Advances in Atmospheric Trace Gas Monitoring Systems: Quantification of Methane Sources by Solar Column Observations in the San Joaquin Valley of California & Characterization of a Portable Air Toxics Sensor

Anthropogenic trace gases such as greenhouse gases and air toxics emitted to the atmosphere contribute to radiative forcing, degradation of air quality, and negative impacts on human health. Quantification and characterization of these important trace gases are required to mitigate the global climate crisis and improve the air quality. My dissertation focuses on constraining methane (CH4) emissions from California’s San Joaquin Valley (SJV) dairy farms and characterizing wildfire emissions using ground-based solar spectroscopy observations. Additionally, I characterize a portable gas chromatograph coupled to a photoionization detector (GC-PID) for measuring concentrations of air toxics at ambient levels. In the first study, I studied the seasonality of CH4 emissions from dairy farms across four seasons from Spring 2019 to Winter 2020 in the SJV to investigate whether emissions varied across time and to discern the environmental factors driving temporal differences. Measurements collected during different seasons provided insight into the meteorological and management factors that drive the time-varying patterns observed during the year. This research showed that seasonal variability exists within dairy farm emissions and mitigation should focus in the summer. Wildfires are increasing in the Western United States making it critical to understand the impacts of greenhouse gases and air pollutants emitted to the atmosphere. I used a ground-based remote sensing technique to measure the amount of greenhouse gases and aerosol present in the atmosphere. I isolated a large smoke plume from the Sequoia Lightning Fire Complex (SQF) and calculated variables to understand the fuel properties. This revealed that a significant amount of CH4 was emitted from the 2020 wildfire season. In the third study, I characterized the performance of a compact GC-PID and optimize the configuration to detect ambient levels of benzene, toluene, ethylbenzene, and xylene isomers (BTEX). With an analysis time of less than 15 minutes, the compact GC-PID is ideal for field deployment of background and polluted atmospheres for near-real time measurements of BTEX. The results highlight the application of the compact and easily deployable GC-PID for community monitoring and screening of BTEX