Role of Aerosol Acidity in Secondary Organic Aerosol Formation
TVA and EPRI researchers have looked at measurements from several sites in the Southeast to see if laboratory experiments relating acidity to secondary organic aerosol (SOA) formation are supported by real-world data.  Laboratory tests suggest that the presence of strong acids in the atmosphere increases the formation of SOA.  Researchers examined hourly speciated fine particle data to determine if there were greater increases in the concentrations of organic aerosol mass on days when the aerosol was more acidic (based on lower ammonium-to-sulfate ratios).  They found that field data could only weakly support the laboratory hypothesis of acid-catalyzed enhancement of SOA formation and that, if confirmed, the effect may be indistinguishable from meteorological effects on SOA.  A paper on the research is in press (Atmospheric Environment, (doi:10.1016/j.atmosenv.2009.03.045).  For more information, contact Stephanie Shaw, (650) 855-2353, sshaw@epri.com, or Eladio Knipping, 202-293-2691, eknippin@epri.com.