1. ECOLOGY & ENVIRONMENT
1. Environment (Concept, characteristics) & its components, types
2. Ecology, objectives, scope
Environment is a very complex multifaceted term. It is not as easy task to say
what actually environment is. The term finds its wide & wild usage each & every
living being experience various stage of life from conception till death. These
experiences are related to his diverse surroundings. This whole range of diverse
surroundings in which one perceives, experience, reacts to events and changes is
conceived as Environment. This wide array of environment includes the land, water,
air, the other living organisms and individual‟s interaction with these all. It is also
concerned with man‟s ability to adopt both physically and mentally to the continuous
chain of changes in the environment.
1. Environment: The word environment has been derived from a French word
“environier” which means to surround. The surroundings or conditions in which a
person, animal or plant lives or operate constitute environment.
The external factors such as air, water etc. Which affect an organism?
2. The totality of circumstances surrounding an organism or group of organisms
especially
(a) the combination of external physical conditions that affect and influence the
growth, development and survival of organisms. “We shall never understand the
natural environment until we se it as a living organism” (Paul Brooks).
(b) The complex of social & cultural conditions affecting the nature of an individual &
community.

2. (3) Merriam-Webster: The complex of physical, chemical & biotic factors (as climate,
soil and living things) that act upon an organism or an ecological community and
ultimately determine its form and survival.
The word „environment‟ is most commonly used describing natural environment &
means the sum of all living and nonliving things that surround an organism or group
of organisms. It includes all elements factors and conditions that have some impact on
growth & development of certain organisms.
In the words of M.J. Herkovitts :- Environment is the aggregate of external forces
which affect the life and development of living organisms.
P. Gisbert: Environment is something surrounding us from all sides and affecting one
life directly.
It covers all those circumstances which asset their influence on the individual since
conception to death. Whatever found around the individual may be covered by the
term environment. It has been defined by various psychologists and scientist as
follows:
Boring: A person‟s environment consists of the sum total of the stimulation which he
receives from his conception until his death.
Anastasi: The environment is everything that affects the individual except his genes.
Douglas & Holland: the term environment is used to describe in the aggregate, all the
external factors influence and conditions which affect the life, nature, behaviour and
the growth, development and maturity of living organisms.
In fact environment is composed of all elements that exist on earth in different forms.
These may be biotic or a biotic, social or economic.

3. The term environment refers to the surroundings of an organism which includes both
living and nonliving components. The word meaning of environment is to surround
and to develop. The words „surround‟ and „develop‟ raise two basic questions:
(1) What is surrounded and developed? The answer is man.
(2) What surrounds and develops the ma
The simple answer is other organisms e.g. other living organisms social cultural &
economic surroundings and all non living components hand, water, air, rain, humidity,
atmospheric pressure.
Thus environment consists of natural as well as socio-cultural environment.
Man has to improve the quality of his environment because these are so many hazards
deterioting the environment and have led to life threatening ecological imbalance.
Basic characteristics of environment
Wood worth and marquis: Environment covers all the outside factors that have acted
on the individual since he began life.
In the words of Grouter (1983), “Environment is any evening or condition outside the
organism that is presumed to influence or be influenced by person‟s development.
According to Marshall McLuhan, “Environment is not just containers, but is processes
that change the content totally.
According to good (1959), “Environment as a term designates the entire objects and
conditions that affect the individual through such stimuli as he is able to receive.
According to Chapman & Reiss (1992): Environment is surrounding of an organism,
including other organism and other physical features.
Basic Characteristics of environment

4. Above discussion leads us to following basic characteristics of environment.
(1) Sum total of conditions which surround man at given point in space & time.
(2) Sum total of the stimulus man receives from the time of conception until his
death.
(3) Everything affecting the individual except his genes.
(4) All external forces affecting growth & development of living organisms.
(5) Includes biotic as well as a biotic components as well as physical, chemical,
biological, social, economic, political & cultural processes.
(6) It has direct as well as indirect effect.
(7) Biome, Habitat and energy constitute the three basic components of the
environment‟s structure.
(8) Well organised system of mutually interacting and well integrated elements,
with elements of a component interacting not only among themselves but also
with elements of other components.
(9) Open system characterised by a perfectly continuous system of input and
output of matter & energy.
Perfect functioning system in which each unit is intimately related with each other
unit through a series of large cyclic mechanisms such as biogeochemical cycles,
water cycle, energy cycle.
Empowered mainly by the input of solar energy.
Is self sustaining & has its own productivity. It generates organic matter. Its rate of
growth of course depends upon the availability and amount of energy.

5. Normally maintains ecological balance unless there is disturbance in one or more
controlling factors.

6. Components of Environment
Experts engrossed in the study of environment opine that environment is both
physical and biological concept which encompasses both living and nonliving
components and they in turn are empowered by energy component. So we can say
that environment consists of three basic components.
(a) Abiotic (physical or inorganic or nonliving)
(b) Biotic (Organic or living or biological)
(c) Energy
Abiotic Component
The physical and the chemical components of the ecosystem build up the
abiotic structure. They consist of
(a) Lithosphere (physical space)
(b) Atmosphere (Climate)
(c) Hydrosphere (Water)
Lithosphere: It consists of the soils and the sediments which are the chief reservoir
of mineral nutrients. It occupies 29% of earth‟s area and provides the habitat for
most of the plants and animals. Lithosphere is a dynamic component and is
undergoes continuous formation & modification through forces which may be
endogenetic (internal) and exogenetic (external). Endogenetic forces perform the
role of modification. Exogenetic forces have their origin point in atmosphere,
hydrosphere and even in the sun and moon also. There are innumerable no of
forces like geochemical cycles, tectonic processes, hydrologic cycle, geological &
geothermal processes. Which alone or their combined effect have produced a

7. tremendous variety of geological & geomorphic features each of which is of great
significance for human beings.
Atmosphere
It is the blanket of air around the earth which is a chief reservoir of gases essential for
organic life. It performs many crucial functions for the sustenance of life on earth.
It protects the living organisms from various harmful cosmic radiations and maintains
the favourable climate on earth. By permitting the penetrations of adequate quantities
of life giving sunlight to earth‟s surface.
It also acts as filter or well as thermal insulator. Keeping the earth‟s surface
much warmer. It also provides the media for transporting energy and moisture from
one place to another. So atmosphere shapes the climate of the earth and determines the
nature and distributions of life.
The various constituents of atmosphere interact in an extremely complex way
not only with in an extremely complex way not only with incoming solar energy but
also with solar energy escaping from the earth which lead to variations in temperature.
It height varies from 16-29 kilometres from seal end. Its general composition is
as follows:-
Table Composition of atmosphere
Nitrogen Water vapour
Oxygen Particulates
Argon
Carbon dioxide
Other inert gases

