Chapter 16: Pollution
The traffic thickens a little after seven. By eight the road outside the school is a solid line of buses, cars and auto-rickshaws, the horns overlapping until no single horn can be picked out of the sound. A student waiting at the gate is standing inside three kinds of pollution at once, and can name only one of them. The one she notices is the noise, because it is loud. The second she can smell — the exhaust from the engines around her, pushed into air that now has to carry it. The third she cannot see at all, because it has not been made yet. Through the morning the sun works on those exhaust gases, and by mid-afternoon the air holds substances that no engine ever released. They were built out of what the engines gave it. The haze at four o’clock is not what is left over from the morning rush. It is what the morning rush turned into. Below her feet, meanwhile, last night’s washing water is moving through a drain, into a channel, into a river. Nothing about that water looks dangerous. It reaches the sea anyway, and something in the sea eats it. Pollution is hardly ever found where it was made.
Diagram
Fig. 16.A1 Caption: One street, four kinds of pollution, and not one of them stays where it started. Brief: Wide street scene labelled at four points — horns and traffic as noise, exhaust rising from vehicles as air, a roadside drain running off the frame towards a river as water, an open heap of dumped waste as soil; every label carries an arrow leading away from its source, none pointing back into the street.
16.1 What Pollution Means
Pollution is any change in the natural quality of the environment brought about by chemical, physical or biological factors. The word ‘environment’ here means everything around a living thing — the air it breathes, the water it drinks, the soil it stands on and the other organisms it lives among. Notice that the definition does not begin with dirt or smoke. It begins with a change in quality.
That change can be brought about in three different ways, and the definition names all three. (a) A chemical factor works by adding a substance that alters what the air, water or soil is made of, so that its composition is no longer what it was. (b) A physical factor works without changing composition at all, by altering a physical condition such as the temperature of a river or the loudness of the air over a street. (c) A biological factor works through living matter, as when sewage carries organisms into water that did not hold them before.
Environmental pollution is any unfavourable alteration of our surroundings, wholly or largely as a by-product of man’s actions. Two words in that definition are doing quiet work. ‘Unfavourable’ tells you that not every change counts, only one that makes the surroundings worse for living things. ‘By-product’ tells you that nobody set out to cause it — it came out of the side of some activity that was being carried on for a quite different reason. These changes go on to affect man and other organisms alike.
16.1.1 Pollutants
Pollutants are the products which are released into the biosphere in large quantities and which affect the normal functioning of ecosystems and have an adverse effect on plants, animals and man. The biosphere is the thin zone of the earth in which life is actually found, taking in the lower air, the surface water and the upper soil together. An ecosystem is a community of living things and the surroundings they depend on, working as one unit.
Pollution and a pollutant are not the same thing, and the two words are easy to swap by accident. Pollution is the change itself — the loss of quality — while a pollutant is the substance that brings the change about. One is the effect, the other is the cause.
A substance earns the name pollutant only when three conditions are met together. (a) It is present in the environment in harmful concentration, which means the quantity in a given volume of air, water or soil has risen high enough to do damage. (b) It contaminates air, water or soil, so it has entered one of the surroundings that living things cannot avoid using. (c) It affects the environment, human beings and other organisms adversely, which is what separates a pollutant from any other substance drifting about in nature.
The chain from an ordinary human activity to a damaged ecosystem runs in a fixed order, shown in Fig. 16.A2.
Flowchart
Fig. 16.A2 Caption: Nobody sets out to pollute — the harm arrives as a by-product of something else being done. Nodes: human activity carried on for its own purpose → substance released into the biosphere in large quantities → concentration in air, water or soil rises to a harmful level → natural quality of the environment altered → normal functioning of the ecosystem disturbed → plants, animals and man adversely affected
Read that chain from the far end and a useful habit follows. When something in the environment goes wrong, the question is not only what substance is present, but how much of it, where it has collected, and which activity kept sending it there.
16.2 Types Of Pollutants
Pollutants are sorted in three different ways, and the three are not rival systems. Each asks a different question about the same substance: how it behaves once it is out there, where it came from, and whether nature was already carrying it. A single pollutant therefore has a place in all three lists at once, as Fig. 16.A3 shows.
