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Ozone Production from Wildfires in the West Part 1: Factors Influencing Ozone Production

Ozone Production from Wildfires in the West Part 1: Factors Influencing Ozone Production. Nicole Wigder Ph.D. Candidate University of Washington, Department of Atmospheric Sciences 5 March 2013. Ozone production in wildfire plumes is complex. VOCs & OVOCs + NOx → O 3 downwind transport.

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Ozone Production from Wildfires in the West Part 1: Factors Influencing Ozone Production

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  1. Ozone Production from Wildfires in the WestPart 1: Factors Influencing Ozone Production Nicole Wigder Ph.D. Candidate University of Washington, Department of Atmospheric Sciences 5 March 2013

  2. Ozone production in wildfire plumes is complex VOCs & OVOCs + NOx → O3 downwind transport • CO • CO2 • VOCs • OVOCs • NOx • PM • CH3CHO • Etc. ozone production? Photo by Jon Hee Why do some wildfires produce ozone while others do not?

  3. Review article of 132 studies Normalized Enhancement Ratios allow an analysis of variability that is not influenced by fire size or dilution: ∆O3/∆CO or ∆O3/∆CO2

  4. ∆O3/∆CO depends on biome and transport time Tropics/ Subtropics Jaffe & Wigder (2012) Boreal/ Temperate

  5. In all biomes, ozone production in wildfire plumes is NOx-limited sunlight NOx/CO2 emission factors 4.8x10-4 – 2.3x10-3 g g-1 Variation by a factor of 5! • Fuel nitrogen content: 0.2 - 4% • Combustion efficiency (smoldering ↔ flaming) • Photochemistry Photo credits: NPS, USFS VOCs & OVOCs + NOx O3

  6. NOx, PAN and downwind ozone production Aerosol NO3- HNO3 PAN: temperature dependent reservoir O3 • Within hours: • ~40% of NOx → PAN (boreal; Alvarado et al., 2010) • ~22% of NOx → PAN (temperate; Akagi et al., 2012) NOx

  7. Mount Bachelor Observatory • MBO: research site in central Oregon since 2004 • 2763 meters a.s.l. • Meteorological parameters, CO, PM1, O3, mercury • 2012 fire season: CO2, NOx, NOy, EC/OC

  8. Wildfire identification O3 CO PM1 • multiple chemical & PM measurements • HYPSLIT backward airmass trajectories • MODIS near real-time images • FIRMS fire hotspots (NASA)

  9. Wildfire PM and ozone are not always correlated Two fire plumes observed at MBO in 2012: r = 0.65 r = 0.14

  10. Ozone production in 2004-2011 wildfires • 32 wildfires • 13 produced ozone These 13 fires: • ∆O3/∆CO range: 0.01-0.51 • Large variation within a small geographic area MBO Wigder et al., submitted to Atmos. Environ.

  11. Mixed urban/ fire events • That’s a factor of 7 increase in mixed plumes! • Similar results for Californian plumes (Singh et al., 2012) Wildfire plumes transported < 1 day:

  12. 2012 wildfires: a local fire with high ozone production MBO fire

  13. July 5-13: international wildfire

  14. Future work: nonlinear relationship between combustion efficiency and pollutant enhancements(to be linked to satellite measurements) smoldering flaming

  15. Future work: ozone production from fires transported < 2 days 975 µg/m3 Photo by Jon Hee

  16. Summary • Wildfire identification easiest using a combination of multiple chemical measurements, satellite data and models • Ozone enhancements not necessarily related to PM enhancements • Large variability in ozone production, even within one biome • Evidence that ozone production affected by: • Combustion efficiency • PM • Transport distance • PAN

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