<?xml version="1.0" encoding="utf-8" standalone="no"?>
<!DOCTYPE article SYSTEM "http://www.atmos-chem-phys.net/inc/acp/copernicus.dtd">
<article language="en">
	<journal>
		<journal_title>Atmospheric Chemistry and Physics</journal_title>
		<journal_url>www.atmos-chem-phys.net</journal_url>
		<issn>1680-7316</issn>
		<eissn>1680-7324</eissn>
		<volume_number>6</volume_number>
		<issue_number>10</issue_number>
		<publication_year>2006</publication_year>
	</journal>
	<doi>10.5194/acp-6-3163-2006</doi>
	<article_url>http://www.atmos-chem-phys.net/6/3163/2006/</article_url>
	<abstract_html>http://www.atmos-chem-phys.net/6/3163/2006/acp-6-3163-2006.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys.net/6/3163/2006/acp-6-3163-2006.pdf</fulltext_pdf>
	<start_page>3163</start_page>
	<end_page>3180</end_page>
	<publication_date>2006-08-01</publication_date>
	<article_title content_type="html">Technical note: Evaluation of standard ultraviolet absorption ozone monitors in a polluted urban environment</article_title>
	<authors>
		<author numeration="1" affiliations="1,7">
			<name>E. J. Dunlea</name>
			<email>edward.dunlea@colorado.edu</email>
		</author>
		<author numeration="2" affiliations="2">
			<name>S. C. Herndon</name>
		</author>
		<author numeration="3" affiliations="2">
			<name>D. D. Nelson</name>
		</author>
		<author numeration="4" affiliations="1">
			<name>R. M. Volkamer</name>
		</author>
		<author numeration="5" affiliations="3">
			<name>B. K. Lamb</name>
		</author>
		<author numeration="6" affiliations="3">
			<name>E. J. Allwine</name>
		</author>
		<author numeration="7" affiliations="4">
			<name>M. Grutter</name>
		</author>
		<author numeration="8" affiliations="5">
			<name>C. R. Ramos Villegas</name>
		</author>
		<author numeration="9" affiliations="6">
			<name>C. Marquez</name>
		</author>
		<author numeration="10" affiliations="6">
			<name>S. Blanco</name>
		</author>
		<author numeration="11" affiliations="6">
			<name>B. Cardenas</name>
		</author>
		<author numeration="12" affiliations="2">
			<name>C. E. Kolb</name>
		</author>
		<author numeration="13" affiliations="1">
			<name>L. T. Molina</name>
		</author>
		<author numeration="14" affiliations="1">
			<name>M. J. Molina</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Department of Earth, Atmospheric and Planetary Sciences,  Massachusetts Institute of Technology, Bldg. 54, 77 Massachusetts Ave,  Cambridge, MA 02139, USA</affiliation>
		<affiliation numeration="2" content_type="html">Aerodyne Research Inc., 45 Manning Road, Billerica MA 01821-3876, USA</affiliation>
		<affiliation numeration="3" content_type="html">Laboratory for Atmospheric Research, Department of Civil and  Environmental Engineering, Washington State University, 101 Sload Hall,  Spokane Street, Pullman, WA 99164-2910, USA</affiliation>
		<affiliation numeration="4" content_type="html">Centro de Ciencias de la Atm&amp;oacute;sfera, UNAM, Ciudad Universitaria,  04510 Mexico City, Mexico</affiliation>
		<affiliation numeration="5" content_type="html">Gobierno del Distrito Federal, Agricultura 21, Piso 1, Col.  Escandon, Del. M. Hidalgo, CP 11800, Mexico, D.F., Mexico</affiliation>
		<affiliation numeration="6" content_type="html">Centro Nacional de Investigacion y Capacitacion Ambiental-INE, Av.  Periférico 5000, Col. Insurgentes Cuicuilco, CP 04530, Mexico, D.F.  Mexico</affiliation>
		<affiliation numeration="7" content_type="html">now at: University of Colorado at Boulder, Cooperative Institute for  Research in Environmental Sciences, UCB 216, Boulder, CO 80309, USA</affiliation>
	</affiliations>