Flowchart
Fig. 16.A3 Caption: The same pollutant is classified three times over, because each basis asks a different question about it. Nodes: pollutants → basis of degradation → biodegradable / non-biodegradable; pollutants → basis of origin in environment → primary / secondary; pollutants → basis of existence in nature → quantitative / qualitative
On The Basis Of Degradation
To degrade means to be broken down into simpler substances, so that what was released stops existing in its original form. Biodegradable pollutants are the pollutants which can be degraded by biological or microbial actions — that is, living things, mostly microbes, feed on them and take them apart. Sewage and domestic garbage are the examples the chapter gives, and both are the remains of once-living material, which is why microbes can handle them.
Non-biodegradable pollutants are the pollutants which are not degraded by microbes, or which degrade at a very slow rate. Glass, plastics, radioactive substances and pesticides belong here. The contrast between the two groups is not one of harm but of time. A biodegradable pollutant does damage while it is present and then disappears; a non-biodegradable one stays, and every fresh release adds to what is already lying there.
On The Basis Of Origin In Environment
Primary pollutants are the pollutants which are directly introduced by their sources into the environment. What leaves the chimney or the exhaust pipe is what reaches the air. Ash, smoke, fumes, dust, carbon dioxide (CO2), sulphur dioxide (SO2) and hydrocarbons such as methane, acetylene and benzene are all primary pollutants. A hydrocarbon is a compound built only of hydrogen and carbon, and fuels are largely made of them.
Secondary pollutants are the pollutants which are formed from the chemical reaction of primary pollutants in the environment. Nothing releases them; the air itself manufactures them out of what it has been given. Nitrogen oxides and hydrocarbons are two primary pollutants released from automobiles. These pollutants react in the presence of sunlight to form Peroxyacetyl Nitrate (PAN) and Ozone, two secondary pollutants which are far more toxic than the primary pollutants from which they are derived.
That last point is the one worth holding on to. A secondary pollutant can be more dangerous than anything that was actually emitted, so a count of what comes out of the exhaust pipes does not measure the whole of the harm.
On The Basis Of Existence In Nature
Quantitative pollutants are substances that exist in nature but act as pollutants when their concentration or quantity increases up to a critical level in the atmosphere. Carbon dioxide and nitrogen oxide are the chapter’s examples. Nothing has been introduced that was not there before; only the amount has changed, and past a critical level the same familiar substance begins to do harm.
Qualitative pollutants are pollutants which do not exist in the environment at all. They are introduced into the environment through man’s activities, and pesticides such as DDT, chemical fertilizers and herbicides are examples. For these there is no natural level to exceed, because nature was carrying none of them to begin with.
This last basis carries a warning about how pollution is measured. For a qualitative pollutant, finding any of it at all is the finding. For a quantitative pollutant, finding it proves nothing, because it belongs there; only the concentration, measured against a critical level, tells you whether the air has been polluted.
16.3 Types Of Pollution
Section 16.2 sorted the pollutants. This section sorts the pollution itself, and again there are three ways of doing it — by where it happens, by what set it off, and by what kind of thing the pollutant physically is.
By The Part Of The Environment
The commonest classification takes the part of the environment where the pollution takes place. Fig. 16.A4 shows the three parts side by side.
Diagram
Fig. 16.A4 Caption: The three parts of the environment, and the name pollution takes in each. Brief: Simple vertical cross-section of the earth’s surface — air above labelled atmosphere and air pollution, a river and sea in the middle labelled hydrosphere and water pollution, rock and soil below labelled lithosphere and soil pollution; a downward arrow at one side showing that pollutants can pass from the upper zone into the ones beneath.
Each part of the environment gives the pollution its name. (a) The atmosphere is the envelope of air wrapped around the earth, and pollution taking place in it is known as air pollution. (b) The hydrosphere is all the water of the earth — its oceans, rivers, lakes and groundwater — and pollution taking place in it is known as water pollution. (c) The lithosphere is the solid rocky outer shell of the earth, along with the soil that forms on top of it, and pollution taking place in it is known as soil pollution.
By Origin
On the basis of origin, pollution may be natural or anthropogenic. Natural pollution arises from the working of the earth itself, without anybody’s help, as when a volcanic eruption sends ash and gas into the air. Anthropogenic pollution, also called man-made pollution, comes out of human activity, industrial pollution being the standard example. The two differ in cause but not in effect: air does not treat volcanic ash more gently than factory ash.
