Ammonium Addition (and Aerosol pH) Has a Dramatic Impact on the Volatility and Yield of Glyoxal Secondary Organic Aerosol

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• 作者：Diana L. Ortiz-Montalvo ; Silja A. K. H?kkinen ; Allison N. Schwier ; Yong B. Lim ; V. Faye McNeill ; Barbara J. Turpin
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：January 7, 2014
• 年：2014
• 卷：48
• 期：1
• 页码：255-262
• 全文大小：370K
• ISSN：1520-5851

文摘

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 (SOA_Cld). This work uses kinetic modeling for droplet composition, droplet evaporation experiments and temperature-programmed desorption aerosol鈥揷hemical ionization mass spectrometer analysis of gas-particle partitioning. An effective vapor pressure (p鈥?sub>L,eff) of 10^鈥? atm and an enthalpy of vaporization (螖H_vap,eff) of 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鈥?sub>L,eff to <10^鈥? atm and increased the 螖H_vap,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 10^鈥?1 atm. We conclude that ammonium addition has a large effect on the gas-particle partitioning of the mixture, substantially enhancing the yield of SOA_Cld from glyoxal.