scholarly journals Terpenes and their oxidation products in the French Landes forest: insight from Vocus PTR-TOF measurements

2019 ◽  
Author(s):  
Haiyan Li ◽  
Matthieu Riva ◽  
Pekka Rantala ◽  
Liine Heikkinen ◽  
Kaspar Daellenbach ◽  
...  
Keyword(s):  
Gas Phase ◽  
Detection Efficiency ◽  
Ambient Air ◽  
Reaction Rates ◽  
Early Morning ◽  
Oxidation Products ◽  
Atmospheric Oxidation ◽  
Organic Nitrates ◽  
Reaction Products ◽  
Wide Range

Abstract. The capabilities of the recently developed Vocus proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF) are reported for the first time based on ambient measurements. With the deployment of the Vocus PTR-TOF, we present an overview of the observed gas-phase (oxygenated) molecules in the French Landes forest during summertime 2018 and gain insights into the atmospheric oxidation of terpenes, which are emitted in large quantities in the atmosphere and play important roles in secondary organic aerosol production. Due to the greatly improved detection efficiency compared to traditional PTR instruments, the Vocus PTR-TOF identifies a large amount of gas-phase signals with elemental composition categories including CH, CHO, CHN, CHS, CHON, CHOS, and others. Multiple hydrocarbons are detected, with carbon numbers up to 20. Particularly, we report the first direct observations of low-volatility diterpenes in the ambient air. The diurnal cycle of diterpenes is similar to that of monoterpenes and sesquiterpenes, but contrary to that of isoprene. Various types of terpene reaction products and intermediates are also characterized. Generally, the more oxidized products from terpene oxidations show a broad peak in the day due to the strong photochemical effects, while the less oxygenated products peak in the early morning and/or in the evening. To evaluate the importance of different formation pathways in terpene chemistry, the reaction rates of terpenes with main oxidants (i.e., hydroxyl radical, OH; ozone, O3; and nitrate radical, NO3) are calculated. For the less oxidized non-nitrate monoterpene oxidation products, their morning peaks likely have contributions from both O3- and OH-initiated monoterpene oxidation. Due to the decreased OH concentration at night, monoterpene ozonolysis becomes more important in the evening. For the monoterpene-derived organic nitrates, oxidations by O3, OH, and NO3 radicals all contribute to their formation, with their relative roles varying considerably over the course of the day. Through a detailed analysis of terpene chemistry, this study demonstrates the capability of the Vocus PTR-TOF in the detection of a wide range of oxidized reaction products in ambient and remote conditions, which highlights its importance in investigating atmospheric oxidation processes.

scholarly journals Terpenes and their oxidation products in the French Landes forest: insights from Vocus PTR-TOF measurements

2020 ◽  
Vol 20 (4) ◽  
pp. 1941-1959 ◽  
Author(s):  
Haiyan Li ◽  
Matthieu Riva ◽  
Pekka Rantala ◽  
Liine Heikkinen ◽  
Kaspar Daellenbach ◽  
...  
Keyword(s):  
Gas Phase ◽  
Detection Efficiency ◽  
Ambient Air ◽  
Reaction Rates ◽  
Early Morning ◽  
Oxidation Products ◽  
Atmospheric Oxidation ◽  
Organic Nitrates ◽  
Reaction Products ◽  
Wide Range

Abstract. The capabilities of the recently developed Vocus proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF) are reported for the first time based on ambient measurements. With the deployment of the Vocus PTR-TOF, we present an overview of the observed gas-phase (oxygenated) molecules in the French Landes forest during summertime 2018 and gain insights into the atmospheric oxidation of terpenes, which are emitted in large quantities in the atmosphere and play important roles in secondary organic aerosol production. Due to the greatly improved detection efficiency compared to conventional PTR instruments, the Vocus PTR-TOF identifies a large number of gas-phase signals with elemental composition categories including CH, CHO, CHN, CHS, CHON, CHOS, and others. Multiple hydrocarbons are detected, with carbon numbers up to 20. Particularly, we report the first direct observations of low-volatility diterpenes in the ambient air. The diurnal cycle of diterpenes is similar to that of monoterpenes and sesquiterpenes but contrary to that of isoprene. Various types of terpene reaction products and intermediates are also characterized. Generally, the more oxidized products from terpene oxidations show a broad peak in the day due to the strong photochemical effects, while the less oxygenated products peak in the early morning and/or in the evening. To evaluate the importance of different formation pathways in terpene chemistry, the reaction rates of terpenes with main oxidants (i.e., hydroxyl radical, OH; ozone, O3; and nitrate radical, NO3) are calculated. For the less oxidized non-nitrate monoterpene oxidation products, their morning and evening peaks have contributions from both O3- and OH-initiated monoterpene oxidation. For the monoterpene-derived organic nitrates, oxidations by O3, OH, and NO3 radicals all contribute to their formation, with their relative roles varying considerably over the course of the day. Through a detailed analysis of terpene chemistry, this study demonstrates the capability of the Vocus PTR-TOF in the detection of a wide range of oxidized reaction products in ambient and remote conditions, which highlights its importance in investigating atmospheric oxidation processes.

