[O.sub.3] is a secondary pollutant
and has as its precursors nitrogen oxides and hydrocarbons, and S[O.sub.2] is produced by vehicle and industrial combustion (12,13).
Ground-level ozone is a secondary pollutant
and may actually be scavenged from the air by fresh combustion pollutants.
Pollutants emitted directly from vehicles are not the only cause for concern but on warm days, hydrocarbons react with oxides of nitrogen to create a secondary pollutant
, the ozone.
2) Secondary air pollutants--formed by the interactions of primary pollutants or secondary pollutant
precursors, which are not pollutants in and of themselves.
Ozone ([O.sub.3]): Secondary pollutant
formed when other pollutants react in sunlight.
In addition to the primary pollutants, levels of ozone - a secondary pollutant
- were also reduced due to the lack of sunshine.
'Nitrogen dioxide is a secondary pollutant
and is not produced individually but when nitrogen and oxygen mix at high temperatures.
Meanwhile, a secondary pollutant
is not directly emitted as a primary pollutant, but forms when primary pollutants react in the atmosphere.
The same is true of tropospheric ozone, a secondary pollutant
that results when volatile organic compounds react with sunlight.
Ozone ([O.sub.3]) is not emitted as such from a source and is considered a secondary pollutant
. So the sequence of reaction shows how gases leading to photochemical smog are formed.