This document discusses various topics related to the environment and pollution. It defines key terms like environment, biotic and abiotic factors, and major environmental problems. It also summarizes the hydrologic cycle and impacts of human activities on it. It describes different types of pollutants based on degradability and sources. Finally, it discusses environmental problems, the precautionary principle, and challenges related to pollution in Bangladesh.

1. 4204
Lecture 1
Water Pollution (Introduction)

2. What is Environment?
 Humans inhabit the natural world as well as the "built" or
technological, social, and cultural world, all constitute important
parts of our environment.
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 The surroundings or conditions in
which a person, animal, or plant
lives or operates.
 All the things (living and non-
living) around us is part of our
environment.
 The word ‘Environment’ is derived
from the French word ‘Environner’
which means to encircle, around
or surround.

3. Environment
➢ Abiotic means non-living components (Air, Water,
Land, Table, Chair etc.)
➢ Biotic means living components (Plants, Animals,
Human beings etc.)
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4. Major Environmental Problems
Major
Environmental
Problems
Food Supply Problems
• Overgrazing
• Farmland loss and
degradation
• Wetland loss and
degradation
• Overfishing
• Coastal Pollution
• Soil erosion
• Soil salinization
• Soil water logging
• Water shortages
• Groundwater depletion
• Loss of biodiversity
• Poor nutrition
Waste Production
• Solid waste
• Hazardous waste
Biodiversity Depletion
• Habitat destruction
• Habitat degradation
• Extinction
Air Pollution
• Global climate
change
• Stratospheric ozone
depletion
• Urban air pollution
• Acid deposition
• Outdoor pollutants
• Indoor pollutants
Water Pollution
• Sediment
• Nutrient overload
• Toxic chemicals
• Infectious agents
• Oxygen depletion
• Pesticides
• Oil spills
• Excess heat
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5. Food Chain
The sequence of organisms
each of which is a source of
food for the next, is called a
Food chain. The arrow
means “is eaten by”.
It determines how energy
and nutrients move from
one organism to another
through an ecosystem.
All food chains must start
with a producer. All
organisms in a food chain,
except the first organism,
are consumers.
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6. Extinction of species
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More species of plants and animals are threatened with extinction now than
at any other time in human history.

7. Extinction
(Biodiversity losses and species extinction)
• In biology and ecology, extinction is the end of an organism or of a
group of organisms (taxon), normally a species. The moment of
extinction is generally considered to be the death of the last individual of
the group.
• Extinction occurs when conditions change, and a species must either
evolve, or move to a more favorable area. If not, they will become
extinct.
• Extinction: 2 types (Background & Mass Extinction)
Background Extinction occurs when localized environmental
conditions change, and a certain number of species die at a low rate;
Mass Extinction occurs when species die at huge rates (between 25-
75% of all species) due to a catastrophic event. Mass extinctions are
relatively rare events; however, isolated extinctions are quite common.
• Only recently have extinctions been recorded and scientists have
become alarmed at the high rates of recent extinctions. Some scientists
estimate that up to half of presently existing species may become extinct
by 2100 if the business as usual scenario continues.
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9. Factors affecting extinction
• Natural extinctions
– Climate change
– Catastrophic event (volcano, earthquake)
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• Human activities
– Habitat loss
– Pollution
– Commercial harvesting
– Accidental killing
– Urbanization
– Damming/Flooding
– Agricultural conversion

