scholarly journals Modeling secondary organic aerosol formation from isoprene oxidation under dry and humid conditions

2010 ◽  
Vol 10 (8) ◽  
pp. 20559-20605
Author(s):  
F. Couvidat ◽  
C. Seigneur
Keyword(s):  
Experimental Data ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Organic Nitrates ◽  
Atmospheric Conditions ◽  
Aerosol Formation ◽  
Yield Increase ◽  
Isoprene Oxidation ◽  
Smog Chambers

Abstract. A new model for the formation of secondary organic aerosol (SOA) from isoprene was developed. This model uses surrogate molecular species (hydroxy-hydroperoxides, tetrols, methylglyceric acid, organic nitrates) to represent SOA formation. The development of this model used available experimental data on yields and molecular composition of SOA from isoprene and methacrolein oxidation. This model reproduces the amount of particles measured in smog chambers under both low-NOx and high-NOx conditions. Under low-NOx conditions, the model reproduces the transitional formation of hydroxy-hydroperoxides particles, which are photolyzed and lead to SOA mass decrease after reaching a maximum. Under high-NOx conditions, particles are assumed to be formed mostly from the photo-oxidation of a PAN-type molecule derived from methacrolein (MPAN). This model successfully reproduces the complex NOx-dependence of isoprene oxidation and suggests a possible yield increase under some high-NOx conditions. Experimental data correspond to dry conditions (RH<10%). However, particles formed from isoprene are expected to be highly hydrophilic, and isoprene oxidation products would likely partition between an aqueous phase and the gas phase at high humidity in the atmosphere. The model was extended to take into account the hydrophilic properties of SOA, which are relevant under atmospheric conditions, and investigate the effect of particulate liquid water on SOA formation. An important increase in SOA mass was estimated for atmospheric conditions due to the hydrophilic properties. Experiments should be conducted to confirm the results of this study, which have implications for SOA modeling.

scholarly journals Modeling secondary organic aerosol formation from isoprene oxidation under dry and humid conditions

2011 ◽  
Vol 11 (2) ◽  
pp. 893-909 ◽  
Author(s):  
F. Couvidat ◽  
C. Seigneur
Keyword(s):  
Experimental Data ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Organic Nitrates ◽  
Atmospheric Conditions ◽  
Aerosol Formation ◽  
Yield Increase ◽  
Isoprene Oxidation ◽  
Smog Chambers

Abstract. A new model for the formation of secondary organic aerosol (SOA) from isoprene was developed. This model uses surrogate molecular species (hydroxy-hydroperoxides, tetrols, methylglyceric acid, organic nitrates) to represent SOA formation. The development of this model used available experimental data on yields and molecular composition of SOA from isoprene and methacrolein oxidation. This model reproduces the amount of particles measured in smog chambers under both low-NOx and high-NOx conditions. Under low-NOx conditions, the model reproduces the transitional formation of hydroxy-hydroperoxides particles, which are photolyzed and lead to SOA mass decrease after reaching a maximum. Under high-NOx conditions, particles are assumed to be formed mostly from the photo-oxidation of a PAN-type molecule derived from methacrolein (MPAN). This model successfully reproduces the complex NOx-dependence of isoprene oxidation and suggests a possible yield increase under some high-NOx conditions. Experimental data correspond to dry conditions (RH < 10%). However, particles formed from isoprene are expected to be highly hydrophilic, and isoprene oxidation products would likely partition between an aqueous phase and the gas phase at high humidity in the atmosphere. The model was extended to take into account the hydrophilic properties of SOA, which are relevant under atmospheric conditions, and investigate the effect of particulate liquid water on SOA formation. An important increase in SOA mass was estimated for humid conditions due to the hydrophilic properties. Experiments under high relative humidity conditions should be conducted to confirm the results of this study, which have implications for SOA modeling.

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

2016 ◽  
Author(s):  
Yuemei Han ◽  
Craig A. Stroud ◽  
John Liggo ◽  
Shao-Meng Li
Keyword(s):  
Secondary Organic Aerosol ◽  
Chemical Properties ◽  
Organic Aerosol ◽  
Reaction Chamber ◽  
Oxidation Products ◽  
Strong Increase ◽  
Nitrate Content ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Aerosol Formation

Abstract. Secondary organic aerosol (SOA) formation from OH-initiated photooxidation of α-pinene has been investigated in a photochemical reaction chamber under varied particle acidity levels. The effect of particle acidity on SOA yield and chemical composition was examined under high- and low-NOx conditions. The SOA yield (4.0 %–7.3 %) increased nearly linearly with the increase in particle acidity under high-NOx conditions. In contrast, the SOA yield (27.9 %–35.6 %) 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 under high-NOx conditions, which is likely due to the inaccessibility of the acidity over time with the coating of α-pinene SOA. 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. The fraction of oxygen-containing organic fragments (CxHyO1+ 33–35 % and CxHyO2+ 16–17 %) in the total organics and the O/C ratio (0.49–0.54) of α-pinene SOA were lower under high-NOx conditions than those under low-NOx conditions (39–40 %, 17–19 %, and 0.60–0.62), 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. The results of this study suggest that inorganic acidity have a significant role to play in determining various organic aerosol chemical properties such as oxidation state, mass yields and organic nitrate content. It is also an important parameter in the modeling of SOA, which is further dependent on the time scale of SOA formation. Additional research is required to understand the complex physical and chemical interactions facilitated by aerosol acidity.

