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Determination of the photolysis rate coefficient of Monochlorodimethyl Sulfide (MClDMS) in the atmosphere and its implications for the enhancement of SO2 production from the DMS + Cl2 reaction

Determination of the photolysis rate coefficient of Monochlorodimethyl Sulfide (MClDMS) in the atmosphere and its implications for the enhancement of SO2 production from the DMS + Cl2 reaction
Determination of the photolysis rate coefficient of Monochlorodimethyl Sulfide (MClDMS) in the atmosphere and its implications for the enhancement of SO2 production from the DMS + Cl2 reaction
In this work, the photolysis rate coefficient of CH3SCH2Cl (MClDMS) in the lower atmosphere has been determined and has been used in a marine boundary layer (MBL) box model to determine the enhancement of SO2 production arising from the reaction DMS + Cl2. Absorption cross sections measured in the 28000-34000 cm(-1) region have been used to determine photolysis rate coefficients of MClDMS in the troposphere at 10 solar zenith angles (SZAs). These have been used to determine the lifetimes of MClDMS in the troposphere. At 0° SZA, a photolysis lifetime of 3-4 h has been obtained. The results show that the photolysis lifetime of MClDMS is significantly smaller than the lifetimes with respect to reaction with OH (?4.6 days) and with Cl atoms (?1.2 days). It has also been shown, using experimentally derived dissociation energies with supporting quantum-chemical calculations, that the dominant photodissocation route of MClDMS is dissociation of the C-S bond to give CH3S and CH2Cl. MBL box modeling calculations show that buildup of MClDMS at night from the Cl2 + DMS reaction leads to enhanced SO2 production during the day. The extra SO2 arises from photolysis of MClDMS to give CH3S and CH2Cl, followed by subsequent oxidation of CH3S.
0013-936X
1557-1565
Copeland, G.
b93b9211-ba28-4c89-af6d-4fc9b1f80f05
Lee, E.P.F.
f47c6d5d-2d1f-4f03-a3ff-03658812d80b
Williams, R.G.
2f69a4a4-acdc-4871-8e62-1ac1b84329b0
Archibald, A.T.
3c6c6430-f4ff-4d33-96c8-c5e7a76d01ec
Shallcross, D.E.
9b36ee5a-feb1-4fea-a34c-f56e64dfae28
Dyke, J.
46393b45-6694-46f3-af20-d7369d26199f
Copeland, G.
b93b9211-ba28-4c89-af6d-4fc9b1f80f05
Lee, E.P.F.
f47c6d5d-2d1f-4f03-a3ff-03658812d80b
Williams, R.G.
2f69a4a4-acdc-4871-8e62-1ac1b84329b0
Archibald, A.T.
3c6c6430-f4ff-4d33-96c8-c5e7a76d01ec
Shallcross, D.E.
9b36ee5a-feb1-4fea-a34c-f56e64dfae28
Dyke, J.
46393b45-6694-46f3-af20-d7369d26199f

Copeland, G., Lee, E.P.F., Williams, R.G., Archibald, A.T., Shallcross, D.E. and Dyke, J. (2014) Determination of the photolysis rate coefficient of Monochlorodimethyl Sulfide (MClDMS) in the atmosphere and its implications for the enhancement of SO2 production from the DMS + Cl2 reaction. Environmental Science & Technology, 48 (3), 1557-1565. (doi:10.1021/es402956r).

Record type: Article

Abstract

In this work, the photolysis rate coefficient of CH3SCH2Cl (MClDMS) in the lower atmosphere has been determined and has been used in a marine boundary layer (MBL) box model to determine the enhancement of SO2 production arising from the reaction DMS + Cl2. Absorption cross sections measured in the 28000-34000 cm(-1) region have been used to determine photolysis rate coefficients of MClDMS in the troposphere at 10 solar zenith angles (SZAs). These have been used to determine the lifetimes of MClDMS in the troposphere. At 0° SZA, a photolysis lifetime of 3-4 h has been obtained. The results show that the photolysis lifetime of MClDMS is significantly smaller than the lifetimes with respect to reaction with OH (?4.6 days) and with Cl atoms (?1.2 days). It has also been shown, using experimentally derived dissociation energies with supporting quantum-chemical calculations, that the dominant photodissocation route of MClDMS is dissociation of the C-S bond to give CH3S and CH2Cl. MBL box modeling calculations show that buildup of MClDMS at night from the Cl2 + DMS reaction leads to enhanced SO2 production during the day. The extra SO2 arises from photolysis of MClDMS to give CH3S and CH2Cl, followed by subsequent oxidation of CH3S.

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e-pub ahead of print date: 21 January 2014
Published date: 21 January 2014
Organisations: Computational Systems Chemistry

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Local EPrints ID: 362938
URI: http://eprints.soton.ac.uk/id/eprint/362938
ISSN: 0013-936X
PURE UUID: 5051dd0b-8097-4c4e-b36c-5834a79d41a9
ORCID for J. Dyke: ORCID iD orcid.org/0000-0002-9808-303X

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Date deposited: 17 Mar 2014 16:29
Last modified: 20 Jul 2019 01:27

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Contributors

Author: G. Copeland
Author: E.P.F. Lee
Author: R.G. Williams
Author: A.T. Archibald
Author: D.E. Shallcross
Author: J. Dyke ORCID iD

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