Lesson 17. INTRODUCTION AND CLASSIFICATION OF POLLUTION

Module 5. Environmental pollution

Lesson 17
INTRODUCTION AND CLASSIFICATION OF POLLUTION

17.1 Introduction

Pollution is defined as ‘an undesirable change in physical, chemical and biological characteristics of air, water and land that may be harmful to living organisms. The Pollution Control Board, defined pollution as unfavorable alteration of our surrounding, largely as a by-product of human activities.

17.1.1 Pollutant

Pollutant is a substance which causes pollution. Unlimited exploitation of nature has disturbed the ecological balance between living and non living components in the biosphere. The major environment pollutants are deposited matter, gases, metals, fluorides, acid droplets, agro chemicals, photo chemical accidents, radioactive waste and solid waste.

17.1.2 Classification of pollutants

Environment pollution is of many types like air pollution, water pollution, noise pollution, soil pollution, marine pollution, etc. In developing countries major source of environment pollutions are air pollution, water pollution and soil pollution.

1. On the Basis of Nature

Depending upon the nature of the pollutants and their interaction with environment process, the pollution caused by different agents can be classified into the following categories:
  1. Solid pollutants.
  2. Liquid pollutants
  3. Gaseous pollutants
  4. Pollution from Waste without Weight: This type of pollution is also known as pollution by energy waste; Wastes without weight may be of the following types:
  • Radio-active Substance: Despite of all possible precautions in the functioning and maintenance of nuclear reactors, it is seen that minute quantity of radio-active waste escapes out into the environment.
  • Heat
  • Noise
2. On the Basis of Decomposition
  1. Non-Degradable Pollutants: These are not broken down by the natural processes like action of microbes.
  2. Degradable Pollutants or Bio-degradable Pollutants: These are natural organic substances which can be decomposed, removed or consumed and thus, reduced to acceptable levels either by natural processes like biological or microbial action or by some engineered systems, like sewage treatment plants.
17.2 Air Pollution

Air pollution is the resultant of direct or indirect change in physical, chemical and biological characteristics of atmosphere, which mainly results from gases emission from industry, thermal power station, auto mobile and domestic combustions, etc.

17.2.1 Air pollutants
  • “Air Pollutant” can be defined as any solid, liquid or gaseous substance present in the atmosphere in high concentration more than prescribed limits that may be harmful to the living creatures.
  • Pollutants can be classified as primary and secondary pollutants.
  • Primary pollutants are carbon dioxide, nitrogen oxides, sulphur dioxide, carbon monoxide and CFC.
  • Secondary pollutants are acid rain and ozone.
17.2.2 Sources of air pollution

The sources of Air pollution are natural and man-made (anthropogenic).

17.2.2.1 Natural sources

The natural sources of air pollution are volcanic eruptions, forest fires, thunder storms, cyclones, typhoons, fog, biological decay, photochemical oxidation, deposition of dead matters, vegetation and animals etc. Radioactive minerals present in the earth crust are the sources of radioactivity in the atmosphere.

17.2.2.2 Man-made sources

Man made sources include industry, thermal power stations, industrial units, vehicular emissions, automobiles, farming practises, domestic equipments, nuclear weapons and test, etc.

17.2.3 Indoor air pollution

The most important indoor air pollution is radon gas. This is responsible for a large number of lung cancer deaths each year. These could be emitted from building materials like bricks, concrete, tiles etc. Many houses in the underdeveloped countries including India use fuels like coal, dung-cakes, wood and kerosene in their kitchens.

17.2.4 Air pollutants criteria

Major pollutants responsible for air pollution are: Sulfur dioxide (SO2), nitrogen oxides (NO2 and NO) , carbon dioxide (CO2) and carbon monoxide (CO), solid or liquid particulates (smaller than 10 µm).

