Pollution

Concept of pollution
Pollution can be defined as the introduction of contaminants or pollutants into the n.atural environment.

The environment comprises of living (biotic) and non-living (abiotic) things such as plants, animals, air, land and water.

Contaminants or pollutants
Are harmful substances introduced into the environment that disturb the balance of nature.

Pollution can be in the form of chemical substances or energy such as noise, heat or light.

Human activities
Human activities play a major role in the pollution of the environment. Humans engage in a myriad of activities such as agriculture, manufacturing, transport, waste disposal, mining etc.

All of these activities contribute to environmental pollution in one way or another.

Types of pollution
There are three main types of pollution:

1. Terrestrial (land) pollution 
2. Aquatic (water) pollution 
3. Aerial (air) pollution 

 Terrestrial pollution 
Is the degradation or destruction of the earth's surface and soil, directly or indirectly, as a result of human activities.

The human activities refer to any activities performed by man that lessens the quality and or productivity of the land as an ideal resource for agriculture, forestation, construction, etc.

Human Activities which Cause Terrestrial Pollution 

 The human activities responsible for this kind of pollution include poor agricultural practices, mining, waste dumping and urban waste disposal. Below are some causes of terrestrial pollution.

1. Agricultural activities.
Because of the ever-increasing human population, demand for food has increased rapidly. Farmers often use fertilizers to increase crop production and pesticides to get rid of pests, fungi and bacteria that destroy the crops or harm animals. The overuse of such agrochemicals results in the contamination and poisoning of the soil.
Other causes of soil pollution from agricultural activities include:

√poor methods of irrigation which causes the leaching of cations down the soil surface;

√manure heaped on land, which may leach down the soil; and

√oil spillages that seep into the soil.

2. Mining activities
 During mineral extraction, several land spaces are created beneath the soil surface. The underground holes dug during mining causes the land to sag or subside (caving in). This is nothing but the nature‟s way of filling the spaces left out after mining or extraction activities. This destroys the land and makes it unfit for use. Mining involves the use of toxic chemicals used for mineral separation. When these chemicals drain into the soil, it gets polluted. Rain water often leaches harmful substances from the exposed mining waste into the ground. These harmful substances are like heavy metals (e.g. arsenic) and sulphuric acid or chemicals used in processing the ores (e.g. cyanide. These chemicals are another cause of soil contamination.

3.Deforestation and soil erosion Deforestation refers to indiscrimate cutting of trees in search of land for agriculture, settlement, mining, industrialization etc. Trees have got a number of advantages which include attracting rainfall, checking soil erosion and breaking strong winds. The act of cutting down trees carelessly leaves the land bare and hence exposes it to agents of erosion.

Soil erosion causes land pollution. The eroded soil loses its nutrients and organic matter, as well as its ability to hold water. As such, soil erosion can render a fertile land as no longer suited for agriculture, or even turn originally fertile lands into barren deserts. Other than causing soil erosion, deforestation has also been linked to floods which can, in turn, be seen as another cause of land and water pollution.

4. Sewage disposal
Sewage refers to a waste, in solution or suspension, carried off in sewers or drains with intention of removing it from the community. In areas where there are no water bodies into which to dump urban sewage directly, it is dumped into sewage pools that are usually dug far away from residential areas to avoid bad smell emitted by the deposited sewage.

 The toxins and poisonous chemicals in the sewage gradually seep down into the ground, thus polluting the land and killing beneficial soil microorganisms.

5. Garbage disposal 
Tonnes of garbage are produced each year, especially in urban and industrial areas.
Garbage is collected and moved to the dumping sites allocated for that purpose. The garbage in dumping sites comprises of biodegradable and non-biodegradable wastes.

The biodegradable wastes are those that can be broken down easily by the action of microorganisms,e.g. bacteria and fungi. The degradable waste matter may include materials such as rotten foods, kitchen wastes etc. The non-biodegradable wastes are those that cannot be decomposed by microorganisms and thus remain on the ground for a long time. The non-biodegradable wastes are such as plastic, polythene bags, metal, some clothing and glass.

5. One of the common causes of land pollution in dumping sites is the contamination of the soil with toxic and even hazardous substances. Needless to say, the ability of this soil to support life is significantly affected. Transfer of toxic wastes Industries in developed countries produce much toxic wastes, including the deadly, reactive nuclear wastes. However, these countries have very strict laws which prohibit the dumping of such toxic wastes in their countries.

The easiest and cheapest alternative is to dump them in the developing third-world countries. This is because of the greedy and selfish leaders in poor countries are easily that agree to sign contracts to allow the disposal of such dangerous wastes on their lands for their own economic gains.