By The Physical Nature Of The Pollutant
The third classification looks at what the pollutant physically is, rather than at where it landed. The categories include gases, particulate matter, temperature, noise and radioactivity, and each gives its own named form of pollution. Particulate matter simply means matter present as tiny separate particles rather than as a gas. (a) Gaseous pollution is caused by pollutants in the gaseous state, which mix into the air and travel with it wherever it moves. (b) Dust pollution is caused by particulate matter, which is heavy enough to settle out onto surfaces instead of staying mixed for ever. (c) Thermal pollution is caused by a change in temperature, so nothing at all has been added to the water or the air except heat. (d) Noise pollution is caused by sound, which carries no substance whatsoever and yet still counts, because the definition of pollution rests on a loss of quality and not on a substance being added.
Thermal and noise pollution are the two that make the classification worth learning. Both prove that the physical nature of a pollutant need not be a substance at all, and a test that looks only for chemicals in a sample will miss both of them completely.
16.4 Air Pollution
Air pollution is defined as the excessive concentration of foreign matter in the air which adversely affects the well-being of human beings, animals, plants and their environment. Foreign matter here means anything that is not part of the ordinary make-up of clean air, or anything that belongs there in far smaller amounts than are now present.
The definition is built out of two elements, and both must hold before air pollution can be said to have occurred. The first is a concentration of foreign matter in the air, while the second is that this concentration adversely affects living and non-living things alike. Take away the second element and there is only a change in the air; take away the first and there is nothing to cause a change at all.
The word ‘excessive’ is what carries the first element. Air is never a pure single substance, and small quantities of many things drift about in it without doing any harm. Pollution begins where the quantity crosses the level at which harm starts, which is why air pollution is always a question of how much, not simply of what.
16.4.1 Causes Of Air Pollution
Air pollution takes place through pollutants of gas, solid particles and liquid particles, and these may be either organic or inorganic chemicals. An organic chemical is one built around carbon, of the kind that living things and fuels are made of; an inorganic chemical is anything else.
The pollutants therefore reach the air in three physical forms. (a) Gases mix completely into the air and are carried wherever the air goes, so they cannot be filtered out by settling. (b) Solid particles are carried while the air is moving and drop out onto surfaces when it slows, which is why they collect on leaves, roofs and window ledges. (c) Liquid particles travel as a fine spray of droplets suspended in the air, small enough to stay up for a long time.
Gases such as sulphur dioxide, carbon monoxide, hydrogen sulphide and pollens from plants are continuously added to the air, and each addition lowers its quality a little further. The word ‘continuously’ matters. Air pollution is not usually a single event but a steady supply, and the concentration in the air is the result of that supply arriving faster than the air can carry it away and disperse it.
The result is the same whichever direction the pollutants come from: the natural composition of the air is disturbed, by natural sources or by man-made ones. Pollens make the point neatly, since no factory produces them and yet they lower air quality exactly as industrial gases do. Fig. 16.1 shows what the man-made side of this looks like.
Diagram
Fig. 16.1 Caption: Air pollution. Brief: Photograph of an industrial plant discharging smoke from tall chimneys into the surrounding air; keep the plume and its spread across the sky clearly visible, with the chimney mouths as the point of release.
16.5 Water Pollution
Water pollution can be defined as an alteration in the physical, chemical or biological characteristics of water, making it unsuitable for designated use in its natural state. A designated use is simply the use the water is meant for — drinking, bathing, irrigation, supporting fish — and the phrase is important, because water that has become unfit for one use may still serve another. There is no single line dividing clean water from polluted water; the line moves with what the water is wanted for.
The World Health Organization, the health agency of the United Nations, defines water pollution as any foreign material, from natural or other sources, that may contaminate the water supply and make it harmful to life. Fig. 16.2 shows what such contamination looks like where waste is left along a waterside.
Diagram
Fig. 16.2 Caption: Water pollution. Brief: Photograph of a river bank strewn with waste and refuse, with the polluted water in the foreground and the built-up shoreline behind; keep both the water surface and the accumulated waste on the bank clearly visible.
What Polluted Water Does
Once water is polluted, several different kinds of damage follow from the same water body. (a) The normal oxygen level of the water is reduced, and since fish and other water animals take dissolved oxygen from the water itself, less oxygen means fewer of them can survive there. (b) Aesthetically unpalatable effects appear — the water begins to look, smell and taste bad, so people avoid it even where it is not yet dangerous. (c) Epidemic diseases spread, because water carries disease organisms quickly and to everybody drawing on the same supply at once.
