Ann M. Middlebrook,3 Charles A. Brock,3 Joost A. de Gouw,2,3 Stuart A. McKeen2,3 Leah R. Williams,4 Kelly E. Daumit,5 Andrew T. Lambe,4,6 Paul Massoli,4 Manjula R. Canagaratna,4 Ravan Ahmadov,2,3 Anthony J. Carrasquillo,5 Eben S. Cross,5 Barbara Ervens,2,3 John S. Holloway,2,3 James F. Hunter,5 Timothy B. Onasch,4,6 Ilana B. Pollack,2,3 James M. Roberts,3 Thomas B. Ryerson,3 Carsten Warneke,2,3 Paul Davidovits, x6 Douglas R. Worsnop,4 and Jesse H. Kroll5,7. (1) Department of Environmental Sciences, University of California, Riverside, 92507, United States. (2) Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, Colorado, United States. (3) Chemical Sciences Division, Earth System Research Laboratory, NOAA, Boulder, Colorado, United States (4) Aerodyne Research Inc., Billerica, Massachusetts, United States (5) Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States (6) Chemistry Department, Boston College, Chestnut Hill, Massachusetts, United States (7) Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
The explosion at the Deepwater Horizon (DWH) oil rig in April 2010 resulted in a massive oil spill in the Gulf of Mexico. Here we present results from airborne gaseous and aerosol measurements from one of the NOAA WP-3D survey flights conducted around and downwind of the oil spill site in June 2010. The analysis indicated that intermediate volatility organic compounds emitted from the aged, surface oil contributed to significant formation of secondary organic aerosol (SOA). Mass spectra of the SOA were similar to that of fresh organic aerosol typically observed in urban areas although contribution of oxygenated fragments with a hydrocarbon backbone was relatively higher. In each transect downwind of the spill site, a gradient in SOA oxygen content was observed: higher degree of oxygenation was observed in the SOA downwind of the fresher surface oil. Furthermore, size-resolved composition measurements indicated that growth of the newly formed particles with downwind distance from the site was not due to condensation of heavily oxidized SOA, but rather by condensation of moderately oxygenated hydrocarbon species. To support observations from the field, laboratory oxidation experiments of evaporated crude oil were conducted. Mass spectral comparisons between ambient SOA and laboratory-generated SOA will be presented.