AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Influence of Seed Aerosol Surface Area and Oxidation Rate on Vapor-Wall Deposition and SOA Mass Yields: A case study with α-pinene Ozonolysis
THEODORA NAH, Renee McVay, Xuan Zhang, Christopher Boyd, John Seinfeld, Nga Lee Ng, Georgia Institute of Technology
Abstract Number: 47 Working Group: Aerosol Chemistry
Abstract Laboratory chambers, invaluable in atmospheric chemistry and aerosol formation studies, are subject to particle and vapor wall deposition, processes that need to be accounted for in order to accurately determine secondary organic aerosol (SOA) mass yields. We studied the influence of seed aerosol surface area and oxidation rate on SOA formation in α-pinene ozonolysis. The observations are analyzed using a coupled vapor-particle dynamics model to interpret the roles of gas-particle partitioning (quasi-equilibrium vs. kinetically-limited SOA growth) and α-pinene oxidation rate in influencing vapor wall deposition. SOA growth rate and mass yields are found to be independent of seed surface area within the range of seed surface area concentrations used in this study. This behavior arises when the condensation of SOA-forming vapors is dominated by quasi-equilibrium growth. Faster α-pinene oxidation rates and higher SOA mass yields are observed at increasing O3 concentrations for the same initial α-pinene concentration. When the α-pinene oxidation rate increases relative to vapor wall deposition, rapidly produced SOA-forming oxidation products condense more readily onto seed aerosol particles, resulting in higher SOA mass yields. These results indicate that the extent to which vapor wall deposition affects SOA mass yields depends on the particular VOC system, and can be mitigated through the use of excess oxidant concentrations.