Hazards Caused by Terrestrial Pollution
pollution is often overlooked because its effects are not well evident to most people. However, land pollution has got a number of negative effects to soil, soil organisms, man, plants and animals.

Effect of terrestrial pollution
 The following are some effects of terrestrial pollution:

• Wastes dumped carelessly can endanger the health of man as well as other organisms. Broken glass, metal and other sharp objects may pierce one‟s skin and introduce disease germs into the body. Empty cans, glass and plastic containers are potential breeding grounds for mosquitoes which spread malaria and other diseases. Rotten organic matter may harbour many disease germs and they also produce noxious smell when they rot. The rotten wastes also attract flies which transmit a number of enteric diseases like dysentery, cholera, diarrhoea, etc. 
• Land pollution causes chemical contamination to the ecosystem. This occurs when the chemicals in the waste matter poison the soil. Then plants growing on the poisoned soil, animals that eat these plants and even humans are all affected by these chemicals. This process is called biomagnifications and is a serious threat to the ecology. It can lead to the loss of some types of plants and animal life as well as create long-term health problems such as cancer and other deformities in humans. Radiation from nuclear wastes causes healthy problems such as cancers and other deformities.
•  Piles of waste in urban areas keep growing due to increase in waste. When this waste is burned it produces a lot of smoke that leads to air pollution. Soil erosion (as a form of land pollution) leads to loss of land for agriculture, settlement, forest cover, fodder patches for grazing, etc.
•  Land pollution leads to loss of ecosystem and hence directly or indirectly cause change in climatic patterns. 
• Deforestation causes imbalance in the rain cycle. A disturbed rain cycle affects a lot of factors such as reduction in the green cover. Plants help absorb excess carbon dioxide from the air and release oxygen to the atmosphere. This process helps to balance the atmosphere. Without vegetation cover, excessive accumulation of carbon dioxide in the atmosphere causesconcerns like global warming, the greenhouse effect, irregular rainfall, and floods among other imbalances. 
• Land pollution damages terrestrial life, especially plants. This greatly affects wildlife and other animal species which are forced to move further away and adapt to new regions or die trying to adjust. Heaps of different wastes from mining activities make the environment unsightly and ugly. 
• Terrestrial pollution is a big problem in urban areas where waste production outweighs waste disposal. In such areas you find poor and blocked sewage system, effluent from domestic toilets flowing on the streets and roads, and dirty water carelessly poured on the ground. This makes life in urban areas uncomfortable and a mere nuisance.

Different Methods of Preventing Terrestrial Pollution 
The following are some measures that can be taken to prevent and control land pollution:

1. Recycling and reuse Recycling is the processing of changing used materials into usable raw materials instead of discarding them as wastes altogether. Scrap metals, plastic bottles and glass should be recycled instead of being dumped into the environment. Packaging materials such as plastic bags, beverage and water bottles can be recycled or re-used for packaging or carrying goods.
2.  Using biodegradable materials Emphasis should be put on manufacturing and using materials that can easily be broken down (biodegradable). For example, paper bags should be manufactured and used instead of plastic (polythene) bags, which are non-biodegradable. Biodegradable plastics have been developed and are used. Some biodegradable plastics include biopolymers such as those used in making surgical sutures; photodegradable plastics, which break down upon exposure to light: and soluble plastics which can be broken down by water Proper disposal of wastes 
3. Urban waste should only be dumped in allocated dumping sites. These sites must be far away from residential areas to avoid the risk of spreading diseases, pest infestation and a bad smell. 
4. The sewage should be properly treated before being drained into dumping pools. Some of the methods that can be used to curb urban waste problem include incineration and recycling. Paraffin should be poured onto the sewage pools to suffocate and kill mosquito larvae and hence prevent the spread of malaria to residents living in the vicinity of the dumping pools. 
5. Reducing the use of agrochemicals Farmers should be advised and encouraged to avoid dependency on agricultural chemicals (fertilizers, herbicides pesticides, etc). All of these chemicals pollute the soil and affect soil microorganisms a great deal. 
6. Farmers should use organic manures and chemicals in their agricultural operations. These do not pollute the land or affect crops and animals as compared to artificial chemicals. They help to improve soil structure and hence prevent soil erosion. 
7. Making and enacting environmental laws and policies The government should make and implement laws and regulations to prevent and control terrestrial pollution. Likewise, local government authorities should make by-laws aiming at curbing the problem of environmental pollution. The laws must clearly state guidelines and procedures to be followed by everybody regarding environment sanitation. These may include: discharge and treatment of sewage; disposal of lethal nuclear wastes; use of agrochemicals in agricultural production; use of plastic and related materials; disposal of toxic chemicals and solid wastes from industries; and careless littering of the environment by irresponsible people. 
8. Creating public awareness The general public should be educated about the importance of keeping the environment clean and the benefit of living in a clean environment. This knowledge can be conveyed through meetings or via mass media such as television, radio and newspapers. It may also be conveyed via announcements, posters and other social media.