8. Its composition varies from place to place but still wind & diffusion of gases
helps in maintaining uniformity water vapours also vary in amount from place to place
and there amount decreases from equator to poles. Particulates help in scattering of
solar radiations giving various colours & hues to the sky. Besides this they help in
cloud formation and condensation.
Besides these constituents, atmosphere has one another important feature that
controls life i.e. temperature. It is highest near the earth‟s surface and goes on
decreasing upward at the rate of 1o
F for every 300 feet upto tropopause. Beyond this
temparture is either steady or slightly rises Fig. Layers atmosphere.
Hydrosphere
It is the chief reservoir of water and includes all the water and includes all the
water bodies like oceans, lakes, ponds, rivers and even the ice caps & glaciers,
underground water, and the water in the soil. It plays an important role in the
circulation of nutrients. Its flow determines the configurations of earth‟s surface and is
the basis for human settlements & transportation. Its flow in nature is regulated by the
sun in the form of water cycle. Total amount of water in the environment remains
constant. Only its form and location undergoes change from time to time and place to
place.
Fig. 3 Pg -18 (R.C. Chandna)

9. Out of all the sources of water, oceans provide one of the most hospitable
environments for organism life. They constitute the largest single habitat. They put a
tremendous effect on the coastal environment through sea waves, ocean currents and
tides.
Abiotic components may also be further divided into two categories.
Diagram............
BIOTIC COMPONENTS
Earth is the only known planet to have life in various forms that too upto few
kilometres of the earth‟s layers. There is no sign of life below or above this belt. This
belt of earth that sustains life is called biosphere. This whole life in the biosphere can
be further categorised into three.
(a) Producers
(b) Consumers
(c) Decomposers
Producers
These are mainly consists of green leafy trees and plants. They are called
producers because only they have the capacity to trap solar energy and to use elements
from earth to convert them a form that can be used both by them as well as other
forms of life. In other words only they can perform photo synthesis to make their own
food. They are also termed as autotrophs.

10. Consumers
Consumers or the heterotrophs are those organisms which depend upon green
plants for their food either directly or indirectly. All animals including man fall under
this category. They are further of 3 types.
(a) Herbivores – eat only plants
(b) Carnivores – eat only animals
(c) Omnivores – eat both plants as well as animals.
All these cannot produce food themselves they consume food produced by
plants.
Decomposers
Or the Scavengers they are the nature‟s way of cleansing this earth. They form
an important link in returning back the nutrients taken from earth by plants and
animals in various forms. These include all the micro organisms like bacteria & fungi
which decompose the dead animals and plants and recycle the nutrients.
All these abiotic components are not living but support other living organisms.
If any of these components loses its balance. Whole of the life gets disturbed and
where are these three reservoirs intermingle in optimum amount that area becomes the
most fertile area for organic life.
All flesh is grass. This simple statement conveys the basic principle of biology.
It means that fundamental source of food for all consumers is green plants the grass.
These consumers including man may be herbivorous, carnivores or omnivorous. They
all obtain energy and nutrients for their sustenance, growth & reproduction directly or

11. indirectly (by eating animals that have eaten animals which in turn have eaten plants)
on plants.
Energy Component
Energy is another vital component of the environment without which life could
not have existed on the planet. Energy is essential for generation and reproduction of
all biological life on this planet. It is the input of matter and energy which makes the
life a possibility. The pattern of energy flow in the environment is governed by first
two laws of thermodynamics.
1st
law: Energy can neither be created nor be destroyed. It can only be converted
into other form.
2nd
law: In any transfer of energy, there is always a loss of available energy.
All sources of energy whether in the form of solar energy, wind energy,
hydro energy or tidal energy lie virtually outside the biosphere sun of course is the
major source of energy for proper functioning of the ecosystem. Flow of energy is
unidirectional and this energy flow and the system of matter distribution and
circulation are most critical for functioning of the ecosystem.

12. Types of Environment
The term environment is a very comprehensive term. However by adding a pre-fix to
the term environment, its meaning gets restricted. According, authors have recognised
following types of environment with each type carrying only a restricted meaning.
Physical Environment: Only nonliving elements it comprises surrounding
an organism.
Biological Environment: Comprises only living elements that surround and
organism including the organism itself.
Socio-Cultural Environment: Comprises all human activities, his interactions
with other humans and his living conditions
facilities and equipments he uses and his
settlements.
Perceptual Environment: It is the environment as perceived by an organism
so it varies from person to person and is an abstract
concept.
Conceptual Environment: It comprises the ideas that govern the form and the
use of the constructs. It emphasises the superiority
of human mind in relation to other organism.
Human Environment: It comprises of interactions between organisms and
their surroundings. Among all organisms, man is
bestowed with intelligence and is superior to other
organisms. HE is the one who can modify his

13. environment to suit his requirements. He has
turned the natural environment of earth to
manmade landscapes.
Operational Environment: Comprises all those factors which are perceivable
as well as non-perceivable, living as well as
nonliving including viruses.
Total Environment: All the forces and materials on earth in any
situation that may or may not influence behaviour
in a specific situation e.g. gravitational force,
magnetic field of earth, attitude etc.
So from above we can see that all these types cannot be isolated from each other.
They are not enclosed in water tight compartments. There is a relationship of give and
take environment is a conglomeration of all of these. It is a comprehensive term.

14. Ecology
The term ecology was coined by Ernst Haeckel as Oecology or Oekology
(derived from two greek words „Oikos‟ meaning dwelling or house or habitat and
„Logos meaning the study of).
So we can say ecology is the study of habitats or the study of relationships between
organisms and their environment.
Alles et al. (1949) considered ecology as, “the science of inter-relation between living
organisms and their environment, including both the physical and biological
environments and emphasizing inter-species as well as intra-species relations.”
G.L. Clarke (1954) defines ecology as “The study of inter-relations of plants and
animals with their environment which includes the influences of other plants and
animals as well as those of the physical features.
McFadden (1957) defined ecology as, “a science which concerns itself with the inter-
relationships of living organisms, plants, animals and their environments”.
L.R. Taylor (1967) have defined ecology as “the study of the way in which individual
organisms, populations of some species and communities respond to those changes.”
Southwide (1976) defined ecology as, “the scientific study of the relationship of living
organisms with each other and with their environments.” He further explained his
definition of ecology by stating that, “it is the science of biological interactions among
individuals, populations and communities, and it is also the science of ecosystems the
inter-relations of biotic communities with their non-living environments.
Pinalea (1973) described ecology as, “the study of relations between organisms & the
totality of the biological & physical factors affecting them or influenced by them.