17.2.5 Gaseous pollutants

Major gaseous pollutants are
  1. Sulfur dioxide (SO2)
  2. Nitrogen oxides
  3. Carbon monoxide and carbon dioxide
17.2.6 Ozone, photochemical smog hydrocarbon and fluorocarbons
  • Ozone (O3) is outcome of chemical reaction between nitrogen dioxide and volatile organic components. Ozone layer in stratosphere protects from harmful UV rays via absorbs ultra violet radiation. Ozone is the key component of photochemical smog.
17.1

Fig. 17.1 Photochemical smog (courtesy: users.rcn.com)
  • Nitric oxide in the atmosphere with ozone causes elimination of ozone layer. Thinning or hole of ozone layer can cause skin cancer .It is estimated that 1% reduction in ozone increases UV radiation by 2%.
  • The main hydrocarbon are benzene, venzbyrene and methane and it emerges from motor vehicles. Hydrocarbons combine with nitrites under UV radiation and form other pollutants known as photochemical products such as Aldehydes, Ozone Pans, Olifins, etc.
  • On the other hand fluorocarbons at higher level are toxic and creates problem of fluorosis, the source of fluoride in the environment are industrial process of phosphate fertilizers, aluminum, fluorinated plastics, uranium and other metals
17.2.7 Ozone layer depletion

Earth's stratospheric ozone layer, which contains about 90 percent of the ozone in the atmosphere, makes the planet habitable by absorbing harmful solar ultraviolet (UV) radiation before it reaches the planet's surface. UV radiation at higher levels it can cause skin cancer and immune system suppression.depletion of ozone layer was identified during 1970’s.this is mainly happened due to more release of manmade industrial chemicals called chlorofluorocarbons (CFCs), which at the time were widely used as refrigerants, in aerosol sprays, and in manufacturing plastic foams. CFC molecules are inert in the troposphere, so they are transported to the stratosphere, where they photolyze and release chlorine (Cl) atoms. Chlorine atoms cause catalytic ozone loss by cycling with ClO (Fig. 17.2).
Figure
FIg. 17.2 Chlorine-catalyzed ozone depletion mechanism (courtesy : learner.org)

17.2.8 Particulate matters
  • Discrete mass of any material which exist as a solid or liquid droplets and microscopic, sub microscopic dimension is known as particulate matter(PM).The main source of particulate matter are fuel combustions and industrial operations like mining, smelting ,polishing ,pesticides, fertilizer and chemical fertilizers,
  • Particulate matters can have adverse effect on human health and are generally less than 10 µm size.
17.2.9 Effects of air pollution
  • Nitrogen dioxide has more harmful effect as compare to nitric oxide. Exposure to NO2 causes resistance in air movement in lungs.
  • Nitric oxide and carbon monoxide can combine haemoglobin to reduce oxygen caring capacity of blood.
  • These pollutants affect plants by entering through stomata. Particulate pollutants affect the photo synthetic activity which may damage the plants and can affect productivity. Air pollutants can enhance the acidity of water resources therefore can adversely affect aquatic life. Material can be damaged due to effect of pollutants when exposed to the environment
17.2.10 Prevention and control of air pollution

Steps to control and prevention of air pollution
  • Engineers should consider the possibility by changing the manufacturing process. For example to minimise the high level of lead in air simple solution is to eliminate lead in gasoline (supply of unleaded petrol)
  • Use CNG (compressed natural gas) as an alternative fuel .
  • Use gas additives to improve combustions.
  • Control devices: The following items are commonly used as pollution control devices by industry or transportation devices. They can either destroy contaminants or remove them from an exhaust stream before they are emitted into the atmosphere.
  1. Mechanical collectors (dust cyclones, multicyclones)
  2. Electrostatic precipitators An electrostatic precipitator (ESP), or electrostatic air cleaner is a particulate collection device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge.
  3. Baghouses Designed to handle heavy dust loads, a dust collector consists of a blower, dust filter, a filter-cleaning system, and a dust receptacle or dust removal system.
  4. Wet scrubber is a form of pollution control technology. The term describes a variety of devices that use pollutants from a furnace flue gas or from other gas streams.
17.3 Noise Pollution

Noise can be defined as wrong sound in wrong place at wrong time. Sound at undesirable level creates pollution because it cause discomfort to the people. There are two basic properties of sound i.e. loudness and frequency. Loudness is strength of sensation of sound perceived by individual and is measured in terms of decibel, where as frequency of sound defined as number of vibrations per second and measured as hertz (Hz).

