AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Effect of Temperature and Dilution on SOA Derived from Reaction of Beta-pinene with Nitrate Radical
CHRISTOPHER BOYD, Lu Xu, Javier Sanchez, Xiaoxi Liu, Wing-Yin Tuet, Greg Huey, Nga Lee Ng, Georgia Institute of Technology
Abstract Number: 366 Working Group: Aerosol Chemistry
Abstract Secondary organic aerosol (SOA) is a major component of atmospheric aerosol, which has important implications on health, climate, and visibility. Studies have shown that nighttime chemistry can account for about 20-50% of biogenic precursor oxidation in polluted urban areas. The primary nighttime oxidant is the nitrate radical (NO3) formed by reaction of ozone and anthropogenic NO2. The interactions of biogenic VOCs with NO3 radical represent a direct way for positively linking anthropogenic and biogenic emissions. Since reaction with nitrate radical is predominant at night, it often reacts at colder temperatures and at a time when the boundary layer height is at its lowest. Beta-pinene is an important biogenic precursor in nighttime aerosol chemistry because of its relatively high abundance and high SOA yields when oxidized by NO3. However, the temperature effects on SOA formation from NO3 oxidation of beta-pinene at lower temperatures have not been quantified. In this study, chamber experiments with beta-pinene are performed at the Georgia Institute of Technology Environmental Chamber facility, which has the capability to perform reactions in the range of 4-40 degrees C. Reactions are carried out at lower temperatures to simulate lower nighttime temperatures of the ambient environment. N2O5 is injected into the chamber by pre-reacting NO2 and O3 in a flow tube to initiate beta-pinene oxidation. Aerosol chemical composition is characterized by a High Resolution-Time of Flight-Aerosol Mass Spectrometer (HR-TOF-AMS) with corresponding gas-phase oxidation products measured by a Chemical Ionization Mass Spectrometer (CIMS). Aerosol products formed at lower temperatures have different compositions when compared to higher temperature experiments of similar mass loading. Preliminary results show that the SOA yield of beta-pinene with nitrate radical increases by about 25% for every increase in 10 degrees C. More detailed analysis will discuss the influence of reaction temperature and dilution on gas-phase and aerosol composition.