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### OUR ENVIRONMENT

#### INTRODUCTION

The physical and biological world we-live in is called our environment. It has the following three important parts:
1. Living organisms                   2. Physical surroundings             3. Meteorological factors (or climatic factors).

• The living organisms which constitute environment are plants; animals, human beings and micro-organisms.
• The physical surroundings, which make up the environment are land, water bodies and air.
• The meteorological factor or climatic factors, which form a part of our environment, are sunlight, temperature, rainfall, humidity, In this chapter we are going to learn about interaction of various factors of the environment and effect of human activities affecting various biogeochemical cycles or environment.

#### ENVIRONMENTAL PROBLEMS

Effect of human activity is an important factor which causes difference in the environment of different places. Through overuse, misuse and mismanagement of natural resources to fulfil his needs, man has done great damage to the environment himself. Various environment problems have arisen as a result of pollution, increasing population and coming up of advanced science and technology. There is crowding, very less number of trees, large number of factories, which emit black smoke and large number of motor vehicles which emit poisonous gases. Moreover, due to large population there is lot of garbage, which is thrown indiscriminately on roads and other common places. These uncontrolled human activities not only pollute the city environment like soil, air and water but also harm the living organisms that are so essential for our survival. All these activities lead to ecological imbalance.

#### POLLUTION AND POLLUTANTS

With the increase in human population and advancement in technology waste materials have multiplied in quantity as well as quality. Contamination of environment with these waste material is called pollution. Not only the wastes but certain useful materials like fertilizers may also contaminate the environment. Thus, pollution may be defined as a change in the physical, chemical or biological aspects of environment which make it harmful for living organisms. Materials or agents which cause pollution of the environment are termed as pollutants e.g., smoke from vehicles, industries, sewage, various radioactive substances.

Pollutants are categorized into two types.

Biodegradable pollutants can be quickly degraded by natural means i.e., by the action of various micro-organisms e.g. , sewage, paper, wool, bones and wood.

are either not degraded or degraded very slowly. They are not easily broken down e.g., DDT, plastics, radioactive wastes, silver foil, aluminium cans, glass and plastics. These pollutants may accumulate in large concentration as they pass through various food chains. Pollution is of five main types-Air, Water, Land, Radioactive and Noise.

ADDITION OF WASTES TO THE ENVIRONMENT

Different waste materials produced by various activities of man can be broadly classified into two categories:

Biodegradable wastes materials are those waste materials which can be broken. down into simpler, non-poisonous substances by the action of micro-orgarusms. As we know various enzymes are required to digestlhydrolyse or break food into simpler forms. These enzymes are specific in action and act only on a specific material. That is why various man made materials like plastic cannot be degraded by action of bacteria or saprophytes. They can be changed only by physical processes like heat and pressure. Some examples of biodegradable wastes are: cattle dung, paper, wool, wood, bones, leather, plant products such as wheat, maize, etc. Many industries also produce biodegradable wastes. All biodegradable wastes should be treatedptop’erJy before discharging them into soil or water. Any industrial unit, which dumps untreated wastes into soil or water, should be severely punished.

Recycling of Biodegradable Waste Materials Sometimes biodegradable wastes are recycled. In the recycling process, the nutrients withdrawn from various nutrient pools are returned back. Use of cattle dung . for the manufacture of gobar gas and use of waste vegetable matter for preparing compost· are two examples of recycling of biodegradable wastes.

Recycling of waste materials helps in maintaining ecological balance because during this process various nutrients present in the waste are returned back to the natural poolsfromwher.e they were initially withdrawn. For example, plants draw various nutrients from soil for their growth. When the plants die, they change into waste, which can be converted into compost by the action of bacteria. When compost is added to the soil as manure the various nutrients are returned back to it. Thus, recycling of waste materials helps in maintaining ecological balance. If the various nutrients are continuously drawn from the soil but are not returned back, it may create an imbalance in nature.

The waste materials, which cannot be broken down .into simpler substances easily in .nature, are known as non-biodegradable wastes. Aluminium cans, silver foil, iron, nails, plastics, glass, DDT and radioactive wastes are some examples of non-biodegradable wastes. These nonbiodegradable wastes are major pollutants of the environinent.

