Chemical Speciation of PM2.5 Collected during Prescribed Fires of the Coconino National Forest near Flagstaff, Arizona

• Published in: Journal of the Air & Waste Management Association (1995) 2004-09, Vol.54 (9), p.1112-1123
• Main Authors: Robinson, Marin S., Chavez, Jesus, Velazquez, Sergio, Jayanty, R.K.M.
• Format: Article
• Language: English
• Subjects: Air Pollutants - analysis; Ammonia - analysis; Applied sciences; Arizona; Environmental Monitoring; Exact sciences and technology; Fires; Forestry; Nitrates - analysis; Particle Size; Pollution; Trees
• ISSN: 1096-2247; 2162-2906
• DOI: 10.1080/10473289.2004.10470985

The use of prescribed fire is expected to increase in an effort to reduce the risk of catastrophic fire, particularly at urban/forest interfaces. Fire is a well-known source of particulate matter (PM) with particle sizes ≤2.5 μm (PM 2.5 ), small diameter PM known to affect climate, visibility, and human health. In this work, PM 2.5 was collected during seven first-entry burns (flaming and smoldering stages) and one maintenance burn of the Coconino National Forest. Samples were analyzed for organic and elemental carbon, cations (sodium, potassium [K + ], and ammonium [NH 4 + ]), anions (nitrate [NO 3 − ] and sulfate), and 48 elements (with atomic weights between sodium and lead). The PM 2.5 contained high organic carbon levels (typically >90% by mass), commonly observed ions (K + , NH 4 + , and NO 3 − ) and elements (K + , chlorine, sulfur, and silicon), as well as titanium and chromium. Flaming produced higher K + and NH 4 + levels than smoldering, and the elemental signature was more complex (20 versus 7 elements). Average organic carbon × 1.4 mass fractions (± standard deviation) were lower during flaming (92 ± 14%) than during smoldering (124 ± 24%). The maintenance (grassland) burn produced lower particle concentrations, lower NH 4 + and NO 3 − levels, and higher K and chlorine levels than did the first-entry fires.