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 Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach

2005 ◽  
Vol 5 (9) ◽  
pp. 2497-2517 ◽  
Author(s):  
B. Aumont ◽  
S. Szopa ◽  
S. Madronich
Keyword(s):  
Organic Carbon ◽  
Gas Phase ◽  
Organic Compounds ◽  
Parent Compound ◽  
Oxidation Products ◽  
Gradual Change ◽  
Reaction Products ◽  
Test Species ◽  
Lack Of Information ◽  
Data Processing Tool

Abstract. Organic compounds emitted in the atmosphere are oxidized in complex reaction sequences that produce a myriad of intermediates. Although the cumulative importance of these organic intermediates is widely acknowledged, there is still a critical lack of information concerning the detailed composition of the highly functionalized secondary organics in the gas and condensed phases. The evaluation of their impacts on pollution episodes, climate, and the tropospheric oxidizing capacity requires modelling tools that track the identity and reactivity of organic carbon in the various phases down to the ultimate oxidation products, CO and CO2. However, a fully detailed representation of the atmospheric transformations of organic compounds involves a very large number of intermediate species, far in excess of the number that can be reasonably written manually. This paper describes (1) the development of a data processing tool to generate the explicit gas-phase oxidation schemes of acyclic hydrocarbons and their oxidation products under tropospheric conditions and (2) the protocol used to select the reaction products and the rate constants. Results are presented using the fully explicit oxidation schemes generated for two test species: n-heptane and isoprene. Comparisons with well-established mechanisms were performed to evaluate these generated schemes. Some preliminary results describing the gradual change of organic carbon during the oxidation of a given parent compound are presented.

scholarly journals Technical Note: Synthesis of isoprene atmospheric oxidation products: isomeric epoxydiols and the rearrangement products <i>cis</i>- and <i>trans</i>-3-methyl-3,4-dihydroxytetrahydrofuran

2012 ◽  
Vol 12 (6) ◽  
pp. 14247-14268
Author(s):  
Z. Zhang ◽  
Y.-H. Lin ◽  
H. Zhang ◽  
J. D. Surratt ◽  
L. M. Ball ◽  
...  
Keyword(s):  
Air Quality ◽  
Gas Phase ◽  
Good Yield ◽  
Organic Aerosols ◽  
Technical Note ◽  
Oxidation Products ◽  
Atmospheric Oxidation ◽  
Aerosol Formation ◽  
Cis And Trans ◽  
Oxidation Mechanisms

Abstract. Isoprene epoxydiol (IEPOX) isomers are key gas-phase intermediates of isoprene atmospheric oxidation. Secondary organic aerosols derived from such intermediates have important impacts on air quality and health. We report here convergent and unambiguous pathways developed for the synthesis of isomeric IEPOX species and the rearrangement products cis- and trans-3-methyl-3,4-dihydroxytetrahydrofuran in good yield. The availability of such compounds is necessary to expedite research on isoprene atmospheric oxidation mechanisms and subsequent aerosol formation as well as the toxicological properties of the aerosols.

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.

