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Traffic Related Emissions of Radical Precursors HCHO and HONO in Los Angeles During CalNex

This study examines the traffic-related emissions of formaldehyde (HCHO) and nitrous acid (HONO) in Los Angeles during the CalNex campaign. The results show an increase in HCHO and HONO during rush hours and a higher HCHO/CO and HONO/CO ratio compared to roadside measurements in Houston.

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Traffic Related Emissions of Radical Precursors HCHO and HONO in Los Angeles During CalNex

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  1. Traffic Related Emissions of Radical Precursors HCHO and HONO in Los Angeles During CalNex S. Alvarez1, B. Rappenglück1, P.R. Veres2,3, J.M. Roberts2, A.K. Cochran4, C. Afif5,6, V. Michoud5, J.F. Doussin5, A. Borbon5, H. Osthoff7 (1) Department of Earth and Atmospheric Sciences, University of Houston, TX/USA (2) NOAA Earth System Research Laboratory, Boulder, CO/USA (3) Max-Planck Institut für Chemie, Mainz, Germany (4) North Carolina Agricultural and Technical State University, Greensboro, NC/USA (5) LISA, UMR-CNRS 7583, Université Paris Est Créteil, Université Paris Diderot, Créteil, France (6) Department of Chemistry, Faculty of Science, Saint Joseph University, Beirut, Lebanon (7) University of Calgary, Canada

  2. Sources of OH • early morning • midmorning • afternoon nm nm

  3. Secondary formation through photochemical breakdown of anthropogenic and biogenic VOCs. Primary emission through incomplete combustion. Potential sources: mobile sources (traffic exhaust) point sources (in petrochemical production). Formation of Formaldehyde (HCHO) Formation of Nitrous Acid (HONO) • Gas phase • NO + OH → HONO • Heterogeneous formation • 2NO2 + H2O → HONO + HNO3 • Photo-enhanced heterogeneous reactions • Primary emission through combustion processes

  4. Traffic Related Emissions of HONO and HCHO • So far only scarce traffic emissions data is available which includes both compounds. `

  5. Traffic Related Emissions of HONO and HCHO • So far only scarce traffic emissions data is available which includes both compounds. • In particular for HONO traffic related data was obtained more than a decade ago. - mostly in Europe - tunnel measurements (heavy duty vehicles?) `

  6. Traffic Related Emissions of HONO and HCHO • So far only scarce traffic emissions data is available which includes both compounds. • In particular for HONO traffic related data was obtained more than a decade ago. - mostly in Europe - tunnel measurements (heavy duty vehicles?) • However, this knowledge is needed to further refine and validate air quality modeling. `

  7. Traffic Related Emissions of HONO and HCHO • So far only scarce traffic emissions data is available which includes both compounds. • In particular for HONO traffic related data was obtained more than a decade ago. - mostly in Europe - tunnel measurements (heavy duty vehicles?) • However, this knowledge is needed to further refine and validate air quality modeling. • Primary goal: HCHO/CO, HONO/CO (CO: traffic marker) `

  8. Measurements CalNex Pasadena Site

  9. Measurements CalNex Pasadena Site CalNex Pasadena Site

  10. Measurements CalNex Pasadena Site CalNex Pasadena Site

  11. Day (6 am – 8 pm) Night (8 pm – 6 am) CO Night Day

  12. Day (6 am – 8 pm) Night (8 pm – 6 am) PAN Night Day

  13. Day (6 am – 8 pm) Night (8 pm – 6 am) HCHO Night Day

  14. Day (6 am – 8 pm) Night (8 pm – 6 am) HONO Night Day

  15. Evening rush hour Morning rush hour

  16. Morning rush hour Morning

  17. Noon Morning rush hour Morning Noon

  18. Noon Evening rush hour Morning rush hour Evening Morning Noon

  19. Evening Morning Noon

  20. Evening Morning Noon

  21. Evening rush hour Morning rush hour Evening Morning Noon

  22. 8:00-10:00 pm 4:30-6:00 am Time frames taken for correlation analysis Evening Morning

