Download - ENVR-252 : Envr. Pollution · PDF fileENVR-252 : Envr. Pollution 2 industrial effluents with toxic substances and sewage water with human and animal wastes pollute our water thoroughly

ENVR-252 : Envr. Pollution

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CHAPTER 2 & 3

Environmental Pollution and types of Pollution

Environmental Pollution

Developmental activities such as construction, transportation and manufacturing not only deplete the

natural resources but also produce large amount of wastes that leads to pollution of air, water, soil, and

oceans; global warming and acid rains. Untreated or improperly treated waste is a major cause of pollution

of rivers and environmental degradation causing ill health and loss of crop productivity. In this lesson you

will study about the major causes of pollution, their effects on our environment and the various measures

that can be taken to control such pollutions.

Pollution and Pollutants

Human activities directly or indirectly affect the environment adversely. A stone crusher adds a lot of

suspended particulate matter and noise into the atmosphere. Automobiles emit from their tail pipes oxides

of nitrogen, Sulphur dioxide, carbon dioxide, carbon monoxide and a complex mixture of unburnt

hydrocarbons and black soot which pollute the atmosphere. Domestic sewage and run off from

agricultural fields, laden with pesticides and fertilizers, pollute water bodies. Effluents from tanneries

contain many harmful chemicals and emit foul smell. These are only a few examples which show how

human activities pollute the environment. Pollution may be defined as addition of undesirable material

into the environment as a result of human activities. The agents which cause environmental pollution are

called pollutants. A pollutant may be defined as a physical, chemical or biological substance

unintentionally released into the environment which is directly or indirectly harmful to humans and other

living organisms.

Types of Pollution

1. Water pollution

2. Soil pollution

3. Noise pollution

4. Air pollution

5. Radiation pollution

1. Water Pollution Addition or presence of undesirable substances in water (surface water including rivers, streams, lakes &

oceans and ground water including aquifers) is called water pollution. Water pollution is one of the most

serious environmental problems. Water pollution is caused by a variety of human activities such as

industrial, agricultural and domestic. Agricultural run-off laden with excess fertilizers and pesticides,


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industrial effluents with toxic substances and sewage water with human and animal wastes pollute our

water thoroughly. Natural sources of pollution of water are soil erosion, leaching of minerals from rocks

and decaying of organic matter. Rivers, lakes, seas, oceans, estuaries and ground water sources may be

polluted by point or non-point sources. When pollutants are discharged from a specific location such as a

drain pipe carrying industrial effluents discharged directly into water body it represents point source

pollution. In contrast non-point sources include discharge of pollutants from diffused sources or from a

larger area such as run off from agricultural fields, grazing lands, construction sites, abandoned mines and

pits, roads and streets.

Figure: Point and nonpoint sources of water pollution

Sources of water pollution

Water pollution is the major source of water borne diseases and other health problems. Sediments brought

by runoff water from agricultural fields and discharge of untreated or partially treated sewage and

industrial effluents, disposal of fly ash or solid waste into or close to a water body cause severe problems

of water pollution. Increased turbidity of water because of sediments reduces penetration of light in water

that reduces photosynthesis by aquatic plants. Some major sources of water pollution are discussed below:

i. Water Pollution due to pesticides and inorganic chemicals

NONPOINT SOURCES

Urban streets

Suburban

development Wastewater

treatment plant

Rural homes

Cropland

Factory

Animal feedlot

POINT SOURCES


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Pesticides like DDT and others used in agriculture may contaminate water bodies. Aquatic organisms take

up pesticides from water get into the food chain (aquatic in this case) and move up the food chain. At

higher trophic level they get concentrated and may reach the upper end of the food chain.

•Metals like lead, zinc, arsenic, copper, mercury and cadmium in industrial waste waters adversely affect

humans and other animals. Arsenic pollution of ground water has been reported from West Bengal,

Orissa, Bihar, Western U.P . Consumption of such arsenic polluted water leads to accumulation of arsenic

in the body parts like blood, nails and hairs causing skin lesions, rough skin, dry and thickening of skin

and ultimately skin cancer.

•Pollution of water bodies by mercury causes Minamata diseasein humans and dropsyin fishes. Lead

causes displexia, cadmium poisoning causes Itai – Itai disease etc.

