scholarly journals Secondary organic aerosol (SOA) formation from reaction of isoprene with nitrate radicals (NO<sub>3</sub>)

2008 ◽  
Vol 8 (1) ◽  
pp. 3163-3226 ◽  
Author(s):  
N. L. Ng ◽  
A. J. Kwan ◽  
J. D. Surratt ◽  
A. W. H. Chan ◽  
P. S. Chhabra ◽  
...  
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Organic Nitrates ◽  
Peroxy Radicals ◽  
Formation Pathway ◽  
Nitrate Radicals ◽  
Dry Conditions ◽  
Phase Data ◽  
A Minor

Abstract. Secondary organic aerosol (SOA) formation from the reaction of isoprene with nitrate radicals (NO3) is investigated in the Caltech indoor chambers. Experiments are performed in the dark and under dry conditions (RH<10%) using N2O5 as a source of NO3 radicals. For an initial isoprene concentration of 18.4 to 101.6 ppb, the SOA yield (defined as the ratio of the mass of organic aerosol formed to the mass of parent hydrocarbon reacted) ranges from 4.3% to 23.8%. By examining the time evolutions of gas-phase intermediate products and aerosol volume in real time, we are able to constrain the chemistry that leads to the formation of low-volatility products. Although the formation of ROOR from the reaction of two peroxy radicals (RO2) has generally been considered as a minor channel, based on the gas-phase and aerosol-phase data it appears that RO2+RO2 reaction (self reaction or cross-reaction) in the gas phase yielding ROOR products is a dominant SOA formation pathway. A wide array of organic nitrates and peroxides are identified in the aerosol formed and mechanisms for SOA formation are proposed. Using a uniform SOA yield of 10% (corresponding to Mo≅10 μg m−3), it is estimated that ~2 to 3 Tg yr−1 of SOA results from isoprene + NO3. The extent to which the results from this study can be applied to conditions in the atmosphere depends on the fate of peroxy radicals (i.e. the relative importance of RO2+RO2 versus RO2+NO3 reactions) in the nighttime troposphere.

scholarly journals Secondary organic aerosol (SOA) formation from reaction of isoprene with nitrate radicals (NO<sub>3</sub>)

2008 ◽  
Vol 8 (14) ◽  
pp. 4117-4140 ◽  
Author(s):  
N. L. Ng ◽  
A. J. Kwan ◽  
J. D. Surratt ◽  
A. W. H. Chan ◽  
P. S. Chhabra ◽  
...  
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Organic Nitrates ◽  
Peroxy Radicals ◽  
Formation Pathway ◽  
Nitrate Radicals ◽  
Dry Conditions ◽  
Phase Data ◽  
A Minor

Abstract. Secondary organic aerosol (SOA) formation from the reaction of isoprene with nitrate radicals (NO3) is investigated in the Caltech indoor chambers. Experiments are performed in the dark and under dry conditions (RH&amp;lt10%) using N2O5 as a source of NO3 radicals. For an initial isoprene concentration of 18.4 to 101.6 ppb, the SOA yield (defined as the ratio of the mass of organic aerosol formed to the mass of parent hydrocarbon reacted) ranges from 4.3% to 23.8%. By examining the time evolutions of gas-phase intermediate products and aerosol volume in real time, we are able to constrain the chemistry that leads to the formation of low-volatility products. Although the formation of ROOR from the reaction of two peroxy radicals (RO2) has generally been considered as a minor channel, based on the gas-phase and aerosol-phase data it appears that RO2+RO2 reaction (self reaction or cross-reaction) in the gas phase yielding ROOR products is a dominant SOA formation pathway. A wide array of organic nitrates and peroxides are identified in the aerosol formed and mechanisms for SOA formation are proposed. Using a uniform SOA yield of 10% (corresponding to Mo≅10 μg m−3), it is estimated that ~2 to 3 Tg yr−1 of SOA results from isoprene+NO3. The extent to which the results from this study can be applied to conditions in the atmosphere depends on the fate of peroxy radicals in the nighttime troposphere.

