Evaluation of detailed aromatic mechanisms (MCMv3 and MCMv3.1) against environmental chamber data

Abstract. A high quality dataset on the photo-oxidation of benzene, toluene, p-xylene and 1,3,5-trimethylbenzene has been obtained from experiments in the European Photoreactor (EUPHORE), a large outdoor environmental reaction chamber. The experiments were designed to test sensitive features of detailed aromatic mechanisms, and the dataset has been used to evaluate the performance of the Master Chemical Mechanism Version 3 (MCMv3). An updated version (MCMv3.1) was constructed based on recent experimental data, and details of its development are described in a companion paper. The MCMv3.1 aromatic mechanisms have also been evaluated using the EUPHORE dataset. Significant deficiencies have been identified in the mechanisms, in particular: 1) an over-estimation of the ozone concentration, 2) an under-estimation of the NO oxidation rate, 3) an under-estimation of OH. The use of MCMv3.1 improves the model-measurement agreement in some areas but significant discrepancies remain.

Download Full-text

Development of a detailed chemical mechanism (MCMv3.1) for the atmospheric oxidation of aromatic hydrocarbons

Atmospheric Chemistry and Physics ◽

10.5194/acp-5-641-2005 ◽

2005 ◽

Vol 5 (3) ◽

pp. 641-664 ◽

Cited By ~ 297

Author(s):

C. Bloss ◽

V. Wagner ◽

M. E. Jenkin ◽

R. Volkamer ◽

W. J. Bloss ◽

...

Keyword(s):

First Generation ◽

Companion Paper ◽

Chemical Mechanism ◽

Degradation Mechanisms ◽

Photo Oxidation ◽

New Information ◽

Benzene Toluene ◽

Master Chemical Mechanism ◽

Using Data ◽

High Yields

Abstract. The Master Chemical Mechanism has been updated from MCMv3 to MCMv3.1 in order to take into account recent improvements in the understanding of aromatic photo-oxidation. Newly available kinetic and product data from the literature have been incorporated into the mechanism. In particular, the degradation mechanisms for hydroxyarenes have been revised following the observation of high yields of ring-retained products, and product studies of aromatic oxidation under relatively low NOx conditions have provided new information on the branching ratios to first generation products. Experiments have been carried out at the European Photoreactor (EUPHORE) to investigate key subsets of the toluene system. These results have been used to test our understanding of toluene oxidation, and, where possible, refine the degradation mechanisms. The evaluation of MCMv3 and MCMv3.1 using data on benzene, toluene, p-xylene and 1,3,5-trimethylbenzene photosmog systems is described in a companion paper, and significant model shortcomings are identified. Ideas for additional modifications to the mechanisms, and for future experiments to further our knowledge of the details of aromatic photo-oxidation are discussed.

Download Full-text

Development of a detailed chemical mechanism (MCMv3.1) for the atmospheric oxidation of aromatic hydrocarbons

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-4-5733-2004 ◽

2004 ◽

Vol 4 (5) ◽

pp. 5733-5788 ◽

Cited By ~ 7

Author(s):

C. Bloss ◽

V. Wagner ◽

M. E. Jenkin ◽

R. Volkamer ◽

W. J. Bloss ◽

...

Keyword(s):

First Generation ◽

Companion Paper ◽

Chemical Mechanism ◽

Degradation Mechanisms ◽

Photo Oxidation ◽

New Information ◽

Benzene Toluene ◽

Master Chemical Mechanism ◽

Using Data ◽

High Yields

Abstract. The Master Chemical Mechanism has been updated from MCMv3 to MCMv3.1 in order to take into account recent improvements in the understanding of aromatic photo-oxidation. Newly available kinetic and product data from the literature has been incorporated into the mechanism. In particular, the degradation mechanisms for hydroxyarenes have been revised following the observation of high yields of ring-retained products, and product studies of aromatic oxidation under relatively low NOx conditions have provided new information on the branching ratios to first generation products. Experiments have been carried out at the European Photoreactor (EUPHORE) to investigate key subsets of the toluene system. These results have been used to test our understanding of toluene oxidation, and where possible, refine the degradation mechanisms. The evaluation of MCMv3 and MCMv3.1 using data on benzene, toluene, p-xylene and 1,3,5-trimethylbenzene photosmog systems is described in a companion paper, and significant model shortcomings are identified. Ideas for additional modifications to the mechanisms, and for future experiments to further our knowledge of the details of aromatic photo-oxidation are discussed.

