AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Brown Carbon Formation from Reactions of Limonene-derived Ketoaldehydes with Ammonium Sulfate and Amino Acids
TRAN NGUYEN, Sergey Nizkorodov, University of California, Irvine
Abstract Number: 566 Working Group: Aerosol Chemistry
Abstract Limonene (C10H16), an important monoterpene, forms SOA that produces secondary brown carbon through reactions with ammonium sulfate (AS) and amino acids. Brown carbon is believed to make a significant contribution to light absorption by aerosols but the sources of brown carbon are poorly understood. We hypothesize that the reactive ketolimononaldehyde (KLA), the most abundant compound in the aerosol phase, is the species responsible for the brown carbon formation in limonene SOA. Synthesized and purified KLA was demonstrated to produce identical chromophores to limonene SOA when reacted with AS and glycine. Limononaldehyde (LA), a first-generation ketoaldehyde product in limonene oxidation, was also synthesized and used as a control to demonstrate that the unique structure of KLA is necessary to produce brown carbon. UV-Vis, FT-IR and NMR spectroscopy were used to characterize the chemical structures of the chromophores after separation with reverse-phase HPLC-UV. The kinetics of reaction were also quantified in both aqueous and evaporative reactions. The results suggest that KLA is likely the only precursor in the formation of brown carbon for this type of SOA and that the chromophores are nitrogen-containing organic compounds. Results of this study provide useful information on the mechanism of formation of brown carbon from secondary organic aerosols.