Air Quality Impacts of Wildfires in Southeastern Arizona

A conflict exists between the growing acceptance of the ecological and practical benefits of prescribed fires and the potential adverse effects of smoke from fires. Fire managers are facing increasingly stringent air quality regulations at the same time they are attempting to expand their use of prescribed burning. Particulate matter (PM) is the primary pollutant of concern; it is the major component of smoke and has known detrimental influences on human health and the environment. This study utilizes wildfire, climate, and PM data from Tucson, Arizona, to examine correlations between large wildfires and PM concentrations at urban air quality monitoring stations. Tucson provides an excellent case study area due to its juxtaposition of Class I wilderness in close proximity to a major urban area.

Based on the results of this investigation, there appears to be surprisingly little impact on urban air quality during wildfire events. This is in contrast to the recorded visibility impacts that the wildfires have had on the metropolitan area. The lack of high PM concentrations may be due to Tucson's topography, the location of the air quality monitors, or the rapid dispersion of PM. Spatial and temporal analyses have been employed to better delineate the factors involved, including in-depth, daily analyses over the period of the large Bullock and Aspen fires that occurred in 2002 and 2003. Although several days indicate overall elevated PM conditions, the data are not distributed in the expected spatial pattern and are not in synch with wind direction or synoptic conditions. The magnitude of the air quality impacts varies based on the temporal and spatial unit of analysis, however, emphasizing the importance of scale in study design.