Chapter 20: Waste Management — I: Impact of Waste Accumulation
Mumbai throws out close to 6,300 metric tonnes of waste every single day. That is one city, one day — food scraps from kitchens, packaging from shops, rubble from building sites, broken glass, plastic and metal. All of it has to go somewhere, and the city sends it to two very different places. More than 60 per cent of the daily solid waste goes to the Kanjurmarg landfill, where it is scientifically processed. The remainder is sent to the Deonar dumping ground, where it remains untreated. That single difference decides everything that follows. Waste that is tipped out and left behind does not sit quietly. Bacteria get to work inside the heap, and as the buried material decomposes it gives off methane, a gas that catches fire easily. Rain soaks through the pile, dissolves what it meets and carries it downward through the soil into the groundwater. Flies, rats and stray animals come for the food in it and leave carrying germs. None of this is unusual. It is simply what waste does, in every city, whenever it is dumped instead of managed. A dumping ground only makes the process large enough to see.
Diagram
Fig. 20.A1 Caption: An untreated dump sends waste in two directions — gases upward into the air and dissolved matter downward into the groundwater. Brief: Cross-section of an open dump on vacant land — arrows pointing up from the heap for gases released as waste decomposes, arrows pointing down from rainwater soaking through the heap into soil and the water table below, flies and rats drawn at the surface; label the heap, the soil layer, the water table.
20.1 What Waste Is And Why It Accumulates
Waste is any material that is discarded because it has served its purpose and is no longer useful to the person holding it. The word also covers anything left over at the end of a process that has no further use and is therefore thrown away. Notice that both meanings turn on usefulness, not on the material itself.
That is worth pausing over. A glass bottle is not waste while it holds oil in a kitchen, and it is not waste to someone who will refill it. It becomes waste at the moment its owner decides it has nothing more to give. Waste, in other words, is a decision as much as it is a substance.
Why The Heap Keeps Growing
In modern times waste is being generated at an alarming rate, and it is growing in two ways at once — in quantity, meaning how much of it there is, and in complexity, meaning how many different materials are mixed into it. A heap that is only vegetable peel will rot down on its own. A heap of peel mixed with plastic, glass, metal and batteries will not.
Three habits of modern life lie behind the growth.
- The ‘use and throw’ concept — the practice of discarding things after using them once — is one of the significant reasons for waste accumulation, because it turns objects that could have lasted for years into waste within minutes.
- The range of materials we manufacture keeps widening, so the heap grows more complicated even when it does not grow larger.
- As our knowledge of science and technology increases, we continue to exploit natural resources for our own benefit, and every resource pulled out of the ground eventually leaves a residue, so the amount of waste we produce rises along with the amount we produce and consume.
What A Heap Does Where It Stands
One can see heaps of solid waste accumulated in street corners, around hospitals, in school backyards and even near water bodies. Dumping solid waste in these places does more than give an ugly look and a foul smell. It causes serious health hazards, and sometimes the outbreak of epidemics takes place because of the accumulation of waste, particularly near water bodies.
Water is what turns a local nuisance into a wider one. During rains, rainwater may take the decomposed waste along with pathogens — disease causing organisms — into our water bodies such as rivers, ponds and wells, and cause water pollution. The heap stays where it was tipped, but what was inside it travels.
This is the reason a dump near a water source is treated as a more serious problem than the same dump on dry ground far from one. The waste has not changed; its route out has.
20.2 Sources Of Waste
Waste is easier to manage when you know where it came from, because the source usually decides what is in it and how dangerous it is. Depending on their source of origin, wastes are classified into the broad categories shown below.
Flowchart
Fig. 20.A2 Caption: Waste is first sorted by where it came from, and then by how much harm it can do. Nodes: sources of waste → domestic / industrial / agricultural / commercial / construction / mining / electronic (e-waste) / biomedical; each of these → sorted again by the harm it can do → toxic waste / non-toxic waste
These groups overlap, and the chapter says so plainly in places — hospital waste, for instance, is counted as commercial waste and is also biomedical waste. The categories are a way of thinking about waste, not watertight boxes.
20.2.1 Domestic Waste
Domestic waste is the waste generated by the activities of a household. It is the waste a student meets every day without thinking of it as a subject of study.
Domestic waste includes food leftovers, fruit and vegetable peels, bits of paper, packets, polythene bags and bottles. It also includes empty metal and aluminium cans, scrap metals, glass pieces, cotton, rags and discarded clothes. Ashes from burning coal, sewage from toilets, batteries, expired medicines and household chemicals are domestic waste too.
Read that list again and notice what it contains. Vegetable peel and a battery leave the same house, in the same bin, on the same morning. One will rot down quietly; the other holds chemicals that should never reach soil or water. Mixing them is what turns an ordinary household into a source of a difficult waste.
20.2.2 Industrial Waste
Industrial waste is the waste from small and large scale industries. It includes any material that is rendered useless during a manufacturing process, or is left over at the end of it.
The composition depends entirely on what is being made. A textile industry, for example, generates toxic wastes in the form of the chemicals used for dyeing and in the synthetic fibres it works with. Across industry as a whole the waste includes chemicals such as lead, mercury and arsenic, along with paints, sand, paper and paper products, fly ash, industrial by-products and metals.
Not all industrial waste is solid. Industry uses a great deal of energy, and producing that energy produces waste gases and other materials. Sulphur dioxide and nitrogen oxides emitted from power stations cause health hazards because of their link with acid rain, which is rainwater carrying an excess of acid.
20.2.3 Agricultural Waste
Agricultural waste is what is left over from growing crops and processing them. It mainly includes crop residue, husks and straws, wood waste, sawdust, molasses, tobacco waste, coconut waste products, rubber waste, nut shells, fruit and vegetable peels and manure.
Most agricultural waste is recycled. It is used for biogas — the gas given off as organic matter decays, which can be burnt as fuel — and it is returned to the fields as manure. Farm waste is therefore the one large category that is already, for the most part, being put back to work.
The trouble comes when it is not disposed of properly.
- Heaps of farm waste become a breeding ground for harmful insects and rodents, which then move into the fields and houses nearby.
- Burning of wheat or rice stubble gives rise to smoke which pollutes the environment.
- Waste spread along the roads or near residential houses has a nuisance value, spoiling the look and smell of the place people live in.
20.2.4 Commercial Waste
Commercial waste is the waste from commercial houses, stores, godowns, hospitals and offices. A godown is a warehouse where goods are stored before they are sold on.