Water pollution also impacts the entire food chain. Toxins from contaminated fishes, prawns and other water animals get deposited in human tissues, and this leads to cancer, birth defects or long term health problems. The route matters as much as the result: the harm reaches a person who never drank the water, through a meal, and the toxins build up in the body’s tissues rather than passing straight through. Fig. 16.A5 follows that route step by step.
Flowchart
Fig. 16.A5 Caption: Polluted water reaches people who never drank it, by way of what they eat. Nodes: pollutants enter the water → taken in by fishes, prawns and other water animals → these animals eaten by people → toxins deposited in human tissues → cancer, birth defects or long term health problems
16.5.1 Freshwater
Freshwater bodies — the rivers, lakes, ponds and groundwater that carry water with almost no salt in it — are polluted by three kinds of effluents, which are the liquid wastes discharged from a place after use. (a) Domestic effluents are the waste water of households, carrying sewage and washings from ordinary daily use. (b) Industrial effluents are discharged by factories and carry the chemicals used or produced in manufacturing. (c) Agricultural effluents are the water draining off farmland, carrying with it whatever has been applied to the fields.
Two everyday uses are lost as a result. Polluted freshwater is unsafe for drinking, and polluted lakes are unfit for swimming and fishing. Note how quickly the damage travels beyond the people who caused it, since a lake serves a whole settlement and not only the household whose drain reaches it.
Freshwater is also not the end of the journey. All the effluents from freshwater sources, together with their pollutants, finally join the oceans, because rivers run downhill and the sea is where downhill ends.
16.5.2 Marine Water
Marine pollution, also called ocean pollution, is the spreading of harmful substances into the ocean. The substances named are oil, plastic, industrial and agricultural waste, and chemical particles. Eighty per cent of marine pollution comes from land, which tells you that the ocean is mostly being polluted by activities carried on nowhere near it.
Several distinct sources add to the total. (a) Mining for materials such as copper and gold is a major source of contamination in the ocean. (b) Thermal pollution affects the saline water of the oceans, altering its temperature without adding any substance to it at all. (c) Oil spills spread across the surface, where the oil neither dissolves nor sinks. (d) Nuclear waste reaching the sea adds radioactive material to it.
Because these sources act on the ocean from top to bottom, all levels of oceanic life, plants and animals alike, are affected. In the worst cases ‘dead zones’ are created — stretches of ocean in which the conditions can no longer support the life that once lived there.
16.6 Soil Pollution
Soil is the upper layer of the earth’s crust, formed by the weathering of rocks. Weathering is the breaking down of rock where it stands, without the broken material being carried anywhere, and it is what turns solid rock into the loose material that covers so much of the land surface. Rock fragments alone, however, are not yet a living surface. It is the organic matter in the soil — the remains of plants and animals mixed in among the mineral grains — that makes soil suitable for living organisms.
Soil pollution is defined as the change in the physical, chemical and biological conditions of the soil through man’s intervention, resulting in degradation in the quality and productivity of the soil. Productivity here means the soil’s ability to grow crops, so this definition ends where the previous two did not: in a direct loss of what the soil produces for people.
How Soil Pollutants Reach Us
Soil pollutants do not usually reach a person by being touched or breathed. They travel by being eaten. The pollutants enter the food chain at the plant level, since plants draw what they need from the soil and take up whatever else is dissolved there along with it. From that point the pollutants get magnified as we move up the food chain, so the animal that eats many plants carries more than any one plant did, and the animal that eats those animals carries more still. Fig. 16.A6 sets out the steps.
Flowchart
Fig. 16.A6 Caption: A pollutant that enters at the plant level does not stay at the level it entered. Nodes: pollutant present in the soil → taken up by plants along with water and nutrients → plants eaten by plant-eating animals → concentration carried in the body rises at this level → those animals eaten in turn → concentration magnified again at every step up the food chain
Why Soil Pollution Lasts
Soil pollution differs from water and air pollution in one important respect: the pollutants remain in the soil for relatively longer periods. The reason lies in how the three parts of the environment behave. Air moves constantly and carries its pollutants away from the source, spreading them thinner as it goes. Water flows downhill and does much the same, which is how effluents travel from a drain to the sea. Soil does neither. It stays where it is, and so does most of what enters it.