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 Secondary organic aerosol formation from in situ OH, O<sub>3</sub>, and NO<sub>3</sub> oxidation of ambient forest air in an oxidation flow reactor

2017 ◽  
Author(s):  
Brett B. Palm ◽  
Pedro Campuzano-Jost ◽  
Douglas A. Day ◽  
Amber M. Ortega ◽  
Juliane L. Fry ◽  
...  
Keyword(s):  
Mass Loss ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Organic Nitrates ◽  
Aerosol Formation ◽  
Wide Range ◽  
Synoptic Conditions

Abstract. Ambient pine forest air was oxidized by OH, O3, or NO3 radicals using an oxidation flow reactor (OFR) during the BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics &amp; Nitrogen–Rocky Mountain Biogenic Aerosol Study) campaign to study biogenic secondary organic aerosol (SOA) formation and organic aerosol (OA) aging. A wide range of equivalent atmospheric photochemical ages was sampled, from hours up to days (for O3 and NO3) or weeks (for OH). Ambient air processed by the OFR was typically sampled every 20–30 min, in order to determine how the availability of SOA precursor gases in ambient air changed with diurnal and synoptic conditions, for each of the three oxidants. More SOA was formed during nighttime than daytime for all three oxidants, indicating that SOA precursor concentrations were higher at night. At all times of day, OH oxidation led to approximately 4 times more SOA formation than either O3 or NO3 oxidation. This is likely because O3 and NO3 will only react with gases containing C=C bonds (e.g., terpenes) to form SOA, but won’t react appreciably with many of their oxidation products or any species in the gas phase that lacks a C=C bond (e.g., pinonic acid, alkanes). In contrast, OH can continue to react with compounds that lack C=C bonds to produce SOA. Closure was achieved between the amount of SOA formed from O3 and NO3 oxidation in the OFR and the SOA predicted to form from measured concentrations of ambient monoterpenes and sesquiterpenes using published chamber yields. This is in contrast to previous work at this site (Palm et al., 2016), which has shown that a source of SOA from semi- and intermediate-volatility organic compounds (S/IVOCs) 3.4 times larger than the source from measured VOCs is needed to explain the measured SOA formation from OH oxidation. This work suggests that those S/IVOCs typically do not contain C=C bonds. O3 and NO3 oxidation produced SOA with elemental O:C and H:C similar to the least oxidized OA observed in local ambient air, and neither oxidant led to net mass loss at the highest exposures, in contrast with OH oxidation. An OH exposure in the OFR equivalent to several hours of atmospheric aging also produced SOA with O:C and H:C values similar to ambient OA, while higher aging (days–weeks) led to formation of SOA with progressively higher O:C and lower H:C (and net mass loss at the highest exposures). NO3 oxidation led to the production of particulate organic nitrates (pRONO2), while OH and O3 oxidation (under low NO) did not, as expected. These measurements of SOA formation provide the first direct comparison of SOA formation potential and chemical evolution from OH, O3 and NO3 oxidation in the real atmosphere, and help to clarify the oxidation processes that lead to SOA formation from biogenic hydrocarbons.

scholarly journals Secondary organic aerosol formation from in situ OH, O<sub>3</sub>, and NO<sub>3</sub> oxidation of ambient forest air in an oxidation flow reactor

2017 ◽  
Vol 17 (8) ◽  
pp. 5331-5354 ◽  
Author(s):  
Brett B. Palm ◽  
Pedro Campuzano-Jost ◽  
Douglas A. Day ◽  
Amber M. Ortega ◽  
Juliane L. Fry ◽  
...  
Keyword(s):  
Mass Loss ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Organic Nitrates ◽  
Aerosol Formation ◽  
Wide Range ◽  
Synoptic Conditions

