1. Pollution
n Pollution is defined as an undesirable change in physical, chemical or biological characteristics of air, land, water or soil.
n Pollutants are the agents which bring about an undesirable change in the properties of air, water and soil.
n The Government of India has passed the Environment (Protection) Act, 1986 to protect and improve the quality of environment. (air, water and soil)
2. Air Pollution
n Any undesirable change in the physical, chemical and biological characteristics of air that exert adverse effects on living beings is defined as air pollution.
(i) Causes
(a) Smoke from forest fires, volcanic eruptions, etc.
(b) Decomposition of garbage resulting in release of unwanted gases into the atmosphere.
(c) Burning of fossil fuels in automobiles and industries release particulate and air pollutants.
(d) Use of leaded petrol.
(e) Gaseous wastes or particulate matter as by-products of various industries.
(f) Smoke stacks of thermal power plants, smelters and other industrial release, particulate and gaseous air pollutants with harmless gases like N2, O2, etc.
(ii) Air pollutants
n Air pollutants can be classified into two groups:
(a) Particulate pollutants, e.g., metallic particles, dust particles, soot, aerosol and smoke.
(b) Gaseous pollutants, e.g., carbon monoxide (CO), nitrogen dioxide (NO2), hydrogen sulphide (H2S), sulphur dioxide (SO2), etc.
(iii) Harmful effects
n The harmful effects of air pollutants depend on (i) concentration of pollutants, (ii) duration of exposure, and (iii) the organism being exposed.
(a) Carbon monoxide causes giddiness, headache, decreased vision, cardiovascular malfunction and asphyxia.
(b) Hydrogen sulphide causes nausea, eye and throat irritation.
(c) Sulphur dioxide causes respiratory tract diseases like asthma, bronchitis, cancer, emphysema, etc.
(d) In plants, air pollution reduces growth and yield and leads to premature death.
(e) Fine particulates cause breathing and respiratory problems, irritation, inflammation and damage to the lungs.
(iv) Control methods of air pollution
(a) Electrostatic precipitator (ESP)
l It is an electrical device used to remove particulate matter present in the exhaust of thermal power plant.
l More than 99% particulate matter can be removed by this method.
l ESP has electrode wires and a stage of collecting plates.
l Electrode wires are provided with an electric current of several thousand volts, which produces a corona that releases electrons.
l These electrons attach to dust particles and give them a negative charge within a very small fraction of a second.
l Collecting plates are earthed so that they attract charged dust particles.
l The velocity of air passing through plates is slow enough to allow the dust particles to fall.
n Limitations/Disadvantages: Very small particulate matters are not removed by these precipitators.
(b) Scrubber
l It is used to remove gases like sulphur dioxide from industrial exhaust.
l The exhaust is passed through a spray of water or lime.
l Water dissolves gases and lime reacts with sulphur dioxide to form a precipitate of calcium sulphate and sulphide.
(c) Catalytic converters
l These are fitted into automobiles for reducing emission of poisonous gases like NO2 and CO.
l They have expensive metals like platinum–palladium and rhodium as catalysts.
l As the exhaust emission passes through catalytic converter, nitric oxide splits into nitrogen and oxygen; carbon monoxide is oxidised to carbon dioxide and unburnt hydrocarbons get burnt completely into CO2 and H2O.
l Motor vehicles fitted with catalytic converter should use unleaded petrol as lead in petrol inactivates the catalyst.
(v) Control of air pollution in Delhi
n In 1990’s Delhi ranked 4th among 41 most polluted cities of the world. A Public Interest Litigation (PIL) was filed in the Supreme Court.
l All buses of Delhi were converted to run on CNG by the end of 2002 as per the directives of the Supreme Court.
l Advantages of CNG over diesel/petrol:
(a) CNG burns most efficiently without leaving any unburnt remnant behind.
(b) CNG is cheaper than petrol or diesel.
(c) CNG cannot be siphoned off by thieves and adulterated like petrol or diesel.
l Some other steps to reduce vehicular pollution:
(a) Phasing out of old vehicles.
(b) Use of unleaded petrol.
(c) Use of low-sulphur petrol and diesel.
(d) Use of catalytic converters in vehicles.
(e) Applying stringent pollution level norms for vehicles.
(f) Opting for car pooling whenever possible.
(g)Promoting public transport by Government of India to cut down vehicular pollution.
Auto Fuel Policy
(a) Euro II norms were stipulated to control sulphur content at 350 ppm in diesel and 150 ppm in petrol and aromatic hydrocarbons are to be contained at 42%.