This changes what a polluted site means. Polluted air over a road may clear when the traffic stops, but a polluted field is still a polluted field long after the activity that contaminated it has ended, and every fresh addition is added to what is already there rather than replacing it.
16.7 Radioactive Pollution
Radioactive pollution is defined as the increase in natural background radiation, emerging from the activities of man using naturally occurring or artificially produced radioactive materials. Background radiation is the low level of radiation that is present everywhere on earth all the time, and a radioactive material is one whose atoms are unstable and give out radiation as they break down. Notice that the definition is written as an increase. Radiation is not something that human activity introduced; it is something human activity added to.
Radiation From Nature
Environmental radiation is divided into two types, natural and man-made. Natural radiation reaches us along two routes: cosmic radiations from outer space reach the earth’s surface from above, while terrestrial radiation comes from below, given out by the natural radioisotopes present in the earth’s crust. A radioisotope is an unstable form of an element, and ‘terrestrial’ simply means belonging to the earth. Neither route involves anybody’s activity, and neither can be switched off.
Radiation From Human Activity
Man-made radiations originate from the use of radioactive materials, and these materials are used in two main ways: in the production of nuclear weapons, and in the production of nuclear fuel.
The radioactive material used in atom bombs is very destructive. The impact of radioactivity on man and the environment became known during the Second World War, when the US dropped atom bombs on Hiroshima and Nagasaki in Japan in August 1945. Those two attacks are where the effects of radiation on a large population were first seen, and much of what is now understood about the harm it does was learnt from them.
Nuclear fuels in atomic reactors produce pollution as well, although the purpose of a reactor is not destruction but electricity. In a reactor, atoms of the fuel are split, a process known as fission, and the heat given out during fission is converted into electricity. During this process two types of wastes are formed: the fission products remaining in both the primary and secondary fuels, and the waste products in the coolant, the liquid circulated through a reactor to carry its heat away. Fig. 16.A7 follows the fuel through both outcomes.
Flowchart
Fig. 16.A7 Caption: The same reaction produces the electricity and the waste, and neither can be had without the other. Nodes: nuclear fuel loaded into an atomic reactor → fission → heat given out → heat converted into electricity; fission → waste formed in two forms → fission products remaining in the primary and secondary fuels / waste products in the coolant → radioactive waste requiring disposal
Waste And Leakage
The disposal of radioactive wastes causes pollution, and the difficulty is one of time rather than quantity. The high level products of nuclear wastes remain in the environment for several hundred years, which is why radioactive substances were listed in section 16.2 among the non-biodegradable pollutants. No microbe breaks them down, so disposal can only mean moving them and containing them, never removing them.
Leakage in nuclear reactors also causes environmental pollution, and a leak may result in the death of a number of people, as happened at the Chernobyl Atomic Reactor in the erstwhile USSR on April 26, 1986. The word ‘erstwhile’ means former, since the USSR no longer exists as a country.
Radioactive pollution therefore behaves differently from every other type in this chapter. Polluted air disperses and polluted water flows away; even polluted soil is eventually worked and cropped again. Radioactive waste outlasts the reactor that produced it, and the decision to generate it is taken by one generation on behalf of many that follow.
16.8 Noise Pollution
Noise pollution is defined as an unwanted sound that is an irritant and a source of stress. Sound in itself is one of the most useful things we have, being the means of communication and of entertainment alike. What decides whether a sound is noise is not the sound itself but how much of it there is and whether it was wanted. A low sound is pleasant, while a loud sound is unpleasant and is often referred to as noise.
Noise is a physical form of pollution, which places it with thermal pollution among the types where nothing material is added to the environment at all. It is not directly harmful to the life supporting systems, namely air, soil and water, and this is what sets it apart from every other type in this chapter. A polluted river carries its pollution; the air over a road holds its pollutants. Noise leaves nothing behind in any of them. Its effects are felt more directly by the receiver, that is, by man.
Why Noise Cannot Be Overlooked
Noise pollution is not fatal to human life, and it is tempting to dismiss it for that reason. Its effects still cannot be overlooked, and they are of three kinds. (a) Repeated exposure to noise reduces the sleeping hours, so the harm continues through the night, when the person is not even awake to notice the sound. (b) The productivity or efficiency of a human being falls, because concentrated work is difficult to sustain in a sound that keeps interrupting it. (c) It affects the peace of mind and invades the privacy of a human being, since sound passes through walls and doors that keep everything else out.
