TY - JOUR
T1 - DMS oxidation and sulfur aerosol formation in the marine troposphere
T2 - A focus on reactive halogen and multiphase chemistry
AU - Chen, Qianjie
AU - Sherwen, Tomás
AU - Evans, Mathew
AU - Alexander, Becky
N1 - © Author(s) 2018
PY - 2018/9/27
Y1 - 2018/9/27
N2 - The oxidation of dimethyl sulfide (DMS) in the troposphere and subsequent chemical conversion into sulfur dioxide (SO2) and methane sulfonic acid (MSA) are key processes for the formation and growth of sulfur-containing aerosol and cloud condensation nuclei (CCN), but are highly simplified in large-scale models of the atmosphere. In this study, we implement a series of gas-phase and multiphase sulfur oxidation mechanisms into the Goddard Earth Observing System-Chemistry (GEOS-Chem) global chemical transport model-including two important intermediates, dimethyl sulfoxide (DMSO) and methane sulphinic acid (MSIA)-to investigate the sulfur cycle in the global marine troposphere. We found that DMS is mainly oxidized in the gas phase by OH (66%), NO3 (16%) and BrO (12%) globally. DMS+BrO is important for the model's ability to reproduce the observed seasonality of surface DMS mixing ratio in the Southern Hemisphere. MSA is mainly produced from multiphase oxidation of MSIA by OH(aq) (66%) and O3(aq) (30%) in cloud droplets and aerosols. Aqueous-phase reaction with OH accounts for only 12% of MSA removal globally, and a higher MSA removal rate is needed to reproduce observations of the MSA •nssSO42 ratio. The modeled conversion yield of DMS into SO2 and MSA is 75% and 15%, respectively, compared to 91% and 9% in the standard model run that includes only gas-phase oxidation of DMS by OH and NO3. The remaining 10% of DMS is lost via deposition of intermediates DMSO and MSIA. The largest uncertainties for modeling sulfur chemistry in the marine boundary layer (MBL) are unknown concentrations of reactive halogens (BrO and Cl) and OH(aq) concentrations in cloud droplets and aerosols. To reduce uncertainties in MBL sulfur chemistry, we should prioritize observations of reactive halogens and OH(aq).
AB - The oxidation of dimethyl sulfide (DMS) in the troposphere and subsequent chemical conversion into sulfur dioxide (SO2) and methane sulfonic acid (MSA) are key processes for the formation and growth of sulfur-containing aerosol and cloud condensation nuclei (CCN), but are highly simplified in large-scale models of the atmosphere. In this study, we implement a series of gas-phase and multiphase sulfur oxidation mechanisms into the Goddard Earth Observing System-Chemistry (GEOS-Chem) global chemical transport model-including two important intermediates, dimethyl sulfoxide (DMSO) and methane sulphinic acid (MSIA)-to investigate the sulfur cycle in the global marine troposphere. We found that DMS is mainly oxidized in the gas phase by OH (66%), NO3 (16%) and BrO (12%) globally. DMS+BrO is important for the model's ability to reproduce the observed seasonality of surface DMS mixing ratio in the Southern Hemisphere. MSA is mainly produced from multiphase oxidation of MSIA by OH(aq) (66%) and O3(aq) (30%) in cloud droplets and aerosols. Aqueous-phase reaction with OH accounts for only 12% of MSA removal globally, and a higher MSA removal rate is needed to reproduce observations of the MSA •nssSO42 ratio. The modeled conversion yield of DMS into SO2 and MSA is 75% and 15%, respectively, compared to 91% and 9% in the standard model run that includes only gas-phase oxidation of DMS by OH and NO3. The remaining 10% of DMS is lost via deposition of intermediates DMSO and MSIA. The largest uncertainties for modeling sulfur chemistry in the marine boundary layer (MBL) are unknown concentrations of reactive halogens (BrO and Cl) and OH(aq) concentrations in cloud droplets and aerosols. To reduce uncertainties in MBL sulfur chemistry, we should prioritize observations of reactive halogens and OH(aq).
UR - http://www.scopus.com/inward/record.url?scp=85054139891&partnerID=8YFLogxK
U2 - 10.5194/acp-18-13617-2018
DO - 10.5194/acp-18-13617-2018
M3 - Article
SN - 1680-7316
VL - 18
SP - 13617
EP - 13637
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
IS - 18
ER -