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| Titel |
Advanced modelling of the multiphase DMS chemistry with the CAPRAM DMS module 1.0 |
| VerfasserIn |
Erik Hans Hoffmann, Andreas Tilgner, Roland Schrödner, Ralf Wolke, Hartmut Herrmann |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250135593
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| Publikation (Nr.) |
 EGU/EGU2016-16477.pdf |
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| Zusammenfassung |
| Oceans are the general emitter of dimethyl sulphide (DMS), the major natural sulphur source
(Andreae, 1990), and cover approximately 70 % of earth’s surface. The main DMS oxidation
products are SO2, H2SO4 and methyl sulfonic acid (MSA). Hence, DMS is very important
for formation of non-sea salt sulphate (nss SO42-) aerosols and secondary particulate matter
and thus global climate. Despite many previous model studies, there are still important
knowledge gaps, especially in aqueous phase DMS chemistry, of its atmospheric fate (Barnes
et al., 2006).
Therefore, a comprehensive multiphase DMS chemistry mechanism, the CAPRAM DMS
module 1.0 (DM1.0), has been developed. The DM1.0 includes 103 gas phase reactions, 5
phase transfers and 54 aqueous phase reactions. It was coupled with the multiphase chemistry
mechanism MCMv3.2/CAPRAM4.0α (Rickard et al., 2015; Bräuer et al., 2016)
and the extended CAPRAM halogen module 2.1 (HM2.1, Bräuer et al., 2013) for
investigation of multiphase DMS oxidation in the marine boundary layer. Then, a pristine
ocean scenario was simulated using the air parcel model SPACCIM (Wolke et al.,
2005) including 8 non-permanent cloud passages - 4 at noon and 4 at midnight.
This allows the investigation of the influence of deliquesced particles and clouds
on multiphase DMS chemistry during both daytime and nighttime conditions as
well as under cloud formation and evaporation. To test the influence of various
subsystems on multiphase DMS chemistry different sensitivity runs were performed.
Investigations of multiphase chemistry of DMS and its important oxidation products were
done using concentration-time profiles and detailed time-resolved reaction flux
analyses.
The model studies revealed the importance of aqueous phase chemistry for DMS and its
oxidation products. Overall about 7.0% of DMS is effectively oxidised by O3 in the aqueous
phase of clouds. The simulations revealed the importance of halogen and aqueous phase
chemistry for DMS and its oxidation products. Overall halogen compounds contribute with
71% to DMS oxidation with gaseous Cl (23.6%) and BrO (46.1%) as main oxidants. The
conversion efficiency of DMS to SO2 in the gas phase was simulated between 0.2, 0.27 and
0.6 for the full pristine ocean scenario run, a simulation without considered halogen
chemistry and a simulation without treated aqueous phase DMS chemistry, respectively.
Furthermore, the studies indicate that the conversion efficiency of DMS to MSA is
strongly related to DMS oxidation by BrO and treating of aqueous-phase DMS
chemistry. The MSA yield for different sensitivity runs was simulated between 0.01
and 0.47. The lowest yield is reached treating only gas phase chemistry of DMS.
Moreover, the simulation with the whole mechanism indicate that multiphase DMS
oxidation produce as much MSA as sulphate leading to strong implications for
nss-SO42− aerosol formation, activation to cloud condensation nuclei and cloud
albedo.
Andreae, M. O., Mar. Chem., 30, 1-29, 1990.
Barnes, I., et al., Chem. Rev., 106, 940-975, 2006.
Bräuer, P., et al., Atmos. Chem. Phys. Discuss., in preparation, 2016.
Bräuer, P., et al., J. Atmos. Chem., 70, 19-52, 2013.
Rickard, A., et al., The Master Chemical Mechanism Version MCM v3.2, available at:
http://mcm.leeds.ac.uk/MCMv3.2/ (last access: 05 Mai 2015)„ 2015.
Wolke, R., et al., Atmos. Environ., 39, 4375-4388, 2005. |
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