•Oil pollution of sea occurs from leakage from ships, oil tankers, rigs and pipelines. Accidents of oil

tankers spill large quantity of oil in seas which kills marine birds and adversely affects other marine life

and beaches.

ii. Water pollution due to Thermal pollution

Power plants- thermal and nuclear, chemical and other industries use lot of water (about 30 % of all

abstracted water) for cooling purposes and the used hot water is discharged into rivers, streams or oceans.

The waste heat from the boilers and heating processes increases the temperature of the cooling water.

Discharge of hot water may increase the temperature of the receiving water by 10 to 15°C above the

ambient water temperature. This is thermal pollution. Increase in water temperature decreases dissolved

oxygen in water which adversely affects aquatic life. Unlike terrestrial ecosystems, the temperatures of

water bodies remain steady and do not change very much. Accordingly, aquatic organisms are adopted to

a uniform steady temperature of environment and any fluctuation in water temperature severely affects

aquatic plants and animals. Hence discharge of hot water from power plants adversely affects aquatic

organisms. Aquatic plants and animals in the warm tropical water live dangerously close to their upper

limit of temperature, particularly during the warm summer months. It requires only a slight deviation from

this limit to cause a thermal stress to these organisms. Discharge of hot water in water body affects

feeding in fishes, increases their metabolism and affects their growth. Their swimming efficiency

declines. Running away from predators or chasing prey becomes difficult. Their resistance to diseases and

parasites decreases. Due to thermal pollution biological diversity is reduced. One of the best methods of


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reducing thermal pollution is to store the hot water in cooling ponds, allow the water to cool before

releasing into any receiving water body.

Ground water pollution

Lots of people around the world depend on ground water for drinking, domestic, industrial and

agricultural uses. Generally groundwater is a clean source of water. However, human activities such as

improper sewage disposal, dumping of farm yard manures and agricultural chemicals, industrial effluents

are causing pollution of ground water.

Eutrophication

‘Eu’ maens well or healthy and ‘trophy’ means nutrition. The enrichment of water bodies with nutrients

causes eutrophication of the water body. Discharge of domestic waste, agricultural surface runoff, land

drainage and industrial effluents in a water body leads to rapid nutrients enrichment in a water body. The

excessive nutrient enrichment in a water body encourages the growth of algae duckweed, water hyacinth,

phytoplankton and other aquatic plants. The biological demand for oxygen (BOD) increases with the

increase in aquatic organisms. As more plants grow and die, the dead and decaying plants and organic

matter acted upon by heterotrophic protozoans and bacteria, deplete the water of dissolved oxygen (DO).

Decrease in DO result in sudden death of large population of fish and other aquatic organisms including

plants, releasing offensive smell and makes the water unfit for human use. The sudden and explosive

growth of phytoplankton and algae impart green color to the water is known as water bloom, or “algal

blooms”. These phytoplankton release toxic substances in water that causes sudden death of large

population of fishes. This phenomenon of nutrient enrichment of a water body is called eutrophication.

Human activities are mainly responsible for the eutrophication of a growing number of lakes and water

bodies in the country.

Methods to treat the waste or contaminated water

Waste water from domestic or industrial sources or from garbage dumps is generally known as sewage. It

may also contain rain water and surface runoff. The sewage water can be treated to make it safe for

disposal into water bodies like rivers, lakes etc.

The treatment of waste or contaminated water involves three stages: primary, secondary and tertiary. The

primary stage includes the physical treatment processes in which suspended particulate matter or solid


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material is removed from the water such as sedimentation and screening. The secondary treatment

processes are mainly the biological treatment processes in which microorganisms decompose the organic

pollution loading in the wastewater. Favorable conditions are provided for the microorganism to allow

their rapid growth to accelerate the decomposition process. The examples of secondary treatment include

Activated sludge process and Trickling Filters. Effluents after secondary treatment may be clean but

contain large amounts of nitrogen, in form of ammonia, nitrates and phosphorous which can cause

problem of eutrophication upon their discharge into a receiving water body such as river, lake or pond.