Human ear is sensitive to frequency between 20-20000 Hz. whereas best range of hearing is 2000-10000 Hz

17.3.1 Sources of noise pollution

Major sources of noise pollution are industries, transportation, and community, religious and cultural activities. Loudspeaker and amplifiers used in different occasions is another source of noise pollution

17.3.2 Effects of noise pollution
  • Noise pollution is harmful to body and mind. It causes irritation and headache. It may cause number of physiological disorder like neurosis anxiety, insomnia, hipper tension, behaviour and emotional stress.
17.3

Fig. 17.3 Effects of Noise pollution

17.3.3 Control of noise pollution
  • Eliminate the noise at source by use of silencing devises.
  • Control the noise transmission level using sound absorbers and acoustic tiles.
  • Using self precaution measures such as ear plugs and earmuffs.
  • Creating buffer zone between high noise level zone and residential areas by afforestation.
  • Taking strict statuary measure to govern the noise level in sensitive areas like schools, hospitals, etc
17.4 Water Pollution

Water pollution is referred as a presence of foreign substances or impurities which can contribute to health hazards by lowering water qualities and making it unfit for use.

17.4.1 Sources of water pollution

Main sources of water pollution are
  • Pollution due to decaying of plants ,animals and organic matter in water bodies
  • Addition of soil-silt washings, insecticides, herbicide and fungicides are agricultural sources can be water pollution.
  • Ore washing, inert suspended solid and soluble toxic materials.
  • Sewage obtained from domestic promises, institutions and industrial buildings are main sources of pollution of water in cities.
  • Industrial Effluents are one of the important agents of water pollution.
  • Accidental spillage of chemical or petroleum products also contributes towards water pollution.
  • Ground water pollution with arsenic, fluorides and nitrites which are poisonous in nature are posing serious health problems.
  • Major point sources of water pollution are industries, power plants, underground coalmines, offshore oil wells etc.
17.4.2 Water pollutants

Major water pollutants are
  1. Organic pollutants: Water carrying organic pollutants have decreased level of oxygen and such organic pollutants promote disease causing agent.
  2. Inorganic pollutants: Inorganic pollutants include inorganic salts, metallic compounds, trace elements and organ metallic compounds.
  3. Thermal pollutants: Main source of thermal pollutants are coal water plants, nuclear water plants and other industrial process.
  4. Sediments
  5. Radioactive materials
17.4.3 Effects of water pollution
  • Sewage is an excellent medium for growth of pathogens which are responsible for spread of many diseases.
  • Water pollution makes the drinking water unfit for domestic use. Industrial effluents have harmful effect on living organism and can lead to death.
  • Radioactive substances present in the water may cause cancer, eye, cataract and DNA breakage; it may also destroy biological immune system.
  • Residual toxic compounds of pesticides may cause many health problems.
  • Sediments reduce the light penetration in water which lowers the photosynthetic activity of aquatic plants.
  • Toxic substances observed into tissues from polluted water can cause injuries leading death of the plant.
  • Eutrophication: It is the ecosystem response to the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system. One example is the "bloom" or great increase of phytoplankton in a water body as a response to increased levels of nutrients. Negative environmental effects include hypoxia, the depletion of oxygen in the water, which induces reductions in specific fish and other animal populations. Eutrophication can be human-caused or natural. Untreated sewage effluent and agricultural run-off carrying fertilizers are examples of human-caused eutrophication. However, it also occurs naturally in situations where nutrients accumulate (e.g. depositional environments), or where they flow into systems on an ephemeral basis.
17.4.4 Prevention and control of water pollution

