CHARACTERIZING EMISSIONS FROM OIL & GAS OPERATIONS AND WILDFIRES USING AIRCRAFT OBSERVATIONS

Abstract

Methane (CH4), a potent greenhouse gas that traps roughly 80 times more heat than carbon dioxide over a 20-year period, also plays a key role in the global ozone budget. Air pollution, particularly from tropospheric ozone and particulate matter, is one of the leading environmental causes of premature mortality worldwide. Air quality and climate change are closely linked, and this dissertation uses aircraft measurements to address two seemingly independent topics that are intertwined by their influence on both air quality and climate: Emissions from oil and gas (O&G) operations and wildfire emissions.

The Denver-Julesburg Basin (DJB) in Colorado, particularly the Wattenberg Field, contains multiple major CH4 sources, including O&G operations, concentrated animal feeding operations (CAFOs), and landfills. Despite the near doubling of O\&G production over the past decade, emission rates of CH4 remain unchanged. This research introduces a novel tracer for CAFO activity, acetic acid (CH3COOH), used in combination with C2H6 as an O&G tracer. Airborne campaigns conducted in fall 2021 and fall 2023 determined total CH4 and ethane (C2H6) emission rates; we estimate that approximately 2/3 of total CH4 emissions were from O&G operations. Emission intensities show consistent declines, with C2H6 decreasing at more than twice the rate of CH4, supported by technological improvements at the well-heads.

Aircraft observations of smoke transported from Canadian wildfires in June 2023 and western U.S. fires in September 2020 were used to characterize aerosol optical properties and vertical structure. The results highlighted three distinct smoke regimes, underscoring the strong sensitivity of aerosol size, scattering, and absorptive properties to burn characteristics, smoke aging processes, and atmospheric context during transport.

Together, these studies demonstrate the interconnectivity of air quality and climate as human energy demands and emissions change. Despite a nearly double of O&G production in DJB, CH4 and C2H6 emissions per unit of production are declining, demonstrating that mitigation strategies, such as improved technology and stronger regulations, can be effective. However, O&G operations still emit a substantial amount of hydrocarbons, and continued improvements are needed to further reduce CH4 emissions. This work shows that air quality is shaped by both gradual changes in anthropogenic emissions and acute, climate-driven perturbations such as wildfires. Both local emissions and long-range transport are governed by a combination of source characteristics and meteorological conditions. Improving measurement constraints and understanding their interaction is essential for accurately quantifying air quality and climate impacts.