Radioactive waste materials are one of the non-biodegrad,able wastes, which can pollute the earth to dangerous levels of toxicity. These wastes are produced in nuclear reactors, laboratories and hospitals, which use radioactive substances. These radioactive wastes release high-energy particles, which are extremely harmful to all living forms, both animals (including man) and plants. Pollution caused by nuclear wastes assumes a universal dimension because the particles emitted by radioactive wastes spread far and wide in a short period and hence affect the populations, which are quite away from the source of pollution. Thus, pollution due to nuclear wastes is nof a problem of a particular country but is a problem of the whole world.

To conclude, we can say that recycling of waste materials helps in maintaining the ecological balance in the following ways:
1. Recycling of biodegradable wastes such as biomass helps in returning the various nutrients to the soil.
2. Recycling of non-biodegradable wastes reduces the problem of pollution because disposal of these wastes causes pollution.
3. As a result of recycling of waste materials new resources are not used. For example recycling of paper reduces the cutting of trees for the manufacture of paper.
4. Recycling reduces the volume of wastes.
5. Recycling is better than incineration as it prevents pollution.

#### ECOSYSTEM AND ITS COMPONENTS

No organism or a species lives alone, always there are associations influencing each other and organising themselves into communities. The organisms of any community besides interacting among themselves, always have functional relationship with the environment. This structural and functional system of communities and their environment is called an ecosystem.
Two main components of ecosystem are: Biotic (living) and Abiotic (Non-living).

BIOTIC COMPONENTS includes autotrophs and heterotrophs (consumers and decomposers).

Classification of Living Organisms Living organisms are mainly classified as producers, consumers and decomposers.
Producers include plants and some blue green algae which can make their own food in the form of organic compounds like sugar and starch by the process of photosynthesis. They are also called autotrophs.
Consumers depend on producers directly or indirectly. Herbivores directly eating plants are called primary consumers while carnivores consuming herbivores are secondary consumers. Both producers and consumers have their life cycles and new generation of population develop while old ones die. If the materials so locked in the body of the organism are not returned to soil and atmosphere, the cycling of materials will stop and earth will be full of dead organisms. There is continuous, breaking up or decomposition of organic materials everywhere in all ecosystems. This role is played by decomposers.
Decomposers Some organisms with a specialized mode of nutrition and life like bacteria, fungi constantly decompose dead organic materials into simple inorganic substances and during the process derive from them their food and energy. These are called decomposers or reducers. You can understand role of decomposers by not cleaning aquarium.
Parasites Some of the consumers live on or in other organisms and derive their nourishment from host’s body. They are known as parasites e.g., Tape worm, leech.

ABIOTIC COMPONENTS include materials and energy. Materials are like water, mineral salts, atmospheric gases etc. and energy is like light, heat, stored energy in chemical bonds etc.
Abiotic part is divided into 3 components:
1. Inorganic substances like carbon, nitrogen etc.
2. Organic compounds like carbohydrates, proteins, fats etc.
3. Climate like temperature, light, pressure etc.

Components of ecosystem

• The materials continuously keep on cycling i.e., entering into the living system and through death and decay returning to soil and atmosphere. This process in called mineral circulation or the bio-geochemical cycles.
• While materials keep on cycling, fresh energy is continuously trapped from the sun by green plants on one hand and lost in space through respiration by all types of organisms.

TYPES OF ECOSYSTEMS

• Terrestrial ecosystem are named after the type of organism and habital conditions, such as grassland ecosystem, crop ecosystem, forest ecosystem and desert ecosystem.
• Fresh water ecosystems are usually named upon the size and nature of fresh water body, such as river ecosystem, pond ecosystem, lake ecosystem.
• Marine ecosystem is the largest and most uniform aquatic ecosystem. Some of the ecosystems are man made and are called artificial ecosystem. e.g., garden, aquarium etc.
Ecosystem is a functional system which in balanced condition is self-sufficient and self-regulated. But at the same time, several ecosystems are interrelated and combine to form larger ecosystem. e.g., the tree ecosystem in association with have variety of other trees, smaller plants and animals form forest ecosystem.

#### FOOD CHAIN

• The series of organisms fixing energy, eating and being eaten is called a food chain.
• Each step of a food chain is called a trophic level.
• First trophic level alwaysconsist of autotrophs which can fix solar energy.
• Second trophic level is that of herbivores feeding on autotrophs.
• Third trophic level includes primary consumers feeding on herbivores.
• Fourth trophic level includes secondary consumers which feed on primary consumers.

