Transcript WatsonNephPresentation10

SECONDARY ORGANIC AEROSOLS
WORKSHOP OVERVIEW
John G. Watson
Desert Research Institute, Reno, NV
February 5, 2002
Primary and Secondary Aerosol
• Primary aerosol: Directly emitted from
sources as particles
• Secondary aerosol: Formed in the
atmosphere from directly emitted gases
• Secondary inorganic aerosol: Sulfuric acid,
ammonium bisulfate, ammonium sulfate,
ammonium nitrate
• Secondary organic aerosol: Many
oxygenated and nitrated compounds
What We Know
• Organic carbon (OC) is a substantial fraction (20%
to 70%) of average PM2.5 at urban and non-urban
locations
• OC derives from many sources, both natural and
manmade, of ancient (fossil fuels >1M years old)
and recent (<100 year) origin
• OC derives from directly emitted particles (primary
organic aerosol, POA) and gaseous precursors that
change into particles (secondary organic aerosol,
SOA)
• Reductions in SOA precursor emissions may not
result in reductions of SOA, and may result in
SOA, ozone, and secondary inorganic PM2.5
increases under some circumstances
What We Need to Know
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What fraction of ambient OC is SOA?
How does it form in the atmosphere?
Where do the precursors come from?
How is it measured?
How does SOA affect health, visibility, and
climate?
• How will SOA concentrations to changes in
precursor emissions?
Workshop Goals
• Create a snapshot of current knowledge.
• Specify near, medium, and long-term
research needed to advance knowledge.
• Create a research strategy to guide and
promote the specified research.
Workshop Process
• Supply initial answers to specific questions
about SOA guided by a small group of
experts
• Identify knowledge gaps and ways to fill
them
• Solicit additional information from the
broader research community