(b) Goal being to reduce sulphur to 50 ppm in petrol and diesel and bring down to 35%.
(c) According to it, all automobiles were to meet the Euro III emission specifications in eleven Indian cities by April 1, 2005 (Delhi, Mumbai, Kolkata, Chennai, Bangalore, Hyderabad, Ahmedabad, Puna, Surat, Kanpur, Agra).
(d) These eleven new cities have maintained the Euro IV norms since April 1, 2010.
(e) Rest of the country have met Euro III norm complaint vehicles by 2010.
n Air (Prevention and Control of Pollution) Act, came into force in India in 1981, but was amended in 1987 to include noise as an air pollutant.
3. Noise Pollution
n Noise is defined as undesired high level of sound.
(i) Causes
(a) Loudspeakers, music systems and TV, used for entertainment.
(b) Jet planes and rockets (release 150 dB or more sound)
(c) Industrial noises
(d) Social functions
(e) Crackers, detonations
(ii)Harmful effects (Psychological and Physiological disorders)
(a) Sleeplessness
(b) Stress
(c) Increased rate of heartbeat and hypertension
(d) Breathing problems
(e) Damage of ear drums impairing hearing ability permanently (by the sound of jet plane/rocket or chronic exposure to sound).
(f) Gastric problems—nausea
(g) Emotional disturbance
(iii) Control methods
(a) Industrial noise can be reduced by using sound-absorbent materials or by muffling noise.
(b) Delimitation of horn-free zones around hospitals and schools.
(c) Stringent laws should be laid for permissible sound levels of crackers and loudspeakers.
(d) Setting timing after which loudspeakers cannot be played.
4. Water Pollution
n Water pollution is defined as any undesirable change in the physical, chemical and biological properties of water that may affect the human beings and domestic species.
n The Government of India has passed the Water (Prevention and Control of Pollution) Act, 1974, to safeguard our water resources.
Sources of Water Pollution and its Effects on Living Organisms:
(i) Domestic sewage
n It includes everything that comes from residential area to common public sewage system.
n Domestic sewage contains
— Suspended solids, e.g., sand, silt and clay.
— Colloidal materials, e.g., faecal matter, bacteria, paper and cloth fibres.
— Dissolved materials, e.g., nitrates, ammonia phosphate, sodium, calcium salt.
n Domestic sewage mainly contains biodegradable organic wastes which are readily decomposed with the help of decomposers.
n It is possible to estimate the amount of organic matter in sewage water by measuring Biological Oxygen Demand.
(ii) Industrial wastes
n Industries like petroleum, paper manufacturing, metal extraction, processing, etc., release waste water containing heavy metals like mercury and many organic compounds.
n Mercury and DDT are well known for biological magnification.
n Biological magnification or biomagnification is defined as increase in concentration of toxicants at successive trophic levels of a food chain.
n Toxic substances cannot be metabolised or excreted, therefore they get accumulated in an organism and passed on to higher trophic levels.
n Effects of DDT accumulation in birds: Calcium metabolism in birds is disturbed, which results in thinning of eggshell their, premature breaking and this leads to decline in bird population.
5. Some Important Terms
(i) Eutrophication
l It is defined as the natural aging of a lake by biological enrichment of its water.
l Water in a young lake is cold and clear to support life.
l With time, it is enriched with nutrients like nitrogen and phosphorus by streams draining into it.
l This encourages growth of aquatic life—plant and animal life.
l Organic remains deposit at the bottom of the lake and with time makes the water warmer and shallower.
l Marsh plants take root in the shallows and begin to fill in original lake basin.
l Eventually, floating plants develop in the lake, finally converting it into land.
l According to climate, size of the lake and other factors, natural ageing of lake may span up to thousands of years.
l The accelerated aging of lakes due to sewage, agricultural and industrial wastes is called cultural or accelerated eutrophication.
l Prime contaminants are nitrates and phosphates (plant nutrients) that overstimulate algal growth. This causes unsightly scum, unpleasant odour, etc. Which depletes the amount of dissolved oxygen. Other pollutant may also poison fish, whose decomposing remains further depletes the dissolved O2 and thus choke a lake to death.
Heated (thermal) waste waters flowing out of electricity generating units like thermal power plants also act as pollutants.
l Effect: (i) Eliminate or reduce number of organisms sensitive to high temperature.
(ii) Enhance growth of plant and fish in extremely cold areas.
