Final Report

The goal of this project was to quantify organic aerosol precursor concentrations in an urban environment and to measure suitable organic photoproduct species that can act as tracers of photochemical processing to identify the occurrence and rate of secondary organic aerosol formation. Field measurements were made as part of the ASR field program Carbonaceous Aerosols and Radiative Effects Study (CARES) in June 2010. What is new in our approach is the measurement for the total concentration of long chain alkanes (>C10) and heavier alkyl substituted aromatics associated with diesel exhaust gas phase organic compound emissions. A method to measure these so called intermediate volatility organic compounds (IVOCs) was developed by modifying a proton transfer reaction mass spectrometer instrument to perform both volatile organic compound (VOC) and IVOC analysis by thermal desorption from a Tenax adsorbent trap (TD-PTR-MS). Lab and field results show that the TD-PTR-MS technique can measure long chain alkanes associated with diesel engine emissions and thus provide a novel means to measure these compounds to better understand the impact of vehicle emissions on secondary organic aerosol formation