Download Full-text

Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part A): tropospheric degradation of non-aromatic volatile organic compounds

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-2-1847-2002 ◽

2002 ◽

Vol 2 (6) ◽

pp. 1847-1903 ◽

Cited By ~ 2

Author(s):

S. M. Saunders ◽

M. E. Jenkin ◽

R. G. Derwent ◽

M. J. Pilling

Keyword(s):

Volatile Organic Compounds ◽

Organic Compounds ◽

Good Description ◽

Field Studies ◽

Companion Paper ◽

Chemical Mechanism ◽

North West ◽

Radical Intermediates ◽

Volatile Organic ◽

Master Chemical Mechanism

Abstract. Kinetic and mechanistic data relevant to the tropospheric degradation of volatile organic compounds (VOC), and the production of secondary pollutants, have previously been used to define a protocol which underpinned the construction of a near-explicit Master Chemical Mechanism. In this paper, an update to the previous protocol is presented, which has been used to define degradation schemes for 107 non-aromatic VOC as part of version 3 of the Master Chemical Mechanism (MCM v3). The treatment of 18 aromatic VOC is described in a companion paper. The protocol is divided into a series of subsections describing initiation reactions, the reactions of the radical intermediates and the further degradation of first and subsequent generation products. Emphasis is placed on updating the previous information, and outlining the methodology which is specifically applicable to VOC not considered previously (e.g. a- and b-pinene). The present protocol aims to take into consideration work available in the open literature up to the beginning of 2001, and some other studies known by the authors which were under review at the time. Application of MCM v3 in appropriate box models indicates that the representation of isoprene degradation provides a good description of the speciated distribution of oxygenated organic products observed in reported field studies where isoprene was the dominant emitted hydrocarbon, and that the a-pinene degradation chemistry provides a good description of the time dependence of key gas phase species in a-pinene/NOX photo-oxidation experiments carried out in the European Photoreactor (EUPHORE). Photochemical Ozone Creation Potentials (POCP) have been calculated for the 106 non-aromatic non-methane VOC in MCM v3 for idealised conditions appropriate to north-west Europe, using a photochemical trajectory model. The POCP values provide a measure of the relative ozone forming abilities of the VOC. Where applicable, the values are compared with those calculated with previous versions of the MCM.

Download Full-text

Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part B): tropospheric degradation of aromatic volatile organic compounds

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-2-1905-2002 ◽

2002 ◽

Vol 2 (6) ◽

pp. 1905-1938 ◽

Cited By ~ 2

Author(s):

M. E. Jenkin ◽

S. M. Saunders ◽

V. Wagner ◽

M. J. Pilling

Keyword(s):

Volatile Organic Compounds ◽

Organic Compounds ◽

First Generation ◽

Companion Paper ◽

Chemical Mechanism ◽

Subsequent Generation ◽

North West ◽

Volatile Organic ◽

Master Chemical Mechanism ◽

Photochemical Ozone

Abstract. Kinetic and mechanistic data relevant to the tropospheric degradation of aromatic volatile organic compounds (VOC) have been used to define a mechanism development protocol, which has been used to construct degradation schemes for 18 aromatic VOC as part of version 3 of the Master Chemical Mechanism (MCM v3). This is complementary to the treatment of 107 non-aromatic VOC, presented in a companion paper. The protocol is divided into a series of subsections describing initiation reactions, the degradation chemistry to first generation products via a number of competitive routes, and the further degradation of first and subsequent generation products. Emphasis is placed on describing where the treatment differs from that applied to the non-aromatic VOC. The protocol is based on work available in the open literature up to the beginning of 2001, and some other studies known by the authors which were under review at the time. Photochemical Ozone Creation Potentials (POCP) have been calculated for the 18 aromatic VOC in MCM v3 for idealised conditions appropriate to north-west Europe, using a photochemical trajectory model. The POCP values provide a measure of the relative ozone forming abilities of the VOC. These show distinct differences from POCP values calculated previously for the aromatics, using earlier versions of the MCM, and reasons for these differences are discussed.

Download Full-text

Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part B): tropospheric degradation of aromatic volatile organic compounds

Atmospheric Chemistry and Physics ◽

10.5194/acp-3-181-2003 ◽

2003 ◽

Vol 3 (1) ◽

pp. 181-193 ◽

Cited By ~ 423

Author(s):

M. E. Jenkin ◽

S. M. Saunders ◽

V. Wagner ◽

M. J. Pilling

Keyword(s):