These wastes contain waste paper, torn out gunny bags, and waste packing materials such as straw. They also include broken crockery, glasses, food wastes, packing materials, wood pieces and cans. Hospital waste, which comes under this heading because a hospital is a commercial establishment, comprises biomedical waste.
20.2.5 Construction Waste
Construction waste is the waste generated at construction sites, mainly from demolition and from construction rubble. It includes bricks, pipes, plastic, roofing and insulating materials and asbestos pieces.
This is the waste a student sees piled at the edge of any road being widened or any building coming down. It is heavy, it is bulky, and unlike food waste it does not decay away — which is why it sits where it was tipped for months.
20.2.6 Mining Waste
Mining waste is the waste generated during mining operations, excavations and similar work. It includes tailings, which are the crushed rock left behind once the useful mineral has been taken out of it, along with slag heaps and debris.
Mining waste is not only rock. Some mining processes use large volumes of chemicals or liquids, and these add to the waste generated. That is why mining waste can be toxic or hazardous rather than merely bulky.
20.2.7 Electronic Waste Or E-Waste
Electronic waste, or e-waste, refers to the various forms of electric and electronic equipment that have ceased to be of any value to their users, because they have exhausted their utility value due to redundancy, replacement or breakage. It includes refrigerators, televisions, washing machines, microwaves, computers and mobile phones.
Why It Is Growing So Fast
With advancement in Information Technology, new electronic goods are being produced at a fast rate, and this results in an increase in the volume of obsolete electronic products. An item becomes obsolete when something newer takes its place, whether or not the older one has stopped working. E-waste is one of the fastest growing wastes, constituting more than five per cent of all municipal solid waste.
Valuable And Dangerous At The Same Time
E-waste is valuable as a source of secondary raw material, meaning material recovered from a used product and fed back into manufacturing. It is hazardous, though, if treated and discarded improperly. Uncontrolled burning and disposal of e-waste cause environmental problems.
The concern is largely the toxicity of some of the substances in it, such as lead, mercury and cadmium. A computer monitor may contain more than six per cent lead by weight, and up to 36 separate chemical elements are incorporated into e-waste items. That mixture is exactly what makes a burning heap of e-waste dangerous to anyone standing near it.
E-waste also presents difficulties for recycling, for two reasons.
- Each item is complex, built from many materials fixed together, and there is a lack of viable recycling systems able to take it apart economically.
- Many of the plastics used in electronic equipment contain flame retardants, which are generally halogens added to the plastic resin, and these make the plastic difficult to recycle.
20.2.8 Biomedical Waste
Biomedical waste is defined as the waste produced during the diagnosis and treatment of human beings and animals, or during research activities. It is generated at healthcare facilities such as hospitals, nursing homes, immunisation centres and medical research facilities.
It consists of biological wastes in used bandages, cotton swabs and test kits. It also contains wastes such as disposable needles and masks, unused and expired medicines, and toxic wastes like the mercury from thermometers.
Why It Cannot Go Into The Ordinary System
This waste requires sophisticated processing plants, incineration and disassembly centres for proper disposal. Incineration is controlled burning at a high temperature, carried out in a furnace built for the purpose rather than in the open.
The reason for that care can be seen in one example the chapter gives. When medicines are disposed of into the sewage, the sewage treatment plants are not equipped to process them, and the result is antimicrobial resistance, or super bugs — organisms that the medicine no longer kills. The waste has not simply moved somewhere else; it has changed what the medicine can do.
The quantity of this waste is rising. Large scale epidemics, increased healthcare access and home based healthcare have all contributed to the rise in biomedical waste.
20.2.9 Toxic And Non-Toxic Waste
The eight categories so far sort waste by where it came from. This last division sorts it by how much harm it can do, and it cuts across all the others.
Toxic Waste
Certain wastes are classified as toxic wastes because they pose a serious threat to human health and the environment. They result from industrial processes and products, and they also include the chemicals used in modern agriculture and the medical waste from hospitals. The use of chemicals has increased and caused health hazards to living beings, and such chemicals produce toxic wastes during their manufacture as well.
If allowed into the environment, these toxic wastes can contaminate soil, pollute water and enter the food chain, harming plants, animals and human beings. Most of the pesticides sprayed on crops fall on the soil as waste, and they enter the local water supply system when that soil drains away into the rivers and lakes.
Some of the commercial toxic wastes are arsenic, cyanide, lead, cadmium, nickel, beryllium, uranium and mercury and their compounds, along with chlorinated solvents, asbestos, photographic wastes, plating sludges, pesticide residues, waste paints and lubricants. Burning these produces oxides of sulphur and nitrogen, which become toxic at high concentration.
Non-Toxic Waste
Some of the solid wastes are generated by domestic activities — food leftovers, fruit and vegetable peelings, bits of paper and other rubbish often stored in dustbins. The waste produced by shops, offices, restaurants and schools does not pose a serious problem to animals, plants or the environment. Such wastes are called non-toxic wastes.
The difference between the two groups lies in what happens to them after they are thrown away. A toxic waste stays dangerous, and moves through soil, water and the food chain carrying that danger with it. A non-toxic waste is mostly biodegradable, which means it is broken down by living organisms as it decays, and after decomposition it becomes a part of nature again. What the two share is that both must still be collected, because even harmless waste left in a heap attracts vectors and spoils the place it sits in.
Diagram
Fig. 20.1 Caption: Ghazipur Waste Hill Brief: Photograph of the Ghazipur landfill site in Delhi — source an image showing the full height of the waste hill with vehicles or machinery at its base for scale, and the vegetation and surrounding ground in frame.
A heap of that size is not one kind of waste. It holds domestic, commercial, construction and electronic waste together in the same slope, which is exactly why it is so hard to deal with. Sorting waste is easy at the doorstep and close to impossible once it has been tipped onto a hill.
20.3 Impact Of Waste Accumulation
Waste that is collected and treated is a cost. Waste that is left to accumulate is something else — it becomes an active part of the environment around it, moving through air, soil, water and living bodies. The figure below sets out the whole range of that impact before we take the strands one at a time.
Diagram
Fig. 20.4 Caption: Waste accumulation: impact. Brief: Branching chart with ‘Waste Accumulation: Impact’ at the top and five branches — Pollution, Climate Change, Human Health, Economic Impact, Animal and Plants; Pollution branching to Soil Contamination, Water Pollution and Air Pollution; Climate Change branching to GHG Emission, Acid Rain and Ozone Hole; Human Health branching to Disease Transmission and Toxic Exposure/Biomagnification; Economic Impact branching to Cost of Waste Management and Loss of Tourism; Animal and Plants branching to Endangerment and Ingestion, with Biomagnification below Ingestion; arrows running downward throughout.