15. C.J. Krebs (1985) defined ecology in simple and in comprehensive ways as “Ecology
is the scientific study of the interactions between organisms and nature that determine
the range/distribution and abundance of organisms.”

16. Basic Characteristics
1. It is basically science of ecosystems.
2. It is the study of interrelationships and interdependence between organisms and
environment.
3. It include the structure & function together for full understanding of this vast
nature.
4. It is the scientific approach for controlling and regulating the welfare of living
organisms.
5. It emphasises inter organisms as well as intra organismic relations.
6. It is a philosophy in which the world of life is interpreted in terms of natural
processes.
Fundamental Principles
1. Man being an active agent or environmental change, modifies the ecosystem
through the exploitation of natural resources.
2. Ecosystem instability results when an ecosystem becomes unable to adjust with
environmental changes.
3. All living organisms and physical environment are mutually reactive. The
organisms interact among themselves and affect each other and physical
environment.
4. Ecosystem functions through the input of energy mainly solar radiation which
is trapped by green plants and is used to prepare food through the process
photosynthesis. The solar radiation is the main driving force of the ecosystem.

17. In any system of constant mass, energy is neither created nor destroyed but is
can be transformed from one type to another type.
5. Natural hazards affect adversely the biological communities in general and in
particular. When biological processes are associated with physical events, yet
severe hazards are created.
6. Sustained life on earth is a characteristic of ecosystem, not of individual
organisms or population.
7. Ecosystem is a fundamental unit of ecological study because it comprises both
biotic and abiotic components.
8. The ecosystem productivity depends on two factors:
(a) The availability of the amount of solar radiation to the primary producers.
(b) The efficiency of plants to convert solar energy into chemical energy.
9. Environmental principles of holistic nature of natural environment which
largely affect the biological communities in a biospheric ecosystem.
10.The physical and biological processes follow the principle of uniformitarian
which states the same physical and biological processes, as the environment is
influenced by human activity.
Aims and objectives of Ecology
1. To provide the true understanding of the structure and functions of the mother -
nature.
2. To study the wide network of relationships between living beings and their
environment.
3. To analyse the interdependence between various components of environment.

18. 4. Evolving scientific approaches to control and regulate welfare of living
organisms.
5. To study these interrelations from evolutionary point of view of development.
6. Evolving mathematical models of interaction between various components of
environment.
7. Employing system analysis approach to improve the status of environment.
8. Providing comprehensive awareness to the masses of there relationships and
interdependence.
9. To study conservation and management of natural resources and environmental
pollution.
10.To observe the biological productivity of nature and how the products may be
used to improve the quality of life of man.
Branches of Ecology
It is broadly divided into two branches:
1. Autoecology: It concentrates on one species of organism in all aspects
like life cycle, home range, populations, dynamics &
Behaviour e.g. Royal Bengal Tiger.
2. Synecology: It deals with ecological studies of entire ecosystem like a
forest or a desert etc.
Besides this ecology has been classified on the basis of specialization:
Branch of Ecology Area of Study

19. 1. Habitat Ecology : The study of different-habitats on earth and their
effects on the organisms.
2. Geographic Ecology : The study of geographical distribution of plants and
animals
3. Ethology : The interpretation of animal behaviour under
natural surroundings.
4. Human Ecology : The study of man and man‟s relation to the
environment and man‟s effects on biosphere and
implication for man.
5. Community Ecology : The study of the local distribution of animals in
various habitats.
6. Population Ecology : The study of growth, structure and regulation of
population of organisms.
7. Applied Ecology : The study of the human needs and the applications
of ecological concepts e.g. agriculture, forestry,
land use etc.
8. Production Ecology : It deals the production of different ecosystems like
fresh water, crops sea water etc.
9. Sociology : The study of ecology and ethology of mankind.
10. Radiation Ecology : The study of effects of radiation on environment
and organisms.
11. System Ecology : It deals the analysis and understanding of the
structure and function of ecosystem. It employs

20. mathematical models.
Biosphere, Community, Population, ecosystem, levels major ecosystem of the world.
Hierarchy in Nature
Hierarchy is a form of organization in which certain components of a system
regulate the activity of other components. Three kinds of hierarchy are recognized in
nature:
1. Physical
2. Biological
3. Ecological
1. Physical Hierarchy: The smallest structural unit of both nonliving and living are
protons, neutrons and electrons. These particles combine to form atoms. The atoms
combine to form molecules. The latter join together to form complexes of compounds
in living objects, the complexes of compounds form organelles. The organelles form is
living unit called the cell.
2. Biological Hierarchy: It begins from the cell. Cells combine to form tissues which
in turn constitute the organs. The organs form the organ systems. All the organs
systems together form an organism.
3. Ecological Hierarchy: Organism is the smallest unit of ecological hierarchy. It
forms populations, species, biotic communities and ecosystems. All the ecosystems of
the world constitute the biosphere or ecosphere.
Diagram........

21. Organism
It is the basic unit of ecological hierarchy. An individual is a distinct living being
which carries out all the life processes in its body. Separate from these being
performed in the body of others. It may be unicellular or multi cellular. It is the lowest
level which can survive individually. Belo this level, no component can survive
individually. Below this level no component can survive individually separate from it.
It has its distinct identity and has a particular life span. They show movement, growth,
self regulation, self repair, reproduction etc.
Individual organisms are grouped variously to produce populations,
community, ecosystem and biosphere.
Population
It is a nearly permanent aggregation of individuals of the same kind which inhabit a
particular space or geographical area at a particular time. These may be several rather
numerous such geographically localised groups belonging to one type of organism or
species e.g. spotted deer in various forest, a grass in various localities, and bull frogs
in different ponds. The different populations of the same organism are often called
local populations. Members of the local population freely interbreed. A local
population may be adapted genetically to its particular environment. It is then called
ecotype.
Species
All the populations of the same kind of organisms which can interbreed successfully
from a species e.g. all humans form one species Genus-Homo, Species sapiens.