Volatile Organic Compounds ◽

Organic Compounds ◽

First Generation ◽

Companion Paper ◽

Chemical Mechanism ◽

Subsequent Generation ◽

North West ◽

Volatile Organic ◽

Master Chemical Mechanism ◽

Photochemical Ozone

Abstract. Kinetic and mechanistic data relevant to the tropospheric degradation of aromatic volatile organic compounds (VOC) have been used to define a mechanism development protocol, which has been used to construct degradation schemes for 18 aromatic VOC as part of version 3 of the Master Chemical Mechanism (MCM v3). This is complementary to the treatment of 107 non-aromatic VOC, presented in a companion paper. The protocol is divided into a series of subsections describing initiation reactions, the degradation chemistry to first generation products via a number of competitive routes, and the further degradation of first and subsequent generation products. Emphasis is placed on describing where the treatment differs from that applied to the non-aromatic VOC. The protocol is based on work available in the open literature up to the beginning of 2001, and some other studies known by the authors which were under review at the time. Photochemical Ozone Creation Potentials (POCP) have been calculated for the 18 aromatic VOC in MCM v3 for idealised conditions appropriate to north-west Europe, using a photochemical trajectory model. The POCP values provide a measure of the relative ozone forming abilities of the VOC. These show distinct differences from POCP values calculated previously for the aromatics, using earlier versions of the MCM, and reasons for these differences are discussed.

Download Full-text

Measurements of photo-oxidation products from the reaction of a series of alkyl-benzenes with hydroxyl radicals during EXACT using comprehensive gas chromatography

Atmospheric Chemistry and Physics ◽

10.5194/acp-3-1999-2003 ◽

2003 ◽

Vol 3 (6) ◽

pp. 1999-2014 ◽

Cited By ~ 33

Author(s):

J. F. Hamilton ◽

A. C. Lewis ◽

C. Bloss ◽

V. Wagner ◽

A. P. Henderson ◽

...

Keyword(s):

Gas Chromatography ◽

Hydroxyl Radicals ◽

Reaction Chamber ◽

Oxidation Products ◽

Chemical Mechanism ◽

Photo Oxidation ◽

Trimethyl Benzene ◽

Benzene Toluene ◽

Citraconic Anhydride ◽

Alkyl Benzenes

Abstract. Photo-oxidation products from the reaction of a series of alkyl-benzenes, (benzene, toluene, p-xylene and 1,3,5-trimethyl-benzene) with hydroxyl radicals in the presence of NOx have been investigated using comprehensive gas chromatography (GCxGC). A GCxGC system has been developed which utilises valve modulation and independent separations as a function of both volatility and polarity. A number of carbonyl-type compounds were identified during a series of reactions carried out at the European Photoreactor (EUPHORE), a large volume outdoor reaction chamber in Valencia, Spain. Experiments were carried as part of the EXACT project (Effects of the oXidation of Aromatic Compounds in the Troposphere). Two litre chamber air samples were cryo-focused, with a sampling frequency of 30 minutes, allowing the evolution of species to be followed over oxidation periods of 3-6 hours. To facilitate product identification, several carbonyl compounds, which were possible products of the photo-oxidation, were synthesised and used as reference standards. For toluene reactions, observed oxygenated intermediates found included the co-eluting pair a-angelicalactone/4-oxo-2-pentenal, maleic anhydride, citraconic anhydride, benzaldehyde and p-methyl benzoquinone. In the p-xylene experiment, the products identified were E/Z-hex-3-en-2,5-dione and citraconic anhydride. For 1,3,5-TMB reactions, the products identified were 3,5-dimethylbenzaldehyde, 3,5-dimethyl-3H-furan-2-one and 3-methyl-5-methylene-5H-furan-2-one. Preliminary quantification was carried out on identified compounds using liquid standards. Comparison of FTIR and GCxGC for the measurement of the parent aromatics generally showed good agreement. Comparison of the concentrations observed by GCxGC to concentration-time profiles simulated using the Master Chemical Mechanism, MCMv3, demonstrates that this mechanism significantly over-predicts the concentrations of many product compounds and highlights the uncertainties which exist in our understanding of the atmospheric oxidation of aromatics.

Download Full-text

Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part A): tropospheric degradation of non-aromatic volatile organic compounds

Atmospheric Chemistry and Physics ◽

10.5194/acp-3-161-2003 ◽

2003 ◽

Vol 3 (1) ◽

pp. 161-180 ◽

Cited By ~ 877

Author(s):

S. M. Saunders ◽

M. E. Jenkin ◽

R. G. Derwent ◽

M. J. Pilling

Keyword(s):

