•Understanding the
emission source type of a particular air toxic can help the analyst begin to develop a conceptual
model of concentration patterns and
gradients that might be
expected.
•Major source
emissions, for example, are a localized source of toxics and may show steep concentration gradients.
•Area source emissions
are typically well-distributed emissions sources because there are
multiple sources in an area.
•Mobile source air
toxics exhibit
both point source and
area
source characteristics.