The tertiary treatment is meant to remove nutrients, disinfect for removing pathogenic bacteria. The

example of tertiary treatments includes Chlorination. The treatment of waste water or sewage is carried

out in effluent treatment plants especially built for this purpose. These plants are called as waste water

treatment plants. The solid residues obtained from primary/secondary and tertiary treatment are known as

sludge.

Further measures to control the water pollution

The following measures should be adopted to control water pollution:

(a) The water requirement should be minimized by altering the techniques involved.

(b) Water should be reused with or without treatment.

(c) Recycling of water after treatment should be practiced to the maximum extent possible.

(d) The quantity of waste water discharge should be minimized.

Water recycling

With increasing population the requirement for water is increasing rapidly. However, the availability of

water is limited but an ever increasing water withdrawal from different sources such as rivers, lakes and

ground water is depleting these sources. Therefore, it is essential to utilize the available water with

maximum economy. This involves recycling of waste water for certain uses with or without treatment.

Recycling refers to the use of waste-water by the original user prior to the discharge either to a treatment

system or to a receiving water body. Thus, the waste water is recovered and repetitively recycled with or

without treatment by the same user.


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2. Soil Pollution

Addition of substances which adversely affect the quality of soil or its fertility is known as soil pollution.

Generally polluted water also pollutes soil. Solid waste is a mixture of plastics, cloth, glass, metal and

organic matter, sewage, sewage sludge, building debris, generated from households, commercial and

industries establishments add to soil pollution. Fly ash, iron and steel slag, medical and industrial wastes

disposed on land are important sources of soil pollution. In addition, fertilizers and pesticides from

agricultural use which reach soil as run-of f and land filling by municipal waste are growing cause of soil

pollution. Acid rain and dry deposition of pollutants on land surface also contribute to soil pollution.

Sources of Soil pollution

The three major sources of soil pollution are:

1) Agricultural Sources

2) Industrial sources

3) Domestic & urban activities

Agricultural sources – Agricultural chemicals especially fertilizers and pesticides pollute the soil. The

remnants of such pesticides may get adsorbed by the soil particles and contaminate root crops grown in

that soil. On the other hand, fertilizers in the run-off water from these fields can cause eutrophication in

water bodies. Pesticides are highly toxic chemicals which affect humans and other animals adversely

causing respiratory problems, cancer and death.

Industrial sources – It includes fly ash, chemical residues, metallic waste, nuclear wastes and unwanted

industrial wastes generated during manufacturing processes that is dumped over on the surface of soil by

almost all industries with difference in the degree. Large number of industrial chemicals, dyes, acids, etc.

find their way into the soil and are known to create many health hazards including cancer.

Domestic and urban activities – Domestic and urban activities generate large quantities of city wastes

including several biodegradable materials (like vegetables, animal wastes, papers, wooden pieces, plant

twigs, leaves, cloth wastes as well as sweepings) and many non-biodegradable materials (such as plastic

bags, plastic bottles, plastic wastes, glass bottles, glass pieces, stone / cement pieces).

Plastic bags – Plastic bags made from low density polyethylene (LDPE), is virtually

indestructible, create colossal environmental hazard. The discarded bags block drains and sewage


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systems. Leftover food, vegetable waste etc. on which cows and dogs feed may die due to the

choking by plastic bags. Plastic is non-biodegradable and burning of plastic in garbage dumps

release highly toxic and poisonous gases like carbon monoxide, carbon dioxide, phosgene, dioxine

and other poisonous chlorinated compounds.

Control of soil pollution

Indiscriminate disposal of solid waste should be avoided. To control soil pollution, it is essential to stop

the use of plastic bags and instead use bags of degradable materials like paper and cloth. Sewage should

be treated properly before using as fertilizer and as landfills. The organic matter from domestic,

agricultural and other waste should be segregated and subjected to vermicomposting which generates

useful manure as a by-product. The industrial wastes prior to disposal should be properly treated for

removing hazardous materials. Biomedical waste should be separately collected and incinerated in proper

incinerators.