Aquatic Pollution
 Aquatic pollution is the introduction of substances that lower the quality of water into water bodies such as oceans, rivers, lakes, aquifers and ground water. This makes the water unsafe for use in homes and industries. Water pollution also affects living organisms (plants and animals) living in water.



Human Activities which Cause Water Pollution
There are two broad categories of sources of water pollution namely,

1. point source
2. non-pointsources

A point source
 is one that delivers harmful substances directly into a water body. An example of a point source of water pollution is a pipe from an industrial facility discharging effluent (liquid waste) directly into a river, lake or sea.

 A non-point source of water pollution is a source that delivers pollutants into the water body indirectly through transport or environmental change. An example of a non-point source of water pollution is when fertilizer from a farm field is carried into a stream by rain (surface run off).

 Causes of water pollutionThe following are some of the major causes of water pollution:

1. Pesticides Pesticides that are applied to crops and animals drip onto the soil and may eventually run off into the local streams and rivers. They can also seep down to reach ground water. This contaminates the water and makes it unwholesome for human use and can drastically affect the aquatic and other organisms whose lives depend on that water. 
2. Fertilizer (nutrient pollution) Many pollutants, including sewage, manure and chemical fertilizers, contain nutrients such as nitrates and phosphates. Nitrates are very soluble. Rain washes or leaches them out of the soil into rivers. In the rivers, excess levels of nutrients (the nitrates) stimulate the growth of aquatic plants and algae. These form a layer on the water surface. A layer of these algae and aquatic plants on the surface of water will prevent light and oxygen from reaching the organisms under the water. As a result, these organisms will begin to die. When the aquatic organisms and the algae die, bacteria feed on the remains. In the process, they use up the oxygen dissolved in the water. Thus, the amount of oxygen in water drops. As a result, fish and other river life die from oxygen starvation, and the river becomes chocked and lifeless. This is called eutrophication. Water with limited dissolved oxygen supports only a few aquatic organisms. Such areas are called dead zones. 
3. Oil spills Oil spills in oceans and seas cause water pollution and big problems for local wildlife, fishermen and aquatic organisms. Oil spilled onto land is also carried into water bodies by surface run off. This includes drips of oil, fuel and fluid from motor vehicles, oil spilled onto the ground at filling stations; and drips of oil from industrial machinery. These sources and many more combine together to form continual petroleum pollution to all of the world‟s waters. Oil spilled by ships, discharge of oily wastes, and drips from motor boats are all significant sources of marine pollution. Drilling and extraction operations for oil and gas can also contaminate coastal waters and ground water.
4.  Mining Mining causes pollution in a number of ways. They include the following: The mining process exposes heavy metals and sulphur compounds that were previously locked deep in the earth. Rain water leaches these compounds out of the exposed earth, resulting in “acid mine drainage” and heavy metal pollution that can continue long after the mining operations have practically ceased. The action of rain water on piles of mining waste (tailings) transfers pollution to freshwater supplies. In gold mining, cyanide is intentionally poured on piles of mined rock (a leach heap) to chemically extract the gold from the ore. Some of the cyanide ultimately finds its way into nearby water. Huge pools of mining waste slurry (semi-liquid mixture) are often stored behind containment dams. If a dam leaks or bursts, water pollution is likely to take place. Mining companies in developing countries sometimes dump mining waste directly into rivers or other water bodies as a method of disposal. Sediment The act of clearing the forests to get ample land for agriculture, settlement or wood leaves the land bare and exposed to the agents of denudation. This accelerates soil erosion and the sediment is free to run into nearby streams, rivers and lakes. The increased amount of sediment running off the land into nearby water bodies seriously affects the fish and other aquatic life. 
5. Poor farming practices and cultivation along and close to the rivers, exposes the soil to erosion agents. Soil erosion causes water pollution.
6.  Industrial processes Most of the water that is used in the production process in industries is eventually discharged into water bodies. This waste water may contain harmful chemicals such as acids, alkalis, salts, toxic chemicals, oil, heavy metals and even harmful bacteria, and other reagents. These substances affect the quality of water and the lives of aquatic organisms. In some cases, the waste water discharged into a water body may be hot enough to kill any organism living in that water. 
7. Sewage In developing countries about 90% of untreated sewage is discharged directly into rivers and streams. This renders the water unwholesome for domestic and other uses. Untreated sewage harbours a myriad of disease-causing organisms. This is the reason why diseases such as cholera, dysentery, typhoid and bilharzias are very common among African countries. Leaking septic tanks and other sources of sewage can contaminate ground and stream waters as well.
8.  Marine debris (marine litter) Marine debris is trash in the ocean. This is litter that ends up in ocean, seas or other large water bodies. The debris mainly comes from urban sewers and garbage thrown overboard from ships and boats. Examples of marine debris include plastic bags, water bottles, balloons, shoes, lags etc. It can also include items that wash in from the ocean, such as fishing line, ropes, nets and traps, and items from ship such as lost cargo from container ships. 

