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Unit – ii
Environmental Pollution
1.Water Pollution
 Introduction:
Water is the essential element that makes life on Earth possible. Without water there would be no life.
About 97% of the total water available on Earth is found in the oceans and is too salty for drinking or
irrigation. The remaining 3% is fresh water. Of this, 2.997% is locked in ice caps or glaciers. Thus, only
0.003% of the Earth's total volume of water is easily available to us as" soil moisture, groundwater, water
vapor and the water in lakes, streams, rivers and wetlands.
Definition:
Water pollution can be defined as alteration in physical, chemical or biological characteristics of water
making it unsuitable for designated use in its natural state.
 Sources of water pollution:
Pollution of water can be caused by point sources or non-point sources.
 Point sources are specific sites near water which directly discharge effluents into them. Major point
sources of water pollution are industries, power plants, underground coal mines, offshore oil wells
etc.
 Non-point sources is not at any particular site, rather, these sources are scattered, which individually
or collectively pollute water. Surface run-off from agricultural fields, overflowing small drains, rain
water sweeping roads and fields, atmospheric deposition etc. are the non-point sources of water
pollution.
Types of water pollutions
Ground water pollution: there are a number of potential sources of ground water pollution. Septic tanks,
industry (textile, chemical, and tanneries), deep well injection, mining etc. are mainly responsible for ground
water pollution, which is irreversible. Ground water pollution with arsenic, fluoride and nitrate are posing
serious health hazards.
Surface water pollution:
The major sources of surface water pollution are:
1. Sewage: Pouring the drains and sewers in fresh water bodies causes water pollution. The problem is
severe in cities.
2. Industrial effluents: Industrial wastes containing toxic chemicals, acids, alkalis, metallic salts, phenols,
cyanides, ammonia, radioactive substances, etc. are sources of water pollution. They also cause thermal
(heat) pollution of water.
3. Synthetic detergents: Synthetic detergents used in washing and cleaning produce foam and pollute water.
4. Agrochemicals: Agrochemicals like fertilizers (containing nitrates and phosphates) and pesticides
(insecticides, fungicides, herbicides etc.) washed by rain-water and surface run-off pollute water.
5. Oil: Oil spillage into sea-water during drilling and shipment pollute it.
6. Waste heat: Waste heat from industrial discharges increases the temperature of water bodies and affects
distribution and survival of sensitive species.
Nutrient Water pollution:
Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is
a primary cause of eutrophication of surface waters, in which excess nutrients,
usually nitrogen or phosphorus, stimulate algal growth. Excess nitrates and phosphorus encourage the
growth of aquatic plants and algae. Nutrient-boosted algae growth leads to massive algae blooms, visible as
a bright green, foul smelling sheen on the water’s surface. Some of the algae making up the blooms produce
toxins that are dangerous to fish, wildlife, and humans. The blooms eventually die off, and their
decomposition consumes a lot of dissolved oxygen, leaving waters with low oxygen concentrations.
Invertebrates and fish are killed when oxygen levels dip too low.
 Effects of water pollution
1. Presence of the many infectious agents causes many diseases. The different types of organisms and the
water borne diseases are given below in Table
Table: Water Borne Diseases Vs Responsible Organisms
2. Change in colour of water affects the usage of water and growth of plants and organisms in water.
3. The oxygen demanding wastes such as animal manure and plant residues deplete the dissolved oxygen
content of water which is harmful to the aquatic lives.
4. The inorganic substances present in water causes many damages to the water.
a. Makes the water unfit for drinking and other purposes.
b. Corrosion of metals exposed to such waters.
c. Causes skin cancers, damages to spinal, CNS, liver and kidneys.
d. Reduces crop yield
5. Growth of aquatic plants and fishes are affected by the presence of acids, alkalies and toxic substances.
6. Oil and other lubricants affect the self purification of the stream or water body.
7. The organic chemicals such as detergents, pesticides, plastics, oil and gasoline present in the water
damages the CNS and causes birth defects and genetic disorders. Also these are harmful to the lives of
aquatic ecosystem.