(iii) Cause damage to indigenous flora and fauna.
(ii) BOD (Biochemical Oxygen Demand)
l The amount of oxygen required for microbial breakdown of biodegradable organic matter is called BOD.
l It is higher in polluted water and lesser in drinking water.
l Microorganisms use lot of oxygen for degradation of organic matter and thus there is sharp decline in dissolved oxygen downstream from point of sewage discharge. This causes mortality of fish and other aquatic life.
(iii) Algal bloom
l Domestic sewage contains nutrients like nitrogen and phosphorus which favour the excessive growth of planktonic (free-floating) algae called as algal bloom.
l Algal bloom causes fish mortality and deterioration of water quality.
l Some algae are toxic to humans and animals as well.
l Water hyacinth (Eichhornia crassipes), the world’s most problematic aquatic weed, also called “Terror of Bengal”, grows abundantly in eutrophic water bodies and imbalances water ecosystem.
l Eichhornia was introduced into India for its lovely mauve coloured flowers but caused havoc due to excessive growth that caused blockage in waterways as well.
6. Integrated Waste Water Treatment
l In the town of Arcata, situated on northern coast of California, an integrated waste water treatment process was developed with the help of biologists from Humboldt State University.
l The cleaning occurs in two stages:
(i) The conventional sedimentation, filtration and chlorine treatments are given. The treated water still contains lots of heavy metals and other dangerous pollutants.
(ii) Biologists developed series of six connected marshes over 60 hectares of marshland. Appropriate plants, algae, fungi and bacteria were grown in this marshland and these life forms neutralise, absorb and assimilate the pollutants and purify the water naturally.
(iii) Marshes also constitute a sanctuary, with high level of biodiversity in the form of fish, animals and birds that now reside there.
l Citizens group called Friends of the Arcata Marsh (FOAM) are responsible for the upkeep and safeguarding of this project.
l ‘Ecosan’ toilets have been developed in areas of Kerala and Sri Lanka for ecological sanitation.
l Advantages of ecological sanitation:
(i) It is a practical, hygienic and efficient method of human waste disposal.
(ii) It is cost effective.
(iii) Human excreta can be recycled into natural fertiliser to replace chemical fertiliser.
7. Solid Wastes
l These are discarded solid materials which are produced due to various human activities.
l Solid wastes can be biodegradable, recyclable or non-biodegradable.
l Solid wastes can be of the following types:
(i) Municipal solid wastes: Wastes from homes, offices, schools, hospitals, etc., that are collected and disposed by the municipality which generally consists of paper, leather, textile, rubber, glass, etc.
(ii) Industrial wastes: The wastes like scraps, fly ash, etc., generated by industries.
(iii) Hospital wastes: Hazardous wastes containing disinfectants and other harmful chemicals, pathogenic microbes, generated by hospitals.
(iv) Electronic wastes (e-wastes): These are the damaged electronic goods and irreparable computers.
(v) Polystyrene and plastic packaging, used for fruits, vegetables, biscuits, milk, etc.
8. Methods of Solid Waste Disposal
(i) Open burning: Municipal waste is reduced by burning in open dumps but the unburnt waste serve as the breeding ground for rats and flies.
(ii) Sanitary landfills: Wastes are dumped in a depression or trench after compaction and covered with dirt. But seepage of chemicals from these landfills can pollute underground water resources. Landfills are also getting filled.
(iii) Rag-pickers and kabadiwallahs: Wastes are collected and separated out into reusable or recyclable categories.
(iv) Natural breakdown: The biodegradable materials are kept into deep pits in the ground for natural breakdown.
(v) Recycling: E-wastes can be recycled in specifically built factories or manually to recover important metals like copper, iron, silicon, nickel and gold but in eco-friendly manner. Recycling in developing countries involve manual participation, exposing workers to toxic substances present in e-waste.
(vi) Incineration: Majority of e-wastes generated in developed world is exported to developing world (mainly China, India, Pakistan) where they are incinerated. Incinerators are crucial for disposal of hospital wastes.
Remedy for Plastic Waste
l A fine powder of recycle modified plastic is called polyblend. Polyblend has been mixed with bitumen to lay roads in Bangalore. Polyblend was made by company of Ahmed Khan who had been producing plastic sacks for 20 years.
l Polyblend enhanced bitumen’s water repellent properties and helped increase the life of road.
l Against the cost of ™ 0.40/kg for plastic waste, Ahmed Khan now offers ™ 6/kg.
