Oxidation of substituted aromatic hydrocarbons in the tropospheric aqueous phase: kinetic mechanism development and modelling

An aqueous-phase chemistry mechanism for the oxidation of aromatic compounds in the atmosphere is developed based on available kinetic data. Detailed model studies successfully describe the oxidation and functionalization of monoaromatic compounds in the atmosphere.

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An advanced modeling study on the impacts and atmospheric implications of multiphase dimethyl sulfide chemistry

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1606320113 ◽

2016 ◽

Vol 113 (42) ◽

pp. 11776-11781 ◽

Cited By ~ 61

Author(s):

Erik Hans Hoffmann ◽

Andreas Tilgner ◽

Roland Schrödner ◽

Peter Bräuer ◽

Ralf Wolke ◽

...

Keyword(s):

Aqueous Phase ◽

Dimethyl Sulfide ◽

Oxidation Products ◽

Radical Mechanism ◽

Sulfur Source ◽

Aerosol Formation ◽

Detailed Model ◽

Model Studies ◽

Dms Oxidation ◽

Phase Chemistry

Oceans dominate emissions of dimethyl sulfide (DMS), the major natural sulfur source. DMS is important for the formation of non-sea salt sulfate (nss-SO42−) aerosols and secondary particulate matter over oceans and thus, significantly influence global climate. The mechanism of DMS oxidation has accordingly been investigated in several different model studies in the past. However, these studies had restricted oxidation mechanisms that mostly underrepresented important aqueous-phase chemical processes. These neglected but highly effective processes strongly impact direct product yields of DMS oxidation, thereby affecting the climatic influence of aerosols. To address these shortfalls, an extensive multiphase DMS chemistry mechanism, the Chemical Aqueous Phase Radical Mechanism DMS Module 1.0, was developed and used in detailed model investigations of multiphase DMS chemistry in the marine boundary layer. The performed model studies confirmed the importance of aqueous-phase chemistry for the fate of DMS and its oxidation products. Aqueous-phase processes significantly reduce the yield of sulfur dioxide and increase that of methyl sulfonic acid (MSA), which is needed to close the gap between modeled and measured MSA concentrations. Finally, the simulations imply that multiphase DMS oxidation produces equal amounts of MSA and sulfate, a result that has significant implications for nss-SO42− aerosol formation, cloud condensation nuclei concentration, and cloud albedo over oceans. Our findings show the deficiencies of parameterizations currently used in higher-scale models, which only treat gas-phase chemistry. Overall, this study shows that treatment of DMS chemistry in both gas and aqueous phases is essential to improve the accuracy of model predictions.

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Modelling the Tropospheric Multiphase Chemistry of Biomass Burning Trace Compounds Using the Chemical Aqueous Phase Radical Mechanism (CAPRAM)

10.5194/egusphere-egu21-10731 ◽

2021 ◽

Author(s):

Lin He ◽

Erik Hans Hoffmann ◽

Andreas Tilgner ◽

Hartmut Herrmann

Keyword(s):

Aqueous Phase ◽

Biomass Burning ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Laser Flash ◽

Radical Mechanism ◽

Aerosol Formation ◽

Detailed Model ◽

Model Studies ◽

Trace Species

Biomass burning (BB) is a significant contributor to air pollution on global, regional and local scale with impacts on air quality, public health and climate. Anhydrosugars (levoglucosan, mannosan and galactocan) and methoxyphenols (guaiacol, creosol, etc.) are important tracer compounds emitted through biomass burning. Once emitted, they can undergo complex multiphase chemistry in the atmosphere contributing to secondary organic aerosol formation. However, their chemical multiphase processing is not yet well understood and investigated by models. Therefore, the present study aimed at a better understanding of the multiphase chemistry of these BB trace species by means of detailed model studies with a new developed detailed chemical CAPRAM biomass burning module (CAPRAM-BB). This module was developed based on the kinetic data from the laser flash photolysis measurements in our lab at TROPOS and other literature studies. The developed CAPRAM-BB module includes 2991 reactions (thereof 9 phase transfers and 2982 aqueous-phase reactions). By coupling with the multiphase chemistry mechanism MCMv3.2/CAPRAM4.0 and the extended CAPRAM aromatics (CAPRAM-AM1.0) and halogen modules (CAPRAM-HM3.0), it is being applied for some residential wood burning cases in Europe and wildfire cases in the US. Our model results show that the BB chemistry could significantly affect the budgets of important atmospheric oxidants such as H2O2 and HONO, and contribute to the SOA formation especially the fraction of brown carbon and substituted organic acids.

