10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Organic Nitrogen in Aerosols at a Forest Site in Southern Appalachia
XI CHEN, Mingjie Xie, Michael Hays, Eric Edgerton, Donna Schwede, John Walker, US Environmental Protection Agency
Abstract Number: 539 Working Group: Aerosol Chemistry
Abstract This study investigates the composition of organic particulate matter (PM2.5) in a remote montane forest in the southeastern U.S., focusing on the role of organic nitrogen (N) in sulfur-containing secondary organic aerosol (SOA) and in biomass burning aerosols .The average fraction of water soluble organic nitrogen (WSON) in water soluble total nitrogen (WSTN) exhibited a pronounced seasonal pattern, ranging from ~18% w/w in the spring to ~10% w/w in the fall. Nitro-aromatic and nitrooxy-organosulfate compounds accounted for as much as 28% w/w of WSON. Oxidized organic nitrogen species showed a maximum concentration in summer (average of 0.65ngN/m3, maximum of 1.83ngN/m3) consistent with greater relative abundance of aged biogenic SOA tracers (higher generation oxygenated terpenoic acids). Highest concentrations of nitro-aromatics (e.g., nitrocatechol and methyl-nitrocatechol) were observed during the fall season impacted by aged biomass burning plumes. Isoprene derived organosulfate (MW216, 2-methyltetrol derived), which is formed from isoprene epoxydiols (IEPOX) under low NOx conditions, was the most abundant individual organosulfate. Although nitro-aromatics and nitrooxy organosulfates account for a small fraction (seasonal averages of 1.0 to 4.4%) of WSON, our results provide insight into atmospheric formation processes and sources of these largely uncharacterized organic nitrogen species.