Fractional methane emissions from natural gas infrastructure in urban domains in the Eastern United States using airborne measurements and Lagrangian Particle Dispersion Modeling

Emissions of methane from natural gas infrastructure have been studied using many approaches in recent years. Though the total methane loss from the natural gas infrastructure and many of its subsystems is becoming increasingly better understood, loss from the urban domain as a result of market distribution remains relatively unquantified. Likewise, local emissions of methane from biological sources have been shown to have a large effect on the total methane emission from the urban domain though the total magnitude is not well understood for the majority of the cities in the United States. We present a recent analysis of high time resolution aircraft measurements of methane and ethane from a ten cities in the Midwest and East Coast portions of the United States. Using the ethane:methane observations we quantify the relative fraction of biogenic and thermogenic methane emissions from a particular area as well as the effect winter-summer seasonality has on the methane emission source partitioning. We also show how existing emission inventories of carbon dioxide can be coupled to airborne atmospheric observations with a Lagrangian Particle Dispersion Model to make rough estimates of the total methane flux emitted from an urban area. Results are presented as a distribution of domains highlighting the infrastructure we believe to be primarily responsible for the methane emissions from specific urban areas.