Abstract. Ambient pine forest air was oxidized by OH, O3, or NO3 radicals using an oxidation flow reactor (OFR) during the BEACHON-RoMBAS (Bio–hydro–atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen – Rocky Mountain Biogenic Aerosol Study) campaign to study biogenic secondary organic aerosol (SOA) formation and organic aerosol (OA) aging. A wide range of equivalent atmospheric photochemical ages was sampled, from hours up to days (for O3 and NO3) or weeks (for OH). Ambient air processed by the OFR was typically sampled every 20–30 min, in order to determine how the availability of SOA precursor gases in ambient air changed with diurnal and synoptic conditions, for each of the three oxidants. More SOA was formed during nighttime than daytime for all three oxidants, indicating that SOA precursor concentrations were higher at night. At all times of day, OH oxidation led to approximately 4 times more SOA formation than either O3 or NO3 oxidation. This is likely because O3 and NO3 will only react with gases containing C  =  C bonds (e.g., terpenes) to form SOA but will not react appreciably with many of their oxidation products or any species in the gas phase that lacks a C  =  C bond (e.g., pinonic acid, alkanes). In contrast, OH can continue to react with compounds that lack C  =  C bonds to produce SOA. Closure was achieved between the amount of SOA formed from O3 and NO3 oxidation in the OFR and the SOA predicted to form from measured concentrations of ambient monoterpenes and sesquiterpenes using published chamber yields. This is in contrast to previous work at this site (Palm et al., 2016), which has shown that a source of SOA from semi- and intermediate-volatility organic compounds (S/IVOCs) 3.4 times larger than the source from measured VOCs is needed to explain the measured SOA formation from OH oxidation. This work suggests that those S/IVOCs typically do not contain C  =  C bonds. O3 and NO3 oxidation produced SOA with elemental O : C and H : C similar to the least-oxidized OA observed in local ambient air, and neither oxidant led to net mass loss at the highest exposures, in contrast to OH oxidation. An OH exposure in the OFR equivalent to several hours of atmospheric aging also produced SOA with O : C and H : C values similar to ambient OA, while higher aging (days–weeks) led to formation of SOA with progressively higher O : C and lower H : C (and net mass loss at the highest exposures). NO3 oxidation led to the production of particulate organic nitrates (pRONO2), while OH and O3 oxidation (under low NO) did not, as expected. These measurements of SOA formation provide the first direct comparison of SOA formation potential and chemical evolution from OH, O3, and NO3 oxidation in the real atmosphere and help to clarify the oxidation processes that lead to SOA formation from biogenic hydrocarbons.

scholarly journals Contributions of individual reactive biogenic volatile organic compounds to organic nitrates above a mixed forest

2012 ◽  
Vol 12 (7) ◽  
pp. 17031-17086 ◽  
Author(s):  
K. A. Pratt ◽  
L. H. Mielke ◽  
P. B. Shepson ◽  
A. M. Bryan ◽  
A. L. Steiner ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Secondary Organic Aerosol ◽  
Mixed Forest ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Organic Nitrates ◽  
Aerosol Formation ◽  
Biogenic Volatile Organic Compounds ◽  
Volatile Organic

Abstract. Biogenic volatile organic compounds (BVOCs) can react in the atmosphere to form organic nitrates, which serve as NOx (NO + NO2) reservoirs, impacting ozone and secondary organic aerosol production, the oxidative capacity of the atmosphere, and nitrogen availability to ecosystems. To examine the contributions of biogenic emissions and the formation and fate of organic nitrates in a forest environment, we simulated the oxidation of 57 individual BVOCs emitted from a rural mixed forest in Northern Michigan. Of the total simulated organic nitrates, monoterpenes contributed ~70% in the early morning at ~12 m above the forest canopy when isoprene emissions were low. In the afternoon, when vertical mixing and isoprene nitrate production were highest, the simulated contribution of isoprene-derived organic nitrates was greater than 90% at all altitudes, with the concentration of secondary isoprene nitrates increasing with altitude. Key BVOC-oxidant reactions were identified for future laboratory and field investigations into reaction rate constants, yields, and speciation of oxidation products. Forest succession, wherein aspen trees are being replaced by pine and maple trees, was predicted to lead to increased afternoon concentrations of monoterpene-derived organic nitrates. This further underscores the need to understand the formation and fate of these species, which have different chemical pathways and oxidation products compared to isoprene-derived organic nitrates and can lead to secondary organic aerosol formation.

scholarly journals Exploration of oxidative chemistry and secondary organic aerosol formation in the Amazon during the wet season: explicit modeling of the Manaus urban plume with GECKO-A

2020 ◽  
Vol 20 (10) ◽  
pp. 5995-6014 ◽  
Author(s):  
Camille Mouchel-Vallon ◽  
Julia Lee-Taylor ◽  
Alma Hodzic ◽  
Paulo Artaxo ◽  
Bernard Aumont ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Background Level ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Box Model ◽  
Basis Set ◽  
Aerosol Formation ◽  
Wet Season ◽  
Urban Plume ◽  
The Impact