The third effect is worth pausing on. A person can close a window against dust and refuse to drink a suspect water supply, but there is no equally simple way of shutting out a sound that reaches into a house from outside it.
Where The Noise Comes From
Most of the noise originates from modern industrialised urban life, which is why noise pollution is largely a city problem. Six main sources are named. (a) The Industrial Sector produces noise from the machinery that runs in factories, often continuously through the working day. (b) The Transport Sector produces noise from the vehicles that carry people and goods, and this is the source shown in Fig. 16.3. (c) The Household Sector produces noise inside and around homes, from the equipment and activity of ordinary domestic life. (d) The Defence Sector produces noise from its equipment and operations. (e) Loud Speakers produce noise that is deliberately amplified, so that it is made to carry far beyond the people it was meant for. (f) Miscellaneous Sources cover everything else that adds to the total in a crowded place.
Diagram
Fig. 16.3 Caption: Vehicles—Noise Pollution. Brief: Photograph of a congested urban road packed with buses, cars, auto-rickshaws and two-wheelers in slow-moving traffic; keep the density of vehicles and the closeness of the buildings alongside clearly visible.
Loud Speakers are the source that shows most clearly how noise pollution differs from the rest. Nothing has been released, no substance has entered the air, and the equipment is doing exactly what it was built to do. The pollution lies entirely in the sound arriving where it was not wanted.
16.9 Summary
- Pollution is any change in the natural quality of the environment brought about by chemical, physical or biological factors.
- Environmental pollution is any unfavourable alteration of our surroundings, wholly or largely as a by-product of man’s actions, affecting man and other organisms.
- Pollutants are the products released into the biosphere in large quantities which affect the normal functioning of ecosystems and have an adverse effect on plants, animals and man. A pollutant is present in harmful concentration and contaminates air, water or soil.
- Pollutants are classified in three ways, and every pollutant has a place in all three.
- On the basis of degradation, biodegradable pollutants such as sewage and domestic garbage are broken down by biological or microbial action, while non-biodegradable pollutants such as glass, plastics, radioactive substances and pesticides are not, or degrade very slowly.
- On the basis of origin, primary pollutants such as ash, smoke, fumes, dust, carbon dioxide, sulphur dioxide and hydrocarbons are introduced directly by their sources, while secondary pollutants form from the chemical reaction of primary pollutants in the environment.
- Nitrogen oxides and hydrocarbons from automobiles react in sunlight to form PAN and ozone, secondary pollutants far more toxic than the primary pollutants they came from.
- On the basis of existence in nature, quantitative pollutants such as carbon dioxide and nitrogen oxide already exist in nature and act as pollutants only above a critical level, while qualitative pollutants such as pesticides, chemical fertilizers and herbicides do not exist in the environment at all until man introduces them.
- Pollution itself is also classified in three ways.
- By the part of the environment where it takes place — atmosphere, hydrosphere and lithosphere — giving air pollution, water pollution and soil pollution.
- By origin, as natural pollution such as volcanic eruptions, or anthropogenic pollution such as industrial pollution.
- By the physical nature of the pollutant, giving gaseous pollution, dust pollution, thermal pollution and noise pollution.
- Air pollution is the excessive concentration of foreign matter in the air which adversely affects the well-being of human beings, animals, plants and their environment.
- It takes place through pollutants of gas, solid and liquid particles, of both organic and inorganic chemicals.
- Sulphur dioxide, carbon monoxide, hydrogen sulphide and pollens from plants are continuously added to the air, so the natural composition of the air is disturbed by natural and by man-made sources.
- Water pollution is an alteration in the physical, chemical or biological characteristics of water, making it unsuitable for designated use in its natural state.
- It reduces the normal oxygen level of the water, causes aesthetically unpalatable effects and spreads epidemic diseases.
- It impacts the entire food chain, and toxins from contaminated fishes and prawns deposited in human tissues lead to cancer, birth defects or long term health problems.
- Freshwater bodies are polluted by domestic, industrial and agricultural effluents, and all these effluents finally join the oceans.
- Marine pollution is the spreading of oil, plastic, industrial and agricultural waste and chemical particles into the ocean; eighty per cent of it comes from land, and mining for materials such as copper and gold is a major source.
