Chemical Speciation of PM_2.5Collected during Prescribed Fires of the Coconino National Forest near Flagstaff, Arizona

Abstract

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 Յ2.5 m (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. and sulfate), and 48 elements (with atomic weights between sodium and lead). The PM 2.5 contained high organic carbon levels (typically Ͼ90% by mass), commonly observed ions (K ϩ , NH 4 ϩ , and NO 3 Ϫ ) and elements (K ϩ , chlorine, sulfur, and silicon), as well as titanium and chromium. Flaming produced higher K ϩ and NH 4 ϩ levels than smoldering, and the elemental signature was more complex (20 versus 7 elements). Average organic carbon ϫ 1.4 mass fractions (Ϯ standard deviation) were lower during flaming (92 Ϯ 14%) than during smoldering (124 Ϯ 24%). The maintenance (grassland) burn produced lower particle concentrations, lower NH 4 ϩ and NO 3 Ϫ levels, and higher K and chlorine levels than did the firstentry fires.

Cardiopulmonary toxicity of peat wildfire particulate matter and the predictive utility of precision cut lung slices

“…In particular, fine and ultrafine PM from ENCF-1 had higher OC content suggesting they were enriched with wildfire smoke, while the PM samples from the ENCF-4 period had higher concentrations of NH 4 + and SO 4 2− indicating that the pollution from this period reflected typical secondary particulate air pollution for the region [37]. The OC mass fractions from ENCF-1 were in good agreement with reported data from the 2005 peat fires in Indonesia [38], while forest fires often produce even higher OC levels (typically > 90% by mass) [35], suggesting that OC levels are affected not only by the different combustion stages but also the type (i.e., fuel source) of wildfires. It should be noted that the wind speed during ENCF-1 was higher than during ENCF-4 and the prevailing wind was from the South-west, while ENCF-4 wind conditions were in general lighter and more southerly in nature with some periods of wind from other directions.…”

“…Compared to emissions from different wildfire types (e.g., savanna, forest, and woodland fires), peat fires produce >100% more CO and >300% more CH 4 , suggesting that they may have a greater impact on human health and climate change [34]. Robinson et al [35] reported that flaming and smoldering combustion stages of wildfire produced distinctly different ionic and elemental compositions of fine PM, but other size fractions were not assessed. Here we found that the coarse PM from both sampling periods had similar elemental composition, while the fine and ultrafine PM (which form through nucleation, condensation, and coagulation processes) differed between the smoldering and the glowing phases of the burn [36].…”

“…In order to estimate total mass of organic compounds in wildfire PM, we multiplied a measured organic carbon mass by the mass ratio of organic matter (OM) to organic carbon (OC). For wildfire or biomass burning PM, the estimate of OM/OC ratio from the literature is approximately 2.1 [35,68]. A suspension of standard reference material (ambient urban atmospheric particulate NIST 1649a) was prepared in the same concentration as the study PM samples and used to track recovery of major elements, ions, and carbon content.…”

Characterization of aerosol particle episodes in Finland caused by wildfires in Eastern Europe

“…Smouldering burning conditions are more dominant in boreal forest fires and peat fires than in grass, shrub or cereal waste fires, which mainly burn in flaming conditions Lavoue et al, 2000;Ortiz de Zárate et al, 2000;Soja et al, 2004). Thus, it seems likely that aerosols from forest and peat fires were less enriched with K than aerosols from agricultural field burning since the fraction of K is lower in the emissions from smouldering fires than in those from flaming fires Gaudichet et al, 1995;Robinson et al, 2004). Another reason for the relatively low proportion of K was probably the mixing of emissions from fossil fuel burning since air masses arrived from the regions of Eastern Europe with high S emissions (EMEP, 2001).…”

Comparative chemistry and toxicity of diesel and biomass combustion emissions

“…Biomass burning and wildfires emit a vast quantity of soot and OC-bearing smoke [25]. Smoke exposures have been known to exacerbate allergic asthma and increase the severity of cardiovascular disease.…”