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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 111,
D23S60,
doi:10.1029/2006JD007530,
2006
Significant enhancements of nitrogen oxides, black carbon, and ozone in the North Atlantic lower free troposphere resulting
from North American boreal wildfires
M. Val Martín
Department of Civil and Environmental Engineering, Michigan Technological University, Houghton, Michigan, USA
R. E. Honrath
Department of Civil and Environmental Engineering, Michigan Technological University, Houghton, Michigan, USA
R. C. Owen
Department of Civil and Environmental Engineering, Michigan Technological University, Houghton, Michigan, USA
G. Pfister
Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA
P. Fialho
Group of Chemistry and Physics of the Atmosphere, University of the Azores, Terra Chã, Portugal
F. Barata
Group of Chemistry and Physics of the Atmosphere, University of the Azores, Terra Chã, Portugal
Abstract
Extensive wildfires burned in northern North America during summer 2004, releasing large amounts of trace gases and aerosols
into the atmosphere. Emissions from these wildfires frequently impacted the PICO-NARE station, a mountaintop site situated
6–15 days downwind from the fires in the Azores Islands. To assess the impacts of the boreal wildfire emissions on the levels
of aerosol black carbon (BC), nitrogen oxides and O3 downwind from North America, we analyzed measurements of CO, BC, total reactive nitrogen oxides (NO
y
), NO
x
(NO + NO2) and O3 made from June to September 2004 in combination with MOZART chemical transport model simulations. Long-range transport of
boreal wildfire emissions resulted in large enhancements of CO, BC, NO
y
and NO
x
, with levels up to 250 ppbv, 665 ng m−3, 1100 pptv and 135 pptv, respectively. Enhancement ratios relative to CO were variable in the plumes sampled, most likely
because of variations in wildfire emissions and removal processes during transport. Analyses of ΔBC/ΔCO, ΔNO
y
/ΔCO and ΔNO
x
/ΔCO ratios indicate that NO
y
and BC were on average efficiently exported in these plumes and suggest that decomposition of PAN to NO
x
was a significant source of NO
x
. High levels of NO
x
suggest continuing formation of O3 in these well-aged plumes. O3 levels were also significantly enhanced in the plumes, reaching up to 75 ppbv. Analysis of ΔO3/ΔCO ratios showed distinct behaviors of O3 in the plumes, which varied from significant to lower O3 production. We identify several potential reasons for the complex effects of boreal wildfire emissions on O3 and conclude that this behavior needs to be explored further in the future. These observations demonstrate that boreal wildfire
emissions significantly contributed to the NO
x
and O3 budgets in the central North Atlantic lower free troposphere during summer 2004 and imply large-scale impacts on direct radiative
forcing of the atmosphere and on tropospheric NO
x
and O3.
Received 18
May
2006;
accepted 4
October
2006;
published 7
December
2006.
Keywords: boreal wildfires;
North Atlantic troposphere;
ICARTT.
Index Terms: 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 0345 Atmospheric Composition and Structure: Pollution: urban and regional (0305, 0478, 4251); 0368 Atmospheric Composition and Structure: Troposphere: constituent transport and chemistry.
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Citation: Val Martín, M., R. E. Honrath, R. C. Owen, G. Pfister, P. Fialho, and F. Barata
(2006),
Significant enhancements of nitrogen oxides, black carbon, and ozone in the North Atlantic lower free troposphere resulting
from North American boreal wildfires,
J. Geophys. Res.,
111,
D23S60,
doi:10.1029/2006JD007530.
Copyright 2006 by the American Geophysical Union.
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