Chemistry of Secondary Organic Aerosol Formation from the Oxidation of Aromatic Hydrocarbons

EPA Grant Number: R833752
Title: Chemistry of Secondary Organic Aerosol Formation from the Oxidation of Aromatic Hydrocarbons
Investigators: Ziemann, Paul J. , Arey, Janet , Atkinson, Roger
Institution: University of California - Riverside
EPA Project Officer: Chung, Serena
Project Period: October 1, 2007 through September 30, 2010 (Extended to March 31, 2012)
Project Amount: $514,464
RFA: Sources and Atmospheric Formation of Organic Particulate Matter (2007) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air


Secondary organic aerosol (SOA) is formed in the atmosphere from the products of the oxidation of volatile organic compounds (VOCs). It is a major component of PM2.5, but its sources and formation mechanisms are not understood. It is generally thought that the major SOA precursors are aromatic hydrocarbons in urban areas and biogenic compounds globally. In this project, we plan to develop a quantitative understanding of the kinetics, products, and mechanisms of SOA formation from the photooxidation of aromatic hydrocarbons, and to make this information available for incorporation into air quality models for predicting organic PM2.5 concentrations.


The research plan is to use state-of-the art on-line and off-line analytical methods to identify and quantify gas-phase and aerosol products from OH radical-initiated reactions of aromatic hydrocarbons and model compounds carried out in the laboratory, and to evaluate the effects of variables including, humidity, nitrogen oxides, ammonia, seed particles, and VOC mixtures on reaction products and SOA formation. Reactants and gas-phase products will be identified and in some cases quantified in real-time by direct air sampling atmospheric pressure ionization mass spectrometry and by using off-line gas chromatography with flame ionization and mass spectrometry detection. Particle-phase products will be analyzed in real time using a thermal desorption particle beam mass spectrometer and a suite of off-line mass spectrometric methods.

Expected Results:

The experimental data obtained in this project will include reaction rate constants, product branching ratios, and yields of gas-phase and particle-phase products and SOA from OH radical-initiated reactions of aromatic hydrocarbons. These data will be used by atmospheric modelers as inputs into detailed chemical mechanisms, which in turn can be used in urban and regional airshed computer models. These types of models are widely used to evaluate the potential effects of aerosols (and control strategies) on global climate, air pollution and visibility, and human health.

Publications and Presentations:

Publications have been submitted on this project: View all 34 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 16 journal articles for this project

Supplemental Keywords:

tropospheric, particulates, environmental chemistry,

Progress and Final Reports:

  • 2008 Progress Report
  • 2009 Progress Report
  • 2010 Progress Report
  • 2011 Progress Report
  • Final Report