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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. - PowerPoint PPT Presentation
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Nicole WigderPh.D. Candidate
University of Washington, Department of Atmospheric Sciences5 March 2013
VOCs & OVOCs + NOx → O3
downwind transport
Photo by Jon Hee
• CO• CO2
• VOCs• OVOCs• NOx• PM• CH3CHO• Etc.
Why do some wildfires produce ozone while others do not?
ozone production?
Normalized Enhancement Ratios allow an analysis of variability that is not influenced by fire size or dilution:
∆O3/∆CO or ∆O3/∆CO2
Plume Age Mean ∆O3/∆CO (ppbv/ppbv) (# plumes)
Range of ∆O3/∆CO
≤ 1-2 days 0.018 (n=55) -0.032-0.34
2-5 days 0.15 (n=39) -0.07-0.66
≥ 5 days 0.22 (n=29) -0.42-0.93
Boreal/ Temperate
Plume Age Mean ∆O3/∆CO (ppbv/ppbv) (# plumes)
Range of ∆O3/∆CO
≤ 1-2 days 0.14 (n=59) -0.06-0.37
2-5 days 0.35 (n=13) 0.26-0.42
≥ 5 days 0.63 (n=18) 0.19-0.87
Tropics/ Subtropics
Jaffe & Wigder (2012)
VOCs & OVOCs + NOx O3
Photo credits: NPS, USFS
• Fuel nitrogen content: 0.2 - 4%• Combustion efficiency (smoldering ↔ flaming)• Photochemistry
sunlight
NOx/CO2 emission factors4.8x10-4 – 2.3x10-3 g g-1
Variation by a factor of 5!
NOx
Aerosol NO3-
HNO3
PAN: temperature dependent reservoir
Within hours: ~40% of NOx → PAN (boreal; Alvarado et al., 2010)~22% of NOx → PAN (temperate; Akagi et al., 2012)
O3
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
• multiple chemical & PM measurements
• HYPSLIT backward airmass trajectories
• MODIS near real-time images
• FIRMS fire hotspots (NASA)
COPM
1
O3
r = 0.65
r = 0.14
Two fire plumes observed at MBO in 2012:
32 wildfires
13 produced ozone
Wigder et al., submitted to Atmos. Environ.
These 13 fires:
∆O3/∆CO range: 0.01-0.51
Large variation within a small geographic area
MBO
Wildfire plumes transported < 1 day:
∆O3/∆CO wildfire plumes
∆O3/∆CO wildfire/urban mixed plumes
0.04 (n=2) 0.28 (n=2)
That’s a factor of 7 increase in mixed plumes!
Similar results for Californian plumes (Singh et al., 2012)
MBO
fire
flaming
smoldering
975 µg/m3
Photo by Jon Hee
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