Impact of development on the Quality of Environment
I. Impact of Urbanization on the Quality of Environment:
The environment is the aggregate of external conditions that influence the life of individual or
those of the entire population. The components of the natural environment are:
1. Lithologic Environment - It consists of the solid non-living earth crust including the soil,
bedrock and the landform.
2. Atmospheric Environment - It is the layer of gases in which are suspended countless minute
solid and liquid particles enveloping the earth.
3. Hydrologic Environment: It includes all liquid or frozen water standing in bodies, eg. oceans
and lakes, flowing over or under the ground in streams or glaciers or being held almost
motionless in the soil and rock.
4. Biologic Environment: It consists of all the living things, eg. man, animals, vegetation,
micro-organisms living in the world.
A. Cities as an Ecosystem:
The city consists of two components: the urban man (in most cases the modifier of the
environment) and the urban environment. They are interdependent and interconnected. A
change in one will lead to changes in the other. Because of this relationship, the city can best
be studied as an ecosystem. An ecosystem is a functioning interacting system composed of
one or more organisms and their environment both physical and biological.
In the urban ecosystem, the urban man utilizes the environmental resources and expels its
products and waste back to the environment. Through this action that can initiate a chain of
environmental modifications which will in turn affect the man himself. Within the urban
ecosystem, three self-evident interactions are apparent.
- Urbanization involve the modification of the environment or / and the impact of the
environment.
- The physical environment may influence the form, functions and growth of the city.
- A change in either the urban environment or the urban man will affect the other
component of the urban ecosystem.
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The urban ecosystem is an open system. It is not self-contained. It cannot function in
isolation from the other parts of the world. For example, it depends on external food supply
and investment. Thus, a change in the urban ecosystem will affect the region, the country and
the rest of the world.
B. Impact of the Quality of the Lithologic Environment:
1. Landslide from cleaning or building on unstable slope:
A number of man-made disturbances associated with urbanization can result in slope
failures which may seriously affect the time like properties of the urban population. These
disturbances are: cutting and filling for residential hill slope development; building along
the hill slope including extensive cutting; removal of hillside vegetation for building; and
vibration from machineries, eg. pile drivers, motor cars.
2. Ground subsidence because of urban development:
Subsidence is major environmental response to urban activities. It is due to: the presence
of heavy structural loads, eg. weight of multi-storeys buildings, flyovers, especially those
constructed on reclaimed land; alteration of surface mental of mountains and reclamation.
Many cases of subsidence are associated with changes in the ground water regime. Any
urban development that alters the position of the water table, eg. by pumping
underground water supply, by altering the drainage, may cause a change in the elevation
of the ground surface.
3. Impact of the soil:
The reworking of the ground through urbanization changes the distribution and the
quality of the soil in the following ways:
a. Large area of the agriculture will be covered by metropolitan structures or roads. The
fertile top soil had either been scrapped off or buried by the build up area and this will
destroy the agricultural utility of the converted land.
b. The mineral materials such as sand and gravel are excavated from the earth to supply
urban construction demands, eg. to manufacture cement and concrete. The removal of
sand form the beach can increase the marine erosion.
c. Soil erosion and sedimentation - Man's use of the land has increased the rate of soil
erosion. It is estimated that 24 billion tons of materials are now being removed
annually by rivers to the oceans, about 2.5 times the rate before man's intervention.
Erosion by overland flow is a result of urbanization. Waterproofing the surface,
compacting the ground surface and the clearing of surface vegetation can increase the
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amount and velocity of surface runoff and consequently, erosion. In the past, a lot of
water infiltrated into the ground or may be absorbed by vegetation. The presence of
vegetation can retard the rate of flow and protect the soil from rain splash erosion.
