Diel Profile of Hydroperoxymethyl Thioformate: Evidence for Surface Deposition and Multiphase Chemistry

Dimethyl sulfide (DMS; CH3SCH3), a biogenically produced trace gas emitted from the ocean, accounts for a large fraction of natural sulfur released to the marine atmosphere. The oxidation of DMS in the marine boundary layer (MBL), via the hydrogen abstraction pathway, yields the short-lived methylth...

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Bibliographic Details
Published in:Environmental science & technology 2020-10, Vol.54 (19), p.12521-12529
Main Authors: Vermeuel, Michael P, Novak, Gordon A, Jernigan, Christopher M, Bertram, Timothy H
Format: Article
Language:English
Subjects:
Aerosols
Atmosphere
Boundary layers
Chemistry
Clouds
Deposition
Dimethyl sulfide
Diurnal
Energy and Climate
Fluxes
Isomerization
Mixing ratio
Ocean surface
Oxidation
Satellite imagery
Sulfur
Synchronous satellites
Trace gases
Vapor phases
Wind speed
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Summary:Dimethyl sulfide (DMS; CH3SCH3), a biogenically produced trace gas emitted from the ocean, accounts for a large fraction of natural sulfur released to the marine atmosphere. The oxidation of DMS in the marine boundary layer (MBL), via the hydrogen abstraction pathway, yields the short-lived methylthiomethylperoxy radical (MSP; CH3SCH2OO). In the remote MBL, unimolecular isomerization of MSP outpaces bimolecular chemistry leading to the efficient formation of hydroperoxymethyl thioformate (HPMTF; HOOCH2SCHO). Here, we report the first ground observations and diurnal profiles of HPMTF mixing ratios, vertical fluxes, and deposition velocities to the ocean surface. Average daytime HPMTF mixing ratios, fluxes, and deposition velocities were recorded at 12.1 pptv, −0.11 pptv m s–1, and 0.75 cm s–1, respectively. The deposition velocity of HPMTF is comparable to other soluble gas phase compounds (e.g., HCOOH and HNO3), resulting in a deposition lifetime of 30 h under typical windspeeds (3 m s–1). A box model analysis incorporating the current mechanistic understanding of DMS oxidation chemistry and geostationary satellite cloud imagery data suggests that the lifetime of HPMTF in the MBL at this sampling location is likely controlled by heterogeneous loss to aerosol and uptake to clouds in the morning and evening.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.0c04323