Nighttime to daytime transition of the oxidation products of isoprene by NO3 radicals

2020 ◽  
Author(s):  
Epameinondas Tsiligiannis ◽  
Rongrong Wu ◽  
Sungah Kang ◽  
Luisa Hantschke ◽  
Joel Thornton ◽  
...  
Keyword(s):  
Gas Phase ◽  
Oxidation Products ◽  
Ionization Mass ◽  
Mass Spectrometers ◽  
Time Profiles ◽  
Compound C ◽  
Wide Range ◽  
Series Of Experiments ◽  
Seed Aerosol

&lt;p&gt;Biogenic volatile organic compounds (BVOC) dominate the overall VOC emissions. Isoprene is the most common BVOC emitted from vegetation, accounting up to 50% of the total BVOC emissions. Despite being emitted in daytime it can accumulate in the stratified nocturnal layer. Thus, the oxidation of isoprene by nitrate radicals (NO&lt;sub&gt;3&lt;/sub&gt;) may be of high importance. A series of experiments were conducted in the atmospheric simulation chamber SAPHIR in J&amp;#252;lich, Germany, in order to investigate the gas and particle phase products of the oxidation of isoprene by NO&lt;sub&gt;3&lt;/sub&gt;, under a variety of conditions (e.g. high RO&lt;sub&gt;2&lt;/sub&gt;, high HO&lt;sub&gt;2&lt;/sub&gt;, nighttime to daytime transition, with and without seed aerosol) using a wide range of instrumentation. However, herein the focus is on the results of gas-phase product characterisation using high resolution time of flight chemical ionization mass spectrometers (HR-ToF-CIMS) using iodide or bromide as the primary reagent ion. The use of two HR-ToF-CIMS with different primary reagents provides possibilities to scrutinise the time profiles of isomers of selected products.&lt;/p&gt;&lt;p&gt;We will discuss qualitatively and quantitatively how the distribution of oxidation products change under different conditions, with a focus on the nighttime daytime transition of the major products and the role of subsequent OH oxidation on the products initially formed by NO&lt;sub&gt;3&lt;/sub&gt; oxidation. Generally, the dominant gas phase products include compounds like nitrooxy hydroperoxide (INP) &amp; dihydroxy nitrate (IDHN) (C&lt;sub&gt;5&lt;/sub&gt;H&lt;sub&gt;9&lt;/sub&gt;NO&lt;sub&gt;5&lt;/sub&gt;), carbonyl nitrate (ICN) (C&lt;sub&gt;5&lt;/sub&gt;H&lt;sub&gt;7&lt;/sub&gt;NO&lt;sub&gt;5&lt;/sub&gt;), hydroxy nitrate (IHN) (C&lt;sub&gt;5&lt;/sub&gt;H&lt;sub&gt;9&lt;/sub&gt;NO&lt;sub&gt;4&lt;/sub&gt;), hydroxy hydroperoxy nitrate (IHPN) (C&lt;sub&gt;5&lt;/sub&gt;H&lt;sub&gt;9&lt;/sub&gt;NO&lt;sub&gt;6&lt;/sub&gt;), as well as a C&lt;sub&gt;4&lt;/sub&gt; compound (C&lt;sub&gt;4&lt;/sub&gt;H&lt;sub&gt;7&lt;/sub&gt;NO&lt;sub&gt;5&lt;/sub&gt;) among others.&lt;/p&gt;

scholarly journals Technical Note: Synthesis of isoprene atmospheric oxidation products: isomeric epoxydiols and the rearrangement products <i>cis</i>- and <i>trans</i>-3-methyl-3,4-dihydroxytetrahydrofuran

2012 ◽  
Vol 12 (18) ◽  
pp. 8529-8535 ◽  
Author(s):  
Z. Zhang ◽  
Y.-H. Lin ◽  
H. Zhang ◽  
J. D. Surratt ◽  
L. M. Ball ◽  
...  
Keyword(s):  
Air Quality ◽  
Gas Phase ◽  
Good Yield ◽  
Organic Aerosols ◽  
Technical Note ◽  
Oxidation Products ◽  
Atmospheric Oxidation ◽  
Aerosol Formation ◽  
Cis And Trans ◽  
Oxidation Mechanisms

Abstract. Isoprene epoxydiol (IEPOX) isomers are key gas-phase intermediates of isoprene atmospheric oxidation. Secondary organic aerosols derived from such intermediates have important impacts on air quality and health. We report here convergent and unambiguous pathways developed for the synthesis of isomeric IEPOX species and the rearrangement products cis- and trans-3-methyl-3,4-dihydroxytetrahydrofuran in good yield. The availability of such compounds is necessary to expedite research on isoprene atmospheric oxidation mechanisms and subsequent aerosol formation as well as the toxicological properties of the aerosols.

