CHAPTER – 13
Pollution
Pollution is the
damaging and undesirable change in the physical or biological features of
environment (air, land or water), than can adversely affect all aspects of
human life or other desirable species. In other words, pollution is the
unfavourable alteration of the environment due to damaging addition of any
materials or energy in it.
Pollution is the most cCHA Pritical ecological crisis for today’s world. There
is pollution of air, water, land by different material pollutants. Addition of
damaging amounts of energy to the environment is called non-material pollutions
such as radiations pollution and noise pollution.
Air Pollution
When concentration
of harmful substances gases or particulate matter increases in the air beyond
their normal amounts the air is said to be polluted. Air pollution is the most
common type of pollution, particularly in industrial urban areas. Air pollution
is basically caused by burning of fossil fuels such as coal, petrol and natural
gas. Some air pollution is also produced by industrial and agricultural
activity etc. Particular pollutants include carbon particles, lead, asbestos
particles, mineral dust, pollen grains, resins etc. The common gaseous
pollutants are Carbon monoxide, CO₂, SO₂ oxides of nitrogen, chlorine etc. Air pollution has both
pathological as well as effect on climate.
1. Pathalogical Effects of Air Pollution
Air pollution is the cause of many respiratory diseases
like bronchits, cough, asthma, sorc throats, eye irritation, lung cancer and
many nervous disorders. Carbonmonoxide (CO), is a poisonous gas and reduces the
oxygen carrying capacity of the blood. In low quantities it causes nausea, head
aches and sluggishness. Large levels of CO in blood may result in death. SO₂ irritates lining of respiratory
tract, causing cough, bronchitis, asthma, lung cancer etc. Lead is added to air
from automobile exhausts and is absorbed by the blood. It causes lead
poisoning, which produces anaemia, stomach pains, kidney failure. It may also
damage the nervous system and cause many nervous disorders. Asbestos particles
are the main cause of lung cancer in the workers.
2. Environmental Effects of Air Pollution on Climate
Air pollution considerably affects the local as well as
global weather and climate. Following are some of the major effects of air
pollution on the environment
i. Photochemical Smog
In simple terms, smog is the mixture of air and smoke.
Burning of fossil fuels at high temperature by vehicles and industry, releases
nitrogen oxides (NO₂). With the energy supplied by the sunligh, the NO₂ combines with hydrocarbons (methane,
ethane etc) to form secondary pollutants called photochemical oxidants.
Presence of those pollutants scatter the light and a hazy milky smog is formed.
Which is called the photochemical smog. It is very harmful for human health
causes irritation of respiratory tract and lungs, head aches and breathing
difficulties, which may even prove fatal.
ii. Acid Rains
Burning of fossil fuel by transport vehicles and
industries produce pollutants such as SO₂, NO₂, CO₂. In this atmosphere these gases mix with the moisture of the
air and gradually from dilute acids, which fall to the ground with rain. Such
rains are called acid rains. Acid rains cause many respiratory diseases in
humans. Acid rains also increase the acidity of the soil and water thus
damaging crops and aquatic life. Corrosive action of H₂SO4 damages the buildings, statues
and structures of historical and cultural importance.
iii. Green House Efect (Global
Warming)
CO₂ plays an important role in regulating the earth’s surface
temperature. Layer of CO₂ in upper atmosphere allows the sun rays to pass through
atmosphere and reach the earth as short wave electromagnetic radiation.
However, it partially prevents the long wave infra red heat radiation from
escaping to outer space. Thus the globe is kept warm. Due to excessive burning
of fossil fuels, the amount of CO₂ in atmosphere has become abnormally high. It holds back the
increasing quantities of the heat waves and therefore the atmosphere gets over
heated. This phenomenon is called green house effect. The possible effects of
global warming are
§ Melting of the polar ice which in turn would raise the sea level
flooding vast coastal areas.
§ Early melting of shows in the mountains would flood large areas
of farmland.