	<abstract content_type="html">The performance of the EPA Federal Equivalent Method (FEM) technique for
monitoring ambient concentrations of O&lt;sub&gt;3&lt;/sub&gt; via ultraviolet absorption (UV)
has been evaluated using data from the Mexico City Metropolitan Area
 field campaign (MCMA-2003). Comparisons of UV O&lt;sub&gt;3&lt;/sub&gt; monitors with open
path Differential Optical Absorption Spectroscopy (DOAS) and open path
Fourier Transform Infrared (FTIR) spectroscopy instruments in two locations
revealed average discrepancies in the measured concentrations between +13% to
&amp;minus;18%. Good agreement of two separate open path DOAS measurements at one
location indicated that spatial and temporal inhomogeneities were not
substantially influencing comparisons of the point sampling and open path
instruments. The poor agreement between the UV O&lt;sub&gt;3&lt;/sub&gt; monitors and the open
path instruments was attributed to incorrect calibration factors for the UV
monitors, although interferences could not be completely ruled out. Applying
a linear correction to these calibration factors results in excellent
agreement of the UV O&lt;sub&gt;3&lt;/sub&gt; monitors with the co-located open path
measurements; regression slopes of 0.94 to 1.04 and associated R&lt;sup&gt;2&lt;/sup&gt;
values of &amp;gt;0.89. A third UV O&lt;sub&gt;3&lt;/sub&gt; monitor suffered from large spurious
interferences, which were attributed to extinction of UV radiation within
the monitor by fine particles (&amp;lt;0.2 &amp;micro;m). The overall performance of
this particular monitor was poor owing to a combination of interferences
from a contaminated particle filter and/or ozone scrubber. Suggestions for
improved operation practices of these UV O&lt;sub&gt;3&lt;/sub&gt; monitors and
recommendations for future testing are made.</abstract>
	<references>
		<reference numeration="1" content_type="text"> Arshinov, M. Y., Belan, B. D., Krasnov, O. A., Kovalevskii, V. K., Pirogov, V. A., Plotnikov, A. P., Tolmachev, G. N., and Fofonov, A. V.: Comparison of ultraviolet and chemiluminescent ozonometers, Atmos. Oceanic Opt., 15(8), 656&amp;ndash;658, 2002. </reference>
		<reference numeration="2" content_type="text"> ASTM: Standard Test Methods for Continuous Measurement of Ozone in Ambient, Workplace, and Indoor Atmospheres (Ultraviolet Absorption), Annual Book of ASTM Standards, American Society of Testing and Materials International, 2003. </reference>
		<reference numeration="3" content_type="text"> Bass, A. M. and Paur, R. J.: UV Absorption Cross-Sections for Ozone &amp;ndash; the Temperature-Dependence, J. Photochem., 17, 141&amp;ndash;141, 1981. </reference>
		<reference numeration="4" content_type="text"> Butcher, S. and Ruff, R. E.: Effect of Inlet Residence Time on Analysis of Atmospheric Nitrogen Oxides and Ozone, Anal. Chem., 43(13), 1890, 1971. </reference>
		<reference numeration="5" content_type="text"> Canagaratna, M. R., Jayne, J. T., Ghertner, A., Herndon, S. C., Shi, Q., Jimenez, J. L., Silva, P., Williams, P., Lanni, T., Drewnick, F., Demerjian, K. L., Kolb, C. E., and Worsnop, D. R.: Chase Studies of Particulate Emissions from in-use New York City Vehicles, Aerosol Sci. Technol., 38(6), 555&amp;ndash;573, 2004. </reference>
		<reference numeration="6" content_type="text"> Cavanagh, R. R. and Verkouteren, R. M.: Improving the Scientific Basis for Informed Decisions on Atmospheric Issues, NIST-NOAA-Industry Workshop on Atmospheric Measures and Standards, National Institute of Standards and Technology, 2001. </reference>