20.3.1 Spoilage Of Landscape Or Visual Pollution
Spoilage of landscape, or visual pollution, refers to the accumulation of heaps of garbage and waste that is simply dumped onto vacant land and left to decompose. It does two things at once. It ruins the natural beauty of the land, and it provides a home to rats and other disease carrying organisms.
The damage is not only on the surface. Both open dumps and landfills may contain poisonous substances that seep into the groundwater or flow into streams and lakes. A landfill is a site where waste is buried in the ground, while an open dump is waste simply tipped and left uncovered.
These open dumps not only emanate a foul smell but also spoil the visual appeal of a place, and that has a cost people do not always connect to waste. A place that looks and smells like a dump is a place visitors stop coming to, so waste accumulation can negatively impact tourism, and with it the earnings of everyone who lives on that trade.
20.3.2 Pollution
The word ‘pollute’ means to degrade or to contaminate. Pollution is thus an unfavourable modification of the natural world caused entirely or partly by the direct or indirect actions of human beings. The phrase ‘entirely or partly’ matters, because human action often only pushes a natural process out of its normal range rather than creating something new.
Pollution is caused by human activities such as the addition of toxic chemicals through the atmosphere into the biosphere — the biosphere being the thin zone of the earth where living things are found. It is also caused by other substances which may not be particularly dangerous to organisms directly, but which have an adverse influence on the environment.
Accumulation of waste is probably the most visible form of pollution, and the quantity is hard to picture. Every year human beings dispose of billions of metric tonnes of solid waste.
Why Disposal Is Itself A Problem
The handling of solid wastes is a problem because most disposal methods cause harm to the environment. Look at what each route does.
- Both open dumps and landfills may contain toxins that seep into the soil and into water bodies, causing soil pollution and water pollution respectively.
- The uncontrolled burning of accumulated waste creates smoke and other air pollutants that release toxic substances into the environment and cause air pollution.
- Scavengers and stray animals invade the open garbage dumps and spread the waste over a large area, thereby spreading germs and diseases as well as destroying the beauty of the place.
The lead-in point is that waste does not disappear at any of these three doors. It changes state and changes address.
Toxins In The Food Chain
Industrial waste contains harmful chemicals, particulate matter — meaning small particles suspended in air — and toxic heavy metals such as lead and mercury. These toxic chemicals and heavy metals get deposited in animal tissues and harm living things along the food chain.
The chapter gives a chain worth following closely. Grass absorbs toxic chemicals from the soil. Animals eat such grass and get affected by the toxins. Those animals then pass the toxins on to human beings, directly or indirectly, through their dairy products or their meat. Nobody in that chain has touched a dump, yet the dump has reached all of them.
Decomposing waste is dangerous in one more way. As accumulated waste decomposes it produces a large quantity of methane gas, which is highly inflammable and can cause an explosion if it is not managed properly.
Water pollution occurs when people discharge a large amount of waste into water bodies and the natural cleansing process in those water bodies cannot function properly. A river can break down a certain load of organic matter on its own; beyond that load, the cleaning simply stops keeping up.
Where Pollution Comes From
The table below sets out the sources of the four kinds of pollution side by side. Read down a column to see what feeds one kind of pollution, and read across the rows to notice how often the same activity appears in more than one column.
Notice that pesticides appear in the air column and in the soil column, and that radioactive wastes appear under water pollution as well as having a column of their own. What the table does not give is any quantity. It tells you what the sources are, not which one contributes most, and a column with nine entries is not therefore worse than a column with four.
20.3.3 Eutrophication
Eutrophication is the process of depletion of oxygen from water bodies, occurring either naturally or due to human activities. It begins with something that sounds harmless — extra food arriving in the water.
The process takes place due to the introduction of nutrients and chemicals through the discharge of domestic sewage, industrial effluents and fertilizers from agricultural fields. To see what that does, first look at the water body working normally.
Under normal conditions, algae and phytoplankton use carbon dioxide, inorganic nitrogen and phosphate from the water as food. Phytoplankton are microscopic plants that drift in water. They serve as food for microscopic animals called zooplankton, small fish feed on these zooplankton, and large fish in turn consume these small fish.
Now add the nutrients. When nutrients become abundant due to waste accumulation, the growth of phytoplankton and algae increases sharply. This thick surface growth reduces the penetration of oxygen, light and heat into the water body. As a result, aquatic plants below are unable to carry on photosynthesis, which reduces the oxygen content of the water. This causes the death of most of the aquatic organisms, draining the water of all its oxygen.
Flowchart
Fig. 20.A3 Caption: Extra nutrients feed the surface and starve everything below it of oxygen. Nodes: sewage, industrial effluents and fertilizers enter the water → nutrients become abundant → phytoplankton and algae grow rapidly at the surface → oxygen, light and heat cannot penetrate → aquatic plants below cannot photosynthesise → oxygen content of the water falls → most aquatic organisms die
20.3.4 Health Hazards
20.3.4.1 Spread Of Disease Through Contamination
Several incidents around the world have demonstrated the potential harm of waste accumulation to human health. Waste that is not properly managed is a serious health hazard.
Unattended waste dumped in the open attracts flies, rats and other creatures that act as vectors of diseases and spread them among human beings. A vector is a creature that carries a disease organism from one host to another without falling ill itself.
Domestic waste poses a serious threat precisely because it is the ordinary sort. Since it is organic in nature it undergoes fermentation, and that creates conditions favourable for the survival and growth of pathogens. Flies, insects, rodents and similar creatures live in the accumulated waste heaps and carry germs of various diseases to human habitations. Decomposition of wastes also produces harmful gases that pollute the air around us.
Routes Out Of The Heap
Waste dumped near a water source percolates through the soil into the water bodies and contaminates the water. Direct dumping of untreated waste in rivers, seas and lakes results in the accumulation of toxic substances in the water bodies, and further in the food chain through the plants and animals that feed on it, a process called biomagnification.
There is also a route that has nothing to do with toxins at all. Choking of drains and gully pits by solid wastes results in water logging, especially during the rainy season. A gully pit is the small chamber under a roadside drain opening where water enters the drain. The water logging results in the breeding of mosquitoes in the stagnant water, and these spread diseases like malaria and chikungunya.