  23. HCHO vs CO (weekdays) 4:30-6:00 am (PAN < 300 ppt)

  24. HCHO vs CO (weekdays) 4:30-6:00 am (PAN < 300 ppt) 4:30-6:00 am and 8:00-10:00 pm (PAN < 300 ppt)

  25. HCHO vs CO (weekdays) 4:30-6:00 am (PAN < 300 ppt) 4:30-6:00 am and 8:00-10:00 pm (PAN < 300 ppt) Comparison: Houston/TX Highway Junction 07/15-10/15/09 y = 2.66(±0.13) – 140.0(±45.3) R2=0.75 y = 2.98(±0.13) + 484.5(±46.1) R2=0.69 (i) weekdays (ii) rush hour time 5:00-9:00 am (iii) global radiation < 10 Wm-2 (iv) PAN < 50 ppt (v) no precipitation (vi) RH > 80% CalNex-Pasadena “higher”

  26. HONO vs CO (weekdays) 4:30-6:00 am (PAN < 300 ppt)

  27. HONO vs CO (weekdays) 4:30-6:00 am (PAN < 300 ppt) 4:30-6:00 am and 8:00-10:00 pm (PAN < 300 ppt)

  28. HONO vs CO (weekdays) 4:30-6:00 am (PAN < 300 ppt) 4:30-6:00 am and 8:00-10:00 pm (PAN < 300 ppt) Comparison: Houston/TX Highway Junction 07/15-10/15/09 y = 2.66(±0.13) – 140.0(±45.3) R2=0.75 (i) weekdays (ii) rush hour time 5:00-9:00 am (iii) global radiation < 10 Wm-2 (iv) PAN < 50 ppt (v) no precipitation (vi) RH > 80% CalNex-Pasadena “higher”

  29. HCHO and HONO traffic related emissions during CalNex; preliminary results: • Increase of HCHO and HONO during rush hour(s) • HCHO <> CO ratio: slope around 3.5 - 4.9 pptv HCHO/ 1 ppbv CO • HONO <> CO ratio: slope around 3.3 - 4.2 pptv HONO/ 1 ppbv CO • Higher than in roadside study in Houston But: in Houston: PAN < 50 ppt; in CalNex-Pasadena: PAN < 300 ppt) - CalNex-Pasadena: more aged air masses? - Traffic composition? - Traffic flow?

  30. HCHO and HONO traffic related emissions during CalNex; preliminary results: • Increase of HCHO and HONO during rush hour(s) • HCHO <> CO ratio: slope around 3.5 - 4.9 pptv HCHO/ 1 ppbv CO • HONO <> CO ratio: slope around 3.3 - 4.2 pptv HONO/ 1 ppbv CO • Higher than in roadside study in Houston But: in Houston: PAN < 50 ppt; in CalNex-Pasadena: PAN < 300 ppt) - CalNex-Pasadena: more aged air masses? - Traffic composition? - Traffic flow? • What next? • HONO: final QA, inclusion of additional HONO data (NOAA) • PAN: filling gaps in PAN data (GC?) • Merging with VOC and NOx data • Source apportionment • Comparison with MOBILE6 / MOVES2010 traffic emissions modeling

  31. HCHO and HONO traffic related emissions during CalNex; preliminary results: • Increase of HCHO and HONO during rush hour(s) • HCHO <> CO ratio: slope around 3.5 - 4.9 pptv HCHO/ 1 ppbv CO • HONO <> CO ratio: slope around 3.3 - 4.2 pptv HONO/ 1 ppbv CO • Higher than in roadside study in Houston But: in Houston: PAN < 50 ppt; in CalNex-Pasadena: PAN < 300 ppt) - CalNex-Pasadena: more aged air masses? - Traffic composition? - Traffic flow? • What next? • HONO: final QA, inclusion of additional HONO data (NOAA) • PAN: filling gaps in PAN data (GC?) • Merging with VOC and NOx data • Source apportionment • Comparison with MOBILE6 / MOVES2010 traffic emissions modeling Acknowledgements: • NOAA: Roberts et al., Borbon et al., Osthoff • JJJ: Alvarez, Rappenglück

  32. weekend weekend

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