Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 5 4 2005 10.5194/acpd-5-4801-2005 http://www.atmos-chem-phys-discuss.net/5/4801/2005/ http://www.atmos-chem-phys-discuss.net/5/4801/2005/acpd-5-4801-2005.html http://www.atmos-chem-phys-discuss.net/5/4801/2005/acpd-5-4801-2005.pdf 4801 4843 2005-07-13 Observations of total alkyl nitrates within the Sacramento Urban Plume P. A. Cleary J. G. Murphy P. J. Wooldridge D. A. Day D. B. Millet M. McKay A. H. Goldstein R. C. Cohen Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA Department of Environmental Science, Policy and Management, University of California, Berkeley, Berkeley, CA 94720, USA Department of Earth and Planetary Science, University of California, Berkeley, Berkeley, CA 94720, USA Environment Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA now at: Department of Chemistry, University of Leeds, Leeds LS2 9JT, UK now at: Department of Land, Air, and Water Resources, University of California, Davis, Davis, CA, USA now at: Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA During the summer of 2001, NO₂, total peroxy nitrates (ΣPNs), total alkyl nitrates (ΣANs), HNO₃, volatile organic compounds (VOC), CO₂, O₃, and meteorological variables were measured at Granite Bay, CA. The diurnal variation in ΣPNs, ΣANs and HNO₃ were all strongly correlated with sunlight, indicating both that they are photochemically produced and that they have a lifetime of a few hours at this site. The mixing ratios of ΣANs ranged as high as 2 ppbv. Mixing ratios at night averaged 0.4 ppbv. Odd-oxygen (O_x=O₃+NO₂) and ΣANs were strongly correlated reflecting both the common chemical source terms and the similar lifetimes of both species. Several approaches to interpreting the simultaneous variations of O_x and ΣANs are described, and used to derive a best estimate of the ΣAN yield from the VOC mixture at this site of 4.2% and an estimate of the range that is consistent with the observations of 3.9–5.8%. A yield of 4.2% implies termination of the HO_x catalytic cycle by ΣAN formation once every 24 cycles. Analysis of the HNO₃ observations in combination with the ΣAN and O₃ measurements suggests that NO_x terminations limit the HO_x chain length to between 4.7 and 6.3.