AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Molecular Characterization of Optically Active Organo-Nitrogen Species in Organic Aerosol
CHRIS STANGL, Murray Johnston, University of Delaware
Abstract Number: 608 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Nitrogen-containing organics are thought to be a major contributor to the light-absorbing components of aged secondary organic aerosol (SOA). The formation of these “brown carbon” species is initiated via evaporation of water following uptake of volatile organic compounds by seed droplets containing dissolved inorganic salts. The loss of water creates a supersaturated environment where aqueous-phase reactions can occur, resulting in the formation of photoactive compounds e.g secondary imines (Schiff bases) from carbonyls and ammonia. These organo-nitrogen species are capable of absorbing incident solar radiation, thereby contributing to radiative forcing. Extensive studies have been carried out with glyoxal (C2H2O2), a potential brown carbon precursor that has been shown to form light-absorbing species following reaction with ammonium salts. Initial experiments were performed in which bulk solutions of ammonium sulfate and glyoxal were atomized into droplets, which were passed through a diffusion dryer initiating solvent evaporation. The resulting particles were collected onto a filter, extracted into solution and analyzed by UV-visible absorption spectroscopy and high-resolution electrospray ionization mass spectrometry. UV-VIS analysis of the extracted particulate matter showed large absorbance peaks at 220 nm and 280 nm, with a tail extending into the visible region. ESI-MS analysis of the extracted particulate matter indicated the presence of imidazole, a previously identified brown carbon contributor, along with its derivatives. Current work involves characterization of absorbing species produced via other atmospherically relevant SOA precursors, including monoterpenes (alpha pinene, limonene) as well as other small molecules such as methyl glyoxal. Concurrent measurements of absorption and molecular composition will be achieved by LC-UV-MSMS with high mass resolving power.