Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 7 10 2007 10.5194/acp-7-2691-2007 http://www.atmos-chem-phys.net/7/2691/2007/ http://www.atmos-chem-phys.net/7/2691/2007/acp-7-2691-2007.html http://www.atmos-chem-phys.net/7/2691/2007/acp-7-2691-2007.pdf 2691 2704 2007-05-23 Evaluation of nitrogen dioxide chemiluminescence monitors in a polluted urban environment E. J. Dunlea edward.dunlea@colorado.edu S. C. Herndon D. D. Nelson R. M. Volkamer F. San Martini P. M. Sheehy M. S. Zahniser J. H. Shorter J. C. Wormhoudt B. K. Lamb E. J. Allwine J. S. Gaffney N. A. Marley M. Grutter C. Marquez S. Blanco B. Cardenas A. Retama C. R. Ramos Villegas C. E. Kolb L. T. Molina M. J. Molina Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Bldg. 54, 77 Massachusetts Ave, Cambridge, MA 02139, USA Aerodyne Research Inc., 45 Manning Road, Billerica, MA 01821-3876, USA Laboratory for Atmospheric Research, Department of Civil and Environmental Engineering, Washington State University, 101 Sload Hall, Spokane Street, Pullman, WA 99164-2910, USA University of Arkansas at Little Rock, 2801 South University Avenue, Little Rock, AR 72204-1099, USA Centro de Ciencias de la Atmysfera, Universidad Nacional Autónoma de México, Mexico, D.F., Mexico Centro Nacional de Investigacion y Capacitacion Ambiental-INE, Av. Periférico 5000, Col. Insurgentes Cuicuilco, CP 04530, Mexico, D.F., Mexico Gobierno del Distrito Federal, Agricultura 21, Piso 1, Col. Escandon, Del. M. Hidalgo, CP 11800, Mexico, D. F., Mexico Molina Center for Energy and the Environment, 3262 Holiday Ct. Suite, 201 La Jolla CA, 92037, USA now at: University of Colorado at Boulder, Cooperative Institute for Research in Environmental Sciences, UCB 216, Boulder, CO 80309, USA now at: University of California at San Diego, 9500 Gilman Drive, 0356 La Jolla, CA 92093-0356, USA Data from a recent field campaign in Mexico City are used to evaluate the performance of the EPA Federal Reference Method for monitoring the ambient concentrations of NO₂. Measurements of NO₂ from standard chemiluminescence monitors equipped with molybdenum oxide converters are compared with those from Tunable Infrared Laser Differential Absorption Spectroscopy (TILDAS) and Differential Optical Absorption Spectroscopy (DOAS) instruments. A significant interference in the chemiluminescence measurement is shown to account for up to 50% of ambient NO₂ concentration during afternoon hours. As expected, this interference correlates well with non-NO_x reactive nitrogen species (NO_z) as well as with ambient O₃ concentrations, indicating a photochemical source for the interfering species. A combination of ambient gas phase nitric acid and alkyl and multifunctional alkyl nitrates is deduced to be the primary cause of the interference. Observations at four locations at varying proximities to emission sources indicate that the percentage contribution of HNO₃ to the interference decreases with time as the air parcel ages. Alkyl and multifunctional alkyl nitrate concentrations are calculated to reach concentrations as high as several ppb inside the city, on par with the highest values previously observed in other urban locations. Averaged over the MCMA-2003 field campaign, the chemiluminescence monitor interference resulted in an average measured NO₂ concentration up to 22% greater than that from co-located spectroscopic measurements. 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