Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 5 2 2005 10.5194/acp-5-483-2005 http://www.atmos-chem-phys.net/5/483/2005/ http://www.atmos-chem-phys.net/5/483/2005/acp-5-483-2005.html http://www.atmos-chem-phys.net/5/483/2005/acp-5-483-2005.pdf 483 491 2005-02-15 Measurements of N₂O₅, NO₂, and O₃ east of the San Francisco Bay E. C. Wood T. H. Bertram P. J. Wooldridge R. C. Cohen Department of Chemistry, University of California, Berkeley, California Department of Earth and Planetary Sciences, University of California, Berkeley, California Energy and Environment Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California We report in situ measurements of N₂O₅, NO₂, and O₃ in Contra Costa County, California during January 2004. Mixing ratios of N₂O₅, an intermediate compound in the atmosphere's nocturnal cleansing process, ranged up to 200pmol/mol at night. The highest N₂O₅ concentrations were correlated with low O₃ and high NO₂ concentrations. The calculated steady state lifetime for N₂O₅ ranged from 5 to 30min. The total HNO₃ produced by N₂O₅ hydrolysis over a 14h night was comparable to ambient NO₂ concentrations, and is estimated to be a factor of nine bigger than the HNO₃ produced during the day.