10. A. The hydrologic cycle is the transfer of water from oceans to the
atmosphere to the land and back to the oceans. This cycle is driven by
solar energy.
B. The main processes in this water recycling and purification cycle are:
• Evaporation (conversion of water into water vapor),
• Transpiration (evaporation of water from leaves after being
extracted from soil by roots and transported throughout the plant),
• Condensation (conversion of water vapor into droplets of liquid
water),
• Precipitation (rain, hail, and snow),
• Infiltration (movement of water into soil),
• Percolation (downward flow of water through soil to
groundwater storage areas called aquifers), and
• Surface runoff (down slope surface movement back to the sea to
resume the cycle).
The Hydrologic Cycle
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11. The hydrologic cycle….
Of the total 1.3
billion km3 of water
on Earth,
~97% of water in
oceans;
~2% in ice
caps/glaciers;
0.76% is shallow
groundwater;
0.013% is in lakes
and rivers; and only
0.001% is in the
atmosphere.
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12. Human impacts on hydrologic cycle….
• Damming rivers increases evaporation and infiltration
• Altering the surface and vegetation increases runoff and erosion
• Spreading water on agricultural fields depletes rivers, lakes and
streams
• Removing forests and vegetation reduces transpiration and
lowers water tables
• Emitting pollutants changes the nature of precipitation
• The most threatening impact is overdrawing groundwater for
drinking, irrigation, and industrial use
• Pavements reduce infiltration and increase surface runoff which
enhance flood hazard.
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13. Pollutants
Pollutants, the components of pollution, can be either
foreign substances/energies or naturally occurring
contaminants.
The pollutants can be classified into three groups:
1. Degradable Pollutants:
 Can be decomposed, removed or consumed and thus
reduced to acceptable level by natural, physical,
chemical, and biological processes
 Examples - Degradable garbage bags, toilet paper,
sewage, paper products, vegetables, juice, seeds and
leaves
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14. Pollutants…..
2. Biodegradable Pollutants:
 Pollutants which can be broken down into simpler,
harmless substances in nature in due course of time
(by the action of micro-organisms like certain
bacteria)
 Example - domestic wastes (garbage), urine, faecal
matter, sewage, agriculture residues, paper, wood,
cloth, cattle dung, animal bones, leather, wool,
vegetable stuff or plants
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15. Pollutants…..
3. Non-biodegradable Pollutants:
 Pollutants which cannot be broken down into simpler,
harmless substances in nature
 Examples - plastics, polythene, insecticides, pesticides,
mercury, lead, arsenic, metal articles like aluminum
cans, synthetic fibers, glass objects, iron products and
silver foils
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17. Pollutant Based on Sources
Pollution Source
 Naturally (from volcanic eruptions)
 Human (anthropogenic) activities (from burning coal)
 Industrialized agriculture
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18. Pollutant Based on Sources…..
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Two types of pollution sources:
Point sources, where pollutants come from single,
identifiable sources
Examples are the (1) smokestack of a coal-burning
power plant, (2) drainpipe of a factory, or
(3) exhaust pipe of an automobile.

19. Pollutants and Pollution
 A Pollutant is a waste material that pollutes air, water or
soil. Three factors determine the seriousness of a
pollutant: its chemical nature, the concentration and the
persistence.
 Pollutants, the elements of pollution, can enter the
environment naturally (e.g. from volcanic eruptions) or
through human activities (e.g. from burning coal)
 When naturally occurring, they are considered
contaminants when they exceed natural levels.
 Pollution is the introduction of contaminants into a
natural environment that causes instability, disorder, harm
or discomfort to the ecosystem, i.e. physical systems or
living organisms.
 Pollution can take the form of chemical substances or
energy, such as pesticides, noise, heat, or light.
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20.  Most pollution from human activities occurs in or
near urban and industrial areas, where pollutants
are concentrated.
 Industrialized agriculture also is a major source of
pollution.
 Some pollutants contaminate the areas where
they are produced; others are carried by wind or
flowing water to other areas
 The Blacksmith Institute issues an annual list of
the world's worst polluted places.
Pollutants and Pollution……
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21. Pollution…..
Based on the impact, pollution can be classified
into;
 Non-threshold: A substance or condition harmful
to a particular organism at any level or
concentration. Example: mercury, lead, cyanide
etc.
 Threshold: A substance that is harmful to a
particular organism only above a certain
concentration, or threshold level. Example:
chlorine dioxide, carbon monoxide and arsenic etc.
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22. What is an “environmental problem”?
 Individuals and societies have different ideas
about what defines an environmental problem:
 Ex.: DDT, a pesticide
 In developing countries: welcome because it
kills malaria-carrying mosquitoes
 In developed countries: not welcome, due to
health risks.
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23. We face challenges in pollution in Bangladesh
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Waste products and artificial chemicals used in farms,
industries, and households
Each year, millions of people die from pollution

24. The Precautionary Principle
 It can be difficult to prove with absolute
certainty how human activities lead to local
and global environmental problems;
 Environmental problems are complex and
interrelated with issues specific to a given
region.
 When there is a threat of serious
environmental damage, we should not wait
for certain scientific proof before taking
steps to prevent potential harm.
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25.  However, we need to examine the benefits
and costs of taking a particular action
versus taking no action;
 Therefore, a regional approach to solving
environmental problems is ideal.
 The precautionary principle is a useful
technique for preventing problems.
The Precautionary Principle…..
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26. See you next class……
Questions
?
Thanks for your kind attention