It is said that prevention is better than cure. Strict legislation can help to reduce water pollution and policy maker should formulate strategies to prevent water pollution sources.
Following measures can help to control water pollution
  • Prevent generation of pollutants at first place. Control the pollutants to minimise its effects on water pollution.
  • Domestic and industrial waste water should be disposed off only after treatment.
  • Enforce pollution control laws strictly.
  • Use treatment plants to clean discharged industrial waste water and utilise it for irrigation purpose.
  • Discourage excess use of pesticide and insecticide.
  • Water bodies should be regularly cleaned of aquatic weed and wild plants
  • Create public awareness regarding water pollution
  • Afforestation will help to reduce the pollution and water erosion
  • Use methods of biological nitrogen fixation to improve soil health and adopt integrated pest management to minimise chemical contamination in water.
17.5 Thermal Pollution

Thermal pollution, also known as heat pollution, is releasing of heat in air or water causing undesired changes to environment .It can be both natural as in case of forest fires and heat emanating from volcanoes, or it can be from manmade sources.

17.5.1 Sources of thermal pollution

There are several discrete sources of Thermal Pollution
  1. Thermal Power Plants
  2. Industries
  3. Release of domestic sewerage
  4. Nuclear Sources
17.5.2 Effects of thermal pollution
  • Solubility of oxygen has inverse proportionality relationship with temperature. That is, with increase in temperature of water bodies, oxygen content of water decreases. Dissolved oxygen is essential component for survival for aquatic life.
  • High surface water temperature also has detrimental effect on penetration of oxygen in deep cold water. Thus, it also affects on deep sea species.
  • Increase in water temperature has harmful effect on population of aquatic species who are sensitive to temperature changes .On the other hand it propagates temperature change tolerant species. Thus, adversely affecting balance of the aquatic ecosystem.
17.5.3 Control of thermal pollution

17.5.3.1 Cooling towers

Water from water body affected is directed pumped towards the cooling tower having condensers, usually with temperature control. After bringing water temperature to desire level, it is returned to the source. Use of condenser makes this method expensive.

17.5.3.2 Cooling ponds

These are the most cost effective way to tackle thermal pollution. In this method, heat of heating effluents on surface of the water is dissipated in atmosphere.

17.5.3.3 Artificial lake

These are the man made bodies of water .Effluents are discharged into the lake and heat is gradually lost to the atmosphere through evaporation.

17.6 Marine Pollution

Marine Pollution refers to degradation of marine ecosystem by discharge of pollutants in large water bodies, in particular the sea and the oceans.

17.6.1 Sources of marine pollution
  • Major concern for Marine ecosystem is Oil Spills. Origin of oil spills can be attributed to natural phenomenon and also due to human activities. Natural sources are oil seeps at geographical fault lines in the ocean floors .Human activities leading to oil spills include leaking of oil tankers, well blowouts, drilling oil rigs, etc.
  • Addition of pollutants to sea by rivers flowing into seas.
  • Addition of pollutants due to human activities such as industrial activities, agriculture practices and tourism along coastline.
  • Over exploitation of aquatic resources such as excessive fishing in particular region can adversely affect marine ecology.
  • Mining of minerals at coast and sea-bed near coast results in defiling the marine ecological system.
17.6.2 Control of marine pollution
  • Reducing the cases of oil spills due to leaking of tankers and well blowouts.
  • Use of effective measures to control oil spills such as use of sinking material such as chalk and dispersants.
  • Developing no fishing zones in areas where aquatic life has been adversely affected due to excessive fishing.
  • Checking addition of toxic waste to rivers flowing into seas.
  • Banning mining activities in and around coastal regions and on sea bed.
  • Minimizing human activities in coastal regions adjoining areas sensitive marine ecosystem such as coral reefs.
17.7 Soil Pollution

Soil pollution is contamination of upper layer of earth’s crust by chemicals or other toxic substances that lead to either reduction in fertility of soil in terms of crop production or whose addition results in detrimental effects to soil microorganism, insects, plant life and organism who consume those plants.

