1. Contributions of Organic Compound Pollutants to Ozone and Fine Particulate Matter in Mexicali, Mexico Jonathan O. Allen, Daniel A. Gonzales, Qinyue Sun SCERP Research Meeting 12 Dec 2006 Berk Knighton Montana State University Alberto Mendoza, Adriana A. Gutierrez, Erik I. Pardo Instituto Tecnogico y de Estudios Superiores de Monterrey

2. Atmospheric Sampling 13-22 April 2005 at Universidad Autonoma de Baja California At UABC: SUMMA cannisters Quadrupole Aerosol Mass Spectrometer High volume impactor In Aerodyne Mobile Lab: Proton Transfer Reaction Mass Spectrometer Quadrupole Aerosol Mass Spectrometer Tunable Infrared Laser Differential Absorption Sensor Infrared Hygrometer Chemiluminescence (NOx) Monitor (Funded by LASPAU)

3. Volatile Organic Compounds High concentrations mornings and evenings with low wind Low concentrations in afternoons due to vertical mixing

4. Analysis of VOC Data Vehicle emission contributions to VOCs –High correlation between ethene, propylene and benzene –Benzene/toluene ratio of ~0.4 –Strong correlation between TNMOC and CO VOC contributions from non-catalyst equipped vehicles –Ethene/acetylene ratios (~0.8) Little photochemical oxidation (nearby sources) –Xylenes/benzene ratio ~2 Stable and high VOCs since 1997 a Zielinska et al., 1999 b Fujita et al., 2004

5. Quadrupole Aerosol Mass Spectrometer Quantitative speciation of nonrefractory PM 1.0 every 5 min

6. PM 1.0 Composition

7. PM Conclusions Organic compounds were the most important component of nonrefractory PM 1.0. The temporal evolution suggests vehicle source. Concentrations of PAHs and hopanes suggest vehicles as main PM source. Additional, less important sources of PM are –cooking as indicated by cholesterol –agricultural dust as indicated by odd-numbered normal alkanes associated with coarse PM. Local sources and meteorology explains hourly and daily variations in concentration.

8. Acknowledgements Funding by EPA under Federal Grant/Contract No. XA-83239201-0 as part of the Southwest Consortium for Environmental Research and Policy programs Municipality of Mexicali Mexicali’s air quality monitoring network Universidad Autónoma de Baja California Volatile organic compounds in the downtown area of Mexicali, Mexico during the spring of 2005: Analysis of ambient data, A. Mendoza, A. A. Gutierrez, E. I. Pardo, and J. O. Allen. Air and Waste Management Assoc. Conference, 2006.