Food chain can be traced in any ecosystem e.g.,
Food chain in a grassland
Grass → Grasshopper → Frog → Snake → Vulture.

Food chain in a forest
Plants → Deer → Lion.

Food chain in a pond
Phytoplanktons →
Zoo planktons → small fish → big fish.

• The food chain starting from the green plants through herbivores to top carnivore is called grazing food chain.
• Food chain starting from the dead organic matter being consumed by detritus feeding micro-organisms which in turn are eaten by some other predators is called detritus food chain.

In order to understand how an imbalance is created due to disruption of food chains by man’s activities, let us consider the food chain Grasses → Deers → Lions.

1. In the above food chain, if all the lions are removed, the population of deer will increase since there won’t be any lions to kill them and keep the population under control. This will lead to high consumption of grasses (producers) and may even eliminate them.

2. If the deer population is removed instead of lions, it will lead to decrease of lion population since there will not be any prey. The lions may even resort to other preys such as domestic animals or man to survive.  If the deer and lion operate in other food chains in a food web, then the removal of any of them will lead to disruption of the food web and will cause disturbance in the ecosystem

3. If the grasses (producers) are removed, then all life will come to an end. If there is no there will be no herbivores. If there are no herbivores, there will be no carnivores. ultimately all organisms will die.

#### FOOD WEB

• The food relations are not always simple chain like but forms complicated network. The netlike trophic interrelationship is called a food web.

• In a food web, one organism may be linked with several others in an interlocking food linked into a network.

• In all ecosystems not only the different grazing food chains get interlocked but the detritus chain also get interconnected.

• At each trophic level some energy is used for itself, some passes to the next trophic organisms as food and some is routed to the detritus food chain by way of excretion. Food chains do not operate in isolation i.e., various food chains are interconnected to each other forming a complex network. For example, food chains in a grassland, a forest, a crop field or a pond form a network with intercrossed and linkages. Grass may be consumed by rabbit which is in turn consumed by hawks. The grass is also consumed by insects which in turn are consumed by frogs. Frogs are consumed by snakes and snakes by hawks.  The network formed by various food chains which are interconnected with each other is called a food-web.
A particular organism may occupy position in more than one food chains. For example, in the food web shown above, mice are present in two food chains. These chains are :

Plants → Mice → Snakes → Hawks
Plants → Mice → Hawks
In the first food chain mice are consumed by snakes whereas in the second food chain they are consumed by hawks. Other food chains operating in this food web are:

Plants → Grasshopper → Frogs → Snakes → Howks
Plants → Grasshopper → Insects → Frogs → Snakes → Howks
Plants → Rabbits → Hawks
Plants → Seed eating birds → Howks.

THE FLOW OF ENERGY IN AN ECOSYSTEM

In a food chain, food which provides energy is transferred stepwise from one trophic level to another. Thus, energy is used and conveyed from one trophic level to another. This process is called ‘flow of energy’. It is a one way process and energy once used by the food chain of an ecosystem is lost forever. The initial level where energy from the environment enters the living components is at the producer level. Green plants trap solar energy from the sun and utilize it for photosynthesis. Plants are able to trap the sun’s energy due to the presence of green pigment, chlorophyll, present in them. This process converts solar energy into chemical energy which is stored as carbohydrates. About 1% of the total sun’s energy that reaches earth is used up in photosynthesis. The chemical energy stored in plants is used up in their respiration growth (tissue building) and repair. Some of the energy is not utilized and is released into the community environment. Plants are consumed by herbivores (First order consumers). The chemical energy stored in the plants as carbohydrates is consumed by herbivores as food. A portion of this energy is used for metabolic activities and growth of the herbivores. Some of the energy is not utilized and is released by these animals as heat into the environment.

The herbivores are consumed by carnivores (Second order consumers) and the same process is repeated as in herbivores and unutilized energy is released into the environment by these animals as heat. The amount of energy which is released as heat into the environment is taken to be lost. It may be noted that a part of the energy at each trophic level is transferred to the decomposers or decay organisms. The decomposers utilize a part of this energy for maintaining their life prpcesses. The unutilized energy is released as heat into the environment.