§ Warming of atmosphere can cause heavy rains and strong
hurricanes and storms.
iv. Depletion of Ozone Layer
There is a protective layer of Ozone in the upper layers
of the atmosphere. It acts as a shield and reduces the penetration of harmful
ultraviolet rays of the sun. This ozone layer can be broken by release of
chlorine atoms at high altitude. The main source of chlorine atoms is a group
of industrially produced compounds called Chlorofluorocarbon (CFC). These
chemicals are used as refrigerator and also in pressurised acrosol cans CFCs
get accomodated in greater amounts at high altitudes (stratosphere). Under
normal conditions these compounds are inert, but at high altitudes they release
chlorine atoms due to action of intense short wave ultraviolet radiation from
the sun. Chlorine atoms then react with Ozone molecules and convert them to
oxygen. (Each atom of chlorine reacts with about 1,00,000 molecules of ozone).
Reduction in Ozone layer allows greater ultraviolet radiation to reach the
earth. It is thought that this intensified radiation can cause significant
increase in skin cancer and other adverse effects associated with ultraviolet
radiaiton.
Water Pollution
Any contamination
of fresh water or marine is called water pollution. Major sources of water
pollution are
1. Domestic Waste
or Sewerage
2. Industrial Waste
3. Agricultural Waste
1. Pollution of Water by Sewerage
Sewerage may include faccal matter, dissolved organic
matter such as carbohydrates, urea etc, inorganic substances like nitrates,
phosphates, detergents , insecticides etc. Both surface and soil water can be
polluted by the sewage. Most of the components of sewage are biodegradable and
are decomposed by natural processes, but when their intake exceeds the
decomposing capacity of the environment, water becomes polluted. Some of the
ill effects of sewage pollution are
§ It is responsible for water borne diseases like Typhoid, Amoebic
dysentary, hepatitis, cholera etc. Harmful chemicals present in sewage also
damage the tissues of the body can cause several diseases.
§ Organic pollutants in sewage provide favourable medium for
bacterial growth, which consume the oxygen of water. As a result fishes and
other useful animals are killed for lack of oxygen.
§ Anaerobic conditions also produce bad smelling compounds such as
H₂S₂ which make the water unfit for human consumption.
2. Pollution of Water by Industrial Waste
Most of the streams and lakes are polluted by industrial
wastes which include metals like lead, copper, mercury acids, alkalis,
cyanides, arsenic, chlorine and many other toxic materials. These pollutants
cause death to aquatic life and are also harmful for humans when they drink
polluted water. These toxic substances cause various diseases of kidney, liver
and nervous system. Some of which may prove fatal.
3. Pollution of Water by Agricultural Waste
Fertilisers, insecticides and pesticides and poultry feed
contain many harmful components such as chlorine, nitrates etc, which
contaminate soil and surface water. In rivers and streams they kill the aquatic
life. Chlorine reduces the reproductive rate of aquatic animals. High nitrite
concentration in drinking water converts haemoglobin in the blood to
methemoglobin, which reduces blood’s oxygen carrying capacity.
Pollution by Oil
Oil is the main
pollutant of marine water. Leakage from oil tankers and off shore oil wells
kills many marine animals and plants.
Entrophication Or Algal Bloom
Natural lakes are
divided into two types on the basis of production of organic matter. Entrophic
lakes are shallow and contain high amount of nutrients. As a result
phytoplankton growth is very high. This leads to increased number of
heterotrophs which consume oxygen for respiration. Therefore, oxygen content of
such lakes is reduced. The olgatrophic lakes are deeper and contain fewer
amounts of nutrients. Therefore phytoplankton growth is poor and lesser number
of heterotrophs are present and the oxygen content is high. Addition of
agriculture waste, sewage, factory waste, increases the inorganic nutrients of
the lakes. This over-enrichment is called entrophication. It causes algal bloom
or explosive growth of small photosynthetic organisms such as algae. As the
algae die, the activity of decomposers increase and they consume more and more
oxygen. Deficiency of oxygen results in massive death of useful organisms such
as fishes.
Land Pollution
The land can be
polluted by deposition of solid waste and by harmful chemicals and hazardous
waste.
