AIR POLLUTION AND GLOBAL ATMOSPHERIC CHANGE

 

Human beings breathe in and out about once every 4 seconds, 16 times a minute, 960 times an hour and about 8.5 million times a year of air intake. This adds up to about 4 million liters (1 million gallons) of oxygen-containing air every year from the earth's surface.

 

Composition of Natural Dry Air:

Ÿ       A clean dry air is made up of the following elements:

    Nitrogen - - -     78%

    Oxygen - - - -    20.94%

    Argon  - - - - 0.9340%

    Carbon Dioxide 0.0310%

    Neon  - - - - 0.0018

    Helium  - - - 0.0005

    Methane - - - 0.0002

    Krypton - - - 0.0001

    Sulfur Dioxide 0.0001

 

AIR POLLUTION AND GLOBAL ATMOSPHERIC CHANGE

 

Human beings breathe in and out about once every 4 seconds, 16 times a minute, 960 times an hour making up about 8.5 million times a year of air intake. This adds up to about 4 million liters (1 million gallons) of oxygen-containing air every year from the earth's surface.

 

NATURAL SOURCES OF AIR POLLUTION

 

a)  Carbon oxides, nitrogen oxides, ash and other particulate matter from lightning triggered

     forest fires  

b)  Massive eruption of volcanic dust, ash and particulate matter.

c)  Salt spray from the sea, 

d)  Methane and hydrogen sulfide from decaying plants

d)  Pollen (e.g. ragweed) from live plants, 

e)  Dust and other forms of suspended particulate matter from windstorms 

f)  The composition of natural air

 

A clean dry air is made up of the following elements:

    Nitrogen - - -     78%

    Oxygen - - - -    20.94%

    Argon  - - - - 0.9340%

    Carbon Dioxide 0.0310%

    Neon  - - - - 0.0018

    Helium  - - - 0.0005

    Methane - - - 0.0002

    Krypton - - - 0.0001

    Sulfur Dioxide 0.0001

Gases such as carbon dioxide, methane and sulfur dioxide are normal constituents of the clean air. However, they often reach much higher concentrations to make the air polluted and harmful to the environment and human life.

 

Sources of Human-induced Air Pollution

 

a) Stationary Sources:  Pollution sources that are stationary such as Smokestacks, Electric power plants and Smelters

b) Mobile Sources:   Sources of air pollution that are mobile such as Automobiles, Boats, Trains, Aircraft, etc.,

 

Factors that Intensify Air Pollution Problems

 

Air pollution is intensified by the following elements:

    a)   Excessive emission of pollutants, and,

    b)   Insufficient ventilation leading to poor atmospheric dispersal of pollutants

    c)   A very dense population

    d)   A very high concentration of Industries

    e)   The presence of temperature Inversion

 

AIR POLLUTION PROBLEMS

 

1.  Photochemical Smog:  

 

Formed as a result of the action of sunlight on the hydrocarbon emissions from motor cars and other sources in areas of low dispersion. The production of smog ceases at nightfall when human activity ceases. For example, a week from October 26, 1948, a thermal inversion occurred at Donora, 30 miles south of Pittsburgh, in Pennsylvania. In a town of 12,000 people, 43% became ill -5910 people, and 20 people died within only 5 days.

 

2.   Acid Rain:

 

Causes the deposition of Acids on the earth's surface through the processes of precipitation.

Composition:  Sulfur dioxide (SO2) combines with oxygen and water to form sulfuric acid (H2SO4); and Nitrogen oxides (NOx) combine with water to form Nitric acid (NHO3). This results in a pH value in the low 3's and 4's approximating vinegar.

Source:  Derived primarily from combustion of impure fossil fuels mainly in the US manufacturing belt. Coal burning power plants from Illinois to Pennsylvania are the greatest culprits. The largest single source in the world is a nickel smelter at Sudbury in Ontario, Canada.

Effects:  Because a drop in pH makes minerals more soluble, acid rain adversely affects fish, plant communities like forest, drinking water, work of art, building stones and exposed metals.

Control:  Requires International cooperation, but the following might help:

a)  Install sulfur scrubbers in smoke stacks at factories, b)  Reduce combustion temperature, c)  Effective legislation

 

3.   Greenhouse Effect and Global Warming

 

The greenhouse effect results because carbon dioxide in the atmosphere is transparent to the relatively short-wave solar radiation but opaque to the long wave terrestrial radiation. The concentration of carbon dioxide in the atmosphere therefore causes an atmospheric trapping of heat on the earth's surface.

 

4.   Depletion of Ozone Layer

 

A group of synthetic substances which are compounds of chlorine, fluorine and carbon form a new product called Chlorofluorcarbons (CFC’s). These chemical compounds that are widely used in refrigeration, aerosols and in many industrial processes are chemically inert, and remain stable and intact in the atmosphere and do not break down. They reduce ozone in the atmosphere and allow cancer-causing UV radiation to pass through.

 

CRITERIA POLLUTANTS

 

These are specific environmental contaminants that adversely affect human health and welfare and for which the EPA has set air quality standards.

 

1. Carbon Monoxide  (CO):  a tasteless, odorless and colorless gas produced from the incomplete burning of fossil fuels by motor vehicles and some industrial processes.

2. Sulfur Dioxide:  (SO2) A colorless gas with a strong odor resulting from the burning of sulfur-bearing coal

3. Hydrocarbons:  Also called Volatile Organic Compounds. Examples are methane, benzene and ethanol. They react with nitrogen oxides in the presence of sunlight to form photochemical smog

4. Particulate Matter:  refers to solid or liquid particles including soot, dust, pollen and various chemicals and metals.

5. Nitrogen Oxides:   Brownish orange gas produced by motor vehicles and combustion at major industrial sources.

6. Ground level Ozone:  A colorless gas formed from a reaction between motor vehicle emissions and sunlight.

7. Lead: Small particles emitted from motor vehicles and smelters.

 

INDOOR AIR POLLUTION

 

Sources: 

a)        Gas stoves, faulty furnaces, unvented gas stoves and kerosene heaters, wood stoves, burning of    candles etc., release carbon monoxide and nitrogen dioxide into the air

 

b)       Paints and other materials in the home may contain lead

 

c)        Formaldehyde fumes from furniture stuffing foams, insulation in carpets and plywood releases cancer risk fumes.

 

d)       Tobacco Smoking releases carbon monoxide, sulfur dioxide, and oxides of nitrogen in addition to quantities of cancer-causing pollutants like cadmium, nickel and radioactive polonium.

 

e)        Radon-222, radioactive soil and rock surrounding building foundation and water supply

 

f)          Pipe Insulations, Vinyl ceiling and floor tiles may release asbestos into the air.

 

g)        Chlorine-treated water in hot showers may release chloroform

 

Controlling Indoor Pollution:

 

1.  Installation of air-to-heat exchanger to expel heated air and replace it with fresh air.

2.  The use of vegetation as living air purifiers.

3.  The use of a sub-basement vent system

4.  Controlling smoking indoor.