9. Soil Pollution
n Undesirable changes in soil profile affecting its productivity is called soil pollution.
(i) Causes
l Chemical seepage from industries.
l Inorganic fertilisers and pesticides, herbicides, etc.
(ii) Harmful effects
l Non-target organisms in the soil are killed.
l Soil becomes infertile.
l Pesticides can result in biomagnification.
l Eutrophication.
(iii) Control methods
(a) Safe disposal of industrial wastes.
(b) Organic farming: It is a cyclical, zero-waste procedure where waste products from one process are cycled in as nutrients for other processes, allowing maximum utilisation of resource and increasing the efficiency of production.
Case Study of Organic Farming
l Ramesh Chandra Dagar from Sonipat is making maxmium use of resources and his work includes bee-keeping, dairy management, water harvesting, composting and agriculture in a chain of processes that support each other and allows economical and sustainable venture.
Advantages of Organic Farming
l Chemical fertilisers are not required because cattle excreta is used as manure.
l Crop waste is used for making compost which is used as natural fertiliser.
l Compost generates natural gas which is used for energy needs on farm.
l Dagar has created ‘Haryana Kisan Welfare Club’ with membership of 5000 farmers.
10. Radioactive Pollution
n Nuclear energy was assumed to be a natural, non-polluting way of electricity generation till the incidents at Three Mile Island and Chernobyl. It is now considered as the most potent pollutant.
(i) Causes
l Leakage of radioactive materials from power plants.
l Unsafe disposal of radioactive wastes.
(ii) Harmful effects
l Radiations from nuclear wastes cause mutations at a very high rate.
l In high doses, nuclear radiations are lethal.
l In low doses, radiations cause disorders and cancer and hence is a potent pollutant.
(iii) Disposal of radioactive waste
l Nuclear waste should be pre-treated and stored in shielded containers and then buried about 500 m deep below earth’s surface. This method is meeting stiff opposition.
11. Greenhouse Effect
l The phenomenon of keeping the earth warm due to presence of certain gases (CO2, NO2, CH4, CFC’s) in the atmosphere is called greenhouse effect.
l One-fourth of the incoming solar radiation is reflected by the atmospheric gases and clouds and only half of the incoming solar radiation falls on the earth’s surface, heating it. Of this, only a small portion is reflected back.
l Greenhouse gases (CO2, CH4, N2O, chlorofluorocarbons or CFCs) allow the solar radiations to enter but prevent the escape of heat radiations of longer wavelength.
l The absorbed radiations again come to earth’s surface and heat it up. This cycle is repeated many times, considerably heating the Earth.
l Greenhouse gases absorb long wave (infrared) radiation from earth and emit it again towards the earth. Cycle continues till the earth’s surface has no long wave radiation to emit.
l CO2 and methane are called as Greenhouse gases because they are responsible for the greenhouse effect.
12. Global Warming
n The gradual continuous increase in average temperature of surface of the Earth as a result of increase in concentration of greenhouse gases is termed as global warming.
(i) Cause
l Increase in the level of greenhouse gases (CO2, methane, etc.) in the atmosphere. These gases allow the heat waves to reach earth but prevent their escape and thus the earth becomes warm.
(ii) Effects
l The temperature of the earth has increased by 0.6°C in the last three decades, which will lead to changes in precipitation patterns.
l Rise in temperature leads to deleterious changes in environment resulting in odd climatic changes called El Nino effect.
l The rise in temperature will lead to the increased melting of polar ice caps which will cause the rise in sea level and many coastal areas will be submerged.
l Increased temperature will lead to increased weed growth, eruption of diseases and pests. Thus, crop productivity will decrease.
(iii) Control of global warming
l Global warming can be controlled by:
(a) Reducing deforestation
(b) Planting trees (afforestation)
(c) Slowing down the growth of human population
(d) Reduction of emission of greenhouse gases into the atmosphere
(e) Cutting down use of fossil fuels
(f) Improving efficiency of energy usage.
(g) International initiatives requited to reduce emission of greenhouse gases into atmosphere.
13. Ozone Depletion in the Stratosphere
n Ozone is of two types:
(i) ‘Bad’ ozone: formed in troposphere and is harmful to plants and animals.
(ii) ‘Good’ ozone: formed in stratosphere and absorbs harmful UV radiations from the Sun.
n The thickness of ozone is measured in Dobson units (DU).
(i) Formation of ozone
l Nascent oxygen combines with molecular oxygen (O2) to form ozone by the action of UV rays.
l Ozone is degraded into molecular oxygen in the stratosphere by UV action to maintain a balance between production and degradation.