3. Noise Pollution

Noise is one of the most pervasive pollutants. A musical clock may be nice to listen during the day, but

may be an irritant during sleep at night. Noise by definition is “sound without value” or “any noise that is

unwanted by the recipient”. Noise in industries such as stone cutting and crushing, steel forgings ,

loudspeakers, shouting by hawkers selling their wares, movement of heavy transport vehicles, railways

and airports leads to irritation and an increased blood pressure, loss of temper , decrease in work

efficiency, loss of hearing which may be first temporary but can become permanent in the noise stress

continues. It is therefore of utmost importance that excessive noise is controlled. Noise level is measured

in terms of decibels (dB). WHO (World Health Organization) has prescribed optimum noise level as 45

dB by day and 35 dB by night. Anything above 80 dB is hazardous. The table below gives the noise

intensity in some of the common activities.

Table. Sources of some noises and their intensity


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Sources of Noise Pollution

Noise pollution is a growing problem. All human activities contribute to noise pollution to varying extent.

Sources of noise pollution are many and may be located indoors or outdoors.

Indoor sources include noise produced by radio, television, generators, electric fans, air coolers, air

conditioners, different home appliances, and family conflict. Noise pollution is more in cities due to a

higher concentration of population and industries and activities such as transportation. Noise like other

pollutants is a by-product of industrialization, urbanization and modern civilization.

Outdoor sources of noise pollution include indiscriminate use of loudspeakers, industrial activities,

automobiles, rail traffic, airplanes and activities such as those at market place, religious, social, and

cultural functions, sports and political rallies. In rural areas farm machines, pump sets are main sources of

noise pollution. During festivals, marriage and many other occasions, use of fire crackers contribute to

noise pollution.

Effects of Noise Pollution

Noise pollution is highly annoying and irritating. Noise disturbs sleep, causes hypertension (high blood

pressure), emotional problems such as aggression, mental depression and annoyance. Noise pollution

adversely affects efficiency and performance of individuals.

Control Measures

Following steps can be taken to control or minimize noise pollution

• Road traffic noise can be reduced by better designing and proper maintenance of vehicles.


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• Noise abatement measures include creating noise mounds, noise attenuation walls and well maintained

roads and smooth surfacing of roads.

1. Retrofitting of locomotives, continuously welded rail track, use of electric locomotives or

deployment of quieter rolling stock will reduce noises emanating from trains.

2. Air traffic noise can be reduced by appropriate insulation and introduction of noise regulations for

take-off and landing of aircrafts at the airport.

3. Industrial noises can be reduced by sound proofing equipment like generators and areas producing

lot of noise.

4. Power tools, very loud music and land movers, public functions using loudspeakers, etc. should

not be permitted at night. Use of horns, alarms, refrigeration units, etc. is to be restricted. Use of

fire crackers which are noisy and cause air pollution should be restricted.

5. A green belt of trees is an efficient noise absorber.

4. Radioactive Pollution

Radiation is the process by which radiant energy is transferred from one place to another in the form of

electro-magnetic waves.

The various types of radiation differ from one another by their frequency or wavelength. Higher the

frequency or lower the wavelength of a radiation, higher will be its energy. Again, higher the energy of

the radiation, it will cause higher damage to the living organisms.

Radiations can be categorized into two groups namely the non-ionizing radiations and the ionizing

radiations.

Ionizing radiation

These are the radiations which induce the ionization of atoms and molecules. An atom is ionized when

energy supplied to it separates one or more of its electrons. Ionization of a molecule produces two

fragments. The radiation pollution is mainly caused by ionizing radiation.

Alpha (α), beta (β), and gamma (γ) radiations are mainly responsible for radiation pollution. Alpha

radiation contains energetic -alpha particles. Each alpha particle carries two units of positive charges and

interacts strongly with living tissues.


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Beta, radiation is made up of energetics electrons. Each beta particle carries one unit of negative charge

and interacts strongly with matter. Gamma radiations are made up of high energy photons. Photons bring

about strong electro-magnetic interaction with matter.

Electrically charged particles produced in the nuclear processes can have sufficient energy to knock

electrons out of the atoms or molecules of the medium, thereby producing ions. The ions produced in

water molecules, for example, can induce reactions that can break bonds in proteins and other important

molecules. An example of this would be when a gamma ray passes through a cell, the water molecules

near the DNA might be ionized and the ions might react with the DNA causing it to break. They can also

cause chemical changes by breaking the chemical bonds, which can damage living tissues. The ionizing

radiations cause damage to biological systems and are, therefore, pollutants.

