AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Hygroscopicity of Amine Secondary Aerosol – Mixtures of Organic and Inorganic Components
XIAOCHEN TANG, David R. Cocker III, Kathleen Purvis-Roberts, Akua Asa-Awuku, University of California Riverside
Abstract Number: 144 Working Group: Aerosols, Clouds, and Climate
Abstract Aliphatic amines are emitted from both biogenic and anthropogenic sources and contribute to the formation of secondary organic aerosol in reactions with OH, O3 and NO3. However, the cloud condensation nuclei (CCN) ability of amine aerosol has not been explored yet. Here, we study the hygroscopicity of aerosol formed from three amines (trimethylamine, diethylamine and butylamine) in the UCR environmental chamber. NO3 is a dominant night time oxidant and can react with amines in acid-base and/or oxidation reactions. The secondary aerosol formed are composed of both organic and inorganic components. The ability of these particles to uptake water is measured with a hygroscopic tandem differential mobility analyzer (HTDMA) and CCN counter. Results show that aerosol formed from diethylamine and butylamine with NO3 are very hygroscopic (kappa~0.3). Conversely, when amines were oxidized by OH, no inorganic components were detected in the particle phase and were subsequently less hygroscopic. Hence aminium nitrates formed in acid-base reactions greatly improve hygroscopicity of NO3-initiated aerosol.
Presence of water vapor during the NO3-initiated reaction also promoted formation of aminium salts, which correspondingly enhanced CCN activity of formed aerosol. Highest salt fraction is measured in humid reaction between butylamine and NO3, in which kappa value reached as high as 0.8. This is the first research into the hygroscopicity of aliphatic amine aerosol. Our results will significantly impact the estimation and role of amines in atmospheric chemistry and global climate models.