- All levels of oceanic life are affected, and in the worst cases ‘dead zones’ are created.
- Soil pollution is the change in the physical, chemical and biological conditions of the soil through man’s intervention, resulting in degradation in the quality and productivity of the soil.
- Pollutants enter the food chain at the plant level and get magnified as we move up the food chain.
- They remain in the soil for relatively longer periods than pollutants remain in air or water.
- Radioactive pollution is the increase in natural background radiation emerging from the activities of man using naturally occurring or artificially produced radioactive materials.
- Natural radiation is of two kinds: cosmic radiation from outer space, and terrestrial radiation from natural radioisotopes in the earth’s crust.
- Man-made radiation comes from radioactive materials used in nuclear weapons and nuclear fuel; atom bombs were dropped on Hiroshima and Nagasaki in August 1945.
- In atomic reactors the heat of fission is converted into electricity, forming fission products in the fuels and waste products in the coolant.
- High level nuclear wastes remain in the environment for several hundred years, and leakage may cause deaths, as at the Chernobyl Atomic Reactor on April 26, 1986.
- Noise pollution is an unwanted sound that is an irritant and a source of stress.
- It is a physical form of pollution, not directly harmful to air, soil and water, and its effects are felt directly by man.
- It reduces sleeping hours, lowers productivity or efficiency, and affects peace of mind and privacy.
- Its main sources are the Industrial, Transport, Household and Defence Sectors, Loud Speakers and miscellaneous sources, most of them belonging to modern industrialised urban life.
Flowchart
Fig. 16.A8 Caption: Every type of pollution in this chapter is the same chain, differing only in which part of the environment receives the pollutant. Nodes: activity carried on, natural or man-made → pollutant released, primary or secondary → enters a part of the environment → atmosphere → air pollution / hydrosphere → water pollution → freshwater and then marine water / lithosphere → soil pollution; alongside these, radioactive materials → increase above natural background radiation → radioactive pollution, and unwanted sound → noise pollution with no substance released → all paths converge on adverse effects on plants, animals and man
What This Chapter Cannot Tell You
The chapter turns repeatedly on the idea of a harmful concentration and a critical level, but it never states one. Nowhere does it say how much carbon dioxide, sulphur dioxide or noise is too much, so it can tell you what makes a substance a pollutant without letting you judge whether any particular sample of air or water is polluted.
It also carries almost no measurement. One figure appears in the whole chapter — that eighty per cent of marine pollution comes from land — and it is a world total, which says nothing about any one coast or any one country. With no other data, nothing here allows one place to be compared with another, or this year to be compared with the last.
Finally, a classification sorts; it does not weigh. Knowing that a pollutant is non-biodegradable tells you it will persist, and knowing that a secondary pollutant is more toxic than its parent tells you the harm can grow after release. Neither tells you which of the five types of pollution is doing the most damage in any given place. That is a question of measurement, and measurement is what this chapter leaves out.
16.10 Check Your Concepts
Look at Fig. 16.3. A photograph records no sound at all. Explain what in the picture tells you that noise pollution is likely at this spot, and state one thing about the noise that the photograph cannot tell you.
A drain from a town empties into a river far inland, hundreds of kilometres from the sea. Trace, step by step, the route by which a pollutant in that drain could end up deposited in the tissues of a person who has never been near the river.
Carbon dioxide is named in this chapter as a primary pollutant and also as a quantitative pollutant. Explain what each of these two classifications tells you about it, and why the two do not contradict each other.
This chapter states that eighty per cent of marine pollution comes from land. Explain what this figure does not tell you about the pollution along any one stretch of coast, and say what further information you would need before you could describe that stretch as heavily polluted.
Pictures of six kinds of waste are given — construction waste, food service waste, green waste, paper, e-waste and glass. Classify them on the basis of degradation.
Give the difference between natural and man-made pollutants.
What is soil pollution, and why should soil pollution be avoided?
What are the man-made causes of radioactive pollution? Why is radioactive pollution more harmful than other types of pollution?
Give a geographical reason for each of the following.
- Music is relaxing, but playing it loud is a source of pollution.
- Secondary pollutants are toxic.
- Pesticides are qualitative pollutants.
Environmental pollution is an incurable disease which can only be prevented. Justify this statement, giving examples.