From June through November, this region experiences periodic episodes of poor air quality due to fireworks, wildfires and dust storms. Fig. 3 and Figs. S-10-12 illustrate how the TEOM and PMS measurements track PM2.5 and PM10 concentrations during these events. The fireworks on the 4th of July (Independence Day) and 24th of July (Pioneer Day) created spikes in the PM2.5 concentration, which reached an hourly maximum of 29.0 µg/m3 (TEOM). Several wildfires affected air quality, and this effect was confirmed by (a) the Utah Division of Air Quality requesting an exceptional event (Utah Division of Air Quality, 2017), (b) an increase in the contributions of organic carbon (Fig. S-9) to PM2.5 concentrations, (c) wildfire activity reported by the Utah Department of Natural Resources, Utah Division of Forestry, Fire & State Lands, Salt Lake City, and (d) media referring to wildfires causing poor air quality during the period. PM10 concentrations during the wildfire season show a pattern similar to PM2.5 concentrations (Fig. S-10). One additional event provides further evidence of the PMS’s poor response to PM10. On October 20, 2017 the region experienced a dust storm (Lucie, 2017; Steenburgh, 2017), and TEOM PM10 reached 472 µg/m3 while the co-located PMS sensors did not respond significantly to this event (Fig. S-11 B).
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