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

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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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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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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Phototransformation of halogenoaromatic derivatives in aqueous solution

International Journal of Photoenergy ◽

10.1155/s1110662x99000094 ◽

1999 ◽

Vol 1 (1) ◽

pp. 49-54 ◽

Cited By ~ 11

Author(s):

P. Boule ◽

K. Othmen ◽

C. Richard ◽

B. Szczepanik ◽

G. Grabner

Keyword(s):

Aqueous Solution ◽

Halogen Atom ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Intermediate Formation ◽

Laser Flash ◽

Main Reaction ◽

Radical Mechanism ◽

Cationic Form ◽

Photochemical Behaviour

The photochemical behaviour of monohalogeno-phenols and -anilines is highly dependent on the position of the halogen on the ring, but most often it is not significantly influenced by the nature of the halogen (Cl, Br, F). Photohydrolysis is the main reaction observed with 3-halogenated and it is almost specific. With 2-halogenated, photohydrolysis and photocontraction of the ring compete, the latter being very efficient with 2-halogeno-phenolates.The photochemical behaviour of 4-halogeno-phenols and -anilines is more complex. It depends on both concentration and oxygenation. It was rationalized when it was experimentally proved by laser flash photolysis that the first step is the formation of a carbene (in the cationic form in the case of 4-halogenoaniline).ρ-Benzoquinone is the product of photooxidation of 4-halogenophenols, whereas the photooxidation of 4-chloroaniline leads to 4-amino-4´-chlorodiphenylamine.Chlorohydroquinone behaves differently, the formation of the main photoproducts involving a radical mechanism.With dihalogenoanilines photohydrolysis is initially almost quantitative whatever the position of halogen atom on the ring. It occurs more easily in meta than inorthoposition and inorthothan inparaposition. In the case of 2,4- and 2,6-dichloroanilines aminophenoxazones are formed as secondary photoproducts. This reaction involves the intermediate formation of o-benzoquinone monoimine. Several halogenoaromatic herbicides were also studied (bromoxynil, chlorpropham, propanil, diuron, linuron, chlorbromuron, MCPA). The most frequent reaction is photohydrolysis. However some other reactions such as photoreduction and photo-demethoxylation were observed. In some cases a wavelength effect was observed particularly with MCPA and halogenophenylureas.

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