Measure of Air Pollution
What is air pollution?
Types of air pollution
1. Particulate matter
2. Noxious gases, such as sulfur dioxide, carbon monoxide, nitrogen oxides, and
chemical vapors, which take part in chemical reactions in the atmosphere, forming
smog and acid rain.
3. Smog
4. Acid rain
5. Greenhouse effect
6. "Holes" in the ozone layer
Health Effects of Air Pollution
From Lawrence Berkeley National Laboratory website:
http://www.lbl.gov/Education/ELSI/pollution-main.html
Air pollution can affect our health in many ways with both short-term and long-term effects.
Different groups of individuals are affected by air pollution in different ways. Some
individuals are much more sensitive to pollutants than are others. Young children and elderly
people often suffer more from the effects of air pollution. People with health problems such
as asthma, heart and lung disease may also suffer more when the air is polluted. The extent
to which an individual is harmed by air pollution usually depends on the total exposure to
the damaging chemicals, i.e., the duration of exposure and the concentration of the
chemicals must be taken into account.
Examples of short-term effects include irritation to the eyes, nose and throat, and upper
respiratory infections such as bronchitis and pneumonia. Other symptoms can include
headaches, nausea, and allergic reactions. Short-term air pollution can aggravate the medical
conditions of individuals with asthma and emphysema. In the great "Smog Disaster" in
London in 1952, four thousand people died in a few days due to the high concentrations of
pollution.
Long-term health effects can include chronic respiratory disease, lung cancer, heart
disease, and even damage to the brain, nerves, liver, or kidneys. Continual exposure to air
pollution affects the lungs of growing children and may aggravate or complicate medical
conditions in the elderly. It is estimated that half a million people die prematurely every year
in the United States as a result of smoking cigarettes.
Particulate Matter (Soot)
One type of air pollution is the release of particles into the air from burning fuel for energy.
Diesel exhaust is a good example of this particulate matter . This type of pollution is
sometimes referred to as "black carbon" pollution. The exhaust from burning fuels in
automobiles, homes, and industries is a major source of pollution in the air.
Smog
Smog is a type of outdoor pollution caused by chemical reactions between pollutants
derived from various sources, such as automobile exhaust and industrial emissions. Cities are
often centers of these types of activities, and many suffer from the effects of smog,
especially during the warm months of the year.
Air pollution is dispersed differently, depending on the geographical location, temperature,
wind and weather factors. However, sometimes pollution does not disperse, and can build
up to dangerous levels. A temperature inversion occurs when air close to the Earth is
cooler than the air above it. Under these conditions the pollution cannot rise and be
dispersed. Cities surrounded by mountains also experience trapping of pollution. Inversion
can happen in any season. Winter inversions are likely to cause particulate and cabon
monoxide pollution. Summer inversions are more likely to create smog.
Another consequence of outdoor air pollution is acid rain.
Acid Rain
The falling of acids and acid-forming compounds from the atmosphere to Earth’s surface is
referred to as acid deposition. Acid deposition is commonly know as acid rain when it occurs
as the wet deposition of droplets of acids and acid-forming compounds.
Natural precipitation is slightly acidic with a pH of 5.0 to 5.6.
Because of acid deposition, typical rain in the eastern United States is now about ten times
more acidic with a pH of 4.3.
In some areas, rain is 100 times more acidic, with a pH of 3.
Acid deposition can be a serious regional problem, particularly in areas downwind from coalburning power plants, smelters, factories, and large urban areas.
Acid deposition can have many harmful ecological effects in both aquatic and terrestrial
systems. It can damage tree foliage directly and make trees more susceptible to other stresses
such as cold temperatures, diseases, insects, droughts, etc.
In lakes, acid deposition can kill fish and can promote the conversion of moderately toxic
inorganic mercury compounds into highly toxic methylmercury.
It also contributes to human respiratory diseases such as bronchitis and asthma.
Greenhouse Effect
Certain gases in the atmosphere trap heat in the lower atmosphere (troposphere). This
phenomenon has been referred to as the greenhouse effect.
Without the natural thermal insulation of the natural greenhouse effect, the earth would be
covered by ice, and life as we know it would not exist.
