Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 9 19 2009 10.5194/acp-9-7623-2009 http://www.atmos-chem-phys.net/9/7623/2009/ http://www.atmos-chem-phys.net/9/7623/2009/acp-9-7623-2009.html http://www.atmos-chem-phys.net/9/7623/2009/acp-9-7623-2009.pdf 7623 7641 2009-10-12 Closing the peroxy acetyl nitrate budget: observations of acyl peroxy nitrates (PAN, PPN, and MPAN) during BEARPEX 2007 B. W. LaFranchi G. M. Wolfe J. A. Thornton thornton@atmos.washington.edu S. A. Harrold E. C. Browne K. E. Min P. J. Wooldridge J. B. Gilman W. C. Kuster P. D. Goldan J. A. de Gouw M. McKay A. H. Goldstein X. Ren J. Mao R. C. Cohen Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA Department of Chemistry, University of Washington, Seattle, WA, USA Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA Department of Earth and Planetary Science, University of California, Berkeley, CA, USA NOAA/ESRL Chemical Sciences Division, Boulder, CO, USA Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA, USA Department of Meteorology, Penn State University, University Park, PA, USA now at: California Air Resources Board, Sacramento, CA, USA now at: Rubenstein School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA now at: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA Acyl peroxy nitrates (APNs, also known as PANs) are formed from the oxidation of aldehydes and other oxygenated VOC (oVOC) in the presence of NO₂. There are both anthropogenic and biogenic oVOC precursors to APNs, but a detailed evaluation of this chemistry against observations has proven elusive. Here we describe measurements of PAN, PPN, and MPAN along with the majority of chemicals that participate in their production and loss, including OH, HO₂, numerous oVOC, and NO₂. Observations were made during the Biosphere Effects on AeRosols and Photochemistry Experiment (BEARPEX 2007) in the outflow of the Sacramento urban plume. These observations are used to evaluate a detailed chemical model of APN ratios and concentrations. We find that the ratios of APNs are nearly independent of the loss mechanisms and thus an especially good test of our understanding of their sources. 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