Air quality issues
The Atmosphere
Atmospheric layers
The atmosphere is composed of layers as shown in the diagrams below:
Layers of the atmosphere
Temperature profile of atmosphere
Stratosphere
The stratosphere is the layer above the troposphere. Here the temperature increases
slightly versus height.
Contained in the lower part of the stratosphere is the ozone layer.
This ozone absorbs ultraviolet (UV) radiation:
O3 + hν → O2 + O → O3
Thus the ozone protects the Earth from dangerous ultraviolet radiation. If it wasn't
for this layer life could not exist -- too much radiation would reach the surface.
Mesosphere
The mesosphere is where most meteors burn up in the atmosphere. It also has
some interesting, but poorly understood, phenomena such as noctilucent clouds,
blue jets, and sprites.
Thermosphere
In the thermosphere, the temperature starts to increase again due to solar radiation.
An important part of the thermosphere is the ionosphere, a region where the solar
radiation is strong enough to split electrons off atoms to form ions.
A spectacular aspect of the ionosphere are the auroras
Aurora Borealis
Aurora video (timelapse)
Another important aspect of the ionosphere is that it allows radio waves to travel
long distances. The waves refract off the ionosphere directing them back to Earth.
Radio wave propagation by the ionosphere
Atmospheric composition
Composition of the atmosphere
The numbers in the diagram consider a dry atmosphere. Water vapor accounts for
0-4%.
Air Pollution
Primary air pollutants
pollutants emitted directly
Secondary air pollutants
pollutants created from reactions between primary air pollutants
Criteria air pollutants
6 pollutants regulated by the US Environmental Protection Agency (USEPA)
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carbon monoxide
particulate matter
sulfur dioxide
nitrogen dioxide
ozone
lead
Sulfur Dioxide and Acid Rain
Sulfur Dioxide
Sulfur is oxidized to sulfur dioxide:
S + O2 → SO2
This can then be combined with water in the atmosphere to form sulfur dioxide:
2SO2 + 02 + 2H20 → H2SO4
Source:
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burning of sulfur-containing compounds including coal and oil
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smelting of metal ores
Cu2S + O2 → 2Cu + SO2 (metal ore)
Doe Run's lead smelter in Herculaneum, Missouri,USA
Direct Effect
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Absorbed by moist respiratory tissue causing restriction of airway
- especialy severe in people with asthma
Environmental Effect
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Acid Deposition
Acid Deposition
The fallout of sulfuric acid either in rain or as dry particles is called acid deposition
or, more commonly, acid rain.
Effects:

Destruction of concrete and stone structures
Acid rain events on a stone monument
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Acidification of forests, rivers, and lakes
Some lakes have natural buffering, but many do not.
Acidified water causes death of fish and other organisms. It also causes damage to trees and
other plants.
Acid rain damage on woodlands in Czech Republic
Nitrogen dioxide, ozone, and smog
Nitrogen Dioxide
Nitric oxide (NO) and nitrogen dioxide (NO2) are formed from high temperature
combustion. [1]
low temperature combustion: CH4 + O2 + N2 → CO2 + H2O + N2
high temperature combustion:
CH4 + O2 + N2 → CO2 + H2O + NO
NO + O2 → NO2
Nitric oxide and nitrogen dioxide are together called NOx (read as nox).
Health Effects:

lung irritation

increases susceptibility to lung disease
The flask contains nitrogen dioxide. It is was give the characteristic brownish color to smog
Ozone
Nitrogen dioxide reacts with sunlight to form nitric oxide and atomic oxygen. This
oxygen reacts quickly with molecular oxygen (O2) to form ozone. Ozone can then
react with nitric oxide to regenerate nitrogen dioxide.
NO2 + hν → NO + O
O + O2 → O3
O3 + NO → NO2 + O2
Note The ozone formed here is tropospheric ozone ("bad ozone"), not to be
confused with stratospheric ozone ("good ozone")
Health Effects:
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lung problems

eye irritation
Environment Effects:
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damage to plants and trees
Photochemical Smog
Tropospheric ozone reacts with organic chemicals to produce photochemical
smog.
Smog is a toxic soup of NOx, ozone, peroxyacyl nitrates (PANs), aldehydes, and
other organic chemicals.
Smog in Kuala Lumpur, Malaysia
Thermal inversions
Under certain conditions a layer of warm air can occur above cold air. This causes
any pollutants to be trapped and not dispersed.