From above discuussion we conclude :

• One percent of solar energy is trapped by green plants and is converted into food energy by the of process of photosynthesis.
• Part of the chemical energy in plant tissues is passed from organism to organism as they are successively eaten.
•  Ultimately the entire energy trapped by green plants at one time is lost from the ecosystem in several stages.
• 10% energy is passed from one trophic level to another. e.g., when green plants are eaten by herbivores then only 10% of the energy available with plants is passed to them.
• Most of the heat i.e., 80% is lost as heat to the environment and some is used to carry out various metabolic activities like digestion, growth, reproduction etc., and doing work.
• Energy therefore does not move in a free condition, but rather through organic materials from one trophic level to another.
• One important concept of ecological energetics is that energy always flows in one direction in the ecosystem while materials like carbon, nitrogen, hydrogen, oxygen etc. are repeatedly used in the ecosystem cycling from inorganic to organic and back to inorganic forms.
• Since very small amount of energy is passed to the next trophic level, food chains consist of three to four steps. After this, energy left is not sufficient to survive.
• At each trophic level, some energy is transferred to the decomposers. The decomposers utilize a part  of this energy for maintaining their life processes.
• There is a loss of energy at each energy transfer in various trophic levels, which is lost to the environment in the form of heat. Therefore, the amount of energy available at each successive level is less than  the previous level.

Studies of various food chains show that the energy available at each successive level is 10% of the previous level. This is called the 10 per cent law. In the given illustration, 1000 J of energy is available to the plants from the sun. Plants convert 1 per cent of this energy into chemical energy.  Thus, 10 J of energy is stored in plants. This energy is available to herbivores. Herbivores retain 10 per cent of 10 J i.e., 1 J as stored energy and 9 J of energy would be lost to the environment. Thus, only 1 J of energy would be available to carnivore as food.

The flow of energy in the living components of the biosphere is unidirectional.

The energy enters the living components from non-living environment through photosynthesis. The radiant energy of sun converted into chemical energy is never converted back into radiant energy but is dissipated into the atmosphere as heat at every step. In food chain, a large amount of energy remains unutilized and is lost to the environment as heat at each trophic level. The energy lost as heat to the environment cannot be reutilized by plants for photosynthesis.

Energy transfers in the biosphere in food chains obey the laws of thermodynamics.

• The first law of thermodynamics says that energy can be converted from one form to another but can never be created or destroyed. In a food chain it is observed that energy is converted from one form to another. It is frequently transformed into heat energy which is unusable and is released into the environment. But the energy itself is not destroyed.
• According to the second law of thermodynamics energy transformation is never completely efficient. Whenever energy is transformed from one form to another, there is a decrease in the amount of useful energy; a part of energy is converted into heat. Thus, energy transformation in the biosphere among living organisms obeys the laws of thermodynamics.

Vegetarian food habits can provide more energy:
It can be observed that with successive trophic levels, there is decrease in the amount of energy available. Hence, if we are closer to the producer level, we can get more energy (calories) from the food because at the producer level, the amount of energy available is the highest. Consider the two food chains involving man as given below:
Producers (Plants) → Goat → Man
Producers (Plants) → Man

In the second food chain, man is closer to producer level and hence he gets more energy. On the other hand in the first food chain involving three steps man is away from the producer level and hence gets less energy. As an illustration, let us consider a case in which plants receive 1000 J of energy from the sun. Plants convert 1% of the solar energy into food. Thus, 10 J of energy would be stored in plants as food. Now, if the man is vegetarian then he would get 10 J of energy by eating plants.

$Plants\buildrel {10J} \over\longrightarrow Man$

However, if the man is non-vegetarian he would receive only 1 J of energy by eating meat in a three step food chain

$Plants\buildrel {10J} \over\longrightarrow Goat\buildrel {1J} \over\longrightarrow Man$

Here goat receives 10 J of energy and transfers 10% to man. Thus, a non-vegetarian man receives only 1 J of energy. From this we conclude that vegetarian food habits provide more energy than non-vegetarians.

#### ECOLOGICAL PYRAMIDS

Food chains involving various living organisms in a community can also be represented in a graphical manner by drawing pyramids called ecological pyramids.
An ecological pyramid is a graphical representation of a specific parameter (such as number, biomass or energy) of a food chain.
Ecological pyramids have various levels. The producer level is represented by the base of the pyramid. And as the trophic levels increase the pyramid goes on tapering upwards. The carnivores are on top of the pyramid. Ecological pyramids can be of various types-pyramid of number, pyramid of biomass, pyramid of energy. Pyramid of number is constructed on the basis of the number of organisms at each level. Pyramid of weight is constructed on the basis of biomass of all the organisms at each trophic level. Pyramid of energy is constituted on the basis of the energy contained in all the organisms at each trophic level.