Non-ionizing radiations

These are the radiations which are constituted by the electromagnetic waves at the longer wavelength of

the spectrum ranging from near infra-red rays to radio waves. These waves have energies enough to excite

the atoms and molecules of the medium through which they pass, causing them to vibrate faster but not

strong enough to ionize them. In a microwave oven the radiation causes water molecules in the cooking

medium to vibrate faster and thus raising its temperature.

Sources of Radiation Pollution:

Radiation sources are mainly natural but partly manmade.

The natural sources of radiation may be:

1. Radioactive minerals;

2. Cosmic rays;

3. Radio nuclides.

1. Radioactive Minerals:

The minerals containing Uranium- 235 (U235

), Uranium-238 (U238

), Thorium-232 (Th232

), Plutonium- 239

(Pu239

) etc. are capable of emitting energetic radiations causing pollution.


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2. Cosmic Rays:

The cosmic rays containing highly energetic particles reach the surface of the earth causing pollution. The

intensity of cosmic rays depends on latitudes and altitude of the place. The intensity is maximum at the

poles and minimum at the equator.

3 .Radio nuclides:

The unstable radio-nuclides in the atmosphere can be splitted up into smaller parts emitting energetic

radiation. The smaller radio-nuclides enter into the body of organism along with air during respiration.

The various sources of manmade radiation pollutions may be:

1. Nuclear power plants

2. Nuclear explosions; and

3. Radio-isotopes.

1. Nuclear Power Plants:

Nuclear power plants emit radiation to a very smaller extent except accidental leaks. The nuclear reactor

accident at Chernobyl in 1986 led to deaths of many reactor personnel and a very large release of

radionuclide to the environment causing long term radiation damage to the people living in the

neighboring regions. Moreover, the nuclear power plants produce a lot of nuclear radio-active wastes. The

disposal of these wastes has become a global problem. Some countries producing large quantity of nuclear

wastes dump them in ocean near other countries.

2. Nuclear Explosion:

During nuclear explosion, a large number of radio-nuclides are generated in the atmosphere. The radio -

nuclides settle down with rain contaminating the soil and water bodies. Finally, these enter into food chain

causing serious problem to the living organisms.

3. Radio-isotopes:

Radio-isotopes are also prepared artificially either by nuclear fusion or by nuclear fission. If these radio-

isotopes are not properly handled, these emit radiations causing pollution.


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Effects of radiation pollution

Radiation damage

The biological damage resulting from ionizing radiations is generally termed as radiation damage. Large

amounts of radiation can kill cells that can dramatically affect the exposed organism as well as possibly its

offspring. Affected cells can mutate and result in cancer. A large enough dose of radiation can kill the

organism.

Radiation damage can be divided into two types: (a) somatic damage (also called radiation sickness) and

(b) genetic damage. Somatic damage refers to damage to cells that are not associated with reproduction.

Effects of somatic radiation damage include reddening of the skin, loss of hair, ulceration, fibrosis of the

lungs, the formation of holes in tissue, a reduction of white blood cells, and the induction of cataract in the

eyes. This damage can also result in cancer and death. Genetic damage refers to damage to cells

associated with reproduction. This damage can subsequently cause genetic damage from gene mutation

resulting in abnormalities. Genetic damages are passed on to next generation.

Radiation doses

A traditional unit of human-equivalent dose is the rem, which stands for radiation equivalent in man. At

low doses, such as what we receive every day from background radiation (< 1 m rem), the cells repair the

damage rapidly. At higher doses (up to 100 rem), the cells might not be able to repair the damage, and the

cells may either be changed permanently or die. Cells changed permanently may go on to produce

abnormal cells when they divide and may become cancerous. At even higher doses, the cells cannot be

replaced fast enough and tissues fail to function. An example of this would be “radiation sickness.” This is

a condition that results after high doses is given to the whole body (>100 rem). Nuclear explosions and

accidents in nuclear reactors are a serious source of radiation hazard. The effects of atomic explosions in

Nagasaki and Hiroshima are still not forgotten.

5. Air Pollution

Air is a mixture of gases - 78% nitrogen, 21% oxygen, 0.93 % Argon and 0.04% CO2, - with traces of

water vapor and various other components.