Along with the soil, many soil nutrients are removed, so less will be available for plant
growth. Eroded soil will cause sedimentation of reservoirs, lakes and rivers causing
great economic loss, eg. decrease in reservoir storage capacity, harbours and
water-ways have to be dredged inn order to stay navigable, more flooding.
d. Contamination of soil - Urban activities may alter the quality of the urban soil. Soil can
be contaminated by refuse dump, subsurface sewage disposal system and this can lead
to contaminated water supply and to sickly vegetation. Concentrated traffic in the city
had contaminated the soil of vegetation with zinc, lead and cadmium. The metal
concentrations increase with proximity to roads, traffic volume and with nearness to
the ground surface. For example, lead in surface soil near busy streets may reach a
concentration of over 200 ppm (parts per million), about 100 to 1000 times its natural
content. Even the cities' least affected area, the parks, have a higher concentration than
the surrounding rural land. Lead can poison the soil and kill the vegetation. Cadmium
can cause heart and blood diseases.
e. Desiccation of soil - By making the soil impervious and by pumping of the
underground water for industrial and domestic use, soil air and moisture vital plant
growth will be absent.
4. Change in Relief:
a. Conscious remolding of the land by cutting and filling - Cutting and filling create
suitable ground conditions for structural foundations. Earth materials are often
excavated from high places and transported to lowlyling place and this will change the
landscape and the distribution of the soil.
b. Disposal of waste - Refuse dump as solid waste and the settlement of dust (most from
human origin) have contributed to the rising of land surface. In the industrial city of
Britain, dust deposition may exist 300 tons/ km2/ year whereas in the open countryside,
the amount is reduced to 70 tons/ km2 /year.
C. Impact on the Quality of the Atmospheric Environment:
Urbanization changes the climate in the city producing the urban climate. The table below
shows the modification of the atmospheric environment in urban area.
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Atmospheric composition
Carbon dioxide
Sulphur dioxide
Nitrogen oxide
Carbon monoxide
Total hydrocarbons
Particulate matter
2x
200x
10x
200x +
20x
3x to 7x
Radiation
Global solar
Ultra-violet (winter)
Sunshine duration
- 15 to 20%
- 30%
- 5 to 15%
Temperature
Winter minimum (average)
Heating degree days
+ 1o to 2oC
- 10%
Wind speed
Annual mean
Number of clams
- 20 to 30%
+ 5 to 20%
Fog
Winter
Summer
+ 100%
+ 30%
Cloud
+ 5 to 10%
Precipitation
Total
Days with < 5 mm
+ 5 to 10%
+ 10%
1. The Heat Island Effect:
a. Change in Temperature:
Temperature is changed by the formation of heat island. Temperature in the city is
much higher than the rural area surrounding it because of the following reasons.
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i. Change of surface:
Urbanization changes the physical surface of the land by constructing many
buildings and paving much of the ground. This means waterproofing the land,
increasing thermal admittance and increasing its roughness.
- Waterproof the land:
Over 50% of the city surface has been covered by waterproofing cement. Surface
runoff over the paved surface will increase and so less moisture for evaporation.
The cooling effect of evaporation will be absent.
- Thermal Admittance:
The city has higher thermal admittance than the surrounding countryside. The city,
within its areas of concrete, has a higher thermal conductivity (high rate of hear
transmission). Heat flows easily into the concrete during the day and is stored, thus,
the day time temperature is high. At night, while both the city and the countryside
were cooled by radiation, the urban structures gradually give off the additional heat
accumulated during the day time. This keep the urban air warmer than the
surrounding countryside air.
- Roughness of the Surface:
The urban structures increase the irregularity and roughness of the surface. So,
wind speed near the surface will be reduced to about 25% less than in the rural
areas. The lowered wind speed decreases the city's ventilation inhibiting the
in-movement of the cooler air from the rural land.
ii. Heat Production:
Urban man and his activities produced a large amount of heat which affect the
climate of the city. Heat will be produced by : industrial activities; heat produced
from cooling and lighting; human beings (A man produces heat of between 100-300
watts depending on his activities. It is estimated that if 5-6 million people live within
an area of 30000 km2, the human heat emitted a day will be equivalent to 1/6 of the
insolation received in a day).
iii. Increase Turbidity:
By their functions, eg. industrial activities, transport activities, cities introduce a
great quantity of fine particles into the air. This will increase the Turbidity of the air.
Thus, it results in reduction in insolation because the suspending particles may reflect
the sun's rays back into the atmosphere. This will decrease the temperature.
