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.

Ambient air pollutants including aerosols and gas phase pollutants has caused concerns for both air quality and public health, especially in environmental justice region. The Salton Sea region located in southern California, is one such region characterized by high air pollution levels, asthma rates but low socioeconomic status. My dissatisfaction centers around evaluating and comparing the adverse health impacts of ambient air pollution exposure including PM2.5, ozone and windblown dust, as well as characterizing ammonia emissions in the Salton Sea region. In the first study, I examine disparities in air pollution exposure and associated health outcomes in the Coachella Valley. Two different measures of the health outcomes are used to investigate the connections between air pollution exposure and human health. I further investigate whether such relationships vary with socioeconomic status metrics. This research showed that more vulnerable communities are associated with higher levels of PM2.5 and higher emergency room visits, possibly indicating that high exposure, high vulnerability families are less likely to self-report diagnoses relative to more affluent communities. In the second study, I developed a model to separate windblown dust observed in the Salton Sea region by their potential source regions and compare the health impacts of those different dust coming with a case crossover design. Results show increases in both respiratory and cardiovascular hospital admissions with increasing concentrations of dust arriving from over the Salton Sea. Even stronger associations were observed for Salton Sea dust with algae events. These findings are important for air quality mitigation efforts in the region, as they point to the possible significance of water surface sources of toxic particulates alongside the windblown dust sources that currently receive the most attention. In the third study, I characterize potential sources and emission patterns of ammonia in the Salton Sea region through a series of mobile lab measurements. As part of this work, I measured ammonia concentrations near potential sources including cattle feeders and geo-thermal plants. This study fills a knowledge gap of ammonia emissions in the Salton Sea region and contributes to emission inventory development, a major goal of local researchers and policymakers.