Diagram
Fig. 20.3 Caption: Increasing concentration of toxins along the food chain. Brief: Underwater scene with algae at the base, small fish above them and a big fish above those, with upward arrows on the right labelled toxins in water, toxins in algae, toxins in small fish and toxins in big fish; arrows point upward to show the toxins rising through the chain.
Hazardous And Radioactive Waste
Hazardous wastes are toxic substances which cause an increase in the death rate and serious illness that is either irreversible or incapacitating but reversible. Several are worth naming individually, because each attacks a different part of the body.
- Lead is a harmful toxin and it can affect the development of a child’s brain.
- Asbestos can cause a respiratory disease known as asbestosis, as well as chest and lung cancer.
- Mercury is a highly toxic chemical which attacks the nervous system, causing brain damage and even death.
- Arsenic is another chemical that has been shown to cause cancer.
Radioactive waste produced by nuclear reactors and weapon factories causes a potentially serious environmental problem of a different kind. Radioactive waste, although present in small quantities, remains extremely harmful to human health for many years. Quantity is not the measure of danger here; duration is.
Diagram
Fig. 20.2 Caption: Effects of radioactive waste. Brief: Photograph showing the effect of exposure to radioactive waste on a human being — source a documented medical photograph, framed and captioned soberly, with no additional labelling.
20.3.5 Effect On Terrestrial Life
Terrestrial life includes all the organisms that live on land — human beings, plants and animals. Waste reaches each of the three by a different route.
20.3.5.1 Effect On Human Beings
Accumulation of solid waste looks ugly, smells foul, and attracts insects, rats and other animals that spread diseases. Burning of waste in the open dump yards causes smoke and foul smelling air. In addition, rainwater can drain through refuse and carry harmful substances to different places, so the effects are felt well beyond the dump itself.
There is one effect that surprises people. Sanitary landfills are not fit for human settlements, because methane and carbon dioxide gases are released in the first two years. These gases are produced when solid wastes start decomposing underground, out of sight, after the surface has been levelled off.
20.3.5.2 Effect On Plants
Waste accumulation has a dangerous effect on plant life. Plants are affected either by the direct deposition of harmful toxins from wastes on them, or indirectly through the soil they are rooted in. The toxins cause the following damage.
- They cause different types of leaf injuries.
- They cause premature leaf fall, so the plant loses its leaves before its season is done.
- They cause a decrease in transpiration, which is the loss of water vapour from the leaves.
- They cause a reduction in the rate of photosynthesis, so the plant makes less food.
- They cause a reduction in biological nitrogen fixation, the process by which nitrogen from the air is made available to plants through the soil.
- Dust deposited on leaves blocks the stomata of plants, the tiny pores through which a leaf breathes. This decreases the rate of transpiration and inhibits the absorption of nutrients from the soil.
- Smoke emitted by the burning of waste causes a reduction in root and shoot lengths, in the number of leaves, and in the number of grains per spike in the case of crops like wheat.
That last point is the one to hold on to. A field beside a burning dump does not simply look worse — it yields less grain per ear, and the loss is measurable in the harvest.
20.3.5.3 Effect On Animals And Birds
Scavengers and stray animals like dogs, rats, pigs and cows are directly affected by waste when they feed on it for food. Sometimes these animals consume toxins, or non-degradable substances like the plastic carry bags present in the waste, and die due to choking. The wastes consumed by animals also lead to many diseases and other problems.
The damage reaches the next generation as well. According to a study, mice that were fed on high levels of toxins had difficulty in reproducing, and their offspring had higher rates of birth defects and lower body weights. Birds too are adversely affected by feeding on waste — birds feeding on agricultural waste have thinner and weaker egg shells and increased mortality. A thin shell breaks under the weight of the parent bird, so fewer eggs hatch.
20.3.6 Effect On Aquatic Life
Waste accumulation can cause significant damage to aquatic life, in both fresh water and marine environments. Two categories of waste cause the greatest damage — pesticides, which run off agricultural lands, and industrial and domestic wastes that are improperly disposed of into water bodies.
The Plastic Route
Over one million marine animals, including mammals, turtles, fish and sharks, are killed each year due to plastic debris in the oceans. The route that plastic takes is worth tracing, because none of it is dumped at sea. Plastic waste is washed out from our beaches, streets and highways into rivers and streams, and finally into the oceans.
After some time this plastic waste breaks down into smaller pieces, which are easily ingested by marine animals, causing blockages in their digestive tracts and eventually death. Marine turtles are more susceptible to the effects of consuming marine debris, because they have downward facing spines in the throat which prevent the possibility of regurgitation — once swallowed, the debris cannot be brought back up. Drilling for oil also causes harm to marine animals in the form of pollution from oil spills.
Toxins present in the wastes can kill aquatic organisms directly, by sufficiently changing the pH of the water, by covering the water surface, and by causing a reduction in dissolved oxygen. The pH of water is a measure of how acidic or alkaline it is, and aquatic organisms survive only within a narrow range of it. The aquatic organisms are also affected by a slower phenomenon known as biomagnification.
20.3.7 Biomagnification
Biomagnification refers to the increase in the concentration of various toxic substances along the food chain. Toxic substances present at the level of primary producers get concentrated at each trophic level as they move up the chain. A trophic level is one step in a food chain — producers first, then the animals that eat them, then the animals that eat those.
The phenomenon of concentrated toxic deposition at the higher trophic level is known as bio-accumulation. The mechanism behind it is simple and unforgiving. A small amount of a toxic constituent which is neither excreted nor metabolised — that is, neither passed out of the body nor broken down by it — gets increased as the food chain moves upward from one trophic level to the next, and the toxic constituents become concentrated.
Follow the chapter’s own example. If there are traces of toxic chemicals in water, their concentration in algae will be much higher. When fish eat the algae, the concentration of toxins will increase further. It will increase still further when big fish eat smaller fish. Therefore the accumulation of a small amount of toxic chemicals in water can have a serious impact on the fish that live in it.
Diagram
Fig. 20.5 Caption: The numbers are representative values of the concentration of DDT and its derivatives in the tissues, in parts per million. Brief: Four-step pyramid rising from producers at the base through primary consumers and secondary consumers to tertiary consumers at the top, drawn as plants, small fish, large fish and a fish-eating bird, with arrows on the left labelled 0.04 ppm, 0.23 ppm, 2.07 ppm and 13.8 ppm reading upward.