22. Community
The organisms of all the species that live in a particular area and interact in various
ways with one another form biotic community. It is a group higher than population. It
is an assemblage of all the populations of different organisms occurring in an area.
The different Populations of a community do not remain isolated. They show
interactions and inter-dependence.
Ecosystem
Any unit that includes all the organisms in a given area, interact with physical
environment so that flow of energy leads clearly defined trophic structure, biotic
diversity and material cycle within the system is called ecosystem.
All parts of an ecosystem-organic and inorganic, biome and habitat may be regarded
as interacting factor which in a mature ecosystem are in approximate equilibrium, it is
through their interactions that the whole system is maintained. It is an open system
which is characterised by continuous input and output of matter & energy. It is
powered by energy of various sorts but the solar energy is the most significant
radiation and tends to be relatively stable equilibrium. It has the natural resources
system. It is well organized and structure system. It has its own productivity which is
the process of building organic matter based on availability and amount of energy
passing through ecosystem. The productivity refers to the rate of growth of organic
matter in a space unit per time unit.
Components of Ecosystem
There are the three major components of ecosystems:
1. Energy Components – Radiant (Solar) and fixed (fwd) energy.

23. 2. Physical Components – Land, water, air and sunlight
3. Biological Components – Plants & Animals including Human beings.
Table
Types Components & Substances
1. Abiotic (Physical) : Land, Soil, Water, Air & Sunlight
2. Biotic : Plants and animals – carbohydrates, proteins, fats &
liquid substances
3. Biogenic : Carbon, nitrogen, hydrogen, calcium and potassium
4. Energy : Radiant (solar energy) and fixed energy.
Biosphere:
It is the biologically inhabited part the earth comprising of all the ecosystems
of the planet.

24. Classifications of Ecosystems
Characteristics of an eco systems are determined by a no of factors. The important
ones are:
(i). Temprature range (ii) Latitude and attitude
(iii) Intensity and duration of summer & winter.
(iv) Amount and periodicity of rainfall
(v) Soil characteristics
(vi) Geographical barriers like mountain or sea
(vii) Topography
(viii) Water mass
There are different types of ecosystems of nature. Broadly these can be classified into
three categories.
a. Natural Ecosystems
b. Artificial Ecosystems
c. Space Ecosystems
Natural Ecosystems:- They operate by themselves under natural conditions without
any major interference by man and based upon the particular kind of habitat, they are
further divided into two sub categories.
a). Terrestrial b). Aquatic
Terrestrial
It includes latitudinal & attitudinal ones:
A. Latitudinal Ecosystems:

25. The major terrestrial ecosystems are : (i) Tundra (ii) Taiga (iii) Deciduous forest
(iv) Tropical rain forest (v) Chapporal (vi) Tropical Savannah (vii) Grassland and
(viii) Desert
1. Tundra: It lies north of timberline or 60o
N latitude below the polar ice. It
occurs only in the arctic region.
2. Physical Characteristics: This area receives very little precipitation around 25
cm per year that tooin the form of snow. So climate is extremely cold with
winter temp. as low as – 30o
C to 40o
C. Summeris short (i.e. 45 75 days). The
highest summer temp. is 10o
C. Most of the soil is permanently frozen only
upper 10-20 cm melts during summer.
This alternate thawing and freezing of the upper layers produces cracks leading to
formation of ponds, pools, marshes & bogs.
Life: Life is scarce. Both plants and animals exist.
Flora: Flora is characterised by this low growing vegetation devoid of any tree. Only
those plants grow which either complete their life cycle in brief summer or can remain
alive when covered by snow. They are shallow rooted and include mosses like
sphagnum and lichens like Caledonia. Other vegetation includes grasses, sedges,
heaths, a few shrubs, dwarf willows and birches. Plants show xerophytic characters
with small and hairy leaves and folded margins.

26. BIOGEOCHEMICAL CYCLES
A biogeochemical cycle is a pathway by which a chemical element or molecule moves
through both biotic (biosphere) and abiotic (lithosphere), atmosphere, and
hydrosphere) compartments of earth. A cycle is a series of change which comes back
to the starting point and which can be repeated.
The term “biogeochemical” tells that biological, geological and chemical factors are
all involved. The circulation of chemical nutrients like carbon, oxygen, nitrogen,
phosphorous, calcium and water etc. through the biological and physical world are
known as biogeochemical cycles. In effect, the element is recycled, although in some
cycles there may be places (called reservoirs) where the element is accumulated or
held for a long period of time (such as ocean or lake for water).
Hence, a constant interaction between the biotic and abiotic component of the
biosphere makes it a dynamic, but stable system. These interactions coveist of a
transfer of matter and energy between the different components of the biosphere.
The most well known and important biogeochemical cycles, for example, include:-
Water cycle, the nitrogen cycle, oxygen cycle and carbon cycle.

27. WATER CYCLE
The water cycle, also known as the hydrological or H2O cycle, describes the
continuous movement of water on, above and below the surface of the earth. Although
the balance of water on earth remains fairly constant over time, individual water
molecules can come and go, in and out of the atmosphere. The water moves from one
reservoir to another, such as from river to ocean, or from the ocean to the atmosphere,
by the physical processes of evaporation, condensation, precipitation, infiltration, run
off and subsurface flow. In doing so, the water goes through different phases: liquid,
solid (ice) and gas (vapour).
The whole process in which water evaporates and falls on the land as rain and later
flows back into the sea via rivers is known as the water cycle. This cycle is not so
straight forward. All the water that falls on the land does not immediately flow back
into the sea. Some of it seeps into the soil and becomes part of the underground
reservoir of fresh-water. Some of this underground water finds its way to the surface
through springs.
Water is also brought to the surface for use through wells or tube-wells. Water is also
used by terrestrial animals and plants for various life processes. Also, water is capable
of dissolving a large number of substances. As water flows through or over rocks
containing soluble minerals, some of them get dissolved in the water. Thus, rivers
carry many nutrients from the land to the sea, and these are used by marine organisms.
The water cycle involves the exchange of heat, which leads to temperature
changes for instance, when water evaporates; it takes up energy from its surroundings
and cools the environment. When it condenses, it releases energy and warms the

28. environment. These heat exchanges influence climate. By transforming water from
one reservoir to another, the water cycle purifies water, replenishes the land with fresh
water, and transports minerals to different parts of the globe. It is also involved in
reshaping the geological features of the earth, through such processes as erosion and
sedimentation. Finally the water cycle figures significantly in the maintenance of life
and ecosystems on earth.
The various processes unsolved are:
Evaporation: The transformation of water from liquid to gas phases as it moves from
the ground or bodies of water into the overlying atmosphere. The source of energy for
evaporation is solar energy. Evaporation also includes transpiration from plants.
Condensation: The transformation of water vapour to liquid water droplets in the air,
creating clouds and fog.
Precipitation: Condensed water vapour that falls to the earth‟s surface. Most
precipitation occurs as rain, but also includes snow, hail, fog drip and sleet.
Approximately 505,000 km3
(121,000 cumi) of waterfalls as precipitation each year,
398,000 km3
of it over the oceans.
Run off: The variety of ways by which water moves across the land. This includes
both surface run off and channel run off. As it flows, the water may seep into the
ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for
agricultural or other human uses.
Snowmelt: The run off produced by melting snow.
Infiltration: The flow of water from the ground surface into the ground.