8. Enrichment of nutrients (Eutrophication) from surrounding watershed affects the penetration of light
through the water, causing damage to the characteristics of water and aquatic life.
9. Dumping of solid wastes resulting surface water as well as ground water pollution.
10. Disposal of coolant water used in industries increase the temperature of the surface water. This affects
the solubility of oxygen in water and aquatic ecosystem.
11. More amounts of nitrates in water due to the application of artificial fertilizer in agricultural lands can
cause methemoglobinemia known as blue baby. Also it decreases the oxygen carrying capacity of the
blood in the body.
12. Oil spills or leaks from underground storage tanks on land are affecting a large area in a very short
time.oil spills at sea decrease the oxygen level in the water and cause more harm to the marine planktons and
creatures living in the sea
13. Run-off from farms, backyards, and golf courses contain pesticides such as DDT that in turn contaminate
the water.
14. Leachates from landfill sites are another major contaminating source. It damages the ecosystems health
and reproductivity of wildlife. Groundwater is susceptible to contamination, as pesticides are mobile in the
soil.
16. Presence of radioactive materials such as iodine, radon, cesium, uranium and thorium and its isotopes
causes genetic disorders, birth defects and certain cancers.
17. The chlorinated organic pesticides like dieldrin, aldrin and DDT are hazardous mainly due to their
concentration in the food chain. They have high stability, low vapour pressure and very low solubility in
water. As a result of biological magnification (accumulation of concentration from one level to another level
of food chain), these are harmful to the mammals in longer term effects.
18. The presences of sediments (soil and silt) cause the following damages.
a. Fills lakes and reservoirs
b. Obstructs shipping channel
c. Clogs hydroelectric turbines
d. Affects photosynthesis of aquatic plants
e. Disturbs the aquatic food chain
f. Carries pesticides, bacteria and harmful substances to the receiving water body.
g. Makes the water unsuitable for bathing, swimming, boating and other recreational uses.
 Control of Water Pollution
It is easy to reduce water pollution from point sources by legislation. However, due to absence of denied
strategies it becomes difficult to prevent water pollution from non-point sources. The following points may
help in reducing water pollution from non-point sources.
(i) Judicious use of agrochemicals like pesticides and fertilizers which will reduce their surface run-off
and leaching. Avoid use of these on sloped lands.
(ii) Use of nitrogen fixing plants to supplement the use of fertilizers.
(iii)Adopting integrated pest management to reduce reliance on pesticides.
(iv) Prevent run-off of manure. Divert such run-off to basin for settlement. The nutrient rich water can be
used as fertilizer in the fields.
(v) Separate drainage of sewage and rain water should be provided to prevent overflow of sewage with
rainwater.
(vi) Planting trees would reduce pollution by sediments and will also prevent soil erosion.
For controlling water pollution from point sources, treatment of waste water is essential before being
discharged. Parameters which are considered for reduction in such water are-Total solids, biological oxygen
demand (BOD), chemical oxygen demand (COD), nitrates and phosphates, oil and grease, toxic metals etc.
Wastewaters should be properly treated by primary and secondary treatments to reduce the BOD, COD
levels up to the permissible levels for discharge.
Advanced treatment for removal of nitrates and phosphates will prevent eutrophication. Before the
discharge of wastewater, it should be disinfected to kill the disease-causing organisms like bacteria.
Proper chlorination should-be done to prevent the formation of chlorinated hydrocarbons or-disinfection
should be done by ozone or ultraviolet radiations.
2. Noise pollution
Introduction
Noise may not seem as harmful as the contamination of air or water, but it is a pollution problem that
affects human health and can contribute to a general deterioration of environmental quality.
The unpleasant and unwanted sound is called noise. It is not a substance that can accumulate in the
environment like most other pollutants. Sound is measured in a unit called the 'decibel' (dB).