 Air pollution
Air pollution contributes substantially to water pollution. Pollutants like mercury, sulphur dioxide, nitrogen oxides, and ammonia can get into the water bodies from the air.
This can cause problems like mercury contamination in fish, acidification of lakes and eutrophication (nutrient pollution).
Most of the air pollution that affects water comes from coal-fired power plants, vehicle exhaust fumes, and industrial emissions.


 According to a long-term study by the United Nations Environment Programme (UNEP), it has been observed that the earth‟s oceans have absorbed enough carbon dioxide from the air to cause a slight increase in ocean acidification. Most of the carbon dioxide gas that acidifies the ocean results from human activities (man-made carbon dioxide).
It is feared that further carbon dioxide uptake will increase acidification even more and cause the carbonate structure of corals, algae and marine plankton to dissolve. This could have negative impacts on the biological systems of the oceans

 Heat
 Heat is a water pollutant. Increase in water temperature results in deaths of many aquatic organisms. This is because, as water temperature increases, the amount of oxygen that can dissolve in it also decreases. Therefore, warm and shallow water will contain very little oxygen to an extent that the dissolved gas will not sustain aquatic life. These increase in temperature is most often caused by discharge of cooling water (which is always hot) by factories and power plants. Global warming also contributes significantly to heating of the oceans.

Noise
 Many marine organisms, including mammals, sea turtles and fish, use sound to communicate, navigate and hunt. Noise from ship engines and sonars has a negative effect on these organisms.

Following noise pollution, some species may find it hard to hunt or detect predators. Others may not be able to navigate properly.

The Hazards which are Caused by Water Pollution
 The following are some of the effects of water pollution:

1.  Waterborne diseases Human infectious diseases are among the most serious effects of water pollution. Waterborne diseases occur when parasites or other disease-causing microorganisms are transmitted via contaminated water. Water may be contaminated by pathogens originating from excreta. Waterborne diseases include typhoid, diarrhoea, dysentery, cholera, bilharzia and many other diseases caused by bacteria, protozoa and viruses. Contaminated water also spread intestinal parasites such as hook worm, round worm, and ascaris. Polluted beach water can cause skin rashes, ear aches, pink eye, respiratory infection, hepatitis, diarrhoea, vomiting and stomach ache. 
2. Nutrient pollution Nutrient pollution stimulates the overgrowths of algae and other aquatic plants. Algae can have direct toxic effects and finally result in oxygen deficiency in water. Certain species of algae are toxic. Overgrowths of these algae result in harmful algal blooms. These are more colloquiallyreferred to as red tides or brown tides. Zooplankton eat the toxic algae. When fish eat the zooplankton, the toxins are passed to fish. Ultimately, when fish is eaten by seabirds, marine mammals and man, the toxins pass to these organisms. In this way, the toxins pass to the food chain and become part of it. Blooms of algae and seaweed also reduce water clarity. This makes it hard for marine animals to find food. Algal bloom also blocks the sunlight needed by sea plants, which serve as nurseries for many important fish species. When the algal overgrowths finally die, bacteria do feed on the remains. In the process, bacteria use up the oxygen dissolved in the water. In some cases, the process takes enough oxygen from the water such that oxygen level in the water falls too low to support normal aquatic life. As a result, fish and other aquatic organisms die from suffocation. The region becomes a coastal dead zone. Some algae are poisonous to fish and humans. People swimming through these algae or swallowing the water may get rashes, eye irritation, muscle pains, vomiting and diarrhoea. Excess nitrate in the river may get into drinking water. It increases the risk of blue-baby syndrome. What happens is that bacteria in a feeding bottle or a baby‟s body convert the nitrate to nitrite. This gets taken up instead oxygen, by the haemoglobin in blood. The baby turns blue and can die. Nutrient pollution can also trigger unusual outbreaks of fish diseases. 
3. Chemical contamination Every year many types of chemicals are draining into water. Severe chemical spills and leaks into water bodies kill fish and other aquatic life. Chemical pollution is caused by a number of toxic chemicals. The following are some categories of water pollution effects due to chemical contamination: Every year many types of chemicals are draining into water. Severe chemical spills and leaks into water bodies kill fish andother aquatic life. Chemical pollution is caused by a number of toxic chemicals. 

