Source-Oriented Chemical Transport Model for Primary and Secondary Organic AerosolEPA Grant Number: R831082
Title: Source-Oriented Chemical Transport Model for Primary and Secondary Organic Aerosol
Investigators: Kleeman, Michael J. , Clegg, Simon , Griffin, Robert J.
Institution: University of California - Davis , University of New Hampshire - Main Campus
EPA Project Officer: Chung, Serena
Project Period: October 1, 2003 through September 30, 2006 (Extended to September 30, 2008)
Project Amount: $450,000
RFA: Measurement, Modeling, and Analysis Methods for Airborne Carbonaceous Fine Particulate Matter (PM2.5) (2003) RFA Text | Recipients Lists
Research Category: Air , Air Quality and Air Toxics , Particulate Matter
Primary Organic Aerosol (POA) and Secondary Organic Aerosol (SOA) contribute significantly to airborne PM2.5 concentration throughout the United States. Our current understanding about the most significant sources of POA and SOA are limited by the capabilities of receptor-oriented statistical models. In this research we will construct a source-oriented Chemical Transport Model that can identify source contributions to POA and SOA concentrations with improved accuracy and resolution relative to receptor-oriented techniques.
A state-of-the-art secondary organics module that considers activity coefficient corrections for organic-organic and organic-inorganic interactions will be combined with a host source-oriented CTM. The vapor pressure of organic species above the surface of particles released from different sources will be predicted based on thermodynamic principals. The dynamic exchange of semi-volatile organic compounds between the gas and particle phases will be calculated based on particle size, vapor pressure, gas-phase diffusivity, and interfacial mass transfer. The new source-oriented CTM with improved SOA calculations will be used to predict concentrations of elemental carbon (EC), POA, and SOA at EPA Supersite locations in Los Angeles, Fresno, and St. Louis. The sources of POA and SOA will be identified through the unique features of the source-oriented CTM.
Source contributions to EC, POA, and SOA will be identified at three heavily polluted locations: Los Angeles, Fresno, and St. Louis. This will improve our understanding of the health risk posed by different emissions sources in these heavily populated areas. The influence of internal vs. external mixture and bulk equilibrium vs. size-resolved dynamic approaches on predicted SOA formation in air quality models will be quantified so that appropriate techniques can be used in the future. The likely impact of interactions between inorganic and soluble organic compounds in aerosol particles on SOA formation and aerosol water uptake will be established. This will result in a more cost effective allocation of federal and state environmental protection resources during future air quality modeling exercises.