Air pollutants are involved in causing 4 major environmental effects: photochemical smog, acid deposition, global warming, and ozone shield destruction.
Ozone shield Destruction:- Ozone shield destruction is primarily caused by chlorofluorocarbon and halons. Chlorofluorocarbon are heat-transfer agents used in refrigerators and air conditioners. Halons are antifire agents used in fire extinguisher. would drift into the straptosphere and when the temperature drops, these compounds react chemically on Frozen particle surface within straptospheric clouds and release active chlorine, which can react with ozone in the ozone shield. Similarly,halons release bromine which reacts with ozone. Once freed, a single atom of chlorine destroys about 1,00,000 molecules of ozone before settling on Earth's surface as chloride. At the South Pole of antartic, up to 60% of the ozone is destroyed each spring. There is similar reduction called ozone hole, but not as severe, over the north pole of the Arctic as well.
Photochemical smog:- It contains 2 air pollutants nitrogen oxides (NO2) and hydrocarbons (HC)- that react with one another in the presence of sunlight to produce ozone (O3) and PAN ( peroxylacetyl nitrate).
Both nitrogen oxides and hydrocarbons come from fossil fuel combustion. Ozone and PAN are commonly reffered as oxidants. Breathing ozone affects the respiratory and nervous systems, resulting in respiratory distress, headache and exhausion.
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Acid deposition:- The coal and oil burned by power plants release SO2 into air. Automobile exhaust puts NO2 in the air. Both SO2 and NO2 are converted to acids when they combine with water vapour in the atmosphere.
These acids return to the earth as either wet deposition or dry deposition. Acid deposition also corrodes marble, metal and stonework.
Acid deposition:- The coal and oil burned by power plants release SO2 into air. Automobile exhaust puts NO2 in the air. Both SO2 and NO2 are converted to acids when they combine with water vapour in the atmosphere. These acids return to the earth as either wet deposition or dry deposition. Acid deposition also corrodes marble, metal and stonework.
Global warming:- Certain Pollutants allow Ray's of sun to pass through but then absorb and reradiate the heat back towards the earth. This is called the green house effect because the glass of a green house allow sunlight to pass through and then traps the resulting heat inside the structure. The air Pollutants responsible for the greenhouse effect are known as the greenhouse gases, they are as follow-
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- Carbon dioxide (CO2), from fossil fuel and wood burning.
- Nitrous oxide (NO2), primarily from fertilizer use and animal wastes.
- Methane (CH4) from biogas, bacterial decomposition, particularly in the guts of animals, sediments and flooded rice paddies.
- Chlorofluorocarbon (CFCs) from feron, a refrigerant.
- Halons ( halocarbons, CxFxRrx )from the extinguisher.
If nothing is done to control the level of greenhouse gases in the atmosphere, a rise in global temperaturecould be as high as 5°c by the year 2050. The ecological effects of a 5°c rise in global temperature would be severe.
The sea level would rise- melting of polar ice caps would add more water to the sea and in any case water expands when it heats up. There would be coastal flooding and the possible loss because of regional changes in climate.
The sea level would rise- melting of polar ice caps would add more water to the sea and in any case water expands when it heats up. There would be coastal flooding and the possible loss because of regional changes in climate.
Ozone shield Destruction:- Ozone shield destruction is primarily caused by chlorofluorocarbon and halons. Chlorofluorocarbon are heat-transfer agents used in refrigerators and air conditioners. Halons are antifire agents used in fire extinguisher. would drift into the straptosphere and when the temperature drops, these compounds react chemically on Frozen particle surface within straptospheric clouds and release active chlorine, which can react with ozone in the ozone shield. Similarly,halons release bromine which reacts with ozone. Once freed, a single atom of chlorine destroys about 1,00,000 molecules of ozone before settling on Earth's surface as chloride. At the South Pole of antartic, up to 60% of the ozone is destroyed each spring. There is similar reduction called ozone hole, but not as severe, over the north pole of the Arctic as well.
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Depletion:- Depletion of the ozone layer will allow more ultraviolet Ray's to enter the troposphere. The incidence of human cancer, especially skin cancer, is expected to increase, and plants and animals living in the top microlayer of the ocean will begin to die.
Increase of ultraviolet radiation also will hasten the rate at which smog is formed.
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