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 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 Organic nitrate and secondary organic aerosol yield from NO<sub>3</sub> oxidation of β-pinene evaluated using a gas-phase kinetics/aerosol partitioning model

2009 ◽  
Vol 9 (4) ◽  
pp. 1431-1449 ◽  
Author(s):  
J. L. Fry ◽  
A. Kiendler-Scharr ◽  
A. W. Rollins ◽  
P. J. Wooldridge ◽  
S. S. Brown ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Oxidation Mechanism ◽  
Organic Aerosol ◽  
Anthropogenic Source ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Gas Phase Kinetics ◽  
Low Concentrations ◽  
Dry Conditions ◽  
Highly Correlated

Abstract. The yields of organic nitrates and of secondary organic aerosol (SOA) particle formation were measured for the reaction NO3+β-pinene under dry and humid conditions in the atmosphere simulation chamber SAPHIR at Research Center Jülich. These experiments were conducted at low concentrations of NO3 (NO3+N2O5<10 ppb) and β-pinene (peak~15 ppb), with no seed aerosol. SOA formation was observed to be prompt and substantial (~50% mass yield under both dry conditions and at 60% RH), and highly correlated with organic nitrate formation. The observed gas/aerosol partitioning of organic nitrates can be simulated using an absorptive partitioning model to derive an estimated vapor pressure of the condensing nitrate species of pvap~5×10−6 Torr (6.67×10−4 Pa), which constrains speculation about the oxidation mechanism and chemical identity of the organic nitrate. Once formed the SOA in this system continues to evolve, resulting in measurable aerosol volume decrease with time. The observations of high aerosol yield from NOx-dependent oxidation of monoterpenes provide an example of a significant anthropogenic source of SOA from biogenic hydrocarbon precursors. Estimates of the NO3+β-pinene SOA source strength for California and the globe indicate that NO3 reactions with monoterpenes are likely an important source (0.5–8% of the global total) of organic aerosol on regional and global scales.

scholarly journals The effect of particle acidity on secondary organic aerosol formation from <i>α</i>-pinene photooxidation under atmospherically relevant conditions

2016 ◽  
Vol 16 (21) ◽  
pp. 13929-13944 ◽  
Author(s):  
Yuemei Han ◽  
Craig A. Stroud ◽  
John Liggio ◽  
Shao-Meng Li
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Strong Increase ◽  
Nitrate Content ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Particle Phase ◽  
Aerosol Formation

Abstract. Secondary organic aerosol (SOA) formation from photooxidation of α-pinene has been investigated in a photochemical reaction chamber under varied inorganic seed particle acidity levels at moderate relative humidity. The effect of particle acidity on SOA yield and chemical composition was examined under high- and low-NOx conditions. The SOA yield (4.2–7.6 %) increased nearly linearly with the increase in particle acidity under high-NOx conditions. In contrast, the SOA yield (28.6–36.3 %) was substantially higher under low-NOx conditions, but its dependency on particle acidity was insignificant. A relatively strong increase in SOA yield (up to 220 %) was observed in the first hour of α-pinene photooxidation under high-NOx conditions, suggesting that SOA formation was more effective for early α-pinene oxidation products in the presence of fresh acidic particles. The SOA yield decreased gradually with the increase in organic mass in the initial stage (approximately 0–1 h) under high-NOx conditions, which is likely due to the inaccessibility to the acidity over time with the coating of α-pinene SOA, assuming a slow particle-phase diffusion of organic molecules into the inorganic seeds. The formation of later-generation SOA was enhanced by particle acidity even under low-NOx conditions when introducing acidic seed particles after α-pinene photooxidation, suggesting a different acidity effect exists for α-pinene SOA derived from later oxidation stages. This effect could be important in the atmosphere under conditions where α-pinene oxidation products in the gas-phase originating in forested areas (with low NOx and SOx) are transported to regions abundant in acidic aerosols such as power plant plumes or urban regions. The fraction of oxygen-containing organic fragments (CxHyO1+ 33–35 % and CxHyO2+ 16–17 %) in the total organics and the O ∕ C ratio (0.52–0.56) of α-pinene SOA were lower under high-NOx conditions than those under low-NOx conditions (39–40, 17–19, and 0.61–0.64 %), suggesting that α-pinene SOA was less oxygenated in the studied high-NOx conditions. The fraction of nitrogen-containing organic fragments (CxHyNz+ and CxHyOzNp+) in the total organics was enhanced with the increases in particle acidity under high-NOx conditions, indicating that organic nitrates may be formed heterogeneously through a mechanism catalyzed by particle acidity or that acidic conditions facilitate the partitioning of gas-phase organic nitrates into particle phase. The results of this study suggest that inorganic acidity has a significant role to play in determining various organic aerosol chemical properties such as mass yields, oxidation state, and organic nitrate content. The acidity effect being further dependent on the timescale of SOA formation is also an important parameter in the modeling of SOA.

