EMBRACE-AGS-Seed: Decadal Trends of Atmospheric Ethane - Building Capacity for Trace Gas Analysis and Modeling at Portland State University

This EMBRACE SEED project is focused on the study of current and historic ethane and methane concentrations in the atmosphere. Oxidation of these species contributes to production of ozone and secondary organic aerosol and affects the oxidizing capacity of the atmosphere. This research effort makes use of an unpublished archive at the Oregon Graduate Institute (OGI) of atmospheric ethane measurements collected in the early 1980s and will include new analyses for ethane in air samples collected during the period 1978–1998 at Cape Meares, Oregon. This project will lead to a better understanding of the distributions and historical trends of atmospheric ethane and methane and their significant impact on both air quality and climate. The research includes three primary activities: (1) Intercalibration of historic ethane observations from the OGI global monitoring network in the early 1980s with recent surface flask ethane measurements from the NOAA Carbon Cycle Greenhouse Gas Group; (2) Customization of the GEOS-Chem High Performance atmospheric chemistry model for ethane simulations; and (3) Inverse modeling studies of ethane within two periods that bracket the steep decline in concentrations of the gas from the 1980s to the 2000s. Due to its reaction with the hydroxyl radical (OH), ethane indirectly influences the lifetimes of many other trace gases in the atmosphere including methane (CH4). This research will enable the investigators to probe changes in the sources of ethane over decadal scales and develop new research projects that make use of the concentrations of both ethane and methane and their isotopes as tracers of oil and natural gas releases, as well emissions from wildfire and biomass burning. This seed proposal will help build research capacity for ethane and non-methane hydrocarbon gas research at Portland State University (PSU). The PIs plan to use the results from this SEED study to develop a full proposal to conduct future multi-tracer studies using ethane and methane and their isotopes to quantify the fluxes of these gases from natural and anthropogenic sources. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.