		<reference numeration="7" content_type="text"> Chow, J. C.: Diesel Engines: Environmental Impact and Control &amp;ndash; A Critical Review Introduction, J. Air Waste Manage. Assoc., 51, 807&amp;ndash;808, 2001. </reference>
		<reference numeration="8" content_type="text"> de Foy, B., Caetano, E., Maga&amp;ntilde;a, V., Zitácuaro, A., Cardenas, B., Retama, A., Ramos, R., Molina, L. T., and Molina, M. J.: Mexico City basin wind circulation during the MCMA-2003 field campaign, Atmos. Chem. Phys., 5, 2267&amp;ndash;2288, 2005a. </reference>
		<reference numeration="9" content_type="text"> de Foy, B., Molina, L. T., Molina, M. J., Caetano, E., Maga&amp;ntilde;a, V., and Zitácuaro, A.: Meteorological and Photochemical Conditions during the MCMA-2003 Field Campaign, Atmos. Chem. Phys. Discuss., 5, 2503&amp;ndash;2558, 2005b. </reference>
		<reference numeration="10" content_type="text"> Demerjian, K. L.: A review of national monitoring networks in North America, Atmos. Environ., 34, 1861&amp;ndash;1884, 2000. </reference>
		<reference numeration="11" content_type="text"> Environmental Protection Agency, U.S.: Air Quality Criteria for Oxides of Nitrogen, Office of Research and Development, 1993. </reference>
		<reference numeration="12" content_type="text"> Environmental Protection Agency, U.S.: Quality Assurance Handbook for Air Pollution Measurement Systems; Volume II: Part 1; Ambient Air Quality Monitoring Program Quality System Development, Office of Air Quality Planning and Standards, http://www.epa.gov/ttn/amtic/files/ambient/qaqc/redbook.pdf, 1998. </reference>
		<reference numeration="13" content_type="text"> Environmental Protection Agency, U.S.: US EPA Audit of RAMA Network, http://www.sma.df.gob.mx/sma/download/archivos/auditoria_epa_ingles.pdf, 2003. </reference>
		<reference numeration="14" content_type="text"> Environmental Protection Agency, U.S.: National Ambient Air Monitoring Strategy, Office of Air Quality Planning and Standards, http://www.epa.gov/ttn/amtic/files/ambient/monitorstrat/naamstrat2005.pdf, 2005. </reference>
		<reference numeration="15" content_type="text"> Fayt, C. and van Roozendael, M.: WinDoas 2.1 Software User Manual, 2001. </reference>
		<reference numeration="16" content_type="text"> Flores, E., Grutter, M., Galle, B., Mellqvist, J., Samuelsson, J., Knighton, B., Jobson, B. T., Volkamer, R., Molina, L. T., and Molina, M. J.: American Geophysical Union Fall Meeting, EOS Trans., 85 (47), Abstract A11A-0003, 2004. </reference>
		<reference numeration="17" content_type="text"> Grosjean, D. and Harrison, J.: Response of Chemiluminescent NOx Analyzers and Ultraviolet Ozone Analyzers to Organic Air Pollutants, Environ. Sci. Technol., 19(9), 862, 1985. </reference>
		<reference numeration="18" content_type="text"> Grutter, M. and Flores, E.: Air pollution monitoring with two optical remote sensing techniques in Mexico City, SPIE, Proceedings of SPIE, 2004. </reference>
		<reference numeration="19" content_type="text"> Grutter, M., Flores, E., Basaldud, R., and Ruiz-Suarez, L. G.: Open-path FTIR spectroscopic studies of the trace gases over Mexico City, Atmos. Ocean. Opt., 16, 232&amp;ndash;236, 2003. </reference>
		<reference numeration="20" content_type="text"> Herndon, S. C., Shorter, J. H., Zahniser, M. S., Wormhoudt, J., Nelson, D. D., Demerjian, K. L., and Kolb, C. E.: Real-Time Measurements of SO&lt;sub&gt;2&lt;/sub&gt;, H&lt;sub&gt;2&lt;/sub&gt;CO and CH&lt;sub&gt;4&lt;/sub&gt; Emissions from In-Use Curbside Passenger Buses in New York City Using a Chase Vehicle, Environ. Sci. Technol., 39, 7984&amp;ndash;7990, 2005. </reference>