The amount of heat trapped in the troposphere depends mainly on the concentrations of
heat-trapping greenhouse gases and the length of time they stay in the atmosphere.
The major greenhouse gases are:
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Water vapor
Carbon dioxide (CO2),
Ozone (O3),
Methane (CH4),
Nitrous oxide (N2O), and
Chlorofluorocarbons (CFCs).
The two predominant greenhouse gases are water vapor (controlled by the hydrologic
cycle), and carbon dioxide (controlled by the global carbon cycle).
Water vapor
Water vapor added to the atmosphere by human activities has little effect on the
greenhouse effect.
Carbon dioxide
The concentration of carbon dioxide is much smaller than that of water vapor. As a
result, the fairly large input of carbon dioxide from human activities can
significantly affect the amount of heat trapped in the atmosphere.
What might cause carbon dioxide levels to rise?
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Burning of wood and fossil fuels (coal, oil, gas)
Decrease in photosynthesis
o Cutting trees for development
o Burning tropical rainforests to clear land for agriculture
Wild fires
Pollution killing photosynthetic algae and single-celled organisma in
the oceans
o Acid rain destroying foliage
Volcanic outgassing
Increase in respiration by increasing human and animal populations?
Carbonated beverages?
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Atmospheric levels of carbon dioxide, CFCs, methane, and nitrous oxides
have risen significantly in recent decades.
The total amount of CO2 in the atmosphere has increased by about 25% since the
beginning of the industrial revolution. The accumulation of CO2 over the last century
has added as much heat to the Earth's climate system as would a one half percent
increase in the sun's energy output.
Since the late 1800's, the mean global temperature has risen by about 0.3o - 0.6oC,
and over the last 45 years, the temperature has increased by about 0.2 - 0.3oC. Recent
years have been among the warmest on record.
The increase in these greenhouse gases is projected to increase the earth’s natural
greenhouse effect and lead to global warming.
What are the results of global warming?
Possible consequences of global warming include:
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Increase in ocean volume due to thermal expansion of the water
Melting of glacial ice and sea ice
Global rise in sea level
o Flooding of low-lying areas
o Loss of land for agriculture
o Migration of coastal populations inland
(a large percentage of the population lives in coastal areas)
Northward migration of warm climate species of plants and fish
Spread of some tropical diseases
New weather patterns
1. Higher frequency and greater intensity of hurricanes due to warmer
ocean temperatures
2. Shift in the paths of large scale cyclonic storms, affecting the distribution of
precipitation and the occurrence of severe stoms, such as tornadoes
3. More intense heat waves and droughts
Change in distribution of world's water resources (reduction in flow of some rivers
and increased flooding in others) with implications for agriculture and drinking water
supplies
Many uncertainties remain with respect to the exact consequences of global warming.
The Ozone Layer
The ozone layer exists in the stratospheric layer of the earth’s atmosphere where ozone
concentrations are nearly one thousand times higher than in the troposphere.
Ozone is produced by lightning and solar irradiation of oxygen molecules.
Ozone is formed by reactions that start with the splitting of O2to form two atomic oxygen
(O) atoms. Atomic oxygen (O) will react with another O2 molecule to form ozone (O3).
Ozone can be destroyed by catalytic reactions involving chlorine, bromine, etc.
Chlorine has been directly implicated in the formation of the Antarctic ozone hole.
Ozone protects life on earth by absorbing most incoming solar ultraviolet radiation.
The Hole in the Ozone Layer
From Lawrence Berkeley National Laboratory website:
http://www.lbl.gov/Education/ELSI/pollution-main.html
Ozone depletion is another result of pollution. Chemicals released by our activities affect
the stratosphere , one of the atmospheric layers surrounding earth. The ozone layer in the
stratosphere protects the earth from harmful ultraviolet radiation from the sun. Release of
chlorofluorocarbons (CFC's) from aerosol cans, cooling systems and refrigerator equipment
removes some of the ozone, causing "holes"; to open up in this layer and allowing the
radiation to reach the earth. Ultraviolet radiation is known to cause skin cancer and has
damaging effects on plants and wildlife.
Sources:
Managing Out Natural Resources, 4th edition, Camp and Daugherty. 2002, Thomson
Learning, LLC.
http://soil.gsfc.nasa.gov/soilfert/npk.htm