An advanced modeling study on the impacts and atmospheric implications of multiphase dimethyl sulfide chemistry

Abstract

Oceans dominate emissions of dimethyl sulfide (DMS), the major natural sulfur source. DMS is important for the formation of non-sea salt sulfate (nss-SO 4 2− ) 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 aqueousphase 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-SO 4 2− 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. ) contribute to the formation of new aerosol particles as well as secondary particulate matter and are, thus, important for human health and the Earth's climate (1). Globally, anthropogenic sulfur emissions in the form of sulfur dioxide (SO 2 ) dominate atmospheric production of gaseous H 2 SO 4 and particle-phase sulfate. However, the main natural source of sulfur is the oxidation of dimethyl sulfide (DMS) emitted by oceans (2), which is the most important precursor for non-sea salt sulfate (nss-SO 4 2− ) aerosols over the open ocean (3). Sulfate aerosols strongly influence the climate both by direct negative radiative forcing (4) and as a dominant source of cloud condensation nuclei (CCN) over the open ocean (5). Because oceans cover about 70% of Earth's surface (6) and have generally low albedo, DMS oxidation plays a major role in influencing the natural radiative forcing of sulfate aerosols as well as cloud properties (3).Investigations of the effect of DMS oxidation on natural sulfate aerosol concentrations and cloud and aerosol properties require an accurate, reduced DMS oxidation scheme in chemical transport models (CTMs) and global climate models (GCMs). Current parameterizations use fixed yields of SO 2 and methyl sulfonic acid (MSA) to calculate new nss...

Source apportionment of the submicron organic aerosols over the Atlantic Ocean from 53° N to 53° S using HR-ToF-AMS

“…Also, NO3, NH4 and BC showed low mass 30 concentrations (median: 0.04µg m Model studies found that the DMS is mainly (84% globally) removed via the photo-oxidation by OH radical (Kloster et al, 2006). Also, the aqueous-phase oxidation of DMS is dominant by O3 during the cloud process, and yield significantly amount of MSA (Hoffmann et al, 2016). These findings support that the DMS oxidation is controlled by photochemical process and its products should show daytime maximum associated with the solar radiation.…”

Kinetic modeling studies of SOA formation from <i>α</i>-pinene ozonolysis

“…The size-resolved cloud microphysics of deliquesced particles and droplets including cloud droplet formation, evolution, and evaporation is considered using a 1-D sectional approach. Further microphysical features of SPACCIM are already described in Wolke et al (2005) and results owing to these processes are presented in Tilgner et al (2013), Rusumdar et al (2016), and Hoffmann et al (2016). The implemented multiphase chemical model applies a high-order implicit time integration scheme, which utilizes the specific sparse structure of the model equations (Wolke and Knoth, 2002).…”

Size distribution and ionic composition of marine summer aerosol at the continental Antarctic site Kohnen

“…9), in contrast to their simultaneous emergence in the aftermath of LPS02 described in Piel et al (2006). Given that MS -should have been primarily formed by heterogeneous liquid phase chemistry prevalent in the marine boundary layer (Legrand et al, 2001;Bardouki et al, 2002;Hoffmann et al, 2016), the segregated MS -peak indicated a temporary and efficient advection of such air masses. In 5 addition a striking peak of the sea-salt tracer Na + appeared along with the MS -maximum (Supplementary Material, S.4), emphasizing the impact of marine boundary layer air masses during this part of LPS15.…”

“…13, starting point 100 m above Kohnen): Air masses during LPS15 Regarding the chemical composition of the aerosol during the final stage of LPS15, subsequent increasing nss-SO4 2-along with declining MS -concentrations indicated a minor importance of liquid phase chemistry (Hoffmann et al, 2016). We may 25 speculate that now intrusions of marine boundary layer into the so-called buffer layer which Russel et al (1998) assumed to extend from the turbulent marine boundary layer (400 m to 700 m) to a capping inversion (1400 m to 1900 m), were responsible for efficient advection of gaseous DMS photo oxidation products like SO2 and DMSO (Davis et al, 1998;Russel et al, 1998).…”