ratios, than those formed by initial camphene RO2 reacting with hydroperoxyl radicals (HO2) or other RO2. Moreover, particle densities were found to decrease from 1.47 to 1.30 g cm−3 as [HC]0/[NOx]0 increased and O : C decreased. The observed differences in SOA yields were largely explained by the gas-phase RO2 chemistry and the competition between RO2 + HO2, RO2 + NO, RO2 + RO2, and RO2 unimolecular reactions.

scholarly journals Nitrate radical oxidation of γ-terpinene: hydroxy nitrate, total organic nitrate, and secondary organic aerosol yields

2017 ◽  
Author(s):  
Jonathan H. Slade ◽  
Chloé de Perre ◽  
Linda Lee ◽  
Paul B. Shepson
Keyword(s):  
Secondary Organic Aerosol ◽  
Mixed Forest ◽  
Organic Aerosol ◽  
High Reactivity ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Nitrate Radical ◽  
Particle Phase ◽  
Forest Environment ◽  
Radical Oxidation

Abstract. Polyolefinic monoterpenes represent a potentially important but understudied source of organic nitrates (ON) and secondary organic aerosol (SOA) following oxidation due to their high reactivity and propensity for multi-stage chemistry. Recent modeling work suggests that the oxidation of polyolefinic γ-terpinene can be the dominant source of nighttime ON in a mixed forest environment. However, the ON yields, aerosol partitioning behavior, and SOA yields from γ-terpinene oxidation by the nitrate radical (NO3), an important nighttime oxidant, have not been determined experimentally. In this work, we present a comprehensive experimental investigation of the total (gas + particle) ON, hydroxy nitrate, and SOA yields following γ-terpinene oxidation by NO3. Under dry conditions, the hydroxy nitrate yield = 4(+1/−3) %, total ON yield = 14(+3/−2) %, and SOA yield ≤10% under atmospherically-relevant particle mass loadings, similar to those for α-pinene + NO3. Using a chemical box model, we show that the measured concentrations of NO2 and γ-terpinene hydroxy nitrates can be reliably simulated from α-pinene + NO3 chemistry. This suggests that NO3 addition to either of the two internal double bonds of γ-terpinene primarily decomposes forming a relatively volatile keto–aldehyde, reconciling the small SOA yield observed here and for other internal olefinic terpenes. Based on aerosol partitioning analysis and identification of speciated particle-phase ON applying high-resolution liquid chromatography–mass spectrometry, we estimate that a significant fraction of the particle-phase ON has the hydroxy nitrate moiety. This work greatly contributes to our understanding of ON and SOA formation from polyolefin monoterpene oxidation, which could be important in the northern continental U.S. and Midwest, where polyolefinic monoterpene emissions are greatest.

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