17.7.1 Sources of soil pollution
  • Industrial Wastes.
  • Improper Use of fertilizers, insecticides, pesticides, etc.
  • Urban waste consisting of solid waste and sludge also contribute heavily towards soil pollution.
  • Radioactive Pollutants
17.7.2 Effects of soil pollution
  • Industrial effluents containing toxic chemicals dumped on land cause soil pollution and enter in food chain, which has adverse effect on human health .
  • Solid waste dumped on land cause disruption in everyday life and destroys natural beauty of the landscape.
  • Dumped waste and organic waste give rise to foul odour.
  • Pathogenic bacteria cause diseases like cholera.
  • Biomagnification: Biological magnification also known as bioamplification, is the increase in concentration of a substance that occurs in a food chain. Biological magnification refers to the process whereby certain substances such as pesticides or heavy metals move up the food chain, work their way into rivers or lakes, and are eaten by aquatic organisms such as fish, which in turn are eaten by large birds, animals or humans. Bioaccumulants are substances that increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted. There is good evidence that DDT, DDE, PCBs, toxaphene, and the organic forms of mercury and arsenic do biomagnify in nature. e.g endosulphon banned in some states due to overuse on cashewnut plantations.
17.7.3 Control measures of soil pollution
  • Industries should be banned from dumping toxic chemicals on agricultural land and proper disposal methods should be used.
  • Government should provide subsidies, concessions and tax exemption to companies that use recycled raw materials.
  • Application of organic manures and pesticides should be encouraged in agriculture.
  • Plastic carry bags should be replaced by jute bags.
  • Public awareness campaigns should be organized.
  • Solid waste from urban and industrial areas should be disposed of using proper techniques.
  • Trees and grass should be grown to check soil erosion.
17.8 Nuclear Hazards

Radioactive (nuclear) pollution is a special form of physical pollution related to all major life-supporting systems – air, water and soil. It is always convenient to discuss radioactive pollution separately because its nature of contamination is different from other types of pollution. Its effects are also of special kinds.

17.8.1 Sources of nuclear pollution
  1. Source of energy of Sun and other stars is nuclear energy (nuclear fusion reaction taking place in the core), therefore the cosmic rays emanating from sun and other stars are primary source of nuclear hazards.
  2. Use and testing of nuclear weapons leads unprecedented loss to life and property as was the case in Second World War.
  3. Natural emission of radiation from radioactive isotopes, such as Uranium present in earth’s crust.
  4. Mining, processing and extraction of radioactive ores.
  5. Use of radioactive isotopes in nuclear reactors.
  6. Problem associated disposal of nuclear waste from nuclear reactors.
  7. Accidental leakages in nuclear power plants and other nuclear facilities.
17.8.2 Effects of nuclear hazards
  • Effects of nuclear hazards are prolonged and can haunt civilizations for year and can have adverse effect on generations to come.
  • Exposure to nuclear radiations can affect genetic make-up by breaking the chemical bonds that hold the DNA together. Thus the effect can be transferred to future generations.
  • Nuclear explosion and nuclear weapons can cause mass destruction to life and property of a scale unprecedented in history of mankind.
  • Nuclear hazards are transferred in food chains from bottom to top with transfer of nuclear elements from prey to the predator.
  • Continuous exposure to radiation can lead to cancer.
17.8.3 Nuclear disaster

Hiroshima and Nagasaki atomic bombing in World War-II(1945) & Chernobyl Nuclear Power Plant Disaster (1986) and meltdown of nuclear reactors in Fukushima Nuclear Power Plant in March 2011 are examples of nuclear disaster that can be cited from history that have caused mass destruction to life and property.

17.8.4 Nuclear hazard control
  • Nuclear Power plants and research facilities should be set up after careful evaluation in less inhabited areas.
  • Nuclear Power Plants must be carefully designed to minimize risks of leakage.
  • Strict vigilance bodies should be constituted and laws should be enforced to ensure nuclear safety.
  • Summits and conferences must be organized to facilitate the evolution and exchange of new research and ideas in field of nuclear safety.
  • Efficient nuclear waste disposal mechanism should be evolved.
  • Preventive measures must be taken to minimize risks associated with occupation connected to processing of nuclear material.
  • Disarmament of nuclear weapons must be strongly advocated in International Diplomacy
Last modified: Friday, 5 October 2012, 9:20 AM