1. Deposition of Solid Waste
Increase in population and rapid urbanisation has resulted
in creation of enormous amounts of solid waste. It includes house hold garbage,
hospital waste usually contaminated with various germs, agricultural, animal
and industrial waste, dead animals and plants and host of other substances. If
this refuse is dumped in open places without any pre-treatment, it pollutes the
land. Wastes from hospitals carry germs of many dangerous diseases and the
organic matter in the refuse provide favourable conditions for their growth and
multiplication. These dumping sites also provide favourable breeding grounds
for flies, rats and other vectors for pathogenic organisms. All these factors
together pose a grave threat to the health of the population. Huge amounts of
solid waste pose economic problems also because their proper disposal is very
costly.
Harmful Chemicals
and Hazardous Wastes
The land is also
polluted by many harmful chemicals such as fertilisers, pesticides,
insecticides which contain poisonous components. Most of the these pollutants
are bio-nondegradable and stay in the soil for long periods. Solid wastes which
cause human illness and death are called hazardous wastes. They include
substances like mercury, cadmium, lead, nuclear wastes. They can ultimately end
up in human body through food, water and radiation and cause dangerous
disorders including cancer. These substance also interfere with biochemical
cycles, thus decreasing the fertility of the soil.
Non-Material Pollution
Non-material
pollution is the addition of damaging amount of energy to the environment. It
includes radiation pollution, noise pollution, thermal pollution.
1. Radiation Pollution
Radiation, in the sense of pollution, comes from
radio-active isotopes of such substances as Uranium, Radium, Thorium, Plutonium
etc., which are used in nuclear reactors, atomic explosions, x-ray plants and
other such devices. These radiation can penetrate tissues and organs of man and
accumulate there. They may cause diseases like Leukaemia, bone tumour, cancer
of many organs. Radiations also increases the mutation rate in the germ cells,
which can produce genetic abnormalities in future generations.
2. Noise Pollution
Noise is the unwanted sound which the recipient does not
like and which can adversely affect a person mentally, physically or
aesthetically. Noises above 80 decibels are considered loud, uncomfortable and
is harmful for human health. Noise is produced by motor vehicles, aeroplanes,
machines, radio, TV, loud speakers. Loud noise is the serious threat to man’s
physical and mental health. It affects mental peace, distracts the
concentration and thus affects the quality and work output. Calm and quiet
environment is a must for any creative and scholarly work. Loud noise is
responsible for many disorders of cardrovascular and nervous system. People
having continuously in environment of loud sound show symptoms of nervous
stress, such as irritation, high blood pressure, headaches, sleeplessness,
fatigue and depression. Persistent noise damages the internal car and may lead
to impairment of hearing or even permanent deafness.
Energy
Like other natural
resources, the energy resources can also be classified into renewable resources
and non-renewable resources. The renewable energy sources are those which are
almost inexhaustible. These include solar energy, energy of falling water
(hydro energy), wind energy, wave and tidal energy, plant materials etc.
Non-renewable energy sources are those which are found in fixed quantity and
cannot be replaced and are therefore exhaustible. For example fossil fuels like
petroleum, natural gas, caol, nuclear fuels like uranium etc are non-renewable
energy resources.
1. Fossil Fuels
Coal, petroleum and natural gas are collectively called
the fossil fuels. These fuels are derived mostly from plant material that got
buried and fossilized in deeper layers of earth hundreds of million of years
ago. Thus their energy remained separated from energy of the biosphere for a
very long period.
Coal is derived from oxidized carbon of plant tissues. The supplies of coal are
about 10 times the combined supply of petroleum and natural gas. Petroleum and
natural gas are materials of organic origin derived from partial decomposition
of plant tissues, particularly the marine plants.
Fossil fuels supply about 95% of energy requirement of the world. Major gas and
oil fields in Pakistan are located in Sui region of Balochistan, Potohar region
of Punjab and Badin in Sindh.
