AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Dynamic Modeling of Wall Loss in a Teflon Atmospheric Smog Chamber
MEREDITH SCHERVISH, Neil Donahue, Carnegie Mellon University
Abstract Number: 102 Working Group: Aerosol Physics
Abstract Suspended phase organics constitute a large fraction of atmospheric pollutants. These aerosols heavily impact the environment making the determination of their formation and growth critical to our understanding of the atmosphere. Smog chambers provide a controlled experimental environment to probe suspended phase dynamics. Modeling these experiments is crucial to understanding how chamber yields are impacted by the walls of the chamber. While particle deposition has been studied extensively leading to knowledge on the timescale and size dependence of this phenomenon, the vapor wall loss picture remains less clear. Experimental evidence has shown the walls of the chamber can provide a continuous sink for vapors or a phase to which vapors can reversibly partition depending on the compound and the chamber conditions. Due to the current infeasibility of measuring vapors in the walls, we present a model to dynamically partition mass between the suspended and vapor phase as well as the chamber walls using a specified “wall region” to track vapors interacting both with particles deposited on the walls and the Teflon itself. We find that compounds with low volatilities (C*< 100 μg/m3), will reside entirely in the Teflon at equilibrium, however compounds with higher volatilities remain in appreciable amounts in the vapor phase. In addition, we see deposited particles still playing a significant role in the system, evaporating suspended organics once vapor concentrations are low with respect to the compound’s volatility. This model will allow incorporation of wall partitioning into larger more chemically rigorous models for more accurate chamber models.