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ARS Home » Midwest Area » Bowling Green, Kentucky » Food Animal Environmental Systems Research » Research » Publications at this Location » Publication #301788
Title: Proposed chemical mechanisms leading to secondary organic aerosol in the reactions of aliphatic amines with hydroxyl and nitrate radicals

Author
item PRICE, DEREK - University Of California
item CLARK, CHRISTOPHER - University Of California
item TANG, XIAOCHEN - University Of California
item COCKER, DAVID - University Of California
item PURVIS-ROBERTS, KATHLEEN - Claremont Colleges
item Silva, Philip - Phil

Submitted to: Atmospheric Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/2014
Publication Date: 7/15/2014
Citation: Price, D.J., Clark, C., Tang, X., Cocker, D.R., Purvis-Roberts, K.L., Silva, P.J. 2014. Proposed chemical mechanisms leading to secondary organic aerosol in the reactions of aliphatic amines with hydroxyl and nitrate radicals. Atmospheric Environment. 96:135-144.

Interpretive Summary: Amines are a class of volatile organic compounds emitted from waste management methods; they are carbon-containing analogues to ammonia that can participate in atmospheric chemistry to produce aerosols. There is significant uncertainty about the emissions of amines, the chemistry of amines in the atmosphere, and the properties of aerosols produced by atmospheric reactions. This study describes the reaction mechanisms that lead amines to convert from the gas-phase into the aerosol (particulate) phase. Typically, it has been thought that the only way amines convert to the aerosol phase is undergo acid-base reactions to form salts in the atmosphere. This publication gives evidence that amines in the atmosphere can undergo oligomer formation under oxidizing conditions. This is an alternative pathway for why the atmospheric chemistry of amines can quickly produce particulates of much lower vapor pressure than the initial reacting chemical.

Technical Abstract: The presence and importance of amines in the atmosphere continues to gain more attention including aliphatic amines commonly associated with agricultural facilities. The atmospheric reaction mechanisms of these amines with key atmospheric radicals are important to predict both daytime and nighttime atmospheric chemistry. While previous studies have focused on the production of amine salts, this analysis looks at the importance of peroxy radical reactions to the formation of secondary organic aerosol. Atmospheric oxidation mechanisms are presented to explain the observed chemistry. A series of environmental chamber experiments were conducted in which aliphatic tertiary and secondary amines were reacted with either hydroxyl radical (OH) or nitrate radical (NO3). Chemical composition of the aerosol products was obtained with a High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and a Particle Into Liquid Sampler Time of Flight Mass Spectrometer (PILS-ToF-MS), while the chemical composition of the gas-phase products was obtained with a Selected Ion Flow Tube Mass Spectrometer (SIFT-MS). A number of aerosol-phase mass spectra showed highly oxidized fragments at a much higher molecular weight (MW) than the amine precursor. It is proposed that these larger compounds are oligomers formed through peroxy radical reactions with hydrogen rearrangement. Another reaction pathway observed was the formation of amine salts. The relative importance of each pathway to the overall production of aerosol is found to be dependent on the type of amine and oxidant. For example, the oligomers were observed in the secondary and tertiary methyl amines, while the formation of amine salts was more prevalent in the secondary and tertiary ethyl amines.