AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Organic Nitrogen Formation by Aqueous Processing of Condensed Carbonyls and Ammonium Sulfate
CHRIS STANGL, Murray Johnston, University of Delaware
Abstract Number: 13 Working Group: Aerosol Chemistry
Abstract Ambient measurements of atmospheric nanoparticles suggest sulfuric acid vapor to be the main driver of daytime new particle formation (NPF), with neutralization by ammonia/amines the primary cluster stabilization process leading to early particle growth. Much less is known about the chemical mechanisms underlying later stages of particle growth, and recent ambient measurements of NPF events utilizing single particle mass spectrometry have shown evidence of nitrogen-containing species in ~20 nm particles unassociated with sulphate neutralization and unaccounted for by current aerosol models. A potential source of this “excess nitrogen” is thought to be nitrogen-containing organics (i.e. organo-nitrogen) formed via aqueous processing of condensed organics with ammonia/amines. We assess this possibility through a series of simulated droplet-drying experiments, and compare measured elemental ratios of the remaining nonvolatile material with those observed during NPF. Aqueous solutions containing varying amounts of multifunctional volatile carbonyls (e.g. glyoxal, methylglyoxal, glycolaldehyde and hydroxyacetone) and ammonium sulfate were atomized into droplets and subsequently dried to a low (~30%) relative humidity by sending the particles through a silica gel diffusion dryer, which initiated aqueous-processed secondary organic aerosol formation. Collection of the dried particles onto a quartz microfiber filter allowed for offline analysis by high-resolution electrospray ionization mass spectrometry, which revealed various organo-nitrogen species including imidazoles and imidazole derivatives as major products formed from the drying process. Online measurements were also taken by sending particles directly from the dryer to the inlet of a single particle mass spectrometer, allowing for determination of the elemental mole fractions of the particles produced from each system. Current work entails elucidating the correlation between organic functionality and organo-nitrogen production, as well as investigating the effect of UV exposure on particle composition.