Summary
The effects of fires, both prescribed and wildfires, on air quality is increasingly a societal concern for several reasons: (1) climate change and increasing incidence of “megafires”; (2) increased recreational and residential use of wildlands, and thus, human exposure to air pollution from fires and other sources; (3) the need to expand areas treated with prescribed fire as a result of long-term fire suppression; and (4) increasing background levels of ozone in the western United States and fire emissions’ contributions to ozone formation. The 2011 Richardson Fire in northern Alberta was the second-largest wildfire in Canadian province’s history. An extensive air monitoring network was already in place to monitor air quality from oil sands mines and processing facilities. Air quality was measured before, during and after the fire, including pollutants that typically are not measured in fire emissions studies. Fine particulate matter (PM2.5) concentrations in the atmosphere increased dramatically during the fire as expected. In addition, concentrations of a suite of inorganic nitrogen pollutants, such as ammonia (NH3), ammonium (NH4+), nitric acid vapor (HNO3), nitrate (NO3-) and total inorganic reactive nitrogen, increased dramatically. Ozone concentrations increased during the fire at one monitoring site near the fire perimeter, but was not significantly changed throughout the larger air quality monitoring network. This study demonstrates how nitrogen compounds in smoke, simultaneously functioning as plant nutrients, air pollutants and ozone precursors, are transported in the atmosphere and deposited to downwind forests and urban sites.