		<reference numeration="21" content_type="text"> Hudgens, E. E., Kleindienst, T. E., MeElroy, F. F., and Ollison, W. M.: A Study of Interferences in Ozone UV and Chmiluminescence Monitors, Measurement of Toxic and Related Air Pollutants, Air Waste Manage. Assoc., 405, 1994. </reference>
		<reference numeration="22" content_type="text"> Huntzicker, J. J. and Johnson, R. L.: Investigation of an Ambient Interference in the Measurement of Ozone by Ultraviolet Absorption Photometry, Environ. Sci. Technol., 13(11), 1414&amp;ndash;1416, 1979. </reference>
		<reference numeration="23" content_type="text"> Jayne, J. T., Leard, D. C., Zhang, X., Davidovits, P., Smith, K. A., Kolb, C. E., and Worsnop, D. R.: Development of an Aerosol Mass Spectrometer for Size and Composition Analysis of Submicron Particles, Aerosol Sci. Technol., 33(1&amp;ndash;2), 49&amp;ndash;70, 2000. </reference>
		<reference numeration="24" content_type="text"> Jiang, M., Marr, L. C., Dunlea, E. J., Herndon, S. C., Jayne, J. T., Kolb, C. E., Knighton, W. B., Rogers, T. M., Zavala, M., Molina, L. T., and Molina, M. J.: Mobile laboratory measurements of black carbon, polycyclic aromatic hydrocarbons and other vehicle emissions in Mexico City, Atmos. Chem. Phys., 5, 3377&amp;ndash;3387, 2005. </reference>
		<reference numeration="25" content_type="text"> Kittelson, D.: Engines and Nanoparticles: A Review, J. Aerosol Sci., 29, 575&amp;ndash;588, 1998. </reference>
		<reference numeration="26" content_type="text"> Kleindienst, T. E., Hudgens, E. E., Smith, D. F., MeElroy, F. F., and Bufalini, J. J.: Comparison of Chemiluminescence and Ultraviolet Ozone Monitor Responses in the Presence of Humidity and Photochemical Pollutants, J. Air Waste Manage. Assoc., 13, 213, 1993. </reference>
		<reference numeration="27" content_type="text"> Kolb, C. E., Herndon, S. C., Mcmanus, J. B., Shorter, J. H., Zahniser, M. S., Nelson, D. D. J., Jayne, J. T., Canagaratna, M. R., and Worsnop, D. R.: Mobile Laboratory with Rapid Response Instruments for Real-Time Measurements of Urban and Regional Trace Gas and Particulate Distributions and Emission Source Characteristics, Environ. Sci. Technol., 38, 5694&amp;ndash;5703, 2004. </reference>
		<reference numeration="28" content_type="text"> Lamb, B. K., Velasco, E., Allwine, E., Pressley, S., Westberg, H., Knighton, B., Rogers, T., Grimsrud, E., Jobson, T., Alexander, M., Prazeller, P., Volkamer, R., de Foy, B., Molina, L. T., Molina, M. J., Grutter, M., Bueno, E., Blanco, S., Wohrnschimmel, H., Cardenas, B., Arriaga, J. L., Limon, M. T., Escalona, S., Iglesias, G. S., Doskey, P., and Gaffney, J. S.: Ambient VOC Concentration and Emission Measurements during the MCMA 2002 and 2003 Field Campaigns, Eos Trans. AGU, 85, 47, Fall Meet. Suppl., Abstract A13E-01, 2004. </reference>
		<reference numeration="29" content_type="text"> Leston, A. R. and Ollison, W. M.: The impact of ambient aerosols on ozone as measured by ultraviolet photometry, Proceedings of the AWMA Specialty Conference, Measurement of Toxic and Related Air Pollutants, Air Waste Manage. Assoc., Pittsburgh, PA, 2000. </reference>
		<reference numeration="30" content_type="text"> Leston, A. R., Ollison, W. M., Spicer, C. W., and Satola, J.: Potential Interference Bias in Ozone Standard Compliance Monitoring, J. Air Waste Manage. Assoc., 55, 1464&amp;ndash;1472, 2005. </reference>
		<reference numeration="31" content_type="text"> Liu, B., Pui, D., and Rubow, K.: Characteristics of air sampling filter media, Marple VA, L. B., Aerosols in the mining and industrial work environments, Ann Arbor Science, 1983. </reference>