Fig. 20.5 puts numbers on the climb. Parts per million, or ppm, means the number of units of the substance present in every million units of tissue, so 0.04 ppm is a very small trace indeed. Work out how far the trace has travelled by the top of the pyramid:
\[\frac{13.8 \text{ ppm}}{0.04 \text{ ppm}} = 345\]
The tertiary consumer at the top carries 345 times the concentration found in the producers at the base. Nobody added more poison at any stage — the same poison was simply eaten, kept and passed upward.
Marine Pollution And Mercury
Carelessness and the deliberate dumping of wastes and oil spills in the seas and oceans pollute water and damage beaches. Marine pollution is a great threat to sea-life, plants and animals alike.
Oil spills decrease the penetration of light and hamper the photosynthesis process. They also retard the rate of oxygen uptake by water and adversely affect the development of marine organisms, increasing their susceptibility to disease and affecting their reproductive processes. In marine mammals they lead to gastrointestinal irritation, liver and kidney problems, and damage to the nervous system.
Mercury in water can affect marine animals adversely, and the clearest demonstration of that came from a single bay.
The important thing about Minamata is that the mercury never had to be swallowed directly. It arrived on a plate, carried there by fish that had done the concentrating, which is biomagnification working on a human population rather than on a laboratory pyramid. It also shows how far the effects of one industrial discharge can spread — to fishermen who never handled the chemical and to birds that were never anyone’s concern.
Mercury contamination also results from the wastes of other industries, such as the paper and pulp industry, the chlorine industry and the pesticide industry. Pesticides containing mercury add a considerable proportion of mercury to natural water bodies.
20.4 Need For Waste Management
The problem with waste is that it remains in our environment. We move waste from one place to another, but we never get rid of it completely. Every method of disposal is really a method of relocation.
Nature has recycled waste materials for millions of years, breaking down what dies and returning it to soil, water and air. However, the human population has increased so rapidly during the last century that the environment is now threatened by our activities and by the wastes we produce. Much damage is done to the environment by the pollution of air, the degradation of soils and the contamination of water sources such as rivers and lakes.
The quantity involved explains why nature’s own recycling can no longer keep pace. Every year 11.2 billion tonnes of solid waste is collected worldwide, and the decay of the organic matter in that solid waste contributes to 5% of greenhouse gas emissions, according to the UNEP Report. Waste, in other words, is not only a local heap; it is part of a global change in the atmosphere.
Many scientists believe that if we do not learn to use our resources carefully and to reduce waste, we will not be able to survive. There is a close connection between waste, pollution and the damage done to the environment. Waste causes pollution, which in turn causes the damage — and that is why the need for management of waste is urgent.
In India, effective waste management is needed because a significant portion of the waste remains untreated, due to inadequate waste collection infrastructure and practices. This leads to a rapid loss of resources, to environmental pollution, and to growing landfill problems. The dangers set out in the rest of this section, posed by global pollution due to the accumulation of wastes, threaten the survival of the ecosystem and call for waste to be managed.
Diagram
Fig. 20.6 Caption: Waste management is needed for five separate reasons at once. Brief: Central oval labelled ‘Need for Waste Management’ with arrows radiating outward to five surrounding ovals — Public Health, Climate Change Mitigation, Conservation of Resources, Aesthetic and Social Benefits, and Protection of Environment; arrows point outward from the centre to each.
20.4.1 Transmission Of Diseases
20.4.1.1 Waste On Land
Various diseases spread on an epidemic scale due to waste accumulation on land and in water bodies. Vectors like flies, mosquitoes, rodents and pet animals transmit these diseases, and the waste itself is a breeding ground for such vectors. Hence there is an urgent need to manage waste disposal in an effective manner.
The chapter lists the common diseases spread by mosquitoes, flies, rodents and pet animals.
- The housefly spreads typhoid, diarrhoea, dysentery, cholera and gastroenteritis.
- The sandfly spreads kala-azar and sandfly fever.
- The tsetse fly spreads sleeping sickness.
- Mosquitoes spread malaria, filaria, yellow fever, dengue, chikungunya and encephalitis.
- Rodents spread plague and salmonellosis.
- Pet animals spread disease as well.
- The dog spreads rabies and hydatid disease.
- The cat spreads dermatophytosis and anthrax.
Read that list against the waste heap it comes from. Every creature on it is there for the food, the shelter or the standing water that the heap provides. Remove the heap and you remove the breeding ground, which is a far cheaper way of stopping a disease than treating it after it spreads.
Diagram
Fig. 20.7 Caption: Treating a patient is the costly end of a chain that began with waste left unmanaged. Brief: Photograph of hospital staff attending to a patient receiving treatment in a ward; frame to show the medical setting clearly without identifying detail.
20.4.1.2 Waste In Water
Water without human interference is in its pure form. Industrialisation and urbanisation pollute it in four ways.
- Sewage contains organic matter that cannot be decomposed, and besides that, the sewage carries pathogenic agents.
- Industrial and commercial waste has toxic agents, including metal salts and complex synthetic organic chemicals.
- Fertilisers and pesticides produce pollutants.
- There are also other pollutants, such as radioactive substances.
Human beings are then affected by this pollution in two ways — by drinking contaminated water, while also being harmed by using contaminated water for personal hygiene and recreation. Bathing in a polluted river carries a risk even when nobody drinks from it.
20.4.2 Greenhouse Effect And Global Warming
The earth absorbs solar radiation and emits it back into space as infrared waves, and the rate of absorption against the rate of emission is what balances the heat on the earth. This phenomenon plays a very important role in maintaining the surface temperature of the earth. Without it the earth would be far colder than it is.
Carbon dioxide and other gases form a blanket around the globe which prevents the passage of infrared waves from the earth back into space. The concentration of solar radiation held in this way produces much heat, making the earth a very warm place.
This phenomenon is similar to that of a greenhouse, in which the glass enclosed area gets heated up because it is insulated from the rest of the environment. Light gets in; heat cannot easily get out. The warming up of the atmosphere is due to the greenhouse effect, and hence global warming is also known as the greenhouse effect.
Diagram
Fig. 20.8 Caption: Sunlight enters easily, but the heat the earth radiates back does not leave as easily. Brief: Cross-section of the earth’s surface and atmosphere with the sun at upper left and six numbered arrows — (1) about 70% of the sun’s energy that enters the atmosphere reaches the Earth, arrow downward; (2) about 30% of the energy is reflected back into space, arrow upward; (3) water vapour, burning fossil fuels and deforestation increase carbon dioxide in the atmosphere, added to this are CFCs and methane; (4) together, these gases warm the Earth; (5) infrared radiation is emitted from the Earth’s surface, arrow upward; (6) some of the infrared radiation passes through the atmosphere and some is absorbed and re-emitted in all directions by greenhouse gas molecules, warming the Earth’s surface.