It may be noted that air cannot be pure because some gases like Sulphur dioxide, carbon monoxide, oxides

of nitrogen, emission from volcanoes and swamps, salt spray, pollens from plants etc., are continuously


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added to the air by natural processes. Thus, air is polluted when its natural composition is disturbed either

by natural or by man-made sources.

Source of Air Pollution:

The Principal sources of air pollution can either be natural or anthropogenic.

(a) Natural Sources:

The natural sources of air pollution are:

(i) Forest Fire,

(ii) Wind,

(iii) Soil Erosion,

(iv)Volcanic Eruption,

(v) Evaporation of volatile organic matter, and

(vi) Bacterial decomposition products.

(b) Anthropogenic Sources:

(i) Automobile Exhaust:

These contain carbon monoxide (CO), oxides of nitrogen and ethane. These gases are due to incomplete

combustion of petrol and diesel.

(ii) Industrial Exhaust:

The industries mainly Chemical Factories, Paper and Pulp, Sugar, Petroleum Refineries, Steel Plants etc.

are the chief air polluting agents. The industrial exhaust contain gases like CO, CO2, SO2, NO, NO2, N2O,

Cl2, F2, NH3, and particulate matters.

(iii) Release of organic substances : The processes like biological decomposition of organic matter,

seepage from natural gas and oil fields, volatile emission from plants, sewage gas etc. are the causes for

the release of organic substances like CH4, C2H6, C6H5NH2, C2H4 etc.


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(iv) Release of Chlorofluorocarbons (CFCs):

The chlorofluorocarbons are released to the atmosphere from air conditioners, refineries, pre cooler

systems of cold storage etc.

(v) Particulate Pollution:

Solid and liquid aerosols suspended in atmosphere are referred as particulate matters. These arise from

grinding of ores, spraying and soil erosion. Aerosols are chemicals, which are released into the air in the

form of vapors. For example lead containing gasoline fumes from automobiles, constitute the chief source

of lead contamination.

(vi) Agricultural Chemicals:

The agricultural chemicals like pesticides, insecticides, fungicides, herbicides etc. are also released into

the air as pollutants.

(vii) Explosives in War:

A number of poisonous gases are released in the atmosphere during the explosions of sophisticated

explosives in war.

(viii) Photochemical Smogs:

When different gases like SO2, NO, N2O, NO2 and un-burnt hydrocarbons are released into atmosphere,

these form photochemical smog by combining with dust and moisture.

(ix) Mining Activity:

During mining activities i.e. crushing and grinding of ores, a lot of particulate matters are released to

atmosphere.

Classification of Air Pollutants:

Air pollutants are of two types:

(1) Primary air pollutants;

(2) Secondary air pollutants.


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1. Primary air pollutants:

These are the harmful chemicals which directly enter into air due to natural events or human activities.

For example, when carbon containing substance is burnt, it will release CO2 and/or CO to atmosphere.

These gases directly entering into atmosphere influence the biosphere are termed as primary pollutants.

It is seen that there are mainly five primary pollutants which contribute together more than 90% of global

air pollution. These are namely, carbon monoxide (CO) nitrogen oxides (NO2), oxides of sulphur (SO2)

hydrocarbons (HC), and particulates.

Different primary pollutants, their sources and amounts, released to air are given in table 7.2.

2. Secondary Air-Pollutants:

These are the harmful chemicals produced in air due to chemical reaction in between two or more

components i.e. the reaction in between primary air pollutant and some components of air. Usually the

primary air pollutant suffers chemical changes in presence of H2O (v), O2 (g) and ultraviolet radiation of

sun to form secondary pollutants.

http://www.environmentalpollution.in/wp-content/uploads/2014/03/image25.png


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Some reactions showing conversion of primary pollutant to secondary pollutant are described

below:

Primary pollutant Reactant Secondary Pollution

1. CO2 + H2O →H2CO3 (Carbonic acid)

2. H2S + 2O2 →H2SO4 (Sulphuric acid)

3. SO2 + O2 →SO3,

SO3 + H2O →H2SO4 (Sulphuric acid)

4. NO2 + O2 →2N2Os

+ H2O →2HNO3 (Nitric acid)

5. HF (g) + H2O →HF (aq)

6. SiF6 + 2HF →H2SiF6

Important Air Pollutants:

1) Particulate matter

Particulates are the small solid particles and liquid droplets present in the atmosphere in fairly large

numbers. The presence of these particulates in air causes serious environmental consequences.


