Airborne characterization of smoke marker ratios from prescribed burning

Abstract

A Particle-Into-Liquid Sampler-Total Organic Carbon (PILS-TOC) and fraction collector system was flown aboard a Twin Otter aircraft sampling prescribed burning emissions in South Carolina in November 2011 to obtain smoke marker measurements. The fraction collector provided 2 min time-integrated offline samples for carbohydrate (i.e., smoke markers levoglucosan, mannosan, and galactosan) analysis by high-performance anion-exchange chromatography with pulsed amperometric detection. Each fire location appeared to have a unique δlevoglucosanδwater-soluble organic carbon (WSOC) ratio (RF01/RF02/RF03/RF05 Combining double low line 0.163 ± 0.007 μ4g C μ gg-1 C, RF08 Combining double low line 0.115 ± 0.011 μg C μgg-1 C, RF09A Combining double low line 0.072 ± 0.028 μg C μgg-1 C, and RF09B Combining double low line 0.042 ± 0.008 μg C μgg-1 C, where RF means research flight). These ratios were comparable to those obtained from controlled laboratory burns and suggested that the emissions sampled during RF01/F02/RF03/RF05 were dominated by the burning of grasses, RF08 by leaves, RF09A by needles, and RF09B by marsh grasses. These findings were further supported by the δ;galactosan/δlevoglucosan ratios (RF01/RF02/RF03/RF05 Combining double low line 0.067 ± 0.004 μg μgg-1, RF08 Combining double low line 0.085 ± 0.009 μg μgg-1, and RF09A Combining double low line 0.101 ± 0.029 μg μgg-1) obtained as well as by the ground-based fuel and filter sample analyses during RF01/RF02/RF03/RF05. Differences between δpotassium/δlevoglucosan ratios obtained for these prescribed fires vs. laboratory-scale measurements suggest that some laboratory burns may not accurately represent potassium emissions from prescribed burns. The δlevoglucosan/δWSOC ratio had no clear dependence on smoke age or fire dynamics suggesting that this ratio is more dependent on the type of fuel being burned. Levoglucosan was stable over a timescale of at least 1.5 h and could be useful to help estimate the air quality impacts of biomass burning.