Ground-level air pollution changes during a boreal wildland mega-fire

Abstract

The 2011 Richardson wildland mega-fire in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada had large effects on air quality. At a receptor site in the center of the AOSR ambient PM_2.5, O₃, NO, NO₂, SO₂, NH₃, HONO, HNO₃, NH₄⁺ and NO₃^- were measured during the April–August 2011 period. Concentrations of NH₃, HNO₃, NO₂, SO₂ and O₃ were also monitored across the AOSR with passive samplers, providing monthly summer and bi-monthly winter average values in 2010, 2011 and 2012. During the fire, hourly PM_2.5 concentrations, >450 μg m^-3 were measured at the AMS 1 receptor site. The 24-hr National Ambient Air Quality Standard (NAAQS) of 35 μg m^-3 and the Canada Wide Standard (CWS) of 30 μg m^-3 were exceeded on 13 days in May and 7 days in June. During the fire emission periods, sharp increases in NH₃, HONO, HNO₃, NH₄⁺, NO₃^- and total inorganic reactive N concentrations occurred, all closely correlated with the PM_2.5 changes. There were large differences in the relative contribution of various N compounds to total inorganic N between the no-fire emission and fire emission periods. While in the absence of fires NO and NO₂ dominated, their relative contribution during the fires was ~2 fold smaller, mainly due to increased NH₃, NH₄⁺ and NO₃^-. Concentrations of HONO and HNO₃ also greatly increased during the fires, but their contribution to the total inorganic N pool was relatively small. Elevated NH₃ and HNO₃ concentrations affected large areas of northern Alberta during the Richardson Fire. While NH₃ and HNO₃ concentrations were not at levels considered toxic to plants, these gases contributed significantly to atmospheric N deposition. No significant changes in O₃ and SO₂ concentrations were detected and their ambient concentrations were below levels harmful to human health or sensitive vegetation.

Citation

Bytnerowicz, Andrzej; Hsu, Yu-Mei; Percy, Kevin; Legge, Allan; Fenn, Mark E.; Schilling, Susan; Frączek, Witold; Alexander, Diane. 2016. Ground-level air pollution changes during a boreal wildland mega-fire. Science of The Total Environment. 572: 755-769.