20.4.2.1 Greenhouse Gases (GHG)
Five gases are mainly responsible for the greenhouse effect and global warming, and these are known as greenhouse gases.
- Carbon dioxide (CO₂)
- Methane (CH₄)
- Nitrogen oxide (nitrous oxide)
- Chlorofluorocarbons (CFC)
- Water vapour
Human activities like the burning of fossil fuels increase the carbon dioxide content in the atmosphere. This increased concentration of carbon dioxide may bring about drastic changes in the world climate in the near future, in the form of increased temperatures or global warming.
If the carbon dioxide content of the atmosphere increases steadily, it will result in an increase in the present world temperature by about 3.6 °C. It is estimated that if the earth continues to warm up, all the glaciers will recede and the ice caps in the Antarctic and the Arctic will begin to melt. The sea level will then rise by a few metres, most of the cities on the seashore may be submerged, and coastal eco-life will be adversely affected.
20.4.2.2 Our Future In Danger
Our future is in danger if we do not arrest global warming by controlling emissions into the atmosphere. The chapter sets out five effects of global warming.
- The global temperature is likely to rise by 2 °C to 5 °C during the next century.
- Due to this rise of 2 °C to 5 °C there is a chance of melting of the ice caps on the Earth’s poles, and this melting of ice will result in a rise of the sea level. Large stretches of low lying areas will submerge, many island countries will face deep encroachment by seawater, and some may disappear altogether.
- As the increase in temperature will be uniform all over the surface of the world, there will be serious climatic changes, bringing various changes in the wind and rain pattern.
- Higher temperature will cause a rise in transpiration, which in turn will affect the groundwater table — the level below which the ground is saturated with water.
- Insects and pests will increase in the warmer climatic conditions, and thus pathogenic diseases will multiply.
Notice how far that list travels from its starting point. A change of a few degrees in the air ends as a change in coastlines, in rainfall, in the water available under a field, and in the diseases a population has to live with.
20.4.3 Depletion Of Ozone Layer
20.4.3.1 Significance Of Ozone Layer In Atmosphere
The atmosphere is divided into five layers — the troposphere, the stratosphere, the mesosphere, the thermosphere and the exosphere. In the second layer, the stratosphere, which lies at a height of 20 km to 50 km from the Earth’s surface, lies the ozone layer. In spite of its low density, the ozone layer plays an important role in our life.
Due to the presence of the ozone layer, ultraviolet rays and infrared rays from the sun cannot reach the Earth’s surface directly. The ozone layer absorbs the harmful ultraviolet rays from the sun and protects the life on the Earth from their harmful effects.
20.4.3.2 Causes Of Ozone Layer Depletion
Different researches have revealed that when the oxides of nitrogen, NO and NO₂, come in contact with ozone, O₃, their chemical reaction destroys the ozone layer. Besides this, supersonic aeroplanes move through the stratosphere and emit a huge amount of nitrogen gas, which depletes the ozone layer.
Another important causative factor of ozone layer depletion is chlorofluorocarbons, or CFCs, which damage the ozone layer. CFC-type chemicals are used as refrigerants in aerosol, paints, plastics, foam and thermal insulating materials in the spray and packaging industries. During the use of such materials, a lot of CFCs ultimately get dispersed into the atmosphere — which is why an ordinary household product ends up affecting a layer 20 km overhead.
A hole has been observed in the ozone layer in the stratosphere near Antarctica. This hole allows the ultraviolet rays of the sun to reach the Earth directly, without any obstacle or filtration.
Diagram
Fig. 20.9 Caption: Image of the largest ozone hole over the South Pole. Brief: Satellite image of the ozone layer over the South Pole in false colour, with the thinned region over Antarctica shown in a contrasting shade at the centre; include a note that the colours represent ozone concentration and not surface features.
What The Extra Ultraviolet Rays Do
These ultraviolet rays cause many diseases, such as skin cancer and cataract, which is a clouding of the lens of the eye. They also cause genetic disorders which ultimately affect heredity, meaning the damage can be passed to the next generation.
The harm is not confined to human beings. An increased concentration of ultraviolet rays disturbs the ecological balance in the marine ecosystem. Green algae, fish and other animals on the continental shelves get affected by ultraviolet rays, and the young cells and larvae of organisms living in aquatic ecosystems get destroyed.
Vegetables are very sensitive to ultraviolet rays. Ultraviolet rays can damage the physical and chemical properties of any complex chemical substance, and plastics become brittle when they come in contact with them.
20.4.4 Acid Rain
Acid rain means the presence of excessive acids in rainwater. It begins in a furnace and ends in the sky, and the steps between are worth following in order.
Burning of coal, wood or petroleum produces sulphur and nitrogen. These two react with oxygen and are converted into their respective oxides — sulphur dioxide and nitrogen dioxide — which are soluble in water. During rain, these oxides react with large quantities of water vapour in the atmosphere to form acids such as sulphuric acid, sulphurous acid, nitric acid and nitrous acid. These acids, when they precipitate together with rain or snow, form acid rain.
Flowchart
Fig. 20.A4 Caption: Acid rain is made in the air, from fuel burnt on the ground. Nodes: coal, wood or petroleum is burnt → sulphur and nitrogen are produced → they react with oxygen → sulphur dioxide and nitrogen dioxide form → these oxides dissolve in water vapour in the atmosphere → sulphuric, sulphurous, nitric and nitrous acids form → the acids precipitate with rain or snow → acid rain reaches soil, water, plants and buildings
20.4.4.1 Effects Of Acid Rain
Acid rain damages living things and lifeless things alike.
- Acid rain increases acidity in the soil and destroys forests and crops.
- It corrodes buildings, monuments, statues, bridges, fences and railings. For example, acid rain produced by the pollutants from the Mathura oil refinery, in western Uttar Pradesh, has been turning the white marble surface of the Taj Mahal at Agra into yellow.
- It poses a serious threat to human health, since it contaminates air and water.
- It affects the human nervous system by causing neurological diseases.
- Aquatic species are affected due to acid rain.
- Acid rain affects plant growth, and plant leaves get burnt and dry.
