UC Riverside

Anthropogenic air pollution consists of primary and secondary pollutants resulted from human activities. It is related to different environmental and health issues such as climate change, visibility and respiratory diseases.

The maritime transport is an important source of anthropogenic primary air pollution. Natural gas (NG) vessels have become more widely used due to the more stringent emission regulations; however, emission data from NG maritime operations is still limited. This thesis conducted a comprehensive analysis on the air quality, health effects and climate change impacts of switching from diesel to NG. Results showed that PM2.5, NOx, CO2 were reduced by about 93%, 92% and 18%, respectively. However, HCHO and CH4 increased several-fold. A health risk assessment showed the diesel plume increased long-term health risk and the NG plume increased short-term health risk. A global warming potential (GWP) analysis was performed and revealed that the average NG exhaust GWP was increased by 38%. Mitigation strategies for further reducing pollutants from NG exhaust are discussed and showed potential for reducing short-term health and climate impacts.

Anthropogenic secondary organic aerosol (SOA) is formed from the oxidation of volatile organic compounds (VOCs) such as aromatics and is critically impacted by NOx. Global transport models use the SOA parameters from the two major chemical pathways, RO2+NO and RO2+HO2 and the branching ratio of RO2+NO pathway (β), to predict SOA formation. This thesis attempted to improve the model prediction by experimentally investigating the SOA formation from those pathways with a novel approach of maintaining β constant throughout chamber experiments. At low-NOx conditions, multiple SOA yield curves were observed. The yield increased with HO2/RO¬2, indicating the contribution of RO2+RO2 pathway. The GEOS-Chem model showed that for the regions with high aromatic emissions but lower HO2/RO¬2, aromatic SOA was overestimated by up to 100%. At high-NOx conditions, SOA parameters were developed when controlling β at one during the chamber experiments to simulate the RO2+NO pathway without significant contribution from the other pathways. The global surface β was modelled using GEOS-Chem and four β scenarios were observed. SOA formation was investigated when simulating the daytime β profiles for those scenarios.