2. Nuclear Energy
Splitting of atoms of radio-active elements (heavy
elements) is called fission. It releases tremendous amount of energy from a
very small mass. In an atomic reactors, the fission is controlled and the
energy is produced gradually. Here 1 kg of fuel is fissioned in 7 hours and
releases $30,00,000 kilowatts energy. In order to get the same amount of energy
3 million kg of coal would be required.
Use of nuclear fuel poses environmental hazards and health problems. Large
amount of radio active waste is produced. If released on land or in water it
continuous to emit radio-active material which can cause dreadful diseases like
cancer and mutations of genes. Safe disposal of radio-active waste is very
costly. Accidental leakage from nuclear power plants can cause tremendous loss
of human life.
3. Hydro-Electric Power
The falling water has a great amount of energy which can
be used to generate electricity called hydro-electric power. It can be produced
economically in mountainous regions, where river and stream make natural falls.
To ensure constant flow of water, storage sites such as lakes and dams are
built. This ensures generation of the power through out the year. Many
countries of the world has potential sites for building Hydro-electric power
houses. (The world capacity of generating hydroelectric power is estimated to
be around 2900 million kilowatts, but only 250 million kilowatts has been
developed)
Hydro electric power is cheap, clean, pollution free and renewable source of
energy, but dams built at the site for storage of water destroy natural
ecosystem and have limited life to silting.
In Pakistan there are large hydro-electric power plants at Tarbela, Mangla,
Warsak, Dargai. At present maximum power generation from all the major
hydro-electric power units is 4300 Megawatts.
4. Solar Energy
The energy of sun will last for billions of years and thus
can be regarded as inexhaustible. Earth receives a maximum of 1400 watts per
square meter when the sun is at the top. Solar energy can be used in two ways.
One way is to directly capture the sunlight and use it for heating the water,
buildings etc. The second method is to use solar energy to generate
electricity. This method is costly and is not economical for large scale use. Another
disadvantage of solar energy is its non availability during night and cloudy
weather because no reliable method of storing the solar energy is available
presently.
5. Geothermal Energy
Heat produced deep beneath the surface of earth due to
natural decay of radio-active material, is known as the geothermal energy. This
energy comes to the surface as heat in the form volcanic activity, hot water
springs, steam and geysers. At present the use of geothermal energy is very
limited due to high cost involved in its exploration. Only about 0.1% of
world’s requirement is met by geothermal energy.
6. Solid wastes
Solid wastes includes all the domestic and municipal
trash, paper and its products, animals dung, agricultural and industrial waste,
plastic materials, wood material and host of such items. Millions of tons of
solid waste is generated every year and can be converted into energy. Certain
type of solid waste, such as animals dung and plant litter can be converted
into hot gases known as biogas which can be used as a fuel.
7. Ocean Thermal Gradient
The difference of temperature between the surface water
and deeper water of a ocean is called the ocean thermal gradient. This gradient
is very large in tropics, where surface temperature is about 25⁰C and at few hundred meter depth the
temperature is about 5⁰C. Thus the heat is conducted from regions of higher temperature
to regions of lower temperature. This gradient is used to derive ammonia turbine
for production of energy. This technology is still in its infancy.
8. Tidal Power
The high tide derives the water towards the land and the
low tide moves the water away from the land. The difference in height of the
water and low tides is made use of in tidal power stations to generate
electricity. A tidal power station consists of a long barrier called a tidal
barrage. The flow of water across the barrage turns its turbines, which in turn
derive the generators for production of electricity. It is estimated that the
total energy flow due to tides in shallow seas is about 1.1 billion kilowatts
of which 13 million kilowatts can be harnessed presently with existing
technology.
Energy Conservation
The energy sources
of earth are limited and are fast declining. It is therefore necessary to use
the energy in a balanced and planned way. Some of the ways of energy
conservation are
§ Use of energy efficient machines, engines and manufacturing
processes. It has been estimated that 75% of electricity produced is wasted due
to use of inefficient machines and appliances.
§ Reduce wastage by recycling the energy.
§ Reduce the number of transport vehicles by encouraging mass
transit systems in urban areas.
§ Minimizing use of air conditioning and artificial light.
Increasing use of energy efficient bulbs and encouraging use of natural light.
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