#### PYRAMID OF NUMBERS

Pyramid of numbers is constructed on the basis of the number of organisms at each trophic level in the food chain. In a food chain, the number of animals decreases at successive trophic levels. At the bottom of the pyramid are the green plants which synthesize food through photosynthesis, using sun’s energy. Just above the plants are herbivores. The animals at the lowest level of the pyramid are large in number. At the successive higher levels of the pyramid, the number of animals decreases. The top carnivores at the top of the pyramid are very few. For example, in a forest there may be large number of deers but there will be only a few lions.

#### PYRAMID OF NUMBERS

Pyramid of Biomass Biomass means the amount of living matter. The pyramid ofmass is constructed on the basis of mass of all organisms in each trophic level in the food chain. The total biomass of the plants is greater than that of the herbivores. The total biomass is greater than that of first order carnivores. In a food chain only 10 per cent of the biomass is transferred from one trophic level to the next level in the food chain as illustrated

Pyramid of Biomass

Pyramid of Energy The pyramid of energy is constructed on the basis of total energy contained in all the organisms ofeach trophic level of the food chain. As discussed earlier, the amount of usable energy decreases at each trophic level in a food chain because at each step some energy is lost as heat to environment. Plants have the maximum store of chemical energy. Herbivores have less energy which is only about 10 per cent of the energy stored in plants. Only 10 per cent of the chemical energy of previous level is retained by the next trophic level. This is called 10 per cent law. As an illustration let us assume that 10 J of energy is stored in plants. Herbivores feeding upon them would retain 1 J (10% of 10 J ) of energy. Carnivores feeding on herbivores would gain 0.1 J (10% of 1 J) of usable energy. This is illustrated

Pyramid of Energy

#### BIOMAGNIFICATION

Biomagnification is another aspect of food chain in which harmful chemicals enter food chains and are passed from one trophic level to another getting concentrated at each level.

ACCUMULATION OF HARMFUL CHEMlCALS IN FOOD CHAINS

It is seen that through the food chain some harmful chemicals enter our bodies. We know that pesticides and insecticides are used to protect crops from diseases and pests. These chemicals enter  the soil and gradually either enter the water table or get absorbed by plants along with water and mineral salts. Thus, they enter the food chain at the producer leveL At each trophic level these harmful chemicals get more and more concentrated and ultimately reach our bodies. It has been shown by studies that humans have higher concentration of these chemicals than organisms lower in the food chain. For example, DDT which is used against mosquitoes is present in the highest concentration in human beings. Thus, we can conclude that an organism which is on the extreme right .ofthe food chain, has the maximum concentration ofthe harmful chemicals in its body. This phenomenon is known as biomagriification or biological magnification. The following example illustrates the phenomenon of biomagnification.

The process of concentration of harmful chemicals such as pesticides, at each successive step in a food chain is called biological magnification.The process of concentration of harmful chemicals such as pesticides, at each successive step in a food chain is called biological magnification. Man being an omnivorous, eats fish, meat as well as vegetables. Being a powerful and intelligent animal, he is very rarely eaten by any animaL Moreover he disposes his dead ones in such a way that scavengers do generally not consume them. Thus, he is at the top of most food chains. In other words, he is only a consumer. As a result of pollution, there are greater chances of accumulation of harmful chemicals in his body, which can be very harmful. Accumulation of Metallic effluent like mercury and fluorine are very harmful for human health. Mercury can lead to disease namely Minamata and fluorine can lead to knee-knock syndrome i.e., bending of legs. Fluorine may also cause fluorosis.

• Methods to reduce intake of pesticides
— Use of manures rather than fertilizers.
— Minimum use of chemicals like pesticides etc. Instead biological method should be used to control insects and pests.
— Disease resistant varieties of crops should be developed by using hybridisation technique.
— Domestic and Industrial wastes should not be disposed in lakes and rivers.
— Wash fruits and vegetables before their consumption.

