Significant enhancements of nitrogen oxides, black carbon, and ozone in the North Atlantic lower free troposphere resulting from North American boreal

Martín M Val Department of Civil and Environmental Engineering, Michigan Technological University, Houghton, Mich
Honrath R E Department of Civil and Environmental Engineering, Michigan Technological University, Houghton, Mich
Owen R C Department of Civil and Environmental Engineering, Michigan Technological University, Houghton, Mich
Pfister G Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA
Fialho P Group of Chemistry and Physics of the Atmosphere, University of the Azores, Terra Chã, Portugal
Barata F Group of Chemistry and Physics of the Atmosphere, University of the Azores, Terra Chã, Portugal.

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.

(in Journal of geophysical research. D, Atmospheres)