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Pollution is formed from Greek word that means defilement. Pollution can be defined as the discharge into the environment of chemicals or substances or energy through animals or man’s activities in such quantities and for such duration, that damages the environment, thereby making the environment harmful to the health or wellbeing of man and other organism.
The release of these materials and /or energy into the environment;
disturbs the ecosystem
makes the abiotic environment unfit for life
poses danger to the health of plants and animals
The materials and energy that cause pollution are called pollutants. Although industrial, agricultural activities of man, produced most pollutants , natural processes such as excretion , decay and volcanic eruptions also produce pollutants. Some pollutants are said to be biodegradable e.g pesticides like pyrethrum, detergents, sewage, etc. They are harmful only for a limited period because they are broken down by bacteria or react with other chemicals in the environment and become harmless.
Others are described as persistent (non-biodegradable) e.g dielbrin, mercury compounds, pesticides like DDT, etc. do not break down and remain harmful for a long time. They may accumulate in the environment, in organism that absorb them, or in organism along the food chain (Bio magnification i.e. Increase in concentration).
There are three main types of pollutions based on the physical environment that is affected
Atmospheric or air Pollution
Land or Soil Pollution
Water Pollution
Some authors recognize noise as the fourth type.
Noise is unwanted, irritating sound, “dumped” into the atmosphere. Noise is a pollutant. Noise level is measured in decibels (dB). Silence is 0dB; whispering about 20dB; normal talking about 30-60dB; traffic about 75dB; big factories 100db; jet planes 115-200dB. Constant exposure to a noise level of over 85dB can lead to permanent deafness.
Atmospheric Pollution
This may be defined as the release into the atmosphere substance (Pollutants) in such quantities and for such duration, that it may cause harm to living things.
Sulphur dioxide
Sources: The burning of fossil fuels such as coal, oil and natural gases in coal mining, cement factory, electrical power stations, exhaust from vehicles and power plants.
Effects: Sulphur dioxide is an acidic poisonous gas. It readily react with oxygen and rain water to form sulphuric acid. Rain containing sulphuric acid is known as acid rain. (pH less than 5.0) When acid rain falls on vegetation, it reduces their growth and damages their leaves.
When it falls on building and metallic structures, it dissolves them. Acid rain dissolves the aluminium salts in the soil, causing them to build up to toxic levels in underground water, when this water flows into ponds, lakes etc. it affects the sources of drinking water and slowly destroys the aquatic plants and animals.
Sulphur dioxide readily dissolves in moist air to form an acid. When such air is inhaled, it irritates and damages the sensitive lining of the eyes, air passages and the lungs. Prolonged exposure to the gas is linked to respiratory diseases, cancer and heart attacks.
In plants, the gas penetrates the leaves through the stomata, this damages the leaves and kills the plants.
Sulphur dioxide is the main component of killer smog. Smog is a mixture of smoke and fog( chemical pollutants and water droplet).
Carbon monoxide
Sources: The main source of carbon monoxide is from the exhaust of motor vehicles and other combustion engines using petrol or diesel. Carbon monoxide is formed when burning of fuel is incompletely by using little air.
Effects: Carbon monoxide is a poisonous gas. It combines with haemoglobin in the red blood cells to form carboxyhaemoglobin. This reduces the capacity of the blood to transport oxygen round the body. In low concentrations, carbon monoxide causes dizziness, headache, nausea and tiredness. If inhaled for so long, even at low concentrations, it can cause brain damage. At higher concentrations, it can cause unconsciousness and eventually death.
Carbon dioxide
Sources: This is produced when fuels and other carbon compounds e.g wood are burned in plenty of air. Industrialization, increasing number of cars, bush burning, setting refuse dump on fire, etc results in carbon dioxide being released in increasing concentration into the atmosphere. Decay and respiration are natural processes that releases the gas into the air.
Effects: The gas forms a layer over the Earth’s surface. This is called the greenhouse effect. The result may be global warming (rise in the world temperature). In cold regions of the world, ice bergs may melt, leading to an increase in the amount of water in the oceans. If this continues, countries near the sea may be flooded e.g Bangladesh.
Nitrogen oxides
Sources: From burning of coal, exhaust of motor vehicles, power generating stations using diesel.
Effects: Oxides of Nitrogen are poisonous. It can irritate the eyes and skins. In sunlight, it reacts with hydrocarbon (also present in car exhaust fumes) to form ozone(photochemical smog) Ozone damages green plants and may trigger asthma attacks.
Like sulphur dioxide, oxides of nitrogen, damage our air passages and lungs ,it dissolves in rain water to form acid rain. Acid rain, have a toxic effect on vegetation, corrode building and metallic structures.
Sources: They are used as aerosol propellants, as cooling agents in refrigerators and air conditioners and in foam packaging. These chemicals accumulate in the upper atmosphere and react with ozone in the presence of light. During these reactions, ozone is converted to oxygen (ozone depletion). Ozone is a gas that forms a layer over the Earth. It absorbs much of the ultraviolet rays from sunlight.
Effects: It depletes the ozone layer, allowing more ultraviolet light to reach the Earth. This result in cataracts, cancer, sunburn, rapid aging and wrinkle of the skin, lower crop yields, kill useful microorganisms, etc.
Solid pollutants
They include;
Dust: This is fine, dry particles of matter.
Sources: Human activities like construction, mining, quarries and industrial sites. As well as volcanic eruption.
Effects: Asbestos dust is believed to cause lung cancer. Lead dust from exhaust of motor cars using petrol can cause anaemia and brain damage in children and injury to the nervous system in adults. Lead can accumulate in the body causing poisoning.
Fumes: This refers to gaseous products or any thing which contains air borne solid particles that are smaller than dust. Examples are smoke, soot.
Sources: From incineration plants and industrial plants, motor vehicles, burning of coal.
Effects: They cause severe irritation of the respiratory system in human and cause respiratory disease such as catarrh and cough. It also damages vegetation, by covering the leaves, cause the formation of smog and affect the weather.
Pollen grains
Sources: Flowering plants.
Effects: Inhalation triggers an allergic reaction.
Radiation: This is a form of energy, emitted as ray, waves or particles by radioactive substances.
Sources: From sun and outer space, nuclear power plants, nuclear weapons, electronic devices such as lasers, X-ray machines, colour television sets and microwave.
Effects: High levels of exposure can cause defects in unborn child by genetic mutations, cause cancers in humans. It can pass through the food chain from vegetation to cause harm to the final consumer (bio magnification).
Ways of Reducing or Controlling Atmospheric Pollution
Proper maintenance of machinery, motor vehicles, boilers, etc. to ensure that fuel is burnt efficiently.
Use of filters or scrubbers on chimneys to remove pollutants.
Use of alkalis to neutralize acidic waste products from factories before they are released into the environment.
The use of catalytic converters in cars to remove oxides of nitrogen, carbon monoxide and unburnt carbon.
Use of ozone-friendly products to prevent ozone depletion.
Enforcement of the nuclear test ban treaties.
Use of petrol without lead or with a low level lead.
Use of screens to absorb noise from machines.
Turn down volumes of radios and televisions to reduce noise.
Design soundproof filters or silencers for machines and vehicles.
Plant a belt of green plants around air ports to absorb noise of air planes.
Water Pollution
Water Pollution is the discharge into water body of substances (pollutants) in such quantities and for such duration, that may cause harm to living things.