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However, the blanket of pollution over the city also absorb part of the ascending
thermal radiation emitted from the city surface. Thus, the heat instead of being
radiated back into the atmosphere stay near the ground. Part of the heat will be
re-emitted downwards and retained by the ground. This will hinder heat dispersion
and intensity the heat island effect.
iv. Changes in the composition of the atmosphere:
The burning of the fuel will lead to a higher concentration of carbon dioxide and
carbon monoxide in the atmosphere. The presence of these two gases will affect the
heat balance and enhance “green house effect” of the city because they permit the
entrance of light (short-wave radiation) but prohibit the transmission of radiation of
long-wave length, eg. heat, and so higher temperature will be experienced in the
industrial cities with high travel density.
The city is just like a warm or heat island surrounded by the cooler countryside.
Thus, the city tends to have a higher average temperature, lower frequency of
snowfall and a longer frost-free period, eg. Chicago has an average frost-free period
of 197 days while the surrounding rural area experiences a period of 160-170 days.
b. Magnitude of the heat island:
The magnitude of the heat island is governed by the following factors:
i. Size of cities - The heat island effect will increase with the size of the city.
ii. Local Micro-Climate Condition - The wind speed, the amount of cloud cover will
affect the magnitude.
iii.Topography - The heat island effect will be less pronounced among rivers, wood land,
pastures and areas of high elevation.
iv. Diurnal and weekly variation - More pronounced at night and during week days.
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v. Seasonal variation - More pronounced during winter.
vi. Building density - Magnitude of the heat island increases with increasing building
density.
vii. Distance from city centre - Magnitude increases with increasing distance from city
centre.
c. Temperature distribution within the city:
i. Temperature variation within the city:
Within the city, there are surprising temperature variations as the temperature may
be affected by the arrangement of structures at the terrain. The street intersection at
the base of a long gentle slope is typically the coldest place in the city because of cold
area drainage. Heavily travelled main roads are two or three degrees warmer than the
side streets. The areas around the stop light are usually two or three degrees warmer
than the areas between the stop lights because many cars are idle there.
ii. The vertical distribution of temperature:
Often the city is a major contributor to the development of temperature inversion.
The layer of dust and pollutants (aerosol) absorb heat radiated from the city surface
and this layer may be warmer than the city itself. (The following figure)
Normal
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Temperature Inversion
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Helicopter had been sent into the field to measure the distribution of temperature
over the city. It had been found that the inversion is ground-based in the outlying
areas near the city fringe and the inversion is generally elevated to 300 metres above
the city centre. The pollutants cannot be dispersed by conventional terrains although
they may be lifted form the ground by local air circulation. This will result in an urban
heat and pollution dome (dust dome) enveloping the build-up area. (The figure below)
Air circulation within the dome is generated by the higher temperature in the city
core and the cooler air from the periphery may be drawn into the low pressure system.
Since circulation described so far only exist with light wind. The pattern will change
if wind speed exceed 13 km/hr. In this case, the heat and particles will be blown to the
countryside rather than maintaining a dome over the city. Thus, the city spreads a
plume (urban heat and pollution) across the adjacent rural area when the wind is
strong. The plume, carrying the dust in it, may extend hundreds of kilometres beyond
the city affecting the precipitation and temperature over a wide area.
2. Visibility in the city:
As a result of air pollution and associated high turbidity, visibility is much reduced.
When temperature inversion is presented, the aerosols cannot be dissipated via the
convectional currents. The accumulation of these aerosols can reduce visual range by
80-90%. Fogs are more frequent because water vapour rapidly condenses on the particles
and they cannot be dispersed by the low wind speed.
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Visibility in many urban centres has been improved during the last two decades because
of air pollution control and formation of smoke-free zones; substitution of oil and gas for
coal in heat production and energy production; and migration of industries to satellite
towns.
3. Humidity in the city:
The average relative humidity in towns is lower than nearby rural areas because of the
higher temperature. The amount of water vapour required to saturate the air increase with
increasing temperature. The average absolute for evaporation slightly lower because less
water is available for evaporation as a result of rapid runoff on the waterproofed surfaces.
4. Precipitation in the city:
Precipitation increases with urbanization because of two reasons.
a. Higher temperature intensifies the thermal convection. Thus, the cooling and
condensation of water vapour will be promoted.
b. The urban atmosphere contains greater concentration of nuclei for condensation to
occur. Most studies indicate that precipitation increases about 10% in the city.
