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Environ Sci Technol

Title:		Ammonium addition (and aerosol pH) has a dramatic impact on the volatility and yield of glyoxal secondary organic aerosol
Author(s):		Ortiz-Montalvo DL; Hakkinen SA; Schwier AN; Lim YB; McNeill VF; Turpin BJ;
Address:		"Department of Environmental Sciences, Rutgers University , New Brunswick, New Jersey 08901, United States"
Journal Title:		Environ Sci Technol
Year:		2014
Volume:		20131220
Issue:		1
Page Number:		255 - 262
DOI:		10.1021/es4035667
ISSN/ISBN:		1520-5851 (Electronic) 0013-936X (Linking)
Abstract:		"Glyoxal is an important precursor to secondary organic aerosol (SOA) formed through aqueous chemistry in clouds, fogs, and wet aerosols, yet the gas-particle partitioning of the resulting mixture is not well understood. This work characterizes the volatility behavior of the glyoxal precursor/product mix formed after aqueous hydroxyl radical oxidation and droplet evaporation under cloud-relevant conditions for 10 min, thus aiding the prediction of SOA via this pathway (SOACld). This work uses kinetic modeling for droplet composition, droplet evaporation experiments and temperature-programmed desorption aerosol-chemical ionization mass spectrometer analysis of gas-particle partitioning. An effective vapor pressure (p'L,eff) of approximately 10(-7) atm and an enthalpy of vaporization (DeltaHvap,eff) of approximately 70 kJ/mol were estimated for this mixture. These estimates are similar to those of oxalic acid, which is a major product. Addition of ammonium until the pH reached 7 (with ammonium hydroxide) reduced the p'L,eff to <10(-9) atm and increased the DeltaHvap,eff to >80 kJ/mol, at least in part via the formation of ammonium oxalate. pH 7 samples behaved like ammonium oxalate, which has a vapor pressure of approximately 10(-11) atm. We conclude that ammonium addition has a large effect on the gas-particle partitioning of the mixture, substantially enhancing the yield of SOACld from glyoxal"
Keywords:		Aerosols/analysis/*chemistry Ammonium Compounds/*chemistry Glyoxal/*chemistry Hydroxyl Radical/chemistry Kinetics Oxidation-Reduction Volatilization Water/chemistry;
Notes:		"MedlineOrtiz-Montalvo, Diana L Hakkinen, Silja A K Schwier, Allison N Lim, Yong B McNeill, V Faye Turpin, Barbara J eng Research Support, Non-U.S. Gov't 2013/12/18 Environ Sci Technol. 2014; 48(1):255-62. doi: 10.1021/es4035667. Epub 2013 Dec 20"