##### EFFECT OF HUMAN ACTIVITIES ON ENVIRONMENT

Some of the activities of man have disturbed the environment:

1. Deforestation
• For getting wood for fuel and furniture.
• For developing fields for cultivation.
• For developing urban areas.
2. Mining to get various minerals, coal and petroleum.
3. Use of large number of vehicles for transportation.
4. Generation of electricity through
• Thermal power plants.
• Hydroelectric power plants.
• Nuclear power plants.
5. Construction of roads, railway tracks etc.
6. Development of many harmful products such as plastics.
7. Extensive use of pesticides and other chemicals.
8. Use of chlorofluorocarbons. Various human activities change the environment and affect us. In this chapter we are going to discuss two major environmental problems i.e.
• Ozone layer depletion. • Waste disposal.

##### OZONE DEPLETION

As we know that around 23 km from the surface of the earth there is a thick layer of ozone gas. It is formed by the action of sun’s rays on oxygen. This thick layer of ozone also called ozone blanket is very effective in absorbing ultraviolet radiations given out by the sun. Thus, it protects the earth from the harmful effects of ultraviolet rays. In the year 1980 scientists noticed a ‘hole’ in the ozone blanket covering the upper surface around Antarctica. This fact is of great concern as harmful ultraviolet rays can now come to the earth through this hole. This will increase the level of uV-rays reaching the earth. An increased level of ultraviolet rays is very harmful as it can cause skin cancer and genetic disorders.
Main cause of depletion of ozone layer is chlorofluorocarbons (CFCs). Another cause of depletion of ozone layer is emissions from jet aeroplanes. Chlorofluorocarbons have the largest ozone d.epletion potential (ODP). Chlorofluorocarbons when released from air conditioners, refrigerators, spray cans and industrial solvents drift in the stratosphere very slowly. Therefore, each chlorine atom form chlorofluorocarbons gets sufficient time to destroy a large number of ozone molecules (approx. 100,000). The first chlorofluorocarbons produced in 1931 are still in the sky today. Now, all over the world, the use of. chlorofluorocarbons is being banned.

• Ozone iN our atmosphere is formed by interaction between oxygen molecules and ultraviolet light as follows : U.V. light + O2 → O + O

• Single atoms of oxygen are very reactive and combine with O2 to form O3 i.e., ozone
2O + 2O2 → 2O3

#### CAUSES OF OZONE DEPLETION

There are three main causes of ozone depletion :

1. Human activity is by far the most prevalent and destructive source of ozone depletion, while threatening volcanic eruptions are less common. Human activity, such as the release of various compounds containing chlorine or bromine, accounts for approximately 75 to 85 per cent of ozone damage. Perhaps the most evident and destructive molecule of this description is chlorofluorocarbon (CFC). CFCs were first used to clean electronic circuit boards, and as time progressed, were used in aerosols and coolants, such as refrigerators and air conditioners.
• When CFCs from these products are released into the atmosphere, the destruction begins .
• As CFCs are emitted, the molecules float toward the ozone rich stratosphere.
• Then, when UV radiation contacts the CFC molecule, this causes one chlorine atom to liberate.
• This free chlorine then reacts with an ozone (O3) molecule to form chlorine monoxide (ClO) and a single oxygen molecule (O2). This reaction can be illustrated by the following chemical equation

OCl + O3 → O2 + ClO

• Then, a single oxygen atom reacts with a chlorine monoxide molecule, causing the formation of an oxygen molecule (O2) and a single chlorine atom O + ClO → Cl + O2
• This threatening chlorine atom then continues the cycle·and resuits’ in further destruction of the ozone layer.
• Measures have been taken to reduce the amount of CFC emission, but since CFCs have a life · span of 20-100 years, previously emitted CFCs will do damage for years to come.

IntraCtion of CFCs and UV radiationS damaging the ozone layer.

2. Natural sources also contribute to the depletion of the ozone layer, but not nearly as much as human activity. Natural sources can be blamed for approximately 15 to 20 per cent of ozone damage. A common natural source of ozone damage is naturally occurring chlorine. Naturally occurring chlorine, like the chlorine released from the reaction between a CFC molecule and IN radiation, also has detrimental effects and poses danger.to the earth.

3. Volcanic eruptions are a small contributor to ozone damage, accounting for one to five per cent. During large volcanic eruptions, chlorine, as a component of hydrochloric acid (HCl), is released directly into the stratosphere, along with sulphur dioxide. In this case, sulfur dioxide is more harmful than chlorine because it is converted into sulphuric acid aerosols. These aerosols accelerate damaging chemical reactions, which cause chlorine to destroy ozone.