• The following are some categories of water pollution effects due to chemical contamination: 
• Pesticides Pesticides are carried in rain water run off from sources such as farm fields, suburban lawns and home gardens into the nearest rivers and streams. Pesticides contained in drinking water and in the food chain can result in damage to the nervous system, reproductive and endocrine systems and the liver. It can also damage the DNA and cause various cancers. 
• Oil spills Exposure to oil or its constituent chemicals can alter the ecology of aquatic habitats and the physiology of marine organisms. The oil (or chemical component of the oil) can seep into marsh and sub-tidal sediments and remain there for many years. This negatively affects marsh grasses, marine worms, and other aquatic life forms that live in, on or near the sediment. Compounds of crude oil, called the polycyclic aromatic hydrocarbons (PAHs), can remain in the marine environment for many years and are toxic to marine life at even low concentrations. Prolonged exposure to PAHs can affect development of marine organisms, increase susceptibility to disease, and distort normal reproductive cycles in many marine species. 
• Mercury gets into water from coal-fired power plants, gold mining and some other industrial processes. In the water, the elemental mercury is converted to methylmercury, [CH3Hg]+, by certain bacteria. Then this new form of mercury moves up the food chain of fish when small fishes are eaten by a big fish. In the end, the big fish may be eaten by man and the mercury is passed on to him. The effects of mercury on humans are many and are already pretty well understood: Young children and unborn babies are at a higher risk because their body systems are still developing. Exposure to mercury in unborn babies can cause neurological problems such as slower reflexes, learning deficit, delayed or incomplete mental development, autism, and brain damage. Mercury can also cause serious nervous system problems in adults. These problems include Parkinson‟s disease, multiple sclerosis, and Alzheimer‟s disease. It can also cause heart disease and damage to the brain. 
• Industrial chemicals Chemicals used in industrial processes are being discharged into water bodies daily. Many chemicals can have direct toxic effects on aquatic life. Industrial spills into rivers kill fish for many kilometres downstream. A new threat from chemicals is the hormone-disturbing character of many chemicals. The effects of hormone-disturbing chemicals include interrupted sexual development, thyroid system disorders, inability to breed, reduced immune response, and abnormal and parenting behaviour. In humans, endocrine disruptors lead to low immune function, mental impairment, decreased fertility and increase in some types of cancers. 
• Mining There is a good number of negative water-pollution effects from mining operations. 

They include the following:


 √Acid Mine Drainage (AMD):
 This refers to the out flow of acid water from metal mines or coal mines. This is how it is formed: Mining process exposes rocks and soil. When rain or surface water flows over exposed rock and soil, it combines with naturally-occurring sulphur to form sulphuric acid. The acidified water eventually finds its way to streams and ground water. This pollutes the water and affects the local aquatic life. Some streams are so acidic that they destroy the aquatic ecosystem completely.


√ Spills and leaks: Leaks in containment system, cyanide leach heap or breakage in coal-slurry impoundment dam result in pollution of streams, rivers and ground water. This kills fish and poisons drinking water.

√Mountaintop Removal Mining (MTR): In this technique, the tops of coal-rich mountains are removed and the resulting rocks are dumped into nearby valleys. The rocks bury stream habitats altogether. This has catastrophic effect on whatever life forms that live in or around the stream.

√ Marine debris Marine debris, also known as marine litter refers to trash in the ocean. Though trash fouls inland waterways too, it seems to be a particular problem in seas and oceans. The effects of marine debris are many. Marine animals can swallow the trash items mistaking them with food. For example, sea turtles will eat a plastic bag believing it to be a jelly fish. The bag cause intestinal blockage and sometimes death. In some cases, trash can get attached to food and consequently get ingested together with the food. This may harm or even kill the animal that ingests it. Discarded or lost fishing gear (line, rope, nets) and certain trash items can get wrapped around marine animals‟ fins or flippers and cause them to drawn or injure their fins. Marine debris can also degrade coral reefs, sea grass beds, and other aquatic habitats. This can interfere with the normal sea life.