		<reference numeration="32" content_type="text"> Maddy, J. A.: Evaluating a Heated Metal Scrubber&apos;s Effectiveness in Preventing Ozone Monitor Anomalous Behavior during Hot and Humid Ambient Sampling, Proceeding of the Air &amp; Waste Management Association 91st Annual Meeting, 1999. </reference>
		<reference numeration="33" content_type="text"> Marr, L. C., Grogan, L. A., Hohrnschimmel, H., Molina, L. T., Molina, M. J., Smith, T. J., and Garshick, E.: Vehicle Traffic as a Source of Particulate Polycyclic Aromatic Hydrocarbon Exposure in the Mexico City Metropolitan Area, Environ. Sci. Technol., 38(9), 2584&amp;ndash;2592, 2004. </reference>
		<reference numeration="34" content_type="text"> McClenny, W. A., Williams, E. J., Cohen, R. C., and Stutz, J.: Preparing to Measure the Effects of the NO&lt;sub&gt;x&lt;/sub&gt; SIP Call &amp;ndash; Methods for Ambient Air Monitoring of NO, NO&lt;sub&gt;2&lt;/sub&gt;, NO&lt;sub&gt;y&lt;/sub&gt;, and Individual NO$_\rm z$ Species, J. AirWaste Manage. Assoc., 52, 542&amp;ndash;562, 2002. </reference>
		<reference numeration="35" content_type="text"> McKinley, G., Zuk, M., Hojer, M., Avalos, M., González, I., Hernández, M., Iniestra, R., Laguna, I., Martínez, M. &amp;#x00C1;., Osnaya, P., Reynales, L. M., Valdés, R., and Martínez, J.: Final Report of the Second Phase of the Integrated Environmental Strategies Program in Mexico, The Local Benefits of Global Air Pollution Control in Mexico City, Instituto Nacional de Ecología, México Instituto Nacional de Salud Publica, México, http://www.ine.gob.mx/dgicurg/cclimatico/download/benloc.pdf, 2003. </reference>
		<reference numeration="36" content_type="text"> Meyer, C. P., Elsworth, C. M., and Galbally, I. E.: Water vapor interference in the measurement of ozone in ambient air by ultraviolet absorption, Rev. Sci. Inst., 62, 223&amp;ndash;228, 1991. </reference>
		<reference numeration="37" content_type="text"> Molina, L. T. and Molina, M. J.: Air Pollution in Megacities, http://mce2.org/megacities/, 2006. </reference>
		<reference numeration="38" content_type="text"> Moya, M., Grutter, M., and Baez, A.: Diurnal variability of size-differentiated inorganic aerosols and their gas-phase precursors during January and February of 2003 near downtown Mexico City, Atmos. Environ., 38, 5651&amp;ndash;5661, 2004. </reference>
		<reference numeration="39" content_type="text"> Orphal, J. and Chance, K.: Ultraviolet and visible absorption cross-sections for HITRAN, J. Quant. Spectros. Radiat. Transfer, 82, 491&amp;ndash;504, 2003. </reference>
		<reference numeration="40" content_type="text"> Parrish, D. D. and Fehsenfeld, F. C.: Methods for gas-phase measurements of ozone, ozone precursors and aerosol precursors, Atmos. Environ., 34, 1921&amp;ndash;1957, 2000. </reference>
		<reference numeration="41" content_type="text"> Paur, R. J. and McElroy, F. F.: Technical Assistance Document for the Calibration of Ambient Ozone Monitors, United States Environmental Protection Agency, http://www.epa.gov/ttn/amtic/files/ambient/criteria/reldocs/4-79-057.pdf, 1979. </reference>
		<reference numeration="42" content_type="text"> Picquet-Varrault, B., Orphal, J., Doussin, J.-F., Carlier, P., and Flaud, J. M.: Laboratory Intercomparison of the Ozone Absorption Coefficients in the Mid-infrared (10 $\mu $m) and Ultraviolet (300&amp;ndash;350 nm) Spectral Regions, J. Phys. Chem., 109(6), 1008&amp;ndash;1014, 2005. </reference>
		<reference numeration="43" content_type="text"> Platt, U.: Chapter 2, Sigrist, M. W., Monitoring by Spectroscopic Techniques, Wiley &amp; Sons, 1994. </reference>