Sound can propagate through a medium like air, liquid or solid. Sound wave is a pressure perturbation in the
medium through which sound travels. Sound pressure alternately causes compression and rarefaction. The
number of compressions and rarefactions of the molecules of the medium (for example air) in a unit time is
described as frequency. It is expressed in Hertz (Hz) and is equal to the number of cycles per second.
There is a wide range of sound pressures, which encounter human ear. Increase in sound pressure does
not invoke linear response of human ear. A meaningful logarithmic scale has been devised. The noise
measurements are expressed as Sound Pressure Level (SPL) .It is expressed as a dimensionless unit, decibel
(dB). Decibel scale is a measure of loudness. Noise can affect human ear because of its loudness and
frequency (pitch).
 The Central Pollution Control Board (CPCB) Standards
The Central Pollution Control Board (CPCB) committee has recommended permissible noise levels
for different locations
Table: Noise standards by CPCB
 Characteristics of Noise
 Sound pressure
 Frequency
 Duration
 Time of the day
 Location
 Intermittency
 Source of Noise Pollution
There are several sources of noise pollution that contribute to both indoor and outdoor noise pollution.
Household sources
These includes Food mixer, Vacuum cleaner, Washing machines and driers, Air conditioner and
TV’S
Social Events
Place of worship, Disco’s, Parties, Political meetings and place where people sell goods with
loudspeaker
Commercial and Industrial Activities
These include Printing press, construction sites and manufacturing industries. Examples Bulldozers,
motors, drilling machines, dump trucks, pavement breakers etc.
Transportation
These include road traffic noise, Aircraft noise and noise from railroads
Effects of Noise pollution
Noise pollution affects both health and behavior. Unwanted sound (noise) can damage physiological
health. Noise pollution can cause hypertension, high stress levels, hearing loss, sleep
disturbances, and other harmful effects. Interferes with man's communication- In a noisy area
communication is severely affected.
 Hearing damage: Noise can cause temporary or permanent hearing loss. (NITTS-Noise induced
temporary threshold shift means (temporary deafness) NIPTS- Noise induced permanent threshold
shift- (Permanent deafness) ) It depends on intensity and duration of sound level. Auditory
sensitivity is reduced with noise level of over 90 dB sound for more than a few minutes.
 Physiological and Psychological changes: Continuous exposure to noise affects the functioning of
various systems of the body. It may result in hypertension, insomnia (sleeplessness), gastro-intestinal
and digestive disorders, peptic ulcers, blood pressure changes, behavioral changes, emotional changes
etc.
 Control of Noise Pollution
a. Reduction in sources of noise: Sources of noise pollution like heavy vehicles and old vehicles may not
be allowed to play in the populated areas.
b. Noise making machines should be kept in containers with J sound absorbing media. The noise path
will be in interrupted! and will not reach the workers.
c. Proper oiling will reduce the noise from the machinery.
d. Use of sound absorbing silencers: Silencers can reduce noise j by absorbing sound. For this purpose
various types of fibrous ! Material could be used.
e. Planting more trees having broad leaves.
f. Through Law: Legislation can ensure that sound production is minimized at various social functions.
Unnecessary horn blowing should be restricted especially in vehicle-congested areas.
3. Air pollution
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or
discomfort to humans or other living organisms, or damages the natural environment, into the atmosphere.
The atmosphere is a complex, dynamic natural gaseous system that is essential to support life on planet
Earth. An air pollutant is known as a substance in the air that can cause harm to humans and the
environment. Pollutants can be in the form of solid particles, liquid droplets, or gases. In addition, they may
be natural or man-made.
Source of air pollution:
Sources of air pollution refer to the various locations, activities or factors which are responsible for the
releasing of pollutants in the atmosphere. These sources can be classified into two major categories which
are:
 Anthropogenic sources (human activity) mostly related to burning different kinds of fuel.