Thermal pollution
 Discharging the hot water from a power plant into a river could affect aquatic organisms greatly. In fact, industrial thermal pollution is a problem to water bodies.

 Aquatic organisms are adapted to a particular temperature range. Even a small increase in temperature can kill the organisms from thermal shock. Also the extra heat may disrupt spawning or kill young fish.

A high temperature warms the water and lowers the amount of oxygen that can dissolve in that water. Insufficient dissolved oxygen forces the aquatic organisms to increase their respiration rates. This increases the aquatic organisms‟ susceptibility to disease, parasites and the effects of toxic chemicals. Global warming also causes extra heat to the oceans, leading to similar effects explained above.

Noise pollution
 Noise pollution from various ship engines and sonar systems make it difficult for marine organisms like whales, dolphins, and porpoises to communicate, mate, find food and avoid hazards. Excessive noise pollution may cause damage to marine animals‟ sound-sensitive organs. This can result to internal bleeding and even death.


 Ways of Preventing Water Pollution 
 We have been seen that water pollution poses a great threat to aquatic organisms, humans and the environment. Therefore, something must be done to prevent and control this from happening.

The following are some of the methods that can be employed to prevent and control aquatic pollution:

1. Reducing nutrient and pesticide pollution This can be done by adopting good agricultural practices. These include practicing organic farming (farming which does not involve use of artificial chemicals), 
2. controlling soil erosion, and reducing or controlling the use of fertilizers and pesticides in agricultural production. 
3. Treating sewage and industrial wastes Sewage and industrial waste must be treated in order to kill harmful microorganisms and detoxify poisonous chemicals before being discharged into water bodies. This will reduce the hazards that the chemicals and microbes contained in wastes can cause to the environment in general. Sewage treatment plants should be upgraded so that they can filter out chemicals and toxins. Heated up water from industries should be cooled down and detoxified before being release into water bodies or effluent pools.
4.  Stopping deforestation Forests act as a soil cover which prevents soil erosion. They also help to absorb carbon dioxide from the air, the excess of which causes acid rains. Cutting down trees indescrimately exposes the soil to erosion agents. Soil erosion produces sediments which pollute water. So the presence of trees prevents water pollution through cutting off deposition of sediments into water and preventing the formation of acid rain.
5.  Controlling coastal development Infrastructures such as buildings and industries destroy the natural shorelines which serve many purposes like fish nurseries, absorption of hurricane impacts, and filtration of the river water entering the estuary. Furthermore, most of the waste from these establishments is directed into the nearby water body. So prevention of coastal establishment will prevent this kind of water pollution from taking place.
6.  The government should make and enforce laws that prohibit the establishment of settlements and industries near water bodies. This will help control water pollution and its impacts to the environment. 
7. Reducing pollution from oil spills Listed below are some of the ways that can be used to control the occurrence and repercussions of oil spills: Enforcing the regulations and rules that govern maintenance and inspection of commercial ships and other marine vessels that leak oil and fuel into the water. Cleaning oil spills as promptly as they occur. Converting oil tankers into double-hull ships. A double-hull ship has two complete layers of watertight hull surface. The178outer layer forms the normal hull of the ship. A second inner hull forms a protective barrier to sea water in case the outer hull is damaged and leaks. Educating the public how to keep oil out of the environment. 
8. Controlling production of greenhouse gases Greenhouse gases, particularly carbon dioxide and sulphur dioxide, contribute to water pollution through acid rain (acidification) and an increase in ocean temperature (thermal pollution). This can be reduced by a number of ways which include forestation, reducing emission of green house gases from industries and motor vehicles, and employing good agricultural practices. 
9. Reducing mercury emissions The use of mercury in many industrial processes is being phased out. However, some industries continue to use mercury on a large scale. Such industries should apply the appropriate technology to prevent mercury from being released into the environment. Where other alternatives exist, the use of mercury should be stopped completely. Cleaning up existing and abandoned mines 

The following are some of the ways through which water pollution by mines can be controlled:

• Mining companies should clean up abandoned mines which continue to release pollutants to the environment. 
• New mines should not be established in areas where they are likely to cause water pollution problems. 
• Mining practices which cause water pollution should be banned. 
• Cleaning up chemical pollution Chemical pollution on land should be stopped. This is because chemicals on land dissolve in surface run off and finally find their way into water bodies. So preventing chemical pollution on land will automatically help keep our water clean.

