Impact of organic nitrates on urban ozone production

• Main Authors: D. K. Farmer, A. E. Perring, P. J. Wooldridge, D. R. Blake, A. Baker, S. Meinardi, L. G. Huey, D. Tanner, O. Vargas, R. C. Cohen
• Format: Article
• Language: English
• Published: Copernicus Publications 2011-05-01
• Series: Atmospheric Chemistry and Physics
• Online Access: http://www.atmos-chem-phys.net/11/4085/2011/acp-11-4085-2011.pdf

Urban O<sub>3</sub> is produced by photochemical chain reactions that amplify background O<sub>3</sub> in mixtures of gaseous nitrogen oxides (NO<sub>x</sub>) and organic molecules. Current thinking treats NO<sub>x</sub> and organics as independent variables that limit O<sub>3</sub> production depending on the NO<sub>x</sub> to organic ratio; in this paradigm, reducing organics either has no effect or reduces O<sub>3</sub>. We describe a theoretical counterexample where NO<sub>x</sub> and organics are strongly coupled and reducing organics increases O<sub>3</sub> production, and illustrate the example with observations from Mexico City. This effect arises from chain termination in the HO<sub>x</sub> and NO<sub>x</sub> cycles via organic nitrate production. We show that reductions in VOC reactivity that inadvertently reduce organic nitrate production rates will be counterproductive without concurrent reductions in NO<sub>x</sub> or other organics.