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Throughout August and September 2003, Missoula, Montana was heavily impacted by smoke from wildland forest fires burning throughout western Montana. In an effort to study the organic compounds contributing to smoke particulate matter impacting downwind communities, three co-located PM2.5 cyclones collected 24-h samples during significant smoke events in Missoula. Filter samples were then analyzed at two independent laboratories to quantify the concentrations of several chemical markers of wood smoke generated under natural combustion conditions, as well as to provide an intercomparison study of analytical methods (HPLC and GC/MS) used in the determination of levoglucosan concentrations. Concentrations of monosaccharide anhydrides, methoxyphenols and soluble potassium were measured from PM2.5 samples collected during periods of smoke and baseline (non-impacted) conditions. From these analyses, the associations between the wood smoke markers and PM2.5 mass were examined. Levoglucosan was found to be the most useful marker for wood smoke generated from natural forest fire events in the northern Rocky Mountains, whereas measurement of other species (mannosan, methoxyphenols) provided information on the type of vegetative material burned (e.g., hardwood versus softwood). The emission ratios of levoglucosan to PM2.5 and organic carbon from the wildfire smoke was found to be 0.042 and 0.062, respectively. Results of the statistical analyses showed that the GC/MS and HPLC approaches to levoglucosan analysis were statistically equivalent. |
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