scholarly journals Substantial secondary organic aerosol formation in a coniferous forest: observations of both day and night time chemistry

2015 ◽  
Vol 15 (20) ◽  
pp. 28005-28035 ◽  
Author(s):  
A. K. Y. Lee ◽  
J. P. D. Abbatt ◽  
W. R. Leaitch ◽  
S.-M. Li ◽  
S. J. Sjostedt ◽  
...  
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Coniferous Forest ◽  
Organic Aerosol ◽  
Organic Nitrates ◽  
Nitrate Radical ◽  
Aerosol Formation ◽  
Radical Chemistry ◽  
Phase Oxidation ◽  
Gas Phase Oxidation

Abstract. Substantial biogenic secondary organic aerosol (BSOA) formation was investigated in a coniferous forest mountain region at Whistler, British Columbia. A largely biogenic aerosol growth episode was observed, providing a unique opportunity to investigate BSOA formation chemistry in a forested environment with limited influence from anthropogenic emissions. Positive matrix factorization of aerosol mass spectrometry (AMS) measurement identified two types of BSOA (BSOA-1 and BSOA-2), which were primarily generated by gas-phase oxidation of monoterpenes and perhaps sesquiterpenes. The temporal variations of BSOA-1 and BSOA-2 can be explained by gas-particle partitioning in response to ambient temperature and the relative importance of different oxidation mechanisms between day and night. While BSOA-1 will arise from gas-phase ozonolysis and nitrate radical chemistry at night, BSOA-2 is less volatile than BSOA-1 and consists of products formed via gas-phase oxidation by the OH radical and ozone during the day. Organic nitrates produced through nitrate radical chemistry can account for 22–33 % of BSOA-1 mass at night. The mass spectra of BSOA-1 and BSOA-2 have higher values of the mass fraction of m/z 91 (f91) compared to the background organic aerosol, and so f91 is used as an indicator of BSOA formation pathways. A comparison between laboratory studies in the literature and our field observations highlights the potential importance of gas-phase formation chemistry of BSOA-2 type materials that may not be captured in smog chamber experiments, perhaps due to the wall loss of gas-phase intermediate products.

scholarly journals Organic nitrate and secondary organic aerosol yield from NO<sub>3</sub> oxidation of <i>β</i>-pinene evaluated using a gas-phase kinetics/aerosol partitioning model

2008 ◽  
Vol 8 (5) ◽  
pp. 18039-18089 ◽  
Author(s):  
J. L. Fry ◽  
A. Kiendler-Scharr ◽  
A. W. Rollins ◽  
P. J. Wooldridge ◽  
S. S. Brown ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Oxidation Mechanism ◽  
Organic Aerosol ◽  
Anthropogenic Source ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Gas Phase Kinetics ◽  
Low Concentrations ◽  
Dry Conditions ◽  
Highly Correlated

Abstract. The yields of organic nitrates and of secondary organic aerosol (SOA) particle formation were measured for the reaction NO3+β-pinene under dry and humid conditions in the atmosphere simulation chamber SAPHIR at Research Center Jülich. These experiments were conducted at low concentrations of NO3 (NO3+N2O5<10 ppb) and β-pinene (peak~15 ppb), with no seed aerosol. SOA formation was observed to be prompt and substantial (~50% mass yield under both dry conditions and at 60% RH), and highly correlated with organic nitrate formation. The observed gas/aerosol partitioning of organic nitrates can be simulated using an absorptive partitioning model to derive an estimated vapor pressure of the condensing nitrate species of pvap~5×10−6 Torr (6.67×10−4 Pa), which constrains speculation about the oxidation mechanism and chemical identity of the organic nitrate. Once formed the SOA in this system continues to evolve, resulting in measurable aerosol volume decrease with time. The observations of high aerosol yield from NOx-dependent oxidation of monoterpenes provide an example of a significant anthropogenic source of SOA from biogenic hydrocarbon precursors. Estimates of the NO3+β-pinene SOA source strength for California and the globe indicate that NO3 reactions with monoterpenes are likely an important source (0.5–8% of the global total) of organic aerosol on regional and global scales.

scholarly journals Different roles of water in secondary organic aerosol formation from toluene and isoprene

2018 ◽  
Vol 18 (11) ◽  
pp. 8137-8154 ◽  
Author(s):  
Long Jia ◽  
YongFu Xu
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Chemical Components ◽  
Smog Chamber ◽  
Aerosol Formation ◽  
Model Simulations ◽  
Criegee Intermediates ◽  
Dry Conditions ◽  
Major Chemical

