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The purpose
of the SCOS97 aerosol project is to take advantage of the enhanced
monitoring support available during the SCOS97-NARSTO ozone study
period to deploy both advanced surface measurement equipment and
airborne aerosol analyzers to develop a three-dimensional picture of
the generation and evolution of typical late summer aerosols in
Southern California. The participants have various complementary
interests, both regulatory and scientific, in understanding:
- Relationships
between motor vehicle emissions and ambient aerosols,
- Processes
of secondary aerosol formation, especially organics and ammonium
nitrate,
- How ozone
control strategies may influence aerosol formation,
- Contributions
of various sources, particularly heavy duty diesels, to both the
primary and secondary particle burdens in the atmosphere, and
- Movement
of aerosol-laden air masses, and how they evolve as they pass over the
SoCAB landscape and interact with the various gas and particle sources
distributed across the basin.
In addition,
these experiments provide opportunities to refine some of the research
tools available for aerosol analysis; among these R&D goals are:
- Develop
quantitative calibrations for capture and detection efficiencies for
the ATOFMS,
- Refine
and extend the library of organic aerosol source "profiles."
- Improve
aerosol models and source allocation schemes.
The major
tasks of this effort are:
- Conduct
advanced surface measurements, including Aerosol Time of Flight Mass
Spectrometry (ATOFMS) single-particle analysis, impactor sampling for
size-resolved organic chemistry, and aerosol sizing for mass
distributions; these data will then be used to characterize aerosols in
coastal, mid-basin, and interior locations in Southern California.
- Use
aircraft to measure aerosol size and concentration and sample aerosols
and precursors high in the mixed layer.
- Combine
aerosol measurements with gaseous pollutant data collected by the
SCOS97-NARSTO ozone program to investigate the dynamics of secondary
organic aerosol formation.
- Use
real-time ammonia, nitric acid, and aerosol nitrate measurements to
observe the concentration-humidity-temperature phase dependence among
ammonia, nitric acid, and nitrate aerosols in ambient air.
- Develop
speciated hydrocarbon data to distinguish between gasoline and diesel
vehicle exhaust contributions to ambient aerosol.
- Apply
chemical species data from previous source sampling and current field
studies to allocate primary organic and inorganic aerosol components to
their sources in the SoCAB.
- Use
meteorological and statistical analyses to identify temporal and
spatial distributions of source areas for precursors to secondary
aerosols.
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