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Influence of in-cloud oxidation of organic compounds on tropospheric ozone

10.5194/egusphere-egu21-10276 ◽

2021 ◽

Author(s):

Simon Rosanka ◽

Rolf Sander ◽

Bruno Franco ◽

Catherine Wespes ◽

Andreas Wahner ◽

...

Keyword(s):

Gas Phase ◽

Organic Compounds ◽

Aqueous Phase ◽

Phase Transfer ◽

Sulfur Oxidation ◽

Box Model ◽

Atmospheric Models ◽

Model Studies ◽

Phase Chemistry ◽

The Impact

Large parts of the troposphere are affected by clouds, whose aqueous-phase chemistry differs significantly from gas-phase chemistry. Box-model studies have demonstrated that clouds influence the tropospheric oxidation capacity. However, most global atmospheric models do not represent this chemistry reasonably well and are largely limited to sulfur oxidation. Therefore, we have developed the J&#252;lich Aqueous-phase Mechanism of Organic Chemistry (JAMOC), making a detailed in-cloud oxidation model of oxygenated volatile organic compounds (OVOCs) readily available for box as well as for regional and global simulations that are affordable with modern supercomputers. JAMOC includes the phase transfer of species containing up to ten carbon atoms, and the aqueous-phase reactions of a selection of species containing up to four carbon atoms, e.g., ethanol, acetaldehyde, glyoxal. The impact of in-cloud chemistry on tropospheric composition is assessed on a regional and global scale by performing a combination of box-model studies using the Chemistry As A Boxmodel Application (CAABA) and the global atmospheric model ECHAM/MESSy (EMAC). These models are capable to represent the described processes explicitly and integrate the corresponding ODE system with a Rosenbrock solver.&#160;Overall, the explicit in-cloud oxidation leads to a reduction of predicted OVOCs levels. By comparing EMAC's prediction of methanol abundance to spaceborne retrievals from the Infrared Atmospheric Sounding Interferometer (IASI), a reduction in EMAC's overestimation is observed in the tropics. Further, the in-cloud OVOC oxidation shifts the hydroperoxyl radicals (HO2) production from the gas- to the aqueous-phase. As a result, the in-cloud destruction (scavenging) of ozone (O3) by the superoxide anion (O2-) is enhanced and accompanied by a reduction in both sources and sinks of tropospheric O3 in the gas phase. By considering only the in-cloud sulfur oxidation by O3, about 13 Tg a-1 of O3 are scavenged, which increases to 336 Tg a-1 when JAMOC is used. With the full oxidation scheme, the highest O3 reduction of 12 % is predicted in the upper troposphere/lower stratosphere (UTLS). Based on the IASI O3 retrievals, it is demonstrated that these changes in the free troposphere significantly reduce the modelled tropospheric O3 columns, which are known to be generally overestimated by global atmospheric models. Finally, the relevance of aqueous-phase oxidation of organics for ozone in hazy polluted regions will be presented. &#160;

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Development of a protocol for the auto-generation of explicit aqueous-phase oxidation schemes of organic compounds

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-9209-2019 ◽

2019 ◽

Vol 19 (14) ◽

pp. 9209-9239 ◽

Cited By ~ 7

Author(s):

Peter Bräuer ◽

Camille Mouchel-Vallon ◽

Andreas Tilgner ◽

Anke Mutzel ◽

Olaf Böge ◽

...

Keyword(s):