29. Advection: The movement of water-in solid liquid or vapour states through the
atmosphere.

30. Oxygen Cycle
Oxygen is a very abundant element on our earth. It is found in the elemental form in
our atmosphere to the extent of 21%. It also occurs extensively in the combined form
in the earth‟s crust as well as also in the air in the form of carbon dioxide. In the crust,
it is found as the oxides of most metals and silicon, and also as carbonate, sulphate,
nitrate and other minerals. It is also an essential component of most biological
molecules like carbohydrates, proteins, nucleic acids and fats (or lipids)
The oxygen cycle is the biogeochemical cycle that describes the movement of oxygen
within its three main reservoirs; the atmosphere (air), the total content of biological
matter within the biosphere (the global sum of all ecosystems), and the lithosphere
(earth‟s crust). Failures in the oxygen cycles within the
The main driving force for the oxygen cycle is photosynthesis, which is responsible
for the modern earth‟s atmosphere and life as we know it.
Oxygen from the atmosphere is used up in three processes; namely combustion,
respiration and in the formation of oxides of nitrogen. Oxygen is returns to the
atmosphere in only one major process, that is, photosynthesis. Hence it involves:-
Plants does photosynthesis to let off oxygen for organisms to use.
Animals including man use up the oxygen through respiration and let off carbon
dioxide.
The carbon dioxide through various human activities is passed on to the atmosphere
and green plants can use it once again.
This cycle repeats is the form of oxygen cycle.

31. Carbon Cycle
Carbon is found in various forms on the earth. It occurs in the elemental form as
diamonds and graphite. In the combined state, it is found as carbon dioxide in the
atmosphere, as carbonate and hydrogen-carbonate shells and salts in various mineral.
While all the life forms are based on carbon containing molecules like proteins,
carbohydrates, fats, nuclear acids and vitamins. The endoskeletons and exoskeletons
of various animals are also formed from carbonate salts.
Carbon is incorporated into life forms through the basic process of photosynthesis
which is performed in the presence of sunlight by all life-forms that contain
chlorophyll. This process converts carbon dioxide from the atmosphere or dissolved in
water into glucose molecules.
These glucose molecules are either converted into other substances or used to provide
energy for the synthesis of other biologically important molecules. The utilization of
glucose to provide energy to living things involves the process of respiration in which
oxygen may or may not be used to convert glucose back into carbon dioxide. This
carbon dioxide then goes back in to the atmosphere.
Another process that adds to the carbon dioxide in the atmosphere is the process of
combustion where fuels are burnt to provide energy for various needs like heating,
cooking, transportation and industrial processes. In fact, the percentage of carbon
dioxide in the atmosphere is said to have doubled since the industrial revolution when
humans started burning fossil fuels on a very large scale. Carbon like water cycle, is
thus cycled repeatedly through the different forms by the various physical and
chemical and biological activities.

32. Thus, the carbon cycle is the biogeochemical cycle by which carbon is exchanged
among the biosphere, pedosphere, geosphere, hydrosphere and atmosphere of the
earth. The carbon cycle involves a sequence of events of sustaining life; it describes
the movement of carbon as it is recycled and reused through the biosphere. The global
carbon cycle is divided into following major reservoirs of carbon:
 The atmosphere
 The terrestrial biosphere
 The oceans, including dissolved inorganic carbon and living and non-living
marine biota.
 The sediments, including fossil fuels, fresh water systems and non-living
organic material, such as soil carbon.
 The earth‟s interior, carbon from earth‟s menthe and crust.
The carbon exchanges between reservoirs occurs as the result of various chemical,
physical geological and biological processes.
Nitrogen Cycle
Nitrogen gas makes up 78% of our atmosphere and nitrogen is also a part of many
molecules essential to life like proteins, nuclear acids (DNA and RNA) and some
vitamins. Nitrogen is also found in other biologically important compounds such as

33. alkaloids and urea. Nitrogen is thus, an essential nutrient for all life forms and life
would be simple if all there life forms could use the atmospheric nitrogen directly.
However, other than a few forms of bacteria, life-forms are not able to convert the
comparatively inert nitrogen molecule into forms like nitrates and nitrites which can
be taken up and used to make the required molecules. These „nitrogen-fixing‟ bacteria
may be fee-living or be associated with some species of dicot plants. Most commonly,
the „nitrogen-fixing‟ bacteria are found in the roots of legumes (generally the plants
which give us pulses) in special structure called „root modules‟ other than these
bacteria, the only other manner in which the nitrogen molecule is converted to nitrates
and nitrites is by a physical process.
During lightning, the high temperatures and pressures created in the air convert
nitrogen into oxides of nitrogen. These oxides dissolve in water to give nitric and
nitrous acids and fall on land along with rain. These are then utilized by various life-
forms.
Plants generally take up nitrates and nitrites and convert them into amino acids which
are then used to make proteins. Some other biochemical pathways are used to make
the other complex compound containing nitrogen. These proteins and other complex
compounds are subsequently consumed by animals. Once the animal or the plant dies,
other bacteria in the soil converts the various forms of the compounds of nitrogen
back into nitrates and nitrites. A difficult type of bacteria convert nitrates and nitrites
into elemental nitrogen.
Thus, there is a nitrogen cycle in nature in which nitrogen passes from its elemental
form in the atmosphere into simple molecules in the soil and water, which gets

34. converted to more complex molecules in living beings and bank again to the simple
nitrogen molecule in the atmosphere.
Nitrogen cycle in nature
The process of nitrogen cycle, thus, involves following steps:
Nitrogen fixation (Conversion of N2)
Biological fixation – by some symbiotic bacteria and some free living bacteria for e.g.
Rhizobium (Symbiotic) and Azotobaiter (free living).
Industrial N-fixation – Under great pressure, at temperature of 600o
C and with irons
catalyst, hydrogen and nitrogen can be combined to form ammonia (NH3) in the
Haber-Bosch process.
Combustion of fossil fuels – Automobile engines and thermal power plants, which
release various nitrogen oxides (NOx).
Other processes formation of no from N2 and 02 during lightening.
Assimilation: Plants take nitrogen from the soil, by absorption through their roots in
the form of either nitrate ions. Animals, fungi, and other heterotrophic organisms
obtain nitrogen by irgestion of amino acids, nucleotides and other small organic
molecules.
Ammonification: When a plant or animal dies, or an animal expels waste, the initial
form of nitrogen is organic, Bacteria, or fungi in some cases, convert the organic
nitrogen within the remains back into ammonium (NH4
+
), a process called
ammonification or mineralization.
Nitrification:

35. Ammonium (NH4
+
) Nitromones Nitrites (N0-2)
Nitrites (N0-2) Nitrobcuter Nitrates (N0-3)
It is important for the ammonia to be converted to nitrates because nitrites are toxic to
plant life.
Denitrification: Denitrification is the reduction of nitrates back into the largely inert
nitrogen gas (N2), thus completing the nigtrogen cycle.
Ammonium Oxidation (An aerobically): In the biological process, nitrite and
ammonium are converted directly into elemental nitrogen (N2) gas.

36. Air pollution occurs when the concentration of a normal component of air or a new
chemical substance added or formed in air builds up to undesirable buildings & other
materials. The chemical substances causing air pollutions are called air pollutants.
Causes
The air pollution is caused by many natural activities & human activities. The natural
sources of air pollution are forest fires, volcanic eruptions releasing poisonous gases,
pollen disposal, natural bacterial decomposition of organic matter, evaporation of
volatile organic compounds from leaves, wind erosion of soil, natural radio-activity
etc.
The main manmade sources responsible for polluting air are burning of fuel in
domestic & industrial processes (coal, oil, gasoline, etc), emission from vehicles,
industrial emission of gases, thermal power generation stations, deforestation,
agricultural activities, wars, etc. The transportation & rapid industrialization are major
sources of air pollution. With the growing rate of vehicles & setting of industries, the
danger of air pollution is also increasing. The automobiles such as cars, scooters,
motors, teocies, trucks etc. are continuously releasing hug amount of poisons gases
such as corlion monoxide, oxides of nitrogen, hydrocarbons & particular had because
of incomplete combustion of petrol & diesel. A large number of industries such as
chemical industries, paper & pulp mills, textile industries, petroleum refineries,
mining, synthetic rubber industries, metallurgical plants, etc. are polluting the air by
various types of harmful inorganic toxic gases & particular matter.
Air pollution

37. Although there are hundreds of potential air pollutants, about 90% of the air pollution
problem is caused by five groups of pollutants. These are carbon monoxide, nitrogen
oxides, sulphur oxides, volatile compounds & suspended particulate matter.
The air pollutants may be divided into two types:-
1. Primary air pollutants
2. Secondary air pollutants
Primary air pollutants: - The primary air pollutants are the harmful chemical
substances which directly enter the air as a result of natural events & human activities.
Some of the common primary pollutants are oxides of carbon, nitrogen oxides,
sulphur oxides, hydrocarbons, suspended particulate matter etc.
Secondary pollutants: - The secondary pollutants are harmful chemical substances
which are formed in the air because of chemical reactions between two or more air
pollutants or a primary pollutant & one or more air components. For example, sulphur
dioxide is a primary air pollutant. It reacts with oxygen gas in the atmosphere to form
the secondary pollutant sulphur dioxide.
Oxides of carbon
Carbon monoxide is one of the serious air pollutants. It is produced in the atmosphere
by the natural processes such as forest fires, natural gas emission, marsh gas
production, volcanic activity & some human activity mainly automobiles exhausts. Of
the total CO pollution, about 74% is contributed by automobiles exhausts.
Effects of oxides of carbon:
On human health: - CO is very toxic gas because it combines with haemoglobin in the
blood, decreasing its function as an oxygen carrier. Haemoglobin in the blood

38. combines with CO to form carboxy haeglobin for transport of oxygen decreases & it
reduces the blood‟s activity for carrying oxygen. Excessive amount of CO inhalation
leades to fatigue, headache, dizziness, deficiency in awareness & judgement; visual
perception etc. The higher concentration of CO leads to loss of consciousness are even
death.
The smokers have more risks from CO dangers because smoke contains CO due to
incomplete combustion of the cigarettes. Therefore, the haemoglobin in their blood is
chronically tied up as the carboxy haeboglobin complex.
On Plants: Carbon monoxide has detrimental effects on plants such as decrease in
nitrogen fixing ability of bacteria, leaf drop, leaf curling, premature aging of the plants
etc.
On environment:- Normally, CO2 is not very toxic & is not considered as a pollutant.
However, its increasing concentration may effect the atmosphere causing undesirable
change in climate. The excess CO2 in the atmosphere may lead to increase in earth‟s
atmosphere. This effect is known as Geen House effect.
Green House Effect
Green house effect is caused by gases such as CO2, methane produced by fossil fuels,
agricultural activities & deforestation, trap the heat radiated from earth. Thus
increasing earth‟s atmosphere & causing in weather & sea-level. This is due to the fact
that earth receives a large amount of energy from the sun. But the earth absorbs
energy in the visible region & emits in the infrared region of electromagnetic region.
These partially radiated infrared radiations from the earth are absorbed by CO2 in the
air. This results in excessive heating of the earth‟s atmosphere leading to increase in

39. surface temperature. It has been estimated that the average temperature of earth has by
1o
C in the last 50 years. The scientists have predicted that if the global temperature
rises by 4-6o
C due to green house effect, the polar ice caps & glaciers will melt at sea
level resulting increase in sea level.
Remedial Measures:- The main remedies to control CO pollution are to modify
internal combustion engines to reduce the amount of pollutants formed during fuel
combustion.
Oxides of Nitrogen (NOx)
Among the oxides of nitrogen, nitric oxide & nitrogen dioxide are main pollutant;
These oxides come in the atmosphere from the combustion at high temperature in the
automobile engines & electric power stations.
The basic reaction leading to the formation of these oxides are:-
N2 + O2 high temp 2 NO
Nitric oxide
2NO + O2 2NO2
Nitrogen dioxide
These are also formed during natural activities such as bacterial oxidation of ammonia
in soil, forests fires & lightning. Many industries are also rebasing these nitrogen
oxides in the atmosphere.
Effects on health:- The oxides of nitrogen are not very toxic. The health effects of
these vary with the degree of exposure. The smaller concentration of oxides of
nitrogen leads to inflammation of lung tissues but higher concentration may cause
irritation effects on mucous membrane, bronchitis & other respiratory problems.