Abstract. The GoAmazon 2014/5 field campaign took place in Manaus, Brazil, and allowed the investigation of the interaction between background-level biogenic air masses and anthropogenic plumes. We present in this work a box model built to simulate the impact of urban chemistry on biogenic secondary organic aerosol (SOA) formation and composition. An organic chemistry mechanism is generated with the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) to simulate the explicit oxidation of biogenic and anthropogenic compounds. A parameterization is also included to account for the reactive uptake of isoprene oxidation products on aqueous particles. The biogenic emissions estimated from existing emission inventories had to be reduced to match measurements. The model is able to reproduce ozone and NOx for clean and polluted situations. The explicit model is able to reproduce background case SOA mass concentrations but does not capture the enhancement observed in the urban plume. The oxidation of biogenic compounds is the major contributor to SOA mass. A volatility basis set (VBS) parameterization applied to the same cases obtains better results than GECKO-A for predicting SOA mass in the box model. The explicit mechanism may be missing SOA-formation processes related to the oxidation of monoterpenes that could be implicitly accounted for in the VBS parameterization.

scholarly journals Secondary Organic Aerosol Formation Enhanced by Organic Seeds of Similar Polarity at Atmospherically Relative Humidity

2015 ◽  
Vol 1 (2) ◽  
pp. 6-10 ◽  
Author(s):  
Catherine A. Gordon ◽  
Jianhuai Ye ◽  
Arthur W.H. Chan
Keyword(s):  
Climate Models ◽  
Secondary Organic Aerosol ◽  
Phase Particle ◽  
Organic Aerosol ◽  
Atmospheric Particulate Matter ◽  
Oxidation Products ◽  
Tetraethylene Glycol ◽  
Aerosol Formation ◽  
Volatile Oxidation Products ◽  
Low Humidity

Secondary Organic Aerosol (SOA) forms in the atmosphere when semi-volatile oxidation products from biogenic and anthropogenic hydrocarbons condense onto atmospheric particulate matter. Climate models assume that oxidation products and preexisting organic aerosol form a well-mixed particle and enhance condensation, and, as a result, predict that future increases in anthropogenic primary organic aerosol (POA) will cause a significant increase in SOA. However, recent experiments performed at low humidity (<10%) demonstrate a single-phase particle does not always form, challenging the validity of model assumptions. In this work, we investigate the formation of SOA at atmospherically relevant humidities (55 - 65%) and examine this mixing assumption. We hypothesized that humidity leads to decreased viscosity and shorter mixing timescales, which is favorable for aerosol mixing. Here, α-pinene, a biogenic volatile organic compound is oxidized with ozone in a flow tube reactor in the presence of different organic aerosol seeds. Increased humidity did not enhance SOA formation with erythritol or squalane seed as hypothesized, implying that these compounds do not mix with α-pinene SOA in the range of humidities studied (55 – 65%). Yield enhancements were observed with tetraethylene glycol seed, demonstrating interaction between the SOA and seed. These observations suggest increased humidity does not promote mixing between the oxidation products and POA and highlight the need to fully understand the aerosol phase state in the atmosphere in order to better parameterize SOA formation and accurately predict future changes in air quality.

scholarly journals Isoprene oxidation by nitrate radical: alkyl nitrate and secondary organic aerosol yields

2009 ◽  
Vol 9 (2) ◽  
pp. 8857-8902 ◽  
Author(s):  
A. W. Rollins ◽  
A. Kiendler-Scharr ◽  
J. Fry ◽  
T. Brauers ◽  
S. S. Brown ◽  
...  
Keyword(s):  
First Generation ◽  
Secondary Organic Aerosol ◽  
Model Simulation ◽  
Effective Rate Constant ◽  
Organic Aerosol ◽  
Effective Rate ◽  
Oxidation Products ◽  
Alkyl Nitrates ◽  
Alkyl Nitrate ◽  
Isoprene Oxidation

Abstract. Alkyl nitrates and secondary organic aerosol (SOA) produced during the oxidation of isoprene by nitrate radicals has been observed in the SAPHIR chamber. We find the yield of nitrates is 70±8% from the isoprene+NO3 reaction, and the yield for secondary dinitrates produced in the reaction of primary isoprene nitrates with NO3 is 40±20%. We find an effective rate constant for reaction of NO3 with the group of first generation oxidation products to be 7×10−14 cm3 s−1. At the low total organic aerosol concentration in the chamber (max ≈0.6 μg m−3) we observed a mass yield (ΔSOA mass/Δisoprene mass) of 2% for the entire 16 h experiment. However a comparison of the timing of the observed SOA production to a box model simulation of first and second generation oxidation products shows that the yield from the first generation products was <0.2% while the further oxidation of the initial products leads to a yield of 10% (defined as ΔSOA/Δisoprene2x where Δisoprene2x is the mass of isoprene which reacted twice with NO3). The SOA yield of 10% is consistent with equilibrium partitioning of highly functionalized C5 products of isoprene oxidation.

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