Abstract. Roles of water in the formation of secondary organic aerosol (SOA) from the irradiations of toluene-NO2 and isoprene-NO2 were investigated in a smog chamber. Experimental results show that the yield of SOA from toluene almost doubled as relative humidity increased from 5 to 85 %, whereas the yield of SOA from isoprene under humid conditions decreased by 2.6 times as compared to that under dry conditions. The distinct difference of RH effects on SOA formation from toluene and isoprene is well explained with our experiments and model simulations. The increased SOA from humid toluene-NO2 irradiations is mainly contributed by O–H-containing products such as polyalcohols formed from aqueous reactions. The major chemical components of SOA in isoprene-NO2 irradiations are oligomers formed from the gas phase. SOA formation from isoprene-NO2 irradiations is controlled by stable Criegee intermediates (SCIs) that are greatly influenced by water. As a result, high RH can obstruct the oligomerization reaction of SCIs to form SOA.

scholarly journals Different roles of water in secondary organic aerosol formation from toluene and isoprene

2017 ◽  
Author(s):  
Long Jia ◽  
Yongfu Xu
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Chemical Components ◽  
Smog Chamber ◽  
Aerosol Formation ◽  
Model Simulations ◽  
Dry Conditions ◽  
Major Chemical ◽  
Oligomerization Reaction

Abstract. Roles of water in the formation of secondary organic aerosol (SOA) from the irradiations of toluene-NO2 and isoprene-NO2 were investigated in a smog chamber. Experimental results show that the yield of SOA from toluene almost doubled as relative humidity increased from 5 % to 85 %, whereas the yield of SOA from isoprene under humid conditions decreased by 2.6 times as compared to that under dry conditions. The distinct difference of RH effects on SOA formation from toluene and isoprene is well explained with our experiments and model simulations. The increased SOA from humid toluene-NO2 irradiations is mainly contributed by O–H-containing products such as polyalcohols formed from aqueous reactions. The major chemical components of SOA in isoprene-NO2 irradiations are oligomers formed from the gas phase. SOA formation from isoprene-NO2 irradiations is controlled by stable Criegee intermediate (SCI) that is greatly influenced by water. As a result, high RH can obstruct the oligomerization reaction of SCI to form SOA.

scholarly journals Substantial secondary organic aerosol formation in a coniferous forest: observations of both day- and nighttime chemistry

2016 ◽  
Vol 16 (11) ◽  
pp. 6721-6733 ◽  
Author(s):  
Alex K. Y. Lee ◽  
Jonathan P. D. Abbatt ◽  
W. Richard Leaitch ◽  
Shao-Meng Li ◽  
Steve J. Sjostedt ◽  
...  
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Coniferous Forest ◽  
Organic Aerosol ◽  
Organic Nitrates ◽  
Nitrate Radical ◽  
Aerosol Formation ◽  
Radical Chemistry ◽  
Phase Oxidation ◽  
Gas Phase Oxidation

Abstract. Substantial biogenic secondary organic aerosol (BSOA) formation was investigated in a coniferous forest mountain region in Whistler, British Columbia. A largely biogenic aerosol growth episode was observed, providing a unique opportunity to investigate BSOA formation chemistry in a forested environment with limited influence from anthropogenic emissions. Positive matrix factorization of aerosol mass spectrometry (AMS) measurement identified two types of BSOA (BSOA-1 and BSOA-2), which were primarily generated by gas-phase oxidation of monoterpenes and perhaps sesquiterpenes. The temporal variations of BSOA-1 and BSOA-2 can be explained by gas–particle partitioning in response to ambient temperature and the relative importance of different oxidation mechanisms between day and night. While BSOA-1 arises from gas-phase ozonolysis and nitrate radical chemistry at night, BSOA-2 is likely less volatile than BSOA-1 and consists of products formed via gas-phase oxidation by OH radical and ozone during the day. Organic nitrates produced through nitrate radical chemistry can account for 22–33 % of BSOA-1 mass at night. The mass spectra of BSOA-1 and BSOA-2 have higher values of the mass fraction of m/z 91 (f91) compared to the background organic aerosol. Using f91 to evaluate BSOA formation pathways in this unpolluted, forested region, heterogeneous oxidation of BSOA-1 is a minor production pathway of BSOA-2.

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