		<reference numeration="44" content_type="text"> Proffitt, M. H. and McLaughlin, R. J.: Fast-response dualbeam UV-absorption ozone photometer suitable for use on stratospheric balloons, Rev. Sci. Inst., 54, 1719&amp;ndash;1728, 1983. </reference>
		<reference numeration="45" content_type="text"> RAMA: Red Automatica de Monitoreo Atmosferico, http://148.243.232.103/imecaweb/base_datos.htm, 2005. </reference>
		<reference numeration="46" content_type="text"> Reynolds, S. D., Blanchard, C. L., and Ziman, S. D.: Understanding the Effectiveness of Precursor Reductions in Lowering 8-Hr Ozone Concentrations &amp;ndash; Part II. The Eastern United States, J. Air Waste Manage. Assoc., 54, 1452&amp;ndash;1470, 2004. </reference>
		<reference numeration="47" content_type="text"> Riley, D. M., Newby, C. A., Leal-Almeraz, T. O., and Thomas, V. M.: Assessing Elemental Mercury Vapor Exposure from Cultural and Religious Practices, Environ. Health Perspect., 109(8), 779&amp;ndash;784, 2001. </reference>
		<reference numeration="48" content_type="text"> Rogers, T. M., Grimsrud, E. P., Herndon, S. C., Jayne, J. T., Kolb, C. E., Allwine, E., Westberg, H., Lamb, B. K., Zavala, M., Molina, L. T., Molina, M. J., and Knighton, W. B.: On-road measurements of volatile organic compounds in the Mexico City metropolitan area using proton transfer reaction mass spectrometry, Int. Jour. of Mass Spec., 252, 26&amp;ndash;37, 2006.  </reference>
		<reference numeration="49" content_type="text"> Rothman, L. S., Barbe, A., Benner, D. C., Brown, L. R., Camy-Peyret, C., Carleer, M. R., Chance, K., Clerbaux, C., Dana, V., Devi, V. M., Fayt, A., Flaud, J. M., Gamache, R. R., Goldman, A., Jacquemart, D., Jucks, K. W., Lafferty, W. J., Mandin, J. Y., Massie, S. T., Nemtchinov, V., Newnham, D. A., Perrin, A., Rinsland, C. P., Schroeder, J., Smith, K. M., Smith, M. A. H., Tang, K., Toth, R. A., Vander Auwera, J., Varanasi, P., and Yoshino, K.: The HITRAN molecular spectroscopic database: edition of 2000 including updates through 2001, J. Quant. Spectros. Radiat. Transfer, 82, 5&amp;ndash;44, 2003. </reference>
		<reference numeration="50" content_type="text"> Ryerson, T. B., Buhr, M. P., Frost, G. J., Goldan, P. D., Holloway, J. S., Hübler, G., Jobson, B. T., Kuster, W. C., McKeen, S. A., Parrish, D. D., Roberts, J. M., Sueper, D. T., Trainer, M., Williams, J., and Fehsenfeld, F. C.: Emissions lifetimes and ozone formation in power plant plumes, J. Geophys. Res., 103(D17), 22 569&amp;ndash;22 584, doi:10.1029/98JD01620, 1998. </reference>
		<reference numeration="51" content_type="text"> Salcedo, D., Onasch, T. B., Dzepina, K., Canagaratna, M. R., Zhang, Q., Huffman, J. A., DeCarlo, P. F., Jayne, J. T., Mortimer, P., Worsnop, D. R., Kolb, C. E., Johnson, K. S., Zuberi, B., Marr, L. C., Volkamer, R., Molina, L. T., Molina, M. J., Cardenas, B., Bernabe, R. M., Marquez, C., Gaffney, J. S., Marley, N. A., Laskin, A., Shutthanandan, V., Xie, Y., Brune, W., Lesher, R., Shirley, T., and Jimenez, J. L.: Characterization of Ambient Aerosols in Mexico City during the MCMA-2003 Campaign with Aerosol Mass Spectrometry: Results at the CENICA Supersite, Atmos. Chem. Phys., 6, 925&amp;ndash;946, 2006. </reference>
		<reference numeration="52" content_type="text"> Sander, S. P., Kurylo, M. J., Orkin, V. L., Golden, D. M., Huie, R. E., Finlayson-Pitts, B. J., Kolb, C. E., Molina, M. J., Friedl, R. R., Ravishankara, A. R., and Moortgat, G. K.: Chemical kinetics and photochemical data for use in atmospheric studies, Jet Propulsion Laboratory, California Insitute of Technology, 2002. </reference>