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Sources

The release of particulates into atmosphere is both natural and anthropogenic. The natural processes

include volcanic eruption, blowing of dust and soil by wind, spraying of salt and other solid particles by

the seas and oceans etc.

The contributions from manmade activities are: fly ash from power plants, melters and mining operations,

smokes from incomplete combustion processes etc. The incomplete combustion processes are fuel

combustion from stationary sources (wood, coal, oil, natural gas etc.), industrial processes and other

sources like forest fire, structural fires, agricultural burning etc.

Effects

i. Particulates of less than 1 µ reach alveoli of lungs and damage lungs tissues.

ii. Soluble aerosols get absorbed into blood from alveoli while the insoluble aerosols are carried to

the lymphatic stream and get deposited in the pulmonary, lymphatic depot point or lymp glands.

iii. Cause the blockage of stomata in plants and inhibit plant respiration

iv. Deposition of particulate on leaves prevents CO2 absorption and hence decreases the rate of

photosynthesis.

2. Nitrogen Oxide (NOx):

NOx exists as nitrous oxide (N2O), nitric oxide (NO), nitrogen trioxide (N2O3), nitrogen peroxide (NO2)

and nitrogen pentoxide (N2Os). Amongst all these nitrogen oxides, nitrogen peroxide (NO2) and nitric

oxide (NO) are the two main reagents causing air pollution. About 95% of NOx is released to the

atmosphere mainly as NO as remaining as NO2.

Sources

1. Combustion of coal, oil, natural gases and gasoline.

2. By-products of some chemical industries like HN03 am H2SO4.

3. Thermal power plants.


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4. Supersonic aircraft exhaust.

5. Nuclear explosion.

6. Manufacture of nylon intermediates.

Effects

i. NOx causes acid rain by reacting with atmospheric moisture giving acids like nitric acid (HNO3)

and nitrous acid (HNO2)

ii. NOx released to the atmosphere moves up and reacts with ozone layer causing its depletion. Such a

process allows the passage of UV radiation into earth surface.

iii. The presence of excess quantity of NO and NO2 induces smog formation and generates a number

of harmful species like free radicals, PAN (Peroxy acetyl nitrate).

3. Sulphur-dioxide (SO2)

Sulphur-dioxide is the second potent air pollutant as it accounts for 29% of the total weight of all

pollutants.

Sources

There are two sources of SO2

(1) Natural Source, and

(2) Anthropogenic source.

Natural processes like volcanic eruption provide 67% of the S02 pollution which is distributed all over the

globe. Anthropogenic source contribute about 33% of SO2pollution which is localized mainly in urban

areas.

Effects

i. It causes swelling of nasal system and stimulates mucus secretion.

ii. It causes lung cancer at high level.


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iii. Presence of SO2 in moisture and fog becomes more dangerous due to formation of H2SO4 and

H2SO3 which are 5 to 20 time more irritating than SO2 alone.

iv. It kills leaf tissues causing leaf necrosis.

v. It causes chlorosis and dwarfing when the concentration exceeds 1 ppm.

vi. It attacks marble, limestone, roofing state, electrical contacts, textiles and buildings.

4. Carbon monoxide (Co)

Sources

Natural process like volcanic action, electrical discharge during storm or lightening, seed germination,

marsh gas production etc. release small quantity of Carbon monoxide to the atmosphere. The significant

contribution of carbon monoxide is from anthropogenic activities (transportation, agricultural burnings

and industrial processes).

Effects

i. CO interferes with oxygen carrying function of hemoglobin by forming carboxy hemoglobin

complex and inhibits the mobility of oxygen to body organs.

ii. When CO concentration becomes 400-500 ppm, it leads to loss of fertility, premature birth,

spontaneous abortion and deformed babies in pregnant women.

iii. CO inhibits nitrogen fixing ability of bacteria when these are exposed to CO level of 2000 ppm for

33-38 hours.