Observation in various cities, eg. Chicago, indicates that there is increase in
precipitation in the weekdays as compared with the weekend. These higher values
parallel the increase industrial activities during the weekdays. This weekly pattern is
also evident in temperature distribution.
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5. Windspeed and direction in the city:
Three features distinguish the wind pattern in the city from the regional wind flow
pattern:
a. The rough surface of the city exerts an increase frictional drags on air flowing over it.
Thus, the wind speed in town will be reduced.
b. Turbulence (violent disorderly wind) may be created because of the horizontal thermal
gradients within the city and thus, centres of different pressure will be created.
Sometimes, downtown wind speed may be greater than that in the countryside.
c. An air circulation system will be induced by the heat island effect. Usually the urban
heating will lead to the existence of a low pressure area both day and night. However,
this city driven movement is unable to disperse the urban heat air since its strength will
be retarded by friction with the rough city surface. This flow of air into the city is not
steady but act in pulsation. The strongest wind will occur when the temperature gradient
is the steepest.
D. Impact on the Hydrologic Environment:
1. Change in runoff:
By making the surface impervious and by destroying much vegetation, less water
infiltrates into the ground and the volume of overland flow will increase. The
straightening of river channels and the construction of storm sewage will transmit water
quickly to the straight channel. Thus, the discharge during the rainy season will increase
and the discharge during the dry intervals will decrease.
2. Increase in the magnitude and frequency of flood:
It is due to several reasons.
Firstly, it is directly related to increase in discharge mentioned.
Secondly, rapid erosion as a result of land clearing for construction will cause the
shallowing of river bed and thus, reduce the river's capacity to hold water.
Thirdly, the river channels act as temporary storage and can reduce the flood peak
downstream, but since they are straightened, the time required for a given amount of
water to run off shortens and there will be concentrated flow within a short period.
Flooding will be more serious as a result.
Lastly, overflowing onto neighbouring flood plain can also reduce the magnitude of
the flooding downstream, but with urban growth, the flood plain is usually raised and
used for construction and less space will be available for storage.
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3. Degrading the water quality:
Urban and industrial waste will degrade the quality of water, eg. increase in dissolved
mineral contents, decrease in oxygen. Effluents contain a lot of dissolved minerals which
act as nutrients and promote algae and plankton growth. When these plants die, oxygen is
used up. Aerobic bacteria require free oxygen to break down the organic matter to
relatively harmless, odourless product. Excessive pollution will cause depletion of oxygen
and anaerobic bacteria will become more active. The decomposition of organic matter by
this kind of bacteria will result in a different sets of end products, eg. sulphur dioxide
which are objectionable. Some fish may die and be replaced by pollution-resistant fish.
4. Water shortage:
A city dweller required about 675 litres of water a day and concentrated consumption
in a relatively small area will lead to the problem of water shortage.
5. Contamination of water and salt water intrusion:
Consumption of contaminated water will cause death and diseases, eg. cholera and
typhoid. In order to obtain clean water, deeper wells may have to be developed which
might lead to salt water intrusion if the city have a coastal location. If more underground
fresh water is withdrawn, the amount which is replaced from the surface salt water may
move landwards deep underground and the water will be contaminated by salt.
6. Changes in the temperature of water:
The heat island effect and the discharge of heat or hot effluents into water raise the
temperature of the water. Some species of fish cannot withstand the warm water so they
may be replaced by less desirable types of fish. Warm water contains less dissolved
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oxygen, thus anaerobic decomposition will be accelerated. The table at page 14 shows the
effects of water pollution problems.
E. Impact on the Biologic Environment:
In the urban area, wild life is rare, but there is an increase in domestic pests. Urbanization
subtracts and adds various types of plants. The original vegetative cover is differentially
destroyed to make way for construction. Men can bring new plants into the city and plant
them. The increased planting of different and exotic types of trees along the streets increases
the variety of vegetative cover.
Urban plants are subjected to a number of environmental stresses which are absent or less
severe in the countryside, the trees must withstand the reduced supply of water and oxygen in
the paved-over soil. The normal cycle of nutrients is interrupted because men remove the
grass and fallen leaves on the ground rather than allow the incorporation into the soil. Air
pollution will also influence plant lives. Many trees in the city are out in the open space and
so they are more susceptible to damage and ice than in the forest.