Diagram
Fig. 20.10 Caption: Effect of acid rain. Brief: Photograph of the Taj Mahal at Agra showing the white marble surface and the reflecting pool in the foreground; frame the marble facade clearly so its colour is legible.
The Taj Mahal case is worth holding on to, because it shows the geography of the problem. The refinery and the monument are not in the same city. The oxides rise, travel with the air, and come down in rain wherever that air happens to be — so the damage lands on someone who did nothing to cause it.
20.4.5 Soil Health
Soil is the foundation for a healthy biosphere. Precipitation from the air as acid rain, and the dry deposition of pollutants on the land surface, both contribute to soil pollution.
What follows is a chain that ends inside living bodies. The chemicals and minerals in the soil react with the chemical pollutants. These pollutants then combine with plant nutrients, and the plants are in turn consumed by animals.
Polluted soils cause a reduction in mineralisation and decomposition processes — the processes by which dead matter is broken down and its nutrients released for plants to use again. The transformation of sulphur and nitrogen in the soil, the availability of phosphorus, and biological nitrogen fixation are all affected by acid rain. Soil fertility and aeration are also reduced.
The living population of the soil suffers directly as well. Earthworms, nematodes and similar organisms are destroyed by toxic chemicals, and these are exactly the creatures that keep soil loose, aerated and fertile.
Destruction of the soil is synonymous with the destruction of the biosphere. Therefore, to prevent the destruction of the biosphere, it is of the utmost importance to check the accumulation of waste, and thereby to reduce soil pollution and improve the health of the soil.
There is a need to manage waste properly, and public awareness of the health hazards of waste is therefore necessary. No doubt waste disposal has become a big industry employing thousands of workers, but the options for disposal are limited — the main disposal sites are the land, the water or the air, and nothing leaves that set of three.
Diagram
Fig. 20.11 Caption: Soil degradation. Brief: Photograph of a degraded slope with bare, gullied and discoloured soil, sparse vegetation and exposed subsoil; frame to show the extent of the bare surface against the surviving cover.
20.4.6 Thermal Pollution
Thermal pollution is the result of a sudden change in the temperature of a natural body of water, due to natural events or human activities. It is the one form of pollution in this chapter that adds no substance to the water at all.
Aquatic flora and fauna are temperature sensitive, so small changes in temperature lead to a drastic lowering in population. If the temperature is lowered, planktons and fish are unable to multiply, and this disrupts the food chain.
Warm water has two detrimental effects. It decreases the level of dissolved oxygen, because warm water holds less oxygen than cold water. It also causes algal blooms, which create ‘dead zones’ in the water body by reducing its levels of dissolved oxygen.
All these problems result from too much hot water. However, cold water can be just as big a problem. Plankton, fish and fish eggs may die if temperatures are too cold, and this too disrupts the food chain and the balance of the ecosystem.
20.4.6.1 Causes Of Thermal Pollution
Industrial use of water as a coolant is the largest cause. Most industries generate heat, use water as a coolant, and dump the warm water into water bodies. The major contributors are power plants that use fossil fuels, biomass or nuclear energy, which consume a lot of water and are located near natural waterbodies for that reason.
Power generation involves heating water to generate electricity from steam. This heated water, along with the water used as a coolant for machines, gets dumped back into the body of water it came from, raising its temperature as a whole. The process is called ‘once-through’ cooling, because cold water passes through the plant once and leaves as heated wastewater. Other industries that use this process are oil refining, pulp and paper mills, steel mills, chemical plants and desalination plants.
Soil erosion works more slowly. It causes the beds of rivers and streams to become wider and shallower, exposing more area to sunlight and heating up the water.
Deforestation causes thermal pollution in two ways. First, it contributes to erosion along river and stream beds, causing heating of water. Second, it removes shade from lake shores and riverbanks, which exposes the water to more sunlight and causes it to heat up.
Urban runoff is the cause a student can feel underfoot. In the summer, hard surfaces of the city such as roads and buildings get very hot, and this heat travels to the water bodies as runoff, causing thermal pollution.
Natural causes such as heat from lightning strikes, wildfires, volcanoes and underwater thermal vents can all cause sudden spikes in water temperature. However, in some cases these natural causes also have a human element. Wildfires today are more frequent and more severe due to human-caused climate change and the mismanagement of forests. Climate change can also lead to cold-water thermal pollution, because it causes glaciers to melt faster.
20.4.6.2 Reducing Thermal Pollution
Three measures are suggested, and they work at different points in the process.
- Switching to clean energy sources like solar and wind for power generation removes the heat at its source.
- Changing the once-through cooling systems tackles the discharge itself.
- Cool the water before dumping it, using cooling systems.
- Stop dumping effluents in water bodies altogether.
- Recycling the water keeps it inside the plant instead of returning it hot to the river.
20.5 Summary
- Waste is any material that is discarded because it has served its purpose and is no longer useful, or that is left over at the end of a process and has no further use.
- Waste is being generated at an alarming rate, in quantity and in complexity, for reasons that lie in the way we live.
- The ‘use and throw’ concept turns objects that could last for years into waste within minutes.
- As science and technology advance, we exploit more natural resources, and more waste follows.
- Wastes are classified by their source of origin into domestic, industrial, agricultural, commercial, construction, mining, electronic and biomedical waste.
- Domestic waste comes from household activities and mixes harmless peel with batteries, medicines and chemicals.
- Industrial waste is whatever is rendered useless in manufacturing, and includes waste gases from the energy industry uses.
- Agricultural waste is mostly recycled as biogas and manure, but causes harm when it is burnt or left in heaps.
- Commercial waste comes from stores, godowns, offices and hospitals, and hospital waste comprises biomedical waste.
- Construction waste is demolition and construction rubble, which is bulky and does not decay.
- Mining waste includes tailings, slag heaps and debris, and can be toxic because of the chemicals used in mining.
- E-waste is discarded electrical and electronic equipment, one of the fastest growing wastes, at more than five per cent of all municipal solid waste.
- Biomedical waste is produced during diagnosis, treatment and research, and needs sophisticated processing plants, incineration and disassembly centres.
- Waste is also classified by the harm it can do, into toxic and non-toxic waste.
- Toxic wastes threaten human health and the environment, contaminate soil, pollute water and enter the food chain.
- Non-toxic wastes are mostly biodegradable and become a part of nature again after decomposition.
- Spoilage of landscape, or visual pollution, is the accumulation of heaps dumped on vacant land, which ruins the beauty of a place, houses disease carrying organisms, emanates foul smell and can harm tourism.