Aerial pollution
Is the introduction of harmful substances on the earth's atmosphere


Human Activities which Cause Aerial Pollution
Air pollution can result from both human and natural actions.

 Natural events that pollute the air include forest fires,

• volcanic eruptions,
• wind erosion, 
• pollen dispersal, 
•  evaporation of organic compounds,
•  hot springs,
• fumaroles. 

However, pollution from natural occurrences does not occur very often.

Human activities that cause air pollution include

•  gaseous emissions from industries, 
• burning of fossil fuel (e.g. gas, coal), 
• household 
• Agriculturalchemicals, 
• deforestation

 The following are the chief causes of air pollution:

1. Carbon dioxide
 Carbon dioxide (CO2) is one of the main air pollutants. The major man-made sources of carbon dioxide are burning of fossil fuels and deforestation.
   The act of deforestation removes trees that absorb carbon dioxide and help to reduce the level of carbon dioxide gas in the atmosphere.

  Thenatural sources of carbon dioxide include respiration, decay, volcanic eruptions and diffusion out of the oceans.

2. Carbon monoxide
 Carbon monoxide (CO) is formed when fossil fuels burn in too little air (oxygen).
  However, when the fuels are burnt in a plentiful supply of oxygen, carbon dioxide (CO2) is produced.


Other sources of carbon monoxide include

• metal processing and chemical 
• manufacturing activities,
•  forest fires, 
• wood burning for heat or cooking
•  combustion of natural gas. 

3. Ground level ozone (smog) 
This is a product of burning fossil fuels. Smog is formed when oxides of nitrogen (NOx) react with volatile organic compounds (VOCs) in the presence of sunlight.

     It is formed in heavy traffic in hot weather, when sunlight causes the nitrogen oxides and hydrocarbons from car exhausts to react together.

Sunlight and hot weather are catalysts in the NOx/VOCs reactions that cause ground-level ozone (smog) to form. Areas with the highest concentration of motor vehicles and industrial emissions tend to have the worst ground-level ozone problems.

4. Nitrogen oxides
 Nitrogen oxides, nicknamed NOx, are highly reactive gases that contain nitrogen and oxygen in varying molecular combinations. The oxides of nitrogen include nitrogen monoxide (NO), nitrogen dioxide (NO2) and dinitrogen oxide (N2O).

Nitrogen oxides form when fuel is burned at high temperatures, such as in automobile engines, coal-fired power plant, or any process that burns fuel. Inside car engines and power station furnaces, the air gets so hot that nitrogen and oxygen react together to form oxides of nitrogen.

 Nitrogen monoxide (NO) is also formed in the atmosphere by lightning where nitrogen and oxygen combine together to form the oxide: NOx and the pollutants formed from it can be transported by windover long distances.

Thus, these types of pollution are notconfined to areas where they are produced, and controlling them isbest done using regional and national plans.

5.Sulphur compounds
Compounds of sulphur that pollute the air include sulphur dioxide(SO2), sulphur trioxide (SO3) and hydrogen sulphide (H2S).Sulphur dioxide is the most important air pollutant among thecompounds of sulphur. Coal, oil and gas all contain sulphur and sulphur compounds asimpurities. When these sulphur-containing fuels are burned sulphur dioxide gas is formed. The gas is also formed duringpetroleum refinery.

6.Particulate matter (PM)
Particulate matter comprises of extremely small solid particles andliquid droplets. These are mainly particles of carbon (soot) fromburning coal in power stations and petrol in motor engines. Theother particles include smoke, nitrates, sulphates, dust particles,and organic chemicals. Exhaust fumes from leaded petrol alsocontain particles of lead. Lead Lead can pollute the air.


 7. Lead
in air comes mainly from industrialactivities like lead smelting, metal processing, lead-acid batterymanufacturing, waste incineration and power generation. Lead isalso produced from combustion of airplane fuel. Leaded petrol isstill used in some developing countries. Wind-blown soil and roaddust can also contain naturally-occurring lead as well as lead fromother sources.

8. Chlorofluorocarbons (CFCs) Chlorofluorocarbons are organic comp ounds made up of carbon, chlorine and fluorine atoms. CFCs are widely used as refrigerants in refrigerators and air condition systems, solvents in cleaners, blowing agents in the production of foam propellants in aerosol cans, and as fire extinguisher chemicals.

 Hazards Caused by Aerial Pollution 
The following are some effects of air pollution.

1.Health problems
 Exposure to air pollutants can cause serious health problems. The level of effects usually depends on the length of time of exposure as well as the kind and concentration of the pollutants.

