Organic composition of carbonaceous aerosols in an aged prescribed fire plume

Abstract

Abstract. Aged smoke from a prescribed fire (dominated by conifers) impacted Atlanta, GA on 28 February 2007 and dramatically increased hourly ambient concentrations of PM2.5 and organic carbon (OC) up to 140 and 72 μg m−3, respectively. It was estimated that over 1 million residents were exposed to the smoky air lasting from the late afternoon to midnight. To better understand the processes impacting the aging of fire plumes, a detailed chemical speciation of carbonaceous aerosols was conducted by gas chromatography/mass spectrometry (GC/MS) analysis. Ambient concentrations of many organic species (levoglucosan, resin acids, retene, n-alkanes and n-alkanoic acids) associated with wood burning emission were significantly elevated on the event day. Levoglucosan increased by a factor of 10, while hopanes, steranes, cholesterol and major polycyclic aromatic hydrocarbons (PAHs) did not show obvious increases. Strong odd over even carbon number predominance was found for n-alkanes versus even over odd predominance for n-alkanoic acids. Alteration of resin acids during transport from burning sites to monitors is suggested by the observations. Our study also suggests that large quantities of biogenic volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs) were released both as products of combustion and unburned vegetation heated by the fire. Higher leaf temperature can stimulate biogenic VOC and SVOC emissions, which enhanced formation of secondary organic aerosols (SOA) in the atmosphere. This is supported by elevated ambient concentrations of secondary organic tracers (dicarboxylic acids, 2-methyltetrols, pinonic acid and pinic acid). An approximate source profile was built for the aged fire plume to help better understand evolution of wood smoke emission and for use in source impact assessment.

Long-term measurements (2010–2014) of carbonaceous aerosol and carbon monoxide at the Zotino Tall Tower Observatory (ZOTTO) in central Siberia

“…In mixed boreal wildfires, the mean OC / EC ratios for PM 10 in fresh smoke plumes were reported as 6.7 (Saarnio et al, 2010), 6.5 (Popovicheva et al, 2015, and 15 . For aged smoke particles, Yan et al (2008) reported a value of 25.6, which is close to our summer averaged OC / EC ratio of 27.6 ± 1.0 obtained for the entire sampling campaign (Fig. 4c).…”

Compositions and sources of organic acids in fine particles (PM2.5) over the Pearl River Delta region, south China

“…As for the higher succinic acid, it is interesting that significant correlation between succinic acid and levoglucosan (r = 0.62, p < 0.01) was found in the rural site KD, suggesting the contribution of biomass burning to succinic acid in this site. In fact, high levels of succinic acid were observed in aerosols under the influence of biomass burning (Falkovich et al, 2005;Narukawa et al, 1999;Wang et al, 2011;Yan et al, 2008). However, biomass burning should not be the major source for succinic acids at other sites and instead secondary formation would be more important, as much higher levels were observed at the downwind WQS.…”

Impacts of Siberian Biomass Burning on Organic Aerosols over the North Pacific Ocean and the Arctic: Primary and Secondary Organic Tracers

“…As discussed above, the year 2003 witnessed intense forest fires in Siberia with great amount of NO x emitted to the atmosphere, 40 as revealed by the significant enhancement of the troposphere NO 2 recorded by satellites over Siberia when intense forest fires happened during our cruise ( Figure S5 of the SI). Since forest fires could also enhance the emissions of BVOCs, such as isoprene, 22 smoke plumes would contain high NOx and BVOCs. And the high MGA could be due to chemical reactions within the BB plumes.…”

“…As WSOC is mainly derived from BB and SOA 12 and explains a large portion of OC particularly in much aged air, here we can compare carbon fractions shared by BB and SOA tracers in WSOC among fresh, continental, and remote oceanic samples. BB plume 22 and SOA chamber measurements 41−43 are characterized as fresh samples and the data set from southeastern U.S. 12 are typical that of continental samples. Since LEVO, MTLs, PNA, and WSOC were available in above studies, we only compared these species to our oceanic samples split into LO and OO groups based on 5-day BT analysis.…”

“…As BB can directly produce large amounts of VOCs and oxidants, 21 fire events could indirectly enhance the formation of SOA in the atmosphere. 22 Yet there is quite limited knowledge about the enhancement of SOA formation by BB. The intense forest fires in Siberia during 2003 should have significant impact on the marine aerosols over the adjacent North Pacific Ocean, which could be investigated by ship-based observation then over the North Pacific, as the research expedition aboard the icebreaker Both SOA and BB aerosols contain large amounts of oxygenated and polar compounds and are thus closely associated with water-soluble organic carbon (WSOC).…”