The effectiveness of adding fire for air quality benefits challenged: A case study of increased fine particulate matter from wilderness fire smoke with more active fire management

The Lion Fire 2011 (LF11) and Lion Fire 2017 (LF17) were similar in size, location, and smoke transport. The same locations were used to monitor both fires for ground level fine particulate matter (PM2.5). Ground level PM2.5 is used to determine the relative smoke exposure from fire management tactics used during LF11 and LF17. The LF11 had a defined and determined perimeter and the fire, largely, grew to the containment lines with meteorological and fire conditions often determining the fire spread and intensity. For smoke management and air quality concerns, the LF17 introduced additional fire in an effort to speed up the burn and take advantage of good dispersal conditions similar to a prescribed fire. The LF17 had 2151 ha of fire added while the LF11 had only 874 ha. While emissions of PM2.5 for the LF17 (8062 Mg) were less than half the LF11 (19,105 Mg), ground level concentrations of PM2.5 were greater for the LF17 at all smoke impacted sites. The sites of Johnsondale and Camp Nelson experienced the highest concentrations for both fires with an increase mean concentration for the entirety of the fires from 5.8 mu gm(-3) for the LF11 to 26.0 mu gm(-3) for the LF17 at Johnsondale (p = 0.003) and 4.9 mu gm(-3) (LF11) to 35.9 mu gm(-3) (LF17) at Camp Nelson (p = 0.01). The National Ambient Air Quality 98th percentile daily average increased from the 1211 to the LF17 from 35.0 mu gm(-3) to 57.3 mu gm(-3) at Johnsondale and 28.0 mu gm(-3) to 52.6 mu gm(-3) at Camp Nelson. Adding fire as a tactic for good smoke dispersal to mitigate smoke exposure, as was one of the decision parameters for LF17, increased ground concentrations and exposure of smoke to surrounding communities above what was experienced during the LF11.