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II. Impact of Industrialization on the Quality of Environment:
A. Introduction:
Until recently, greater production has mattered more concern for the environment but this
is changing. Now people are much more aware of the damaging effects of unplanned
industrial development. Some progress has been made in the removal of industrial blight
(plant disease), such as the reduction in pollution and in the planning of new industrial
developments.
B. Environmental Pollution:
Man-made environmental pollution is the introduction directly or indirectly through
man's activities into the atmosphere, hydrosphere, lithosphere and biosphere of infusions of
matter and energy at levels of quantity or intensity appreciably higher than natural levels and
usually with undesirable or deleterious (harmful) effects upon environments of the biosphere.
A pollutant is any form of energy or matter causing pollution. In air pollution, the
pollutants include gases and solid and liquid particles of both organic and inorganic chemical
classification. Water pollution includes presence of disease-producing bacteria (biological
pollution) and of undesirable ions and compounds in solution (chemical pollution). Presence
of suspended solids causing turbidity may be include as forms of water pollution. Thermal
pollution of air and water, a form of energy infusion, raises the quantity of sensible heat in
those fluids to abnormally high levels. Noise pollution illustrates energy infusion into the
environment by sound-wave transmission.
1. Air Pollution:
There is virtually an infinity of airborne residuals that may be discharged to the
atmosphere, but the ones of central interest and most commonly measured are carbon
monoxide, sulphur dioxide, oxides of nitrogen, hydrocarbons, and particulates.
Air pollution is an environmental stress, that, in conjunction with a number of other
environmental stresses, tends to increase the incidence and seriousness of a variety of
diseases, including lung cancer, tuberculosis and the common cold.
The contents of the atmosphere can be placed into two basic categories: particulate
matter and gases.
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a. Particulate matter:
Particulate matter consists of particles of matter in either the liquid state. These
particles are usually called particulates. Particulate matter injected into the atmosphere
is of both natural and man-made origins.
i. Natural Forms of Particulate Matter:
It includes sea-salt crystals, mineral dust, volcanic dust, and smoke from forest fire
and grass fires, and living plants release pollens and spores into the air. These
particulate play a vital role in the atmospheric processes by serving as nuclei of
moisture condensation to form clouds, and are important in producing atmospheric
haze that builds up naturally within stagnant air masses far from industrial air
pollution sources.
ii. Man-made Particulate Matter:
It comes from many sources. The major source is in combustion of hydrocarbon
fuels - petroleum products, coal, peat and wood. Other kinds of particulate matter
are introduced into the atmosphere in manufacturing industrial chemicals, refining
fossil fuels, mining and smelting ores, quarrying, cement manufacturing, and
farming activities.
There are two classes of man-made particulates: primary and secondary.
Primary particulates are injected into the atmosphere from ground sources. The
chemical and physical properties of primary particulates are acquired at ground
level sources. Most of the primary particulates are in the size range larger than 1
micron (0.001 mm). They belong to a size grade that settles through the air under
the force of gravity.
Secondary particulates are produced by chemical reactions that take place within
the atmosphere. Gases are involved in the production of many secondary
particulates. Energy for certain of the chemical reaction is supplied by sunlight.
(Photochemical Smog) They are the major source of irritating and dangerous
pollutants in the smog of urban areas. (Los Angles)
The particulates themselves result from the attachment of the newly formed
chemical compounds to the water films that surround solid condensation nuclei,
already present in the atmosphere.
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b. Gaseous Pollutants:
For the most part, these are oxides of sulphur and nitrogen, along with ammonia
and carbon monoxide.
Carbon dioxide gas is given off in large quantities during the combustion of fuels,
but it is not harmful to health and is one of the natural components of pure air, it is not
regarded as a pollutant gas. Two principal gases making up the pure atmosphere oxygen and nitrogen - are of major importance in chemical reactions that produce
secondary particulates. Apart from the above gases, ground emissions are important in
the formation of secondary particulates include hydrocarbon compounds and various
compounds of lead, chlorine and bromine. These take the form of small solid
particulates.
Sulphur dioxide SO2 is a leading culprit (offender) in forming harmful products
through photochemical reactions. The SO2 combines readily with atmospheric oxygen
and with the water films on suspended particulates to produce sulphuric acid.