40. These oxides of nitrogen play important role in the formation of veritants called
photochemical smog.
Effects on plants:-
The oxides of nitrogen can cause damage to plants leading to leaf spotting &
break down of plant tissues.
Oxides of Sulphur (SOx)
Among the oxides of sulphur, sulphur dioxide (SO2) is the main pollutant. Most
of the sulphur dioxide in the atmosphere comes from the combustion of fossil fuels &
from industrial plants which convert certain metal containing ores to metal or metal
oxides. The industries such as smelting & roasting industries, manufacture of
sulphuric acid, fertilizers, rubber industries, manufacture of electricity etc. release SO2
in the atmosphere. Volcanic sourced also contribute SO2 in the atmosphere.
Effects on human health:- SO2 is very irritating gas & adversely affects humans,
animals, plants & materials. It affects respiratory tract producing nose, ey & lung
veritating. Higher concentration of SO2 may cause permanent lung disease & lung
disease & lung cancer. In fact, it has been considered the most serious single air
pollutant causing many health hazards. Air pollution is very harmful disease.
Effects on monuments:-
Acid Rain
Acid rain is one of the most serious environmental problems facing many parts of the
world. It is a manmade pollution problems & the term acid rain was first used by
Robert Augus in 1872. It literally means presence of excessive acids in rain water. The
two predominant acids present in acid rain are sulphuric acid & nitric acid. These

41. acids come from oxides of sulphur & nitrogen. These oxides undergo many
photochemical reactions in the atmosphere & form H2SO4 & HNO3. Both these acids
are soluble in water & are strong acids. During rains, these acids fall to earth with
rain. This polluted rain is called acid rain.
Effects of Acid Rain
Acid rain is very damaging & causes extensive damage to buildings & sculptural
materials of marble, lime stone, slate etc. The Taj-Mahal in India is facing the same
problem. In Greece & Italy many valuable statues have partially by acid rain. The
acid rain water also corrodes metals.
The acid rain damages leaves of trees & plants & has retarded the growth of forests. It
has also resulted in the elimination of life from some fresh water lakes by destroying
the living bodies.
Effects of Oxides of Sulphur on plants:
Atmosheric sulphur dioxide is also harmful for plants. It damages
vegetables crops & affects plant growth & nutrient quality of plant products. The long
exposure of plants to SO2 caused damage to leaf tissue & caused chlorooses (a
lillaching of green portions of leaves). Sulphur dioxide is not only injurious to humans
& plants but it also deteriorates not only injurious to human & plants but it also
deteriorates buildings, statues, roofing etc. Emission of SO2 from Mathura refinery has
been causing serious damage to Taj Mahal of Agra.
Other Gaseous Pollutants

42. Hydrogen Sulphide: Hydrogen sulphide (H2S) is also a gaseous pollutant which
coucists with sulphur dioxide. Volcanic activity & natural decay of animals &
vegetable matterare main natural sources of H2S pollution. Some industrial processes
such as paper mills, oil refineries, natural gas plants add H2S to the atmosphere. It is
very toxic & caused giddiness. It is dangerous to plants gases like ammonia,
phosgene, halgones, hydrogen halides, etc. are air pollutants.
Hydrocarbons: Hydrocarbons are emitted in the atmosphere by natural sources
particularly trees. Methane is the major naturally occurring hydrocarbons produced by
the bacteria during anaerobic decomposition of organic matter in water, soil &
sediments. Automobiles exhausts & some industrial processes are other sources of
hydrocarbon pollution.
The hydrocarbons are not very harmful as such but these are involved in
photochemical reactions forming photochemical songs which causes variation of eyes,
nose, throat & respiratory problems. Some hydrocarbons have carcinogenic effects on
lungs, cause irritation to mucus membrane, cough etc. Benzophyrene which is present
as trace amounts in tobacco, charcoal or gasoline exhausts is a dangerous cancer
including hydrocarbon pollutant.
Particulate pollutants
Air borne small solid particles & liquid droplets having size ranging from 0222 um to
500 um are collectively called particulate. Some of the common examples of
particulate are dust, smoke, fumes, fly, ash, mist spray, fog, smog etc. These include
organic & inorganic matter, several metals, metal salts, mineral particles, radio-active
nucleides etc.

43. The particulate pollutants originate from natural, domestic, industrial & agricultural
sources. The natural process include volcanic eruptions, blowing of dust & soil by the
wind etc. Many inorganic & organic particulates are entering the atmosphere by
manmade activities in the form of dust from many industries, fly ash from power
plants, mining processes & smoke from incomplete combustion processes. The
inorganic particulates many originate from metallic oxides, sulphides, carbonates etc.
during the burning of fuels combustions of fuels, automobiles & vegetations. 10 poly
cyclic aromatic hydrocarbons (PAH) are important components of organic particulates
matter because of their carcinogenic nature.
Effects on Human Health:
The particulate pollutants cause various allergic reaction such as bronchial asthma,
tuberculosis & other infections because these attack the respiratory tract & harm
tissues in the lungs. Workers exposed to aliestos pollutants develop cancer
mesothelioma head, the most serious pollutant released from automobiles ochausts
cause metalislic disturbances in human body & lead to muscular paralysis, mental
retardation, abnormalities in facitlity & pregnancy & other neurological problems.
Effect on Health: Some plants are also adversely affected by particulate matter.
Several particulate pollutants fall on the soil with rain & make the soil unsuitable for
plant growth & make it infertile. Particulate also affect the materials. The particulates
damage the buildings, painted surface & accelerate ceerosion of metals.
Photochemical Smog
The term was originally given to a combination of smoke & fog laced with SO2 Which
was prevalent earlier in London. This was first experienced as brownish colour hoze

44. in the atmosphere in the forties in hos-angeles in California. Therefore, it was earlier
called hog Angeles Smog. The photochemical smog is produced in cities in which the
atmosphere is loaded with large quantities of automobile exhaust, smoke, stagnant air
masses & intense sun light. The prime constituents of the reactions leading to
photochemical smog are oxides of nitrogen & hydrocarbons. It has high concentration
of photochemical oxidants & is, therefore, oxidizing in nature.
Effects: Photochemical smog reduces visibility & causes nose, throat & eye irriation
& many chronic disease. The ozone & peroiyacylnitrate (PAN) components of
photochemical smog affect respiratory tract of human beings. The worst disaster
which focused attention in 1952 in London towards this air pollution caused 4 to 5
thousands direct & indirect deaths. Photochemical smog affects plant growth &
damages plant & other materials.
Sources
Air Pollution by Industries & its Control:- Air Pollution is caused by the industries
engaged in the manufacture of chemicals bricks, pesticides, iron, power, sugar, pulp &
paper, points & caustic soda. All of these industries need simple & inexpensive
treatment technologies to control pollution.
The electrical power supply in India in based primarily on the burning of domestic
coal with a high ash content. Ash content of power plant coal can vary between 20%
& 60% in a day electrostatic precipitators being used are mostly. Ash removed by the
use of wet method & fly ash suspended is dumped leading to soil & ground water
pollution. SO2 missions are seriously polluting air areas expertise for fly ash

