An Examination of Carbon Monoxide and Organic Aerosol Mass Sources in the Southeastern United States during the SENEX Project

Wednesday, 17 December 2014: 2:40 PM
Ann M Middlebrook1, Wayne M Angevine2, Jerome F Brioude3, Charles A Brock4, Joost A De Gouw5, Jessica Gilman4, Martin Graus6, Thomas F Hanisco7, John S Holloway8, Larry Wayne Horowitz9, Jennifer Kaiser10, Frank N Keutsch11, Brian M Lerner12, Jin Liao1, Jingqiu Mao13, Michael Trainer4, Carsten Warneke1, Andre Welti14 and Glenn M Wolfe Jr15, (1)NOAA Boulder, Boulder, CO, United States, (2)CIRES, Boulder, CO, United States, (3)CIRES/CU NOAA, Boulder, CO, United States, (4)NOAA ESRL, Boulder, CO, United States, (5)NOAA Earth System Research Lab, Boulder, CO, United States, (6)Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (7)NASA GSFC, Greenbelt, MD, United States, (8)CIRES/NOAA Earth Systems Lab, Boulder, CO, United States, (9)Princeton Univ, Princeton, NJ, United States, (10)University of Wisconsin- Madison, Madison, WI, United States, (11)UW Madison, Madison, WI, United States, (12)NOAA, Earth System Research La, Boulder, CO, United States, (13)Princeton University, Princeton, NJ, United States, (14)ETH Swiss Federal Institute of Technology Zurich, Zurich, Switzerland, (15)NASA Goddard Space Flight Center, Greenbelt, MD, United States
The NOAA Southeast Nexus (SENEX) project occurred during the summer of 2013 over the southeastern United States and involved studying the interactions between natural and anthropogenic emissions at the nexus of climate change and air quality. As part of the project, a suite of instruments for aerosol and gas–phase species was deployed on the NOAA WP-3D aircraft and models were used to calculate trace gas and aerosol species in the region and along the aircraft flight tracks. Throughout the study, the measured non-refractory submicron aerosol mass was dominated by organic material (58% +/- 9%) with smaller contributions from sulfate (27% +/- 8%), ammonium (10% +/- 3%), nitrate (3% +/- 1%), and chloride (0.1% +/- 0.1%).

Here we examine the influence of urban emissions on the organic aerosol (OA) mass in regions characterized by higher and lower biogenic emissions. For the air around and downwind of urban areas, OA mass is highly correlated with carbon monoxide (CO), a tracer of anthropogenic emissions as well as an oxidation product of isoprene, a biogenic species. The slope of this correlation is roughly 0.15 micrograms per standard cubic meter per ppbv, which is significantly higher than observed in prior studies downwind of urban areas. The enhancement in OA mass relative to the enhancement in CO is independent of the concentration of biogenic species. In contrast, formaldehyde enhancements are clearly higher in the presence of biogenic species in agreement with the NOAA GFDL AM3 model. Downwind from the urban areas, CO and OA mass were not strongly enhanced relatively to a region-wide enhancement in these species that can only be explained from the accumulation of emissions in the eastern U.S. for several days. Back-trajectories of air parcels with emissions from biogenic and anthropogenic sources will be examined to elucidate the impact of both sources on CO and OA mass.