Volatile Organic Compounds ◽

Organic Compounds ◽

Good Description ◽

Field Studies ◽

Companion Paper ◽

Chemical Mechanism ◽

North West ◽

Radical Intermediates ◽

Volatile Organic ◽

Master Chemical Mechanism

Abstract. Kinetic and mechanistic data relevant to the tropospheric degradation of volatile organic compounds (VOC), and the production of secondary pollutants, have previously been used to define a protocol which underpinned the construction of a near-explicit Master Chemical Mechanism. In this paper, an update to the previous protocol is presented, which has been used to define degradation schemes for 107 non-aromatic VOC as part of version 3 of the Master Chemical Mechanism (MCM v3). The treatment of 18 aromatic VOC is described in a companion paper. The protocol is divided into a series of subsections describing initiation reactions, the reactions of the radical intermediates and the further degradation of first and subsequent generation products. Emphasis is placed on updating the previous information, and outlining the methodology which is specifically applicable to VOC not considered previously (e.g. a- and b-pinene). The present protocol aims to take into consideration work available in the open literature up to the beginning of 2001, and some other studies known by the authors which were under review at the time. Application of MCM v3 in appropriate box models indicates that the representation of isoprene degradation provides a good description of the speciated distribution of oxygenated organic products observed in reported field studies where isoprene was the dominant emitted hydrocarbon, and that the a-pinene degradation chemistry provides a good description of the time dependence of key gas phase species in a-pinene/NOX photo-oxidation experiments carried out in the European Photoreactor (EUPHORE). Photochemical Ozone Creation Potentials (POCP) have been calculated for the 106 non-aromatic non-methane VOC in MCM v3 for idealised conditions appropriate to north-west Europe, using a photochemical trajectory model. The POCP values provide a measure of the relative ozone forming abilities of the VOC. Where applicable, the values are compared with those calculated with previous versions of the MCM.

Download Full-text

Catalytic oxidation of benzene, toluene and p-xylene over colloidal gold supported on zinc oxide catalyst

Catalysis Communications ◽

10.1016/j.catcom.2011.02.012 ◽

2011 ◽

Vol 12 (10) ◽

pp. 859-865 ◽

Cited By ~ 97

Author(s):

Hongjing Wu ◽

Liuding Wang ◽

Jiaoqiang Zhang ◽

Zhongyuan Shen ◽

Jinghui Zhao

Keyword(s):

Zinc Oxide ◽

Catalytic Oxidation ◽

Colloidal Gold ◽

Oxide Catalyst ◽

Benzene Toluene ◽

Oxidation Of Benzene

Download Full-text

Investigating the NO-dependent photooxidation of limonene by OH and O3 using the atmosphere simulation chamber SAPHIR

10.5194/egusphere-egu21-11130 ◽

2021 ◽

Author(s):

Yat Sing Pang ◽

Martin Kaminski ◽

Anna Novelli ◽

Philip Carlsson ◽

Ismail-Hakki Acir ◽

...

Keyword(s):

Organic Aerosol ◽

Oxidation Products ◽

Chemical Mechanism ◽

Reaction Pathways ◽

Oh Radicals ◽

Oh Radical ◽

Simulation Experiments ◽

Master Chemical Mechanism ◽

Simulation Results ◽

Atmosphere Simulation Chamber

Limonene is the fourth-most abundant monoterpene in the atmosphere, which upon oxidation leads to the formation of secondary organic aerosol (SOA) and thereby influences climate and air quality.In this study, the oxidation of limonene by OH at different atmospherically relevant NO and HO2 levels (NO: 0.1 &#8211; 10 ppb; HO2: 20 ppt) was investigated in simulation experiments in the SAPHIR chamber at Forschungszentrum J&#252;lich. The analysis focuses on comparing measured radical concentrations (RO2, HO2, OH) and OH reactivity (kOH) with modeled values calculated using the Master Chemical Mechanism (MCM) version 3.3.1.At high and medium NO concentrations, RO2 is expected to quickly react with NO. An HO2 radical is produced during the process that can be converted back to an OH radical by another reaction with NO. Consistently, for experiments conducted at medium NO levels (~0.5 ppb, RO2 lifetime ~10 s), simulated RO2, HO2, and OH agree with observations within the measurement uncertainties, if the OH reactivity of oxidation products is correctly described.At lower NO concentrations, the regeneration of HO2 in the RO2 + NO reaction is slow and the reaction of RO2 with HO2 gains importance in forming peroxides. However, simulation results show a large discrepancy between calculated radical concentrations and measurements at low NO levels (<0.1 ppb, RO2 lifetime ~ 100 s). Simulated RO2 concentrations are found to be overestimated by a factor of three; simulated HO2 concentrations are underestimated by 50 %; simulated OH concentrations are underestimated by about 35%, even if kOH is correctly described. This suggests that there could be additional RO2 reaction pathways that regenerate HO2 and OH radicals become important, but they are not taken into account in the MCM model.

Download Full-text