scholarly journals Chemical composition of nanoparticles from α-pinene nucleation and the influence of isoprene and relative humidity at low temperature

2021 ◽  
Author(s):  
Lucía Caudillo ◽  
Birte Rörup ◽  
Martin Heinritzi ◽  
Guillaume Marie ◽  
Mario Simon ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Relative Humidity ◽  
Gas Phase ◽  
Particle Formation ◽  
Oxidation Products ◽  
Mixed System ◽  
Chemical Information ◽  
New Particle Formation ◽  
Detection Scheme ◽  
Wide Range

Abstract. New Particle Formation (NPF) from biogenic organic precursors is an important atmospheric process. One of the major species is α-pinene, which upon oxidation, can form a suite of products covering a wide range of volatilities. A fraction of the oxidation products is termed Highly Oxygenated Organic Molecules (HOM). These play a crucial role for nucleation and the formation of Secondary Organic Aerosol (SOA). However, measuring the composition of newly formed particles is challenging due to their very small mass. Here, we present results on the gas and particle phase chemical composition for a system where α-pinene was oxidized by ozone, and for a mixed system of α-pinene and isoprene, respectively. The measurements took place at the CERN Cosmics Leaving Outdoor Droplets (CLOUD) chamber at temperatures between −50 °C and −30 °C and at low and high relative humidity (20 % and 60 to 100 % RH). These conditions were chosen to simulate pure biogenic new particle formation in the upper free troposphere. The particle chemical composition was analyzed by the Thermal Desorption-Differential Mobility Analyzer (TD-DMA) coupled to a nitrate chemical ionization time-of-flight mass spectrometer. This instrument can be used for particle and gas phase measurements using the same ionization and detection scheme. Our measurements revealed the presence of C8-10 monomers and C18-20 dimers as the major compounds in the particles (diameter up to ~ 100 nm). Particularly, for the system with isoprene added, C5 (C5H10O5-7) and C15 compounds (C15H24O5-10) are detected. This observation is consistent with the previously observed formation of such compounds in the gas phase. However, although the C5 and C15 compounds do not easily nucleate, our measurements indicate that they can still contribute to the particle growth at free tropospheric conditions. For the experiments reported here, most likely isoprene might enhance growth at particle sizes larger than 15 nm. Besides the chemical information regarding the HOM formation for the α-pinene (plus isoprene) system, we report on the nucleation rates measured at 1.7 nm and found that the lower J1.7nm values compared with previous studies are very likely due to the higher α-pinene and ozone mixing ratios used in the present study

scholarly journals Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach

2005 ◽  
Vol 5 (1) ◽  
pp. 703-754 ◽  
Author(s):  
B. Aumont ◽  
S. Szopa ◽  
S. Madronich
Keyword(s):  
Organic Carbon ◽  
Gas Phase ◽  
Organic Compounds ◽  
Parent Compound ◽  
Oxidation Products ◽  
Gradual Change ◽  
Reaction Products ◽  
Test Species ◽  
Lack Of Information ◽  
Data Processing Tool

Abstract. Organic compounds emitted in the atmosphere are oxidized in complex reaction sequences that produce a myriad of intermediates. Although the cumulative importance of these organic intermediates is widely acknowledged, there is still a critical lack of information concerning the detailed composition of the highly functionalized secondary organics in the gas and condensed phases. The evaluation of their impacts on pollution episodes, climate, and the tropospheric oxidizing capacity requires modelling tools that track the identity and reactivity of organic carbon in the various phases down to the ultimate oxidation products, CO and CO2. However, a fully detailed representation of the atmospheric transformations of organic compounds involves a very large number of intermediate species, far in excess of the number that can be reasonably written manually. This paper describes (1) the development of a data processing tool to generate the explicit gas-phase oxidation schemes of organic compounds under tropospheric conditions and (2) the protocol used to select the reaction products and the rate constants. Results are presented using the fully explicit oxidation schemes generated for two test species: n-heptane and isoprene. Comparisons with well-established mechanisms were performed to evaluate these generated schemes. Some preliminary results describing the gradual change of organic carbon during the oxidation of a given parent compound are presented.

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