Sulphuric acid is extremely corrosive since it impairs the respiratory system of
humans and damages a wide variety of materials with which it comes in contact.
Oxides of nitrogen are another group of major culprits in generating harmful
products in urban smog. Nitrogen oxides can form nitric acid, like sulphuric acid,
which is highly corrosive. Nitric acid can, in turn, react with ordinary salt found in
water films on particulates, to produce hydrochloric acid.
One of the most insidious (doing harm secretly) gases produced in polluted air is
ozone, which is a poisonous gas, and it can also react with hydrocarbon compounds to
produce other toxic compounds. – Photochemical Smog.
c. Harmful effects of air pollution:
Pollutants trapped beneath an inversion lid form a board pollution dome centred
over a city when winds are very light or near calm. When there is general air
movement in response to a pressure gradient. However, pollutants are carried far
downwind to form a pollution plume.
For humans in cities both sulphur dioxide and hydrocarbon compounds, altered by
photochemical reaction to produce sulphuric acid and ethylene, respectively, are
irritants to the eyes and to the respiratory system. Nitrogen dioxide is also an eye and
lung irritant when present in sufficient amount. Carbon monoxide is a cause of death
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when inhaled in sufficient quantities. Carbon monoxide levels are a general indicator
of the degree of air pollution from vehicular exhausts, but concentrations rarely reach
sufficient levels in the open air to be a threat to life. Nevertheless, the long-continued
inhalation of small amounts of carbon monoxide is suspected of harmful effects.
Acid rain refers to all forms of precipitation, snow, rain, hail or dust particles, that
contain a degree of acidity higher than those which normally occur in nature. This
acid rain interacts with water, soil, vegetation, animals, stones and metals in ways that
can be quite destructive. For example, acid rain has increased the acidity of many
lakes to the point where fish can no longer survive in them.
Ozone in urban smog has the most deleterious effect upon plant tissues, and in
some cases has caused the death or severe damage of ornamental trees and shrubs.
Sulphur dioxide is injurious to certain plants and is a cause of loss of productivity in
truck gardens and orchards in polluted air. Atmospheric sulphuric acid in cities has in
places largely wiped out lichen growth.
Lead and other toxic metals in the polluted atmosphere are a particular source of
concern for human health in the future. Although lead poisoning from atmospheric
sources has not yet been documented in humans, there is now evidence that it has
caused the deaths of animals in city zones.
Radioactive substances in the atmosphere are a special form of environmental
hazard because of the genetic damage that is done to plant and animal tissues exposed
to dangerous radiation.
d. Air pollution Control:
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The one device often used is the high stack that releases the pollutants where the
wind speeds are higher and there can be greater dispersion and dilution. Suspended
particulate emissions from flour milling, cement factories and other industrial
operations can be controlled by enclosing the operations in sheds or buildings and
passing the ventilation air through filtering systems before releasing it.
There are also processes for removing particulates and sulphur oxides from the
exhaust gas streams of power plants and incinerators. The particulates which are
recovered have sometimes been found to have economic value as construction
material. The recovered sulphur oxides can be used to manufacture sulphuric acid or
other sulphur products. The most widely used technique for controlling sulphur oxide
emissions involves a reduction of throughput of sulphur. If fuels of low sulphur
content can be found, they can be substituted for high sulphur fuels, with a
corresponding reduction in sulphur oxide emissions. Some oils are now being
processed to remove the sulphur, but sulphur removal from coal is not economically
feasible at present prices. Late in 1970, the federal Clean Air Act was signed into law,
giving the Environmental Protection Agency authority to set national standards for
tolerable limits of pollutants in the air.
2. Water Pollution:
a. Introduction:
Water pollution is defined in a conference in Geneva 1961 on water quality as "a
water is considered polluted when its composition or state is directly or indirectly
modified by human activity on an extent such that it is less suitable for purposes it
could have served in its natural state".
Water pollution in a technological society occurs when man is using more and
more water in more and more ways. Although lakes, rivers, and oceans have
considerable ability to purify themselves by biological action, the quantities of wastes
discharged into water by man now frequently exceed this natural self-cleaning ability.