Organic Compounds ◽

Aqueous Phase ◽

Rate Constants ◽

Particle Growth ◽

Chemical Mechanism ◽

Estimation Methods ◽

Radical Reactivity ◽

Chemical Complexity ◽

Model Studies ◽

Phase Chemistry

Abstract. This paper presents a new CAPRAM–GECKO-A protocol for mechanism auto-generation of aqueous-phase organic processes. For the development, kinetic data in the literature were reviewed and a database with 464 aqueous-phase reactions of the hydroxyl radical with organic compounds and 130 nitrate radical reactions with organic compounds has been compiled and evaluated. Five different methods to predict aqueous-phase rate constants have been evaluated with the help of the kinetics database: gas–aqueous phase correlations, homologous series of various compound classes, radical reactivity comparisons, Evans–Polanyi-type correlations, and structure–activity relationships (SARs). The quality of these prediction methods was tested as well as their suitability for automated mechanism construction. Based on this evaluation, SARs form the basis of the new CAPRAM–GECKO-A protocol. Evans–Polanyi-type correlations have been advanced to consider all available H atoms in a molecule besides the H atoms with only the weakest bond dissociation enthalpies (BDEs). The improved Evans–Polanyi-type correlations are used to predict rate constants for aqueous-phase NO3 and organic compounds reactions. Extensive tests have been performed on essential parameters and on highly uncertain parameters with limited experimental data. These sensitivity studies led to further improvements in the new CAPRAM–GECKO-A protocol but also showed current limitations. Biggest uncertainties were observed in uptake processes and the estimation of Henry's law coefficients as well as radical chemistry, in particular the degradation of alkoxy radicals. Previous estimation methods showed several deficits, which impacted particle growth. For further evaluation, a 1,3,5-trimethylbenzene oxidation experiment has been performed in the aerosol chamber “Leipziger Aerosolkammer” (LEAK) at high relative humidity conditions and compared to a multiphase mechanism using the Master Chemical Mechanism (MCMv3.2) in the gas phase and using a methylglyoxal oxidation scheme of about 600 reactions generated with the new CAPRAM–GECKO-A protocol in the aqueous phase. While it was difficult to evaluate single particle constituents due to concentrations close to the detection limits of the instruments applied, the model studies showed the importance of aqueous-phase chemistry in respect to secondary organic aerosol (SOA) formation and particle growth. The new protocol forms the basis for further CAPRAM mechanism development towards a new version 4.0. Moreover, it can be used as a supplementary tool for aerosol chambers to design and analyse experiments of chemical complexity and help to understand them on a molecular level.

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Modeling the Tropospheric Multiphase Chemistry of Biomass Burning Trace Compounds Using the Chemical Aqueous Phase Radical Mechanism (CAPRAM)

10.5194/dach2022-171 ◽

2021 ◽

Author(s):

Lin He ◽

Erik H. Hoffmann ◽

Andreas Tilgner ◽

Hartmut Herrmann

Keyword(s):

Aqueous Phase ◽

Biomass Burning ◽

Organic Aerosol ◽

Local Scale ◽

Radical Mechanism ◽

Laboratory Measurements ◽

Detailed Model ◽

Model Studies ◽

The Us ◽

Trace Compounds

Biomass burning (BB) is a significant contributor to air pollution on global, regional and local scale with impacts on air quality, public health and climate. Anhydrosugars and methoxyphenols are key tracers emitted through BB. Once emitted, they can undergo complex multiphase chemistry in the atmosphere contributing to secondary organic aerosol (SOA) formation. However, their chemical multiphase processing is not yet well understood and investigated by models. Thus, the present study aimed at a better understanding of the multiphase chemistry of these BB tracers by detailed model studies with a new developed CAPRAM biomass burning module (CAPRAM-BBM).This module was developed based on the kinetic data from our laboratory measurements at TROPOS and other literature studies. The developed CAPRAM-BBM includes 2991 reactions (9 phase transfers and 2982 aqueous-phase reactions). By coupling with the multiphase chemistry mechanism MCMv3.2/CAPRAM4.0 and the extended CAPRAM aromatics (CAPRAM-AM1.0) and halogen modules (CAPRAM-HM3.0), itis being applied for residential wood burning cases in Europeand wildfire cases in the US. Our model results show that levoglucosan and vanillin are effectively oxidized under cloud conditions. Furthermore, the results demonstrate that the chemistry of BB tracers can affect the budgets of key oxidants such as H2O2, and contribute to the SOA formation especially by increasing the fraction of brown carbon and substituted organic acids.

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Development of a protocol for the auto-generation of explicit aqueous-phase oxidation schemes of organic compounds

10.5194/acp-2018-1318 ◽

2019 ◽

Author(s):

Peter Bräuer ◽

Camille Mouchel-Vallon ◽

Andreas Tilgner ◽

Anke Mutzel ◽

Olaf Böge ◽

...

Keyword(s):

