AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Photochemical Aging of 2-Methyltetrol in Aqueous Aerosols
ALISON FANKHAUSER, V. Faye McNeill, Columbia University
Abstract Number: 48 Working Group: The Role of Water in Aerosol Chemistry
Abstract 2-methyltetrol (2-MT) is a well-known particle-phase tracer for isoprene photooxidation, yet very little is known about the rates, mechanisms, and products of the photochemical aging of this species in the atmosphere. To this end, we conducted a series of laboratory experiments using an aerosol flow tube reactor coupled with an Aerosol Chemical Ionization Mass Spectrometer (Aerosol-CIMS) for analysis of the gas and particle phase composition and a scanning-mobility particle sizer (SMPS) to monitor particle size distributions. First, gas-particle partitioning experiments were conducted on aqueous sulfate particles containing 2-MT in order to measure the effective Henry’s Law constant. Then we exposed these particles to hydroxyl (OH) radicals in a continuous flow photocell reactor in order to study the photooxidation of 2-MT. In the presence of OH, 2-MT particles decreased in size, indicating a volatilization of organic material, and small-molecule products such as formic acid were observed in the gas phase. Although the reaction between OH and 2-MT takes place in both the gas and particle phases, kinetic analysis shows that the dominant effect is reaction at the particle surface, allowing us to model the loss process as reactive uptake with gamma ~ 0.02. We model this multiphase process using GAMMA (Gas-Aerosol Model for Mechanism Analysis) [McNeill et al. 2012] in order to provide additional mechanistic insight.