45. utilization, nitrogen dioxide removal, flue gad desulphurization, falueic filters &
continuous waste gas measuring devices is lacking in our thermal plants.
Air pollution is severe in weban centres & undustrial estates. People are now worried
abount health risks due to poor air quality. Air pollution is normally caused by
transport systems & industry is the second culprit for this heatlh hazard.
Air pollution by vehicular emissions:- The single most important source of
atmospheric pollutants fostered by human activity is the motor vehicle. According to
environmental protection agency (EPA) of America, transportation vehicles yearly
emit more than 100 million tons of the major air pollutants.
Autos powered by internal combustion engines emit carbon monoxide, oxides of
nitrogen & hydrocarbons as pollutants. In addition, lead is emitted in exhaust when
leaded gasoline is burned.
A catalytical converter chemically changes the hydrocarbons & carbon mono-oxide is
exhaust into carbon dioxide & water vapour but this device works only when unleaded
petrol is used, in fact lead actually destroys the catalytical converters.
Very recently cases of respiratory troubles, cancer & heart problem have been
documented to increase.
Air pollution due to Foul Gases:
Another big problem of our metropolitan cities & even many other big cities is air-
pollution due to foul smells of all sorts at different places due to purification of leaked
or accumulated siwarage, unhygienic habits of people to defected & pass urine at
public place.

46. These foul smells are a great nuisance & mar the aesthetic sence & beauty of certain
locations in big cities.
Preventive Measures
Check on Vehicles:-
Some ways an individual can help control air pollution is to use alternate means of
transportation to places like shopping and work.
However, if office is too far away to walk on then things like carpool with co-workers
also decrease amount of pollution.
Car should be properly maintained to keep it in good running condition to avoid
smoke emission. Unleaded gasoline should be used in cars.
Old & unrepaired vehicles should be banned as they emit excessive smoke. Similarly,
the pollution level of vehicles should be regularly inspected.
Check on Industries:-
Industries which produces high smoke should be set up out of the city where there are
more number of trees. Direct mixing of smoke and dust particles from stone crusher,
cement factory, brick kiln, biogas, fuel etc. should be checked by applying various
measures.
When it comes to air pollution control on a large scale then it is the job of
businessmen to get the proper equipment needed to control each type of pollution.
There are many different kinds of products that can be purchased to help prevent &
sometimes eliminate pollution of the air. These products include bag house filters,
activated carbon absorbers & gas absorption towers.
Avoid Cigarette Smoking:-

47. It is best to avoid cigarette smoke whenever possible. Government should stop the
business of cigerattes and cigerratte smoking should be banned in public placed
especially. Centres for dereliction of smoking should be opened and smokers should
be encouraged to become a part of such centres.
Select Air Friendly products:-
The home, yard and office are common places where products containing harmful
smog-forming chemicals are used. Preventing this type of air pollution is achieved by
selecting water based products or items that possess low amounts of volatile organic
compounds (VOCs). When painting water-based paints with labels containing the
words „Zero-Voc‟ are used.
Instead of using a sprayer painting with brush is suggested. When storing solvents
airtight containers help contains the product to prevent leaks & skills. When making
the lawn, ignore gas-powered models & purchase a push are electric lawn mover.
Prevent Indoor Pollution:-
The home, yard & common placed where products containing harmful smog forming
chemicals are used.
At least 80% of most people spend their time indoors which supplies its own kind of
harmful air pollution. Smokers send their smoke through the roof with their unhealthy
habits therefore sending them outside to do their dirty work suggested. Limiting the
amount of household products that contain harmful chemicals is also recommended.
This includes cleaning agents a paints & glues.
Ventillation is also required to lessen the amount of indoor air pollution. When
cleaning baking soda may work just as well as harsher chemical cleaners. Gas

48. appliances & heaters should undergo inspections & maintenance. The inside of the
home should be kept clean on a regular basis in order to eradicate dust & mold
accumulation. Use of alternative energy sources should be in spared instead of
traditional sources like firewood, cow dung cake & other agricultural residues etc.
3 Rs. Of Solid waste management:-
Adopt the 3 Rs of solid waste management reduce, reuse and recycle Inorganic
materials such as metals, glass, plastic also organic materials like paper can be
reclaimed & recycled. This takes into account that the proven solution to the problem
of proper waste management is proper disposal in the waste bins for collections &
neet in the street where it could fall into drains, waste degregation & collection &
recycling.
Air pollution control devices
Electrostatic precipitatators: They can handle over 1000,000 m3
/h of dry and wet grass
at operating temperature upon 500o
C. Particulate size of less than .01 km is almost
collected to around 100 percent efficiency by these collectors.
Cycloned:- They are available with high efficiency tubes & medium efficiency tubes
& of hardness of 400-500 BHN. They can tolerate gas temperature upto 550o
C with
efficiency of over 80 percent.
Bag filters:- They are also low ratio & high ratio filters with three different types of
filters cleaning mechanism i.e. shaking, compressed air flow & reverse flow. They can
handle gas nearly 100 percent. The materials of which these filters also made are
polyester polyacrylic, poly propylene, Teflon etc.

49. Wet Scrubbers:- They are available in different capacities for corrosive & high
pressure conditions. Sulphur containing gases emitted from thermal power stations
using lime as scrubbing agent are also available.

50. Water Pollution
Meaning:-
The word „pollution‟ has a greek root means „defilement‟. It one ecosystem is defiled
all other systems are polluted. Man can‟t live in isolation from other forms of animal
life & from plant life bearing layer, which together constitute the biosphere, which is
very shallow layer in comparison with hydro sphere.
The U.S. National Research Council defines pollution as “an underirable change
characteristics of our air, land & water that they may or will harmfully affect human
life or that of the other desirable species, one industrial processes, living conditions &
cultural assets, or that may or will waste or deteriorate our raw material resources.”
It must therefore be