5. Hydrocarbons:

In addition to different gases, a series of hydrocarbons are released to the atmosphere either through

natural processes or through human activities. These hydrocarbons sometimes behave like primary

pollutants and some other times induce the formation of other potent secondary pollutants.

Sources

Natural sources of hydrocarbon release into air includes emission from trees, liberation from anaerobic

decomposition of organic matter in presence of bacteria, liberation from domesticated animals etc. The


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major anthropogenic sources are: automobile exhaust, industrial processes like processing, storage,

transfer of products, incinerator and refuse burning and burning of coal and wood etc.

Effects

i. It has carcinogenic effects on lungs due to its swelling at higher concentration.

ii. Excess of hydrocarbon causes blocking or respiratory tract.

iii. Hydrocarbons retard the growth of plants and also cause chlorosis in plants.

Consequences of Air Pollution

1. Ozone Layer Depletion:

Ozone layer present in the stratosphere strongly absorbs UV radiation of 220-203 nm and thereby protects

life on earth from severe radiation damage. But due to continuous and non- interrupted release of

chloroflurocarbons, oxides of nitrogen etc. by the civilized world, the ozone layer is constantly depleted.

The reaction is medicated through a number of free radicals like CI+, CIO

+,

+ OH etc. and a number of

portent species like (O, NO, SO2 NO2 etc.)

2. Greenhouse gas effect

The green house is that body which allows short wavelength solar radiation to pass through it but does not

allow the long wavelength infrared radiation to escape. Due to rapid and unplanned industrialization the

gases like CO2, chlorofluorocarbons (CFCs), methane (CH4), nitrogen oxides (NOx), ozone (O3)/etc.

accumulate in the atmosphere. The layer of these gases behave like wall of a greenhouse and transmit

short wave solar radiations but does not allow the longer wavelength heat radiation (infrared) to be

reflected back into outer space. That is greenhouse is transparent to solar radiation but not to heat

radiation.

Thus, the greenhouse effect may be defined as the progressive warming up of the atmosphere at the

surface of earth due to blanketing of infrared radiation from the earth’s surface by the greenhouse gases.

The intensity of the effect increases in presence of dust, aerosols, etc.


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3. Somg

Smog is a combination of two words smoke and fog. Smoke is produced as a result of the incomplete

combustion of fuels. The smoke contains various gases and suspended particulate matter. In addition,

another substance responsible for smog formation is dust. Dust is nothing but small particle of solid matter

that can be carried in suspension. Dusts are produced from forest fires, automobile exhaust, industrial

combustion process, soil blowing by wind, ocean spray, mining areas, etc.

Dust combines with smoke and later with fog to produce ‘smog’, which appears in the form of cloudy

layer in the atmosphere. A thick cloud of smog is produced where smoke instead of escaping, the area to

outer atmosphere stays nearer to the surface due to temperature inversion.

Control of Air Pollution

The following control measures should be adopted in order to reduce the level of air pollutants in

environment.

i. Pollution from domestic fire should be controlled to the house holder’s use. Alternative methods

of the fuels like smokeless chullah should be used in order to increase the fuel efficiency and

reduce the emission of solid particulates.

ii. As the plants absorb mainly air polluting gases like CO2, there should be massive afforestation

programme in industrial areas and big cities.

iii. Setting of air quality standard for protection of environment and human health is highly essential.

Ventilation and air-conditioning should be introduced.

iv. More and more flyovers, bridges, bylanes, footpaths for pedestrians, steamers and ferry launches

and other modes of navigational metropolitans public transport systems should be developed with

a view to minimize the usage of individual auto vehicles and thereby smoke emissions. This will

ultimately lead to ecological and environmental preservation.

v. Environmental education and awareness programmes need to be institutionalized by incorporating

these in the essential activities of educational institutions.

vi. Use of unleaded petrol and diesel should be made compulsory.

vii. The use and production of CFCs should be banned with suitable substitute in order to check air

pollution.


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viii. The vehicular exhaust should be minimized by using control valves in the outlets of the exhaust

pipeline of the automobile.

Download - ENVR-252 : Envr. Pollution · PDF fileENVR-252 : Envr. Pollution 2 industrial effluents with toxic substances and sewage water with human and animal wastes pollute our water thoroughly

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