Lesson 79: Air Pollution Essentials
In this lesson, we will learn about air pollutants and factors that
affect air pollution. We will also look at hydroxyl radical, which naturally
helps keep our air clean, and look at some effects of air pollution including
smog and inversions.
Air pollutants are substances in
the atmosphere that have harmful effects. These include certain gases and
aerosols such as dust, carbon, pollen, sea salts and microorganisms. Our
atmosphere contains gases and water vapor that are essential to sustaining life.
3 factors affect amount of air pollution:
- amount of air pollutants entering the air
- amount of space into which they are dispersed
- mechanisms to remove pollution from the air
Pollutants that
enter the troposphere are usually removed within hours and carried by cumulus
clouds into the upper layers of troposphere. The atmosphere naturally cleans
itself but some pollutants are resistant and linger. The worst of these are
ozone-depleting pollutants such as chlorine and bromine compounds.
Hydroxyl Radical (OH) is a naturally occurring cleansing agent in
the atmosphere that
oxidizes many gaseous compounds into harmless products and can also bring these
pollutants down to the ground or water by precipitation.
Human activity has raised concentrations of pollutants in
the air. Some pollutants such as carbon monoxide do not break down easily and
take months to oxidize. Others like methane can even take years.
Air pollution began in volume during the Industrial Revolution in
the 1800s with crowded cities and the use of coal for heating and energy.
Industrial smog is a combination of smoke and fog that lingers in
the air and is irritating. It contains sulfur, soot and water vapor. You can
find this type of smog around industrial plants.
Photochemical smog is a hazy fog produced by pollutants from
automobile exhausts acted upon by sunlight. Nitrogen oxides and volatile
organic carbon compounds (VOCs) produce this brownish, irritating smog.
Atmospheric brown clouds (ABC) are aerosols that create a blanket of pollution
that deplete the ozone. These are new forms of smog common in south and central
Asia and contain soot and carbon from biomass burning. Atmospheric brown clouds
make it hard to see in these areas as they block the sun, reduce snow and ice,
lower crop yields, and reduce rainfall.
Inversion is the condition of cooler air below and
warmer air above. Inversions intensify with smog.
Inversions increase how long pollutants stay in
the air. This can prompt health officials to tell people to
stay indoors if they have breathing problems. Smog can cause headaches, nausea
and eye and throat irritation.