AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Exploring Interfacial Reactions on Ammonium Sulfate Particles Using a Novel Atmospheric Cloud Simulation Chamber
CECILIA SMITH, Angela Ziegler, Matthew Brown, Erin M. Durke, Suresh Dhaniyala, John Morris, Virginia Tech
Abstract Number: 326 Working Group: Instrumentation and Methods
Abstract A novel rotating aerosol suspension chamber with cavity ring down spectroscopy (CRDS) has been developed for the investigation of specific molecule-aerosol and aerosol-aerosol interactions under atmospheric conditions. The Atmospheric Cloud Simulation Chamber (ACSC) design allows for the creation of a well-defined and controllable atmosphere of suspended particles, analyte gases, and background gas molecules, which remains stable up to several days. Concentrations of key gas phase components and aerosol suspension characteristics in the main chamber can be ascertained in real time in response to a perturbation to the model atmosphere, such as the introduction of a gas-phase reactant. Cavity ring down spectroscopy, performed in situ along the center rotational axis, records mid-infrared spectra (1010 cm-1 to 860 cm-1) to determine concentrations and identifications of new gas species evolved from gas-particle chemistry. Aerosols are characterized ex situ with particle-sizing instrumentation, filter collection, or cascade impactor. Preliminary studies have shown that polystyrene latex (Dp = 0.994 µm) and ammonium sulfate (Dp = ~100 nm) particles remain suspended for at least 22 hours while the drum rotates at 2 RPM. Initial investigation into the atmospheric life cycle of ammonia involved studying the efficiency of the monomethylamine–ammonia exchange reaction on ammonium sulfate particles. In accord with previous studies, our results show that this reaction occurs readily on suspended ammonium sulfate particles under atmospheric conditions. CRDS spectra recorded after introducing monomethylamine shows a quantifiable amount of ammonia released from the salt particles. Future studies involve correlating ammonium sulfate acidity to reactive uptake of carbonyl-containing organic molecules, which lead to particle growth and particle composition changes. Overall, the new ACSC approach to atmospheric science provides the opportunity to study the influence of interfacial chemistry on particle growth, aging, and re-admission of gas-phase compounds.