##### IMPACT OF OZONE DEPLETION

Some of the environmental, social and economic effects of ozone depletion are:

1. Plant growth and productivity. UV radiations can affect plant growth and productivity.
2. Marine food chain. Phytoplanktons are microscopic plants that forin the basis of the marine food chain. These are particularly susceptible to increases in UV radiation. Reduced phytoplankton numbers would significantly effect other marine species, including commercial fish stocks.
3. Human health. At high exposure levels, UV radiations can weaken the human iminune system and causes skin cancer, cataracts and eye cancer. Increased levels of UV radiation will contribute to rising Incidences of skin cancer.
4. Deterioration of materials. Increased UV radiat~ons can accelerate the deterioration of plastics, wood, paper, cotton and wool.

##### CONTROL OF OZONE DEPLETION

The currently available substitutes of chlorofluorocarbons are hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). HCFCs contain one chlorine atom less than CFCs and are less harmful than CFCs. HFCs have no chlorine and hence ozone friendly. So, the ideal solution seems to be to use HFCs. But all the three gases are greenhouse gases and have global warming potential.
Montreal Protocol. In 1987, 27 countries signed international agreement to protect stratosphericozone. The main points were:
• To limit the production and use of ozone depleting substances.
• Phasing out of ozone depleting substances.
• Helping the developing countries to implement use of alternatives as CFCs. Uptill now more than 175 countries have signed the Montreal Protocol. In 1987, the United Nations Environment Programme (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 levels.

##### EFFECT OF REGULATIONS TO CONTROL OZONE DEPLETION
• Tasmania lies in the region of the Southern Hemisphere where the first signs of ozone recovery are most likely to ‘be detected, possibly around 2010-2015.
• There has been a rapid decline in the amount of ozone over the Antarctic regions since the 1970s, leading to the formation of the ozone ‘hole’.
• Between 1998 and 2001 the ozone hole covered an area of up to 26 million km2, nearly three times the area of Australia.
• Despite the reduction in use and emissions of ODSs (Ozone depletion substances), it is likely that. evidence of ozone recovery will not be seen until about 2010-2015, as the various ODSs causing the decline continue to persist in the atmosphere.
• In the meantime, Tasmania will experience minimum ozone levels for the next 10 to 15 years.
• There is uncertainty about the timing of the recovery of the ozone layer. The size and duration of the Antarctic ozone ‘hole’ was greatly reduced in 2002, but recovery of the ozone layer remains inconclusive. (in the 2003 ozone hole was the largest yet recorded).
##### LAND POLLUTION

With the rise in population there has been increase in solid wastes from domestic and commercial wastes which lead to land pollution. It is a serious problem specially in large cities where disposable containers are used. Heaps of wastes are found to be lying hen and there. Many of the wastes do not decompose at all while the organic wastes which decompose release foul smell. Few wastes when burnt, release harmful fumes. Problem of land pollution needs to be sorted out scientifically.

##### VARIOUS CAUSES OF LAND POLLUTION
1. Solid wastes from industrial, agricultural field etc.
2. Cow dung from cattle shed.
3. Sewage.
4. Various waste materials like plastics, papers, clothes, rubber, metals, peelings of fruits and vegetables are responsible for land pollution.
5. Unserviceable wooden articles.
6. Leftover eatables.
7. Food items spoilt due to fungal growth.
8. Sand and bricks.
9. Empty bottles.
10. Leather goods.
11. Ash.
##### EFFECTS OF LAND POLLUTION
1. Foul smell released by decomposition of organic wastes.
2. Blocking of the flow of water in the drains.
3. Dirty surroundings.
4. Breeding grounds of houseflies, mosquitoes.
5. Consumption of polluted water leads to spreading of various water borne diseases like cholera, diarrhoea and dysentery.
6. Burning of some wastes leads to production of smoke which is harmful for health.
7. Certain chemicals like lead, sulphur which are released from various industries finally come to land and act as land pollutants.
##### CONTROL OF LAND POLLUTION
2. Recycling of certain waste products like plastics and paper help in controlling water pollution.
3. Organic wastes can be sent to biogas plants.
4. Molten plastic wastes and asphalt can be used for making roads.
5. Volume of wastes can be reduced by burning them at high temperature.
This is known as incineration.
In this method huge volumes of waste materials from houses, hospitals, industries are burnt and thus leaving behind less amount of ash.This can be done in an incinerator.
7. Various metals can be melted and recycled.
8. Organic wastes can be buried and used as a manure after the process of composting.
9. Use of manures and bio-fertilizers can reduce the need for chemical fertilizers.
10.  By improving the mining techniques, spread of mine dust can be reduced.

