UC Riverside

The atmospheric sulfur cycle plays an important role in controlling air quality and climate. Despite their importance, the contribution of sulfur derived aerosols – especially from marine biogenic sources – to cloud formation and the global radiative budget remains highly uncertain in most air quality and climate models due to gaps in our understanding of emissions, fluxes, and chemical oxidation processes of marine sulfur species. My dissertation centers around exploring the impacts of specific marine sulfur emissions and oxidation chemistry on the atmospheric sulfur budget, including the evaluation and improvement of modeling mechanisms. In the first study, I examine the contribution of marine emissions of dimethyl sulfide (DMS), and its oxidation chemistry in influencing the marine atmospheric sulfur budget. I further investigate the contribution of this oxidation chemistry to seasonal variability of the major oxidation products and size distribution of sulfate aerosol. This research shows that our proposed DMS oxidation mechanism, promotes the seasonal particle growth and limits the probability of new particle formation. In the second study, I investigate the impact of Methanethiol (MeSH) emissions and oxidation in changing the atmospheric sulfur budget. For this work I add an emissions inventory to consider the sea-flux of MeSH based on observed correlations of emissions between MeSH and DMS. Results show improved bias for SO2 when compared to ATom-4 aircraft measurements. These findings are important for air quality models to constrain the sulfur budget, with further possible consequence in changing the distribution and composition of marine sulfur aerosols – currently a topic of major interest for atmospheric researchers, especially in regions such as the Southern Ocean. In the third study, I investigate the modeled representation of methanesulphonic acid (MSA) which contributes to sulfate aerosol formation. As part of this work, I evaluate the contribution of specific novel reaction pathways towards improving the seasonality of MSA, along with reductions in model-observation bias. This study addresses a long-standing knowledge gap of secondary marine aerosol formation and contributes to better prediction of air quality and climate over the ocean in a global context.