		<reference numeration="53" content_type="text"> Shirley, T. R., Brune, W. H., Ren, X., Mao, J., Lesher, R., Cardenas, B., Volkamer, R., Molina, L. T., Molina, M. J., Lamb, B., Velasco, E., Jobson, T., and Alexander, M.: Atmospheric oxidation in the Mexico City Metropolitan Area (MCMA) during April 2003, Atmos. Chem. Phys., 6, 2753&amp;ndash;2765, 2006. </reference>
		<reference numeration="54" content_type="text"> Shorter, J. H., Herndon, S. C., Zahniser, M. S., Nelson, D. D., Wormhoudt, J., Demerjian, K. L., and Kolb, C. E.: Real-time Measurements of Nitrogen Oxide Emissions from In-use New York City Transit Buses using a Chase Vehicle, Environ. Sci. Technol., 39, 7991&amp;ndash;8000, 2005. </reference>
		<reference numeration="55" content_type="text"> Sickles II, J. E.: Nriagu, J. O., Gaseous Pollutants: Characterization and Cycling, John Wiley &amp; Sons, Inc., 1992. </reference>
		<reference numeration="56" content_type="text"> Stevens, R. K., Drago, R. J., and Mamane, Y.: A long path differential optical absorption spectrometer and EPA-approved fixed-point methods intercomparison, Atmos. Environ., 27B, 231&amp;ndash;236, 1993. </reference>
		<reference numeration="57" content_type="text"> Stutz, J., Alicke, B., Ackermann, R., Geyer, A., White, A. and Williams, E. J.: Vertical profiles of NO3, N2O5, O3 and NOx in the nocturnal boundary layer: 1. Observations during the Texas Air Quality Study 2000, J. Geophys. Res., 109, D12306, doi:10.1029/2003JD004409, 2004. </reference>
		<reference numeration="58" content_type="text"> Stutz, J. and Platt, U.: Numerical analysis and estimation of the statistical error of differential optical absorption spectroscopy measurements with least-squares methods, Appl. Opt., 35, 6041&amp;ndash;6053, 1996. </reference>
		<reference numeration="59" content_type="text"> TCEQ: Texas Commission on Environmental Quality, http://www.tceq.state.tx.us/, 2006. </reference>
		<reference numeration="60" content_type="text"> Volkamer, R., Etzkorn, T., Geyer, A., and Platt, U.: Correction of the oxygen interference with UV spectroscopic (DOAS) measurements of monocyclic aromatic hydrocarbons in the atmosphere, Atmos. Environ., 32, 3731&amp;ndash;3747, 1998. </reference>
		<reference numeration="61" content_type="text"> Volkamer, R., Molina, L. T., Molina, M. J., Flores, E., Grutter, M., Galle, B., Mellqvist, J., Samuelsson, J., Knighton, B., and Jobson, B. T., Open-path emission factors derived from DOAS and FTIR Measurements in the Mexico City Metropolitan Area, Proc. of &quot;Air Pollution as a Climate Forcing: A Second Workshop&quot;, http://www.giss.nasa.gov/meetings/pollution2005/agenda.html, 2005a. </reference>
		<reference numeration="62" content_type="text"> Volkamer, R., Molina, L. T., Molina, M. J., Shirley, T., and Brune, B.: DOAS measurement of glyoxal as an indicator for fast VOC chemistry in urban air, Geophys. Res. Lett., 32, L08806, doi:10.1029/2005GL022616, 2005b. </reference>
		<reference numeration="63" content_type="text"> Wilson, K. L.: Water vapor interference in the UV absorption measurement of atmospheric ozone, University of Colorado, www.twobtech.com/Wilson_Thesis.pdf, 2005. </reference>
		<reference numeration="64" content_type="text"> Wisbith, A. S.: Laboratory Study to Explore Potential Interferences to Air Quality Monitors, Prepared for the USEPA/OAQPS by Battelle Science and Technology International Battelle Contract 68-D-98-030, 1999. </reference>
		<reference numeration="65" content_type="text"> Yanowitz, J., MCCormick, R. L., and Graboski, M. S.: In-Use Emissions from Heavy-Duty Diesel Vehicles, Environ. Sci. Technol., 34(5), 729&amp;ndash;740, 2000. </reference>
	</references>
</article>