Organic Compounds ◽

Aqueous Phase ◽

Rate Constants ◽

Particle Growth ◽

Estimation Methods ◽

Radical Reactivity ◽

Chemical Complexity ◽

Model Studies ◽

Aerosol Chamber ◽

Phase Chemistry

Abstract. This paper presents a new CAPRAM/GECKO-A protocol for mechanism auto-generation of aqueous-phase organic mechanisms. For the development, kinetic data in the literature was reviewed and a database with 464 aqueous-phase reactions of the hydroxyl radical with organic compounds and 130 nitrate radical reactions with organic compounds has been compiled and evaluated. Five different methods to predict aqueous-phase rate constants have been evaluated with the help of the kinetics database: gas-aqueous correlations, homologous series of various compound classes, radical reactivity comparisons, Evans-Polanyi-type correlations, and structure-activity relationships (SARs). The quality of these prediction methods was tested as well as their suitability for automated mechanism construction. Based on this evaluation, SARs form the basis of the new CAPRAM/GECKO-A protocol. Evans-Polanyi-type correlations have been advanced to consider all available H-atoms in a molecule besides the H-atoms with only the weakest bond dissociation enthalpy (BDE). The improved Evans-Polanyi-type correlations are used to predict rate constants for aqueous-phase NO3 + organic compounds reactions. Extensive tests have been performed on essential parameters and highly uncertain parameters with limited experimental data. These sensitivity studies led to further improvements in the new CAPRAM/GECKO-A protocol, but also showed current limitations. Biggest uncertainties were observed in uptake processes and the estimation of Henry's Law coefficients as well as radical chemistry, in particular the degradation of alkoxy radicals. Previous estimation methods showed several deficits, which impacted particle growth. For further evaluation, a mesitylene oxidation experiment has been performed at the aerosol chamber LEAK at high relative humidity conditions and compared to a multiphase mechanism using the MCMv3.2 in the gas phase and a methylglyoxal oxidation scheme of about 600 reactions generated with the new CAPRAM/GECKO-A protocol in the aqueous phase. While it was difficult to evaluate single particle constituents due to concentrations close to the detection limits of the instruments applied, the model studies showed the importance of aqueous-phase chemistry in respect to SOA formation and particle growth. The new protocol forms the basis for further CAPRAM mechanism development towards a new version 4.0. Moreover, it can be used as supplementary tool for aerosol chambers to design and analyse experiments of chemical complexity and help understanding them on a molecular level.

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Impacts of acidity on multiphase chemistry in aqueous particles and clouds

10.5194/egusphere-egu2020-10045 ◽

2020 ◽

Cited By ~ 1

Author(s):

Thomas Schaefer ◽

Andreas Tilgner ◽

Havala O. T. Pye ◽

V. Faye McNeill ◽

Hartmut Herrmann

Keyword(s):

Organic Compounds ◽

Aqueous Phase ◽

Carbonyl Compounds ◽

Kinetic Data ◽

The Other ◽

Aerosol Composition ◽

Other Hand ◽

Wide Range ◽

Phase Chemistry ◽

The Impact

The acidity of aqueous atmospheric solutions is a key parameter driving both partitioning of semi-volatile acidic or basic trace gases and their linked aqueous-phase chemistry. On the other hand, acidity of atmospheric aqueous phases, e.g. deliquesced aerosol particles, cloud and fog droplets, is conversely affected by aqueous-phase chemistry processes. Those feedbacks in acidity and chemistry have crucial implications for the (i) tropospheric lifetime of air pollutants, hence air quality and atmospheric aerosol composition, (ii) deposition input into other terrestrial and oceanic ecosystems, (iii) the visibility, (iv) climate and (v) human health. Due to their fundamental role, atmospheric research has gained substantial progress in the understanding in feedbacks of acidity and multiphase chemistry. In the present study, the current state of knowledge on the acidity-multiphase chemistry feedbacks has been summarized. From a wide range of topics, two selected issues focusing on impacts of acidity (i) on the hydration of organic carbonyl compounds and (ii) multiphase chemistry of dissociating organic compounds in aqueous particles and clouds will be presented.Hydration processes are typically known to be acid- or base-catalyzed. Thus, the acidity of an aqueous solution can affect the hydration and all other processes linked to it. This comprehensive literature study revealed that the hydration of simple aldehydes and ketones as well as dicarbonyls is less affected by acidity. However, for multifunctional carbonyl compounds such as pyruvic acid, the hydration equilibrium constant of the carbonyl group is strongly influenced by the electronic effects of the adjacent group. The hydration of carbonyl groups in compounds that also contain pH sensitive moieties, such as &#945;-oxocarboxylic acids, is highly influenced by the acidity of the surrounding environment. However, this acidity effect is often not considered in multiphase models.Furthermore, oxidation reactions of dissociating organic compounds can be affected by acidity. To examine the effect of acidity on the chemical processing of dissociating organic compounds, kinetic data for their oxidation by OH, NO3 and O3 have been newly compiled in the present study. Kinetic reactivity data of both protonated and deprotonated organic compounds together with their reactivity ratio &#160;have been investigated to identify possible acidity effects. The present study showed that, for OH reactions, the impact of acidity on the chemical kinetics is often quite small and only important for some specific compounds. On the other hand, for NO3 reaction, particularly under cloud conditions, acidity can substantially affect the chemical NO3-initiated processing of organic compounds. Less acidic conditions will enhance the degradation of dissociating compounds via NO3 because of more rapid oxidation and possibility of additional ETR pathway. Furthermore, the present O3 kinetic data analyses have demonstrated the role of acidity for ozonolysis processes, especially for phenolic compounds. Overall, the present study summarizes atmospheric implications and needs for future investigations, particularly with respect to changing aerosol and cloud acidity conditions in the future.

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