(ii) Cause of ozone depletion
(a) Ozone degradation has increased due to chlorofluorocarbons (CFCs).
(b) CFCs are used as refrigerants, react with UV rays in stratosphere to release chlorine atoms.
(c) Chlorine atoms act as catalyst to degrade ozone and release molecular oxygen,
(i) CFCl3
(ii) CFCl2
(iii)
(iv)
(d) CFCs have permanent and continued effect as chlorine atoms are not consumed.
(e) Over the Antarctic region, there has been thinning of large area of ozone layer that has resulted in formation of ozone hole.
(iii) Harmful effects
(a) UV radiations of wavelength shorter than UV-B are almost completely absorbed by Earth’s atmosphere.
(b) UV-B rays damage DNA and proteins of living organisms causing mutation.
(c) It causes skin aging, skin cell damage and skin cancers.
(d) UV-B rays are absorbed by human eye and in high dose, they cause inflammation of cornea. This is called snow-blindness cataract and it may damage cornea permanently.
(iv) Control of ozone depletion
(a) An international treaty, Montreal Protocol, was signed at Montreal, Canada, in 1987 to curb the emission of ozone depleting substances.
(b) More protocols have been laid down in controlling emission of CFCs and other ozone depleting chemicals.
14. Degradation by Improper Resource Utilisation and Maintenance
(i) Soil erosion and desertification
l Development of fertile top soil takes centuries.
l The fertile top-soil is removed by human activities like over-cultivation, unrestricted grazing, deforestation and poor irrigation practices.
l This leads to formation of arid patches of land.
l These large barren patches when left for a long time, form deserts.
l Desertification has become a major problem due to increased urbanisation.
(ii) Water logging and soil salinity
l Water logging in soil results from irrigation without proper drainage of water.
l This affects the plants and draws salts to the soil surface.
l The salt is either deposited as a layer on land surface or collects at roots of plants.
l Increased salt concentration damages agriculture.
l This is one of the problems arising due to Green Revolution.
15. Deforestation
n Deforestation is defined as the conversion of forested areas to non-forested area.
n Removal of forest areas to fulfil the need of growing human population is called deforestation.
n Almost 40 per cent forests have been lost in the tropics and 1 per cent forests in the temperate region.
n In India, at the beginning of the twentieth century, forests covered about 30 per cent of land whereas by the end of the century, it shrunk to 19.4 per cent.
n The National Forest Policy (1988) of India has recommended 33 per cent forest cover for the plains and 67 per cent for the hills.
(i) Causes for deforestation
(a) Human settlements
(b) Forest fires
(c) Hydroelectric projects
(d) Over-grazing by livestock
(e) Demand for wood, timber
(f) Jhum cultivation or slash and burn agriculture: The farmers cut the forest trees and burn the plant remains. The land is then used for farming or cattle grazing. After cultivation, the land is left barren for years to allow its recovery. The farmer then moves to other areas and repeat the process with increasing population and repeated cultivation, recovery phase is not being provided, causing deforestation.
(ii) Effects of deforestation
(a) Increase in carbon dioxide concentration in atmosphere.
(b) Loss of biodiversity due to habitat destruction.
(c) Disturbance in hydrologic cycle.
(d) Soil erosion that may lead to desertification.
Reforestation
n It is the process of restoring a forest that once existed but was removed at some point of time in the past. It may occur naturally in a deforested area.
l We can plant trees; considering biodiversity that earlier existed in that area.
People’s Participation in Conservation of Forests
n In 1731, a Bishnoi woman Amrita Devi, showed exemplary courage by hugging a tree in order to prevent its cutting. Her three daughters and hundreds of other Bishnois followed her and were killed by soldiers of king of Jodhpur. But the King’s men cut down the Tree along with Amrita Devi and others.
n The Government of India has instituted Amrita Devi Bishnoi Wildlife Protection Award for individuals or communities from rural areas that shows extraordinary courage and dedication in protecting wildlife.
n Chipko Movement was started in Garhwal, Himalayas in 1974 by Shri Sundar Lal Bahuguna to prevent cutting down of trees. Local women hugged trees to prevent their cutting by the contractors.
n In 1980, the Government of India has introduced the concept of ‘Joint Forest Management’ (JFM) to work closely with the local communities for protecting and managing forests. In return for their services to the forest the communities get benefit of various forest products like fruits, gum, rubber, medicines etc.
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