- Pollution is an unfavourable modification of the natural world caused entirely or partly by human action, and waste accumulation is probably its most visible form.
- Toxins from dumps and landfills seep into soil and water, causing soil and water pollution.
- Uncontrolled burning of waste causes air pollution.
- Decomposing waste produces methane, which is highly inflammable and can cause an explosion.
- Eutrophication is the depletion of oxygen from a water body, caused when sewage, effluents and fertilizers add abundant nutrients, algae and phytoplankton grow rapidly, and the plants below can no longer photosynthesise.
- Waste that is not managed is a serious health hazard, because it breeds the vectors that carry disease.
- Flies, mosquitoes, rodents and pet animals transmit diseases such as typhoid, cholera, kala-azar, malaria, dengue, plague and rabies.
- Choked drains cause water logging, and stagnant water breeds mosquitoes that spread malaria and chikungunya.
- Water-borne diseases are viral, bacterial, protozoan or helminthic in origin.
- Waste damages terrestrial life at every level — human beings through disease, smoke and unsafe ground, plants through leaf injury and reduced photosynthesis, and animals and birds through toxins, choking and weakened egg shells.
- Waste damages aquatic life through pesticides and improperly disposed industrial and domestic wastes, and through plastic debris that kills over one million marine animals each year.
- Biomagnification is the increase in the concentration of toxic substances along the food chain, because a toxin that is neither excreted nor metabolised is passed on and concentrated at each trophic level.
- The concentrated deposition of toxins at a higher trophic level is called bio-accumulation.
- Mercury reaching the sea at Minamata Bay caused illness among fishermen who ate the fish, and killed sea birds feeding on them.
- Waste must be managed because it never leaves the environment — the main disposal sites are only the land, the water or the air.
- Greenhouse gases — carbon dioxide, methane, nitrogen oxide, chlorofluorocarbons and water vapour — form a blanket that prevents infrared waves from leaving the earth, causing global warming.
- A steady rise in carbon dioxide would raise world temperature by about 3.6 °C.
- Global temperature is likely to rise by 2 °C to 5 °C during the next century, melting ice caps, raising sea level, changing wind and rain patterns and multiplying pathogenic diseases.
- The ozone layer, in the stratosphere at a height of 20 km to 50 km, absorbs harmful ultraviolet rays, and is depleted by oxides of nitrogen, by nitrogen gas from supersonic aeroplanes and by chlorofluorocarbons.
- The hole observed near Antarctica lets ultraviolet rays reach the Earth unfiltered.
- These rays cause skin cancer and cataract, affect heredity, and damage marine and plant life.
- Acid rain is the presence of excessive acids in rainwater, formed when the sulphur and nitrogen from burning fuels turn into oxides that dissolve in water vapour and precipitate as acid.
- It destroys forests and crops, corrodes buildings and monuments, harms human health and the nervous system, and affects aquatic species and plant growth.
- Pollutants from the Mathura oil refinery have been turning the white marble of the Taj Mahal yellow.
- Soil health is damaged by acid rain and by the dry deposition of pollutants, which reduce fertility, aeration, mineralisation and biological nitrogen fixation, and destroy earthworms and nematodes.
- Thermal pollution is a sudden change in the temperature of a natural water body due to natural events or human activities.
- Warm water holds less dissolved oxygen and causes algal blooms that create dead zones, while water that is too cold kills plankton, fish and fish eggs.
- Its causes include once-through industrial cooling, soil erosion, deforestation, urban runoff and natural events such as wildfires and thermal vents.
- It is reduced by clean energy, by cooling or stopping the discharge, and by recycling the water.
Flowchart
Fig. 20.A5 Caption: Every route out of a waste heap ends somewhere that matters, which is why waste has to be managed rather than moved. Nodes: households, industry, farms, shops, building sites, mines, electronics and hospitals generate waste → waste is accumulated instead of treated → it leaves the heap by three routes only → land: seepage into soil, spoiled landscape, breeding of vectors; water: percolation and direct dumping, eutrophication, biomagnification, thermal change; air: burning and decomposition, methane, greenhouse gases, acid rain, ozone depletion → all three routes reach living things: human health, plants, animals and birds, aquatic life → damage returns to the people who produced the waste → need for waste management
What This Chapter Cannot Tell You
This chapter names the sources of waste and the harm each one does, but it does not measure them. It cannot tell you which source contributes most in India, or how the burden is divided between a large city and a village, because it gives categories rather than quantities.
The numbers it does give are of different kinds and should not be read as one. A world total of 11.2 billion tonnes of solid waste says nothing about any particular place, and the ppm values on the biomagnification pyramid are representative values, not measurements taken from one named lake.
Above all, the chapter stops at the impact of waste and the case for managing it. What actually to do with the waste — how to segregate, dispose of, reduce, reuse and recycle it — lies beyond the point where this chapter ends. ## 20.6 Check Your Concepts
- Study Table 20.1. Name two entries that appear in the columns of more than one kind of pollution, and explain how a single activity can pollute more than one part of the environment.
- Beginning with the burning of coal in a power station and ending with the yellowing of marble on a monument, write out the steps of acid rain formation in the correct order.
- Fig. 20.5 gives the concentration of DDT and its derivatives at four levels of a food chain.
- Calculate how many times greater the concentration in the tertiary consumers is than the concentration in the producers. Show your working.
- No extra toxin is added at any level of the chain. Explain why the concentration still rises at every step.
- Power plants that use fossil fuels, biomass or nuclear energy are located near natural water bodies. Explain why they are built there, and how that choice of site leads to thermal pollution in the water body itself.
- Explain briefly how industrial waste reaches human beings and affects their health.
- Give two differences between toxic and non-toxic waste.
- Explain how eutrophication affects aquatic life.
- Explain briefly the need for management of waste.
20.7 Case-Based Questions
- Study the waste generation figures for seven cities in Table 20.2, and then answer the question that follows it.
- What can be the cause of the lower per capita waste generation in
- Bengaluru
- Mumbai
- As a student of geography, explain why the per capita generation of waste in Ahmedabad and Chennai is high.
- Coral reefs are especially vulnerable to thermal pollution. In warm water, corals expel the algae living inside them and lose their colour, turning completely white. This is called coral bleaching. Corals can survive a bleaching event, but the more often it happens, the weaker they grow.
- List the natural causes of thermal pollution.
- In some cases thermal pollution due to natural causes results from human activities. Explain how.