What is Particulate Matter and How does it Vary

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What is Particulate Matter and How does it Vary?

• What is Particulate Matter?
• How Does PM Vary?
• The Influence of Emissions, Dilution and
  Transformations
• Resource Links

Contact Rudolf Husar, rhusar_at_mecf.wustl.edu
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What is Particulate Matter?

• The term Particulate Matter or aerosol, refers to
  liquid or solid particles suspended in the air.
  Depending on their origin and visual appearance,
  aerosols have acquired different names in the
  everyday language.
• Dust refers to solid airborne material, dispersed
  into aerosol from grainy powders such as soil.
• Combustion processes produce smoke particles, but
  the incombustible residues of coal are called
  flyash.
• In the early days, air pollution had the
  appearance of both smoke and fog, so the term
  smog was created.
• In the open atmosphere, the visibility may often
  be reduced by regional haze, originating from
  various natural or anthropogenic sources.
• Neither water droplets of fog and clouds, snow,
  rain, sleet (hydrometors) nor dust particles
  larger than 100 um (blowing sand) are considered
  to be particulate matter

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How Does PM Vary?Spatially, temporally, with
particle size and by chemical composition

• As all pollutants, the ambient aerosol
  concentration patterns contain endless
  variability in space and time. However, unlike
  gaseous pollutants, particulate matter also
  depends on particle size, shape and chemical
  composition.
• The chemically rich aerosol mix arises from the
  multiplicity of PM sources, each having a unique
  chemical signature at the source.
• The primary aerosol chemical composition is
  further enriched by the addition of secondary
  species during atmospheric transport.
• The effective mixing in the lower atmosphere
  stirs these primary and secondary particles into
  an externally mixed batch with various degrees of
  homogeneity, depending on location and time.
• Lastly, repeated cloud scavenging and evaporation
  tends to mix the particles from different sources
  internally into particles with mixed composition.
• The result is a heterogeneous PM pattern that is
  probably unparalleled in the domain of
  atmospheric sciences. For instance it is common
  to find soot particles within sulfate droplets,
  or nitrate deposited on sea salt particles.

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The Influence of Emissions, Dilution and
Transformations

• The PM concentration, C, at any given location
  and time is determined by the combined
  interaction of emissions, E, atmospheric
  dilution, D, and chemical transformation and
  removal, T, processes
• C f (E, D, T)
• Each of the three processes has its own pattern
  at secular, yearly, weekly, synoptic, diurnal and
  micro time scales.
• The yearly, weekly and the diurnal scales are
  periodic

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Resource Links

• Workbook Table of Contents
• Comment and Feedback Page
• Applications / Reports
• Data sets used in the Applications
• Methods and tools used in the Applications