Short term air pollution can aggravate or complicate medical conditions of individuals with asthma, emphysema, bronchitis, lung and heart diseases, and respiratory allergies.

Long-term health effects can include chronic respiratory diseases, lung cancer, heart diseases, and even damage to the brain, nerves, liver or kidneys. Inhaling or ingesting lead can damage the brain and peripheral nerves resulting to retardation, behaviour disorders and memory loss. It can also cause high blood pressure, heart diseases, anaemia and reproductive disorders.

Carbon monoxide is poisonous even in small concentrations. It combines with haemoglobin in the blood and stops it from transporting oxygen to the body cells. This can cause harmful health effects by reducing oxygen delivery to the body tissues and vital organs (most notably the heart and the brain).

Inhaling high levels of carbon monoxide can cause vision problems, physical or mental impairment, and even death.

Global warming
Global warming is the increase in the average temperature of the earth‟s atmosphere as a result of the greenhouse effect.

Greenhouse gases in the atmosphere allow ultraviolet radiations to pass through them and reach the earth. As the earth‟s surface gets heated up, some of the heat is radiated back to the atmosphere.

A layer of the greenhouse gases in the atmosphere, acting as a blanket, prevents the heat from escaping to the upper atmosphere. This causes excess heat in the air around the earth (atmosphere), a phenomenon called global warming.

Cause of global warming 
Global warming is mainly caused by human activities such as

•  fossil fuel burning and deforestation, which produce green house gases such as carbon dioxide and some oxides of nitrogen (NOx). 
• Carbon dioxide is one of the greenhouse gases that contribute to global warning. Indeed, carbon dioxide is responsible for over 50% of the global warming. 
• One member of the NOx family, nitrogen oxide (N2O), is also a potent greenhouse gas. The gas contributes to the greenhouse effect. 

Effect caused by global warming

• Global warming may result in melting of the polar ice caps, causing an increase in levels of the ocean water. This may lead to flooding of the coastlands and islands. 
• increase in the average temperature of the earth, 
• change in weather patterns, 
• increased desertification, which would in turn cause reduction of the arable land. 

Depletion of the ozone layer
The production and emission of chlorofluorocarbons (CFCs), is the leading cause of ozone layer depletion. CFCs accounts for almost 80% of the total depletion of ozone.

Ozone is a triatomic form of oxygen (O3), found in the earth's atmosphere.

When the CFCs reach the stratosphere (a layer of the atmosphere with high concentrations of ozone), they are broken down by the intense sun rays to release chlorine radicals (•Cl).

These radicals then react with the ozone molecules splitting them into oxygen atoms and free oxygen molecules. This is how the ozone layer is getting depleted.

 Acid rain 
Human activities produce harmful gases such as oxides of nitrogen and sulphur which are released into the atmosphere.

These gases are responsible for the formation of acid rain. Sulphur dioxide gas in air dissolves in rain water to form acid rain and other sulphur compounds.

Acid rain is formed when the sulphur dioxide dissolves in water vapour from the clouds and combines with oxygen from the atmosphere to form an acid rain.

SO2(g) + H2O(l) + ½O2(g) > H2SO4(aq)

Sulphur dioxide attacks the lungs, and can affect people with asthma and heart diseases very badly.

 Nitrogen monoxide and nitrogen dioxide also play a great part in the formation of acid rain and photochemical smog.

Acid rain is formed by the reaction of NOx, oxygen of the air and water vapour.

4NO2(g) + 2H2O(l) + O2(g)→4HNO3(aq)


These acidic solutions then fall on the ground in the form of acid rain.

Acid rain damages plants and corrodes many ancient buildings, monuments and sculptures made of marble. It greatly affects the aquatic life due to the acidification of lakes and streams. Eutrophication Even though most of the nutrient pollution comes from fertilizers and animals wastes that run off from farm fields, deposition of nitrogen from fossil fuel air pollution adds significantly to the problem.

Eutrophication
causes algal bloom which prevents the penetration of air and light into a water body. This deprives aquatic life of oxygen and light.
When algae die, bacteria act on them. The bacteria use dissolved oxygen in the water, depleting the gas from the water. The depletion of oxygen in the water (hypoxia) causes a reduction and even death of certain fish and other aquatic organisms.

 Effect on wildlife
Just like humans, animals also face some devastating effects of air pollution. Toxic chemicals present in air can force wildlife species to move to new places and change their habitat. The toxic pollutants deposited in the water can also affect sea animals. Reduced visibility (haze) Smog reduces visibility, making activities such as driving, surveying and flying difficult.

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