AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Formation of Organic Nitrogen in Aqueous Nanodroplets
CHRIS STANGL, Murray Johnston, University of Delaware
Abstract Number: 118 Working Group: Aerosol Chemistry
Abstract Recent ambient measurements of nanoparticle composition during summertime new particle formation (NPF) events in the eastern United States have found that a significant amount of nitrogen-containing compounds exist in the particle phase that are unassociated with sulfate neutralization, nitrate partitioning or organonitrate formation. A potential source of these compounds is thought to be nitrogen-containing organic species such as imines, which can be formed by aqueous processing of carbonyl-containing compounds in the presence of ammonia. In the work to be presented, aqueous processing of water-soluble carbonyls relevant to the location of study was simulated in the laboratory by partially drying internally-mixed nanodroplets containing ammonium sulfate and various carbonyls (glyoxal, methylglyoxal, glycolaldehyde). Off-line molecular composition analysis with high resolution mass spectrometry showed the presence of many imine-derived organo-nitrogen species in the particle phase. On-line elemental composition measurements with the nano aerosol mass spectrometer (NAMS) confirmed the presence of organic nitrogen. N:C ratios attributed to the organic fraction of the particles showed agreement between both techniques, and alluded that such systems may have the potential to explain organic nitrogen observed in ambient nanoparticles. Our results suggest that aqueous chemistry may significantly impact nanoparticle composition and growth during NPF in locations where emissions of water-soluble organic gases are high, such as the eastern United States.