Environmental Engineering Reference
In-Depth Information
[8.1]
Combustion is the main source of nitrogen oxides and can be formed via three routes (Latta
and Weston, 1998; Colannino and Baukal, 2001):
NO
+
½ O
↔
NO
2
2
1.
Thermal nitrogen oxides form at high temperature combustion by combination of nitro-
gen and oxygen from the air:
N
+↔
O
2NO
[8.2]
2
2
2.
Combustion of natural gas is the main source of thermal nitrogen oxides.
Fuel nitrogen oxides form when bound nitrogen in the fuel is released as a result of the
combustion process:
CxHyN
→↔
(HCN
CN) (unbalanced reaction)
[8.3]
(HCN
↔+→++
CN)
O
NO
CO
H (unbalanced)
2
3.
Prompt nitrogen oxides develop at the combustion flame with air nitrogen:
CHy
+→
N
(HCN
↔
CN) (unbalanced)
[8.4]
2
(HCN
↔+→++
CN)
O
NO
CO
H (unbalanced)
[8.5]
2
The presence of nitrogen oxides in the atmosphere impacts human health, ecosystems, and
infrastructure:
1. The direct exposure to nitrogen dioxide causes respiratory problems, especially in people
with asthma.
2. Nitrogen oxides react with ammonia and water to form aerosols (particle matter),
then penetrate the lungs, and can lead to respiratory illnesses such as emphysema and
bronchitis.
3.
In combination with VOCs, nitrogen oxides react in the presence of heat and sunlight to
form ground-level ozone.
4.
Nitrogen oxide compounds combine with water to form nitric acid that along with sulfuric
acid produce acid rain (Sloss et al., 1992; “Nitrogen dioxide: Health,” n.d.).
Acid rain
Acid rain is the result of the presence of sulfuric acid and nitric acid in rain, fog, or snow that
is deposited as wet precipitation, or as sulfate (SO
4
=
) and nitrate (NO
3
−
) ions attached to
particles that land onto the ground as dry deposition (“Acid Rain,” n.d.).
Acid rain causes acidification of lakes and streams and affects fish and other aquatic
organisms, damages forests and sensitive ecosystems, changes the chemistry of soils, and
accelerates the decay of man-made buildings and structures.
The inhalation of sulfate and nitrate particles coming from dry deposition penetrates the
lungs and may cause severe respiratory illnesses and premature death from heat and lung
disorders (“Acid Rain,” n.d.).
Carbon monoxide
This pollutant comes from the incomplete combustion of any carbon-containing material. The
exposure to high doses of carbon monoxide causes death in people and animals. However, the
continuous exposure to low levels of carbon monoxide may cause chronic health problems,