In addition, industry now contributes large amount of non-degradable pollutants to
these water bodies and results in various extents of pollution.
b. Types of Pollutants:
i. Direct Toxicity:
This is caused by materials which are directly poisonous to aquatic organism or
human beings, eg. soluble metal compounds, radio-active substances, and various
kinds of kinds of acidic and basic substances.
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ii. Oxygen Demand:
Most aquatic organisms and sewage treatment bacteria depend much on oxygen for
their living and the generation of the processes of decomposition. However,
dissolved oxygen can be interfered by reducing agents, such as sulphide which
absorbs oxygen; by organic matters that require oxygen for its bacterial
decomposition; and by substances that reduce the solubility of oxygen in water.
Therefore, if these substances increase for too much, dissolved oxygen in water
will be deprived of.
iii. Indirect Harm:
Indirect harm includes heat, colour, suspended matters and excessive amount of
dissolved materials.
iv. Disease Organisms:
Bacteria and pathogens that causes disease to animals, fish and human beings are
all regards as disease organisms.
c. Sources of Pollutants:
i. Industrial waste:
During the manufacturing processes, a lot of industrial wastes are introduced into
water bodies. There are insoluble metal compounds such as slag from the iron and
steel industry. Soluble metal compounds are from chemical industry. Besides, toxic
chemicals from the chemical industry may kill aquatic organisms. For example, the
textile industry may add to the alkalinity of water. Some substances which
stimulate the growth of aquatic weeds are also discharged into water bodies, eg.
phosphates which may promote aquatic weeds like algae. Moreover, radio-active
substances are discharge from nuclear power stations.
Textile industry will also discharge substances colouring water bodies. Food
processing industries will discharge organic matters which require large amount of
bacterial growth to generate decomposition. As a result, the oxygen demand is
high.
ii. Oil:
Oil will be discharged from ships and spread of oil is always due to wreckages and
oil spillage.
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iii. Others:
Civil engineering projects always introduce mud into water bodies.
Thermal pollution of water may be caused by the discharge of very hot water from
the cooling systems of the power station, iron and steel industry, etc.
d. Relationships between industrialization and water pollution:
Owing to severe industrialization, processes engaging in mass production, large
amount of waste products are the inevitable by-products resulted. Nearly all these
by-products upset the natural environment as it cannot absorb them. Thus, the
environment, both natural and contrived, has deteriorated, particularly through the
process of water pollution.
The most significant feature of industrialization is technological advancement
which brings forth new inventions and new methods of production. For example,
technology brings about the advent of plastics and many insoluble matters. As these
matters cannot be recycled back to the natural system, the original system will be
violated, This induces pollution. Since more particulates are discharged to water
bodies so as to disperse them, water pollution is very outstanding when
industrialization comes into beings.
Technological advancement also makes man greedy and wasteful. They exploit
the nature in an uncontrollable way on one hand and produce a lot of unnecessary
waste products on the other. The natural balance of the nature is upset. The
wastefulness of man produces sewage of various kinds, organic or inorganic, toxic or
benefit tot weed growth.
Industrial growth also constitutes a condition that people like to concentrate on
large industrial cities. This concentration of people around industrial centres leads to a
more serious pollution condition. When industries and people group together, not only
industrial sewage of various kinds increases but also urban sewage. The pressure on
the natural environment is made greater.
Modern industrial development prefers a coastal location or nodes of transport as
river confluence, trans-shipment points. Water transport is convenient at these
locations. However, the pressure exerted by industry on these water bodies is even
greater because industrial wastes can be directly drained to them. For example,
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chemical industry prefers a coastal location because of the supply of raw materials as
well as the discharge of wastes. The chemicals released from the chemical industry
are highly toxic. Natural water quality will be deteriorated very much.
Moreover, some industries need much water for the manufacturing processes or
for the use in the cooling system. Water released out after using may be contaminated.
Some water may be polluted by various toxic chemicals which are dissolved by the
water or contained in the water; some water may be very hot if the water is released
from the cooling system. No matter how, water released after the manufacturing
processes is surely polluted to a small extent or to a large extent. Water quality is
made worse especially when water is released out without any further treatment to
reduce the degree of pollution.
e. Effects of water pollution:
Sewage provides nutrition for bacteria and fungi (decomposers), which have a high
biochemical-oxygen demand and deprive aquatic life of their oxygen supply for life
maintenance, thereby upsetting the balance of the natural ecosystem.