##### MANAGEMENT OF GARBAGE PRODUCED

Solid wastes generated by domestic, commercial and industrial activities are often indiscriminately disposed. Unscientific management of such wastes leads to serious environmental problems. The problems are already acute in cities and towns, as the disposal facilities are not keeping pace with the quantum of waste being generated. It is very common to find large heaps of garbage in disorganized manner at every nook and corner of the cities. In sanitary method being adopted for disposal of solid wastes is a serious health concern. Particularly, during rainy season, run-off and high humid conditions increase the health hazards. The landfill sites, which are not well maintained, are prone to groundwater contamination due to leachate percolation. Open dumping of garbage serves as breeding ground for disease vectors such as flies, mosquitoes, cockroaches, rats and other pests. High risks of spreading diseases like typhoid, cholera, dysentery, yellow fever, encephalitis, plague and dengue fever may not be ruled out. There are three major ste:ps involved in the management of garbage viz. collection, transportation and disposal.

QUANTITY It is estimated that solid waste generated in small, medium and large cities and towns is about 0.1 kg, 0.3-0.4 kg and 0.5 kg per capita per day respectively.

##### COMPOSITION

The composition of garbage in India indicates lower organic matter and high ash or dust contents. It has been.estimated that recyclable content in solid wastes varies from 13 to 20% and combustible material is about 80-85%. A typical composition of municipal solid waste is given below.

##### RESENT GARBAGE MANAGEMENT PRACTICES

Collection of Garbage
Garbage is generated from residential and commercial complexes. Current practices in residential areas for collection of garbage differ from city to city.

Collection Centres
Each city has its own system for setting up of waste collection centers. The waste is collected from communities in a smaller bin, which is then transported, to larger bins known as secondary collection facility.

Transportation of Garbage
Transportation of waste from collection centers to final disposal site is another important step in the management of garbage. It has been estimated that approximately 60% ·of waste is collected for transportation to the disposal sites.

Disposal of Garbage
The disposal of garbage in a well-managed land, adopting scientific methods of operation is termed as sanitary land-fill (SLF). Most important aspect relating to landfill is, identification of a suitable site. Landfilling is a slow and time consuming process. Most of the landfill sites in India are uncontrolled dumps and are not sanitary landfills where domestic, commercial, industrial and hospital wastes are dumped together. The garbage on such sites is not properly speedy and compacted. Thus, sites identified for filling are not properly maintained.

Community Participation

• Creating mass awareness, ensuring public participation in segregation of recyclable material and storage of waste at source;
• Ensuring public participation in community based primary collection system;
• Organizing ragpickers for collection of recyclable material at the community level;
• Providing health education to the ragpickers and suggesting tools for safety;
• Providing employment through organizing door to door collection of waste; and encouraging minimization ofwaste through in-house backyard composting, vermiculture and biogas generation etc;
• Recycling;
• Wealth from wastes: technologies;
• In the recent past, private sectors have taken initiatives to use the garbage as profitable venture, Incineration, Composting, Vermiculture.Sewage treatment includes the following three steps:(a) Primary treatment.  It includes sedimentation, filteration, floatation and passing wastes through thick layer of gravel. After tris, sewage is neutralized.
(b) Secondary (Biological) treatment.  Neutralized material is sent to Upflow Anaerobic Sludge Blanket (UASB) where anaerobic bacteria act on biodegradable material. Mixing wastes with sludge containing bacteria and algae for consumption of organic matter and release of oxygen can prove to be useful in treatment of sewage. Digestion of organic material by bacteria is called biological or secondary treatment.
(c) Tertiary treatment.  Chlorination, evaporation, exchange and absorption constitute tertiary treatment. This treatment is meant for disinfection of the wastes and the removal of all inorganic wastes. With changing time we depend mainly on disposable and packed materials which are
nonbiodegrable. This has negative impact on our environment. Because of the rising problems arising as a result of disposal of non-biodegradable materials, like plastic cups used for tea, some alternative ways were thought. Kulhads made of clay replaced plastic cups. But later it was realized that making of lot of Kulhads led to loss of fertile top soil. This idea was dropped and presently disposable paper cups are used. These can De recycled and does not cause any environmental hazard.