1. Low-Wind/High Particulate Matter Episodes in the Calexico/Mexicali Region 1 The University of Utah 2 Universidad Autónoma de Baja California 3 San Diego State University, Imperial Valley Low-Wind/High Particulate Matter Episodes in the Calexico/Mexicali Region K.E. Kelly 1, I.C. Jaramillo 1, M. Quintero-Núñez 2, K. Collins 3, H.L.C. Meuzelaar 1, J.Villar 2,, C. Gonzalez 2, M. Bejarano 3, D. Wagner 2, and J.S. Lighty 1 1 The University of Utah 2 Universidad Autónoma de Baja California 3 San Diego State University, Imperial Valley Axel Schönbucher: Essen-Duisburg

2. Objectives Determine the frequency and severity of short-term PM episodes in the Imperial/Mexicali Valley. Identify the significant organic species in PM 10 samples. Determine if PM 10 composition varies significantly during high-wind/high PM episodes as compared to low-wind/high PM episodes. Perform a preliminary attribution of PM 10 to its major organic source contributions.

3. Axel Schönbucher: Essen-Duisburg Study Locations

4. Axel Schönbucher: Essen-Duisburg Sampling Setup

5. Axel Schönbucher: Essen-Duisburg PM 10 Hourly Example Calexico DusTrack, and windspeed data from January 17-18 2006.

6. Axel Schönbucher: Essen-Duisburg Summary of Filters A total of 31 sets of filters collected plus 4 blanks (25 used) from Winter 2006 and 5 filters from June 2004. Analyzed all filters for organics and selected filters for inorganics. All GC/MS chromatograms show similar chemistry. Winter filters - alkanes, alkanoic acids, PAHs, terpenoids, esters, benzaldehydes, and heteroaromatic compounds: butoxyethoxyethanol and quinoline.

7. Axel Schönbucher: Essen-Duisburg Hourly average PM 2.5 concentrations and windspeed during December, January, and February (2004-2006), Ethel St. monitoring station, California Air Resources Board. CARB PM 2.5 Hourly Winter Data

8. Axel Schönbucher: Essen-Duisburg Hourly average PM 2.5 concentrations and windspeed during June, July, and August (2004- 2006), Ethel St. monitoring station, California Air Resources Board. CARB PM 2.5 Hourly Summer Data

9. Axel Schönbucher: Essen-Duisburg Count of hours during the winter (December, January, and February) and summer (June, July, and August) that exceed PM 2.5 concentration of 35 μg/m 3 from the California Air Resources Board, Ethel St. monitoring station, Calexico, CA for the years 2004 - 2006. CARB PM 2.5 Hours Exceeding 35  g/m 3

10. Axel Schönbucher: Essen-Duisburg Receptor samples 31 PM10 Calexico/Mexicali samples collected in winter 2006 (25 used) 5 PM10 evening samples collected during June 2004 PM 10 Source Attribution Attribution techniques Reduced compounds to 42 Principal component analysis (PCA)/ principal component regression (PCR) Positive matrix factorization (PMF) Examined correlation coefficients between the reference source profiles and the PCA/PCR and PMF results Source profiles Literature profiles – 19 with 169 compounds for vehicle emissions, road dust, meat cooking, wood burning, and natural gas combustion Local profiles – 7 with 90 organic compounds for agricultural burning of wheat and canola (Imperial Valley) and trash burning (El Paso)

11. Axel Schönbucher: Essen-Duisburg Total Calexico - Winter Total Mexicali- Winter PMF Results – All Samples

12. Axel Schönbucher: Essen-Duisburg Comparison of the relative contribution results produced by PCR for both the average U.S (Calexico) and Mexican (Mexicali) receptor samples. Total Calexico - Winter Total Mexicali- Winter PCRResults – All Samples PCR Results – All Samples

13. Axel Schönbucher: Essen-Duisburg Comparison of the relative contribution results produced by PCR for the average of five Calexico receptor samples, collected during June 2004. PCRResults – Summer Samples PCR Results – Summer Samples

14. Axel Schönbucher: Essen-Duisburg Conclusions Low-wind/high PM episodes are relatively common during winter months. These episodes are responsible for a large portion of the daily PM mass and can involve PM 10 concentrations that exceed 500  g/m 3 and PM spikes of hundreds of  g/m 3. The organic analyses of the filters show that all of the wintertime samples regardless of wind conditions tended have similar organic composition, suggesting that the PM episodes are due to meteorological phenomena. In both Calexico and Mexicali, vehicle emissions (41.1-62.1%), biomass burning (14.1-26.4%), trash burning (16.6-24.1%) and road dust emissions (12.3-14.4%) tended to be the predominant organic sources contributing to the ambient PM concentrations. PM contributions estimated by PMF and PCR were comparable. The summer samples indicated a larger contribution from agricultural burns and no contributions from the home-heating sources (wood burning and natural gas) than found in the winter samples.

15. Axel Schönbucher: Essen-Duisburg This work was sponsored by the Southwest Consortium for Environmental Research and Policy (SCERP) through a cooperative agreement with the U.S. Environmental Protection Agency. SCERP can be contacted for further information through www.scerp.org and scerp@mail.sdsu.edu.scerp@mail.sdsu.edu Thanks to Cristina Jaramillo, one of the co-authors, who helped with this presentation, performed the GC/MS analysis, and source attribution. Acknowledgments