Water pollution can cause acute food poisoning or dysentery when rivers are badly
polluted, they are incapable of supporting fish.
Bathing in sewage-polluted seawater is dangerous because of the risk of infection and
the transmission of fly-borne diseases where untreated sewage collects on the
foreshore.
The aesthetic value of some popular recreational sites may be impaired by water
pollution.
There are adverse effects on fish farming and oyster cultivation.
In Japan, water pollution has become so bad that most of the seafood caught in
Japan’s fishing water is not safe to eat in large quantities. This is because the coastal
water is heavily polluted by sewage containing mercury, rubbish, chemical fertilizers,
insecticide, dyes, detergent from textile mills, waste from slaughter houses and other
industrial waste.
f. Water pollution control:
 Clearance operations to remove sludge and solids from streams.
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Collecting pig and poultry waste from farmhouses.
Deterring local villagers from using the streams for domestic waste.
Constructing new sewage treatment plants to remove nitrogen and phosphorous
from sewage.
Legislation, such as the 1980 Water Pollution Control Ordinance, requiring
industrialists and farmers to treat their effluent through neutralization before
discharge.
Use of incinerators to treat domestic waste from urban population.
Educating people to minimize water pollution.
3. Thermal Pollution:
a. Thermal pollution of water
The heat comes from combustion in production processes, hence thermal pollution is
frequently associated with large variety of industries. Power generation and
manufacturing processes use large amounts of water for cooling. The water becomes
much warmer when it is discharged by the factories, and the temperature of a nearby
body of water can be raised by as much as 20oC.
Effects of thermal pollution in water:
 There is marked reduction in the water’s oxygen level because warm water
holds less dissolved oxygen than cold water and speed up the metabolic rate of
decay of organisms in the water, which increases their demand for oxygen. The
stream environment is fouled.
 Increase in heat may change the timing of a fish hatch and bring young fish
prematurely into an environment in which their natural food sources have yet to
arrive.
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In general, no higher aquatic organisms can continue to survive above 50oC.
Most kinds of fish cannot survive in water with a warmer temperature than
30oC.
b. Thermal pollution of the atmosphere
Modern industrial processes involve the combustion of fossil fuels such as coal,
petroleum and natural gas. The combustion of fuel releases sensible heat and smoke,
water vapour, carbon dioxide and various other chemicals into the atmosphere.
Effects of thermal pollution of the atmosphere
 Change of urban microclimates
 Enhance the heat island effect.
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4. Noise Pollution:
a. Sources of noise pollution
 Aircraft noise: Aircrafts taking off and landing create very high level noise
(95~110dB).
 Traffic noise: Vehicles stop and start in front of traffic lights, creating higher
levels of noise. Noise generated by moving vehicles and horns increase with
increasing volume of traffic.
 Industrial noise: Noise level is between 75-85dB. Textile and metal
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manufacturing industries are noisiest.
Construction noise: Noise from compressors, pneumatic drills, excavators, pile
drivers, concrete mixers reach high decibel levels. This is the noisiest of all
industries.
Domestic noise: Noise nuisance also comes from air-conditioners and
recreational activities (radios, Hi-Fi system,…..)
b. Effects of noise pollution
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Delay or interfere with sleep and result in feelings of fatigue.
High level of noise may cause irreversible effects to the nervous system.
Prolonged exposure to high noise intensity may have an ill effect on hearing,
temporary or even permanent deafness.
Low frequency noise vibrations can cause illnesses ranging from brain damage
to sickness in sensitive people.
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c. Solutions to noise pollution:
 Prohibited from taking off and landing of aircraft between midnight and 6:30am.
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Restricting noise from 11 pm to 6 am in residential areas.
Construction activities are prohibited from 7 pm to 7 am on weekdays, and for
the whole day on Sunday and public holidays.
Educating people to prevent sounding horns in quiet zones.
Imposition of speed limits and prevention of certain types of vehicles from using
the streets as major routes.
Workers in noisy environments have to protect themselves against noise hazards
by wearing specially designed helmets.
Suppression equipments must be installed in all noisy machines.
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