"Stationary Sources" include smoke stacks of power plants, manufacturing facilities (factories) and waste
incinerators, as well as furnaces and other types of fuel-burning heating devices
"Mobile Sources" include motor vehicles, marine vessels, aircraft and the effect of sound etc.
Chemicals, dust and controlled burn practices in agriculture and forestry management. Controlled or
prescribed burning is a technique sometimes used in forest management, farming, prairie restoration or
greenhouse gas abatement. Fire is a natural part of both forest and grassland ecology and controlled fire can
be a tool for foresters. Controlled burning stimulates the germination of some desirable forest trees, thus
renewing the forest.
Fumes from paint, hair spray, varnish, aerosol sprays and other solvents
Waste deposition in landfills, which generate methane. Methane is not toxic; however, it is highly flammable
and may form explosive mixtures with air. Methane is also asphyxia and may displace oxygen in an enclosed
space. Asphyxia or suffocation may result if the oxygen concentration is reduced to below 19.5% by
displacement
 Natural sources
Dust from natural sources, usually large areas of land with little or no vegetation.
Methane, emitted by the digestion of food by animals, for example cattle.
Radon gas from radioactive decay within the Earth's crust. Radon is a colorless, odorless, naturally
occurring, radioactive noble gas that is formed from the decay of radium. It is considered to be a health
hazard Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the
basement and it is the second most frequent cause of lung cancer, after cigarette smoking.
Smoke and carbon monoxide from wildfires.
Volcanic activity, which produce sulfur, chlorine, and ash particulates.
Classification of Air pollutants:
Pollutants can be classified as either primary or secondary. Usually,
Primary pollutants are substances directly emitted from a process, such as ash from a volcanic eruption,
the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories.
Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or
interact. An important example of a secondary pollutant is ground level ozone - one of the many secondary
pollutants that make up photochemical smog.
Note that some pollutants may be both primary and secondary: that is, they are both emitted directly and
formed from other primary pollutants.
Primary pollutants
Primary pollutants produced by human activity include:
Sulfur oxides (SOx) –
Sulfur dioxide, a chemical compound with the formula SO2 produced by volcanoes and in various industrial
processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur
dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus
causes acid rain. Inhalation narrows the airway, causing wheezing and shortness of breath, especially in
those with asthma. This is one of the causes for concern over the environmental impact of the use of these
fuels as power sources.
 Nitrogen oxides (NOx) –
Among oxides of nitrogen, especially nitrogen dioxide is emitted from high temperature combustion. It can
be seen as the brown haze dome above or plume downwind of cities. Nitrogen dioxide is the chemical
compound with the formula NO2. This reddish-brown toxic gas has a characteristic sharp, biting odor which
affects lungs and causes wheezing; increases chance of respiratory infection
 Carbon monoxide - is a colorless, odorless, non-irritating but very poisonous gas. It is a product by
incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of
carbon monoxide. It deprives body of Oxygen causing headaches, fatigue, and impaired vision. Inhalation of
carbon monoxide causes serious impact on respiratory, cardiac and neural systems.
 Carbon dioxide (CO2) - a greenhouse gas emitted from combustion but is also a gas vital to living
organisms. It is a natural gas in the atmosphere. Upon increasing in concentration leads to increase of earth’s
average temperature causing global warming.
 Volatile organic compounds - VOCs are an important outdoor air pollutant. They are often divided into
the separate categories of methane (CH4) and non-methane (NMVOCs). Methane is an extremely efficient
greenhouse gas which contributes to enhance global warming. Other hydrocarbon VOCs are also significant
greenhouse gases via their role in creating ozone and in prolonging the life of methane in the atmosphere,
although the effect varies depending on local air quality. Within the NMVOCs, the aromatic compounds
benzene, toluene and xylene are suspected carcinogens and may lead to leukemia through prolonged
exposure. 1, 3-butadiene is another dangerous compound which is often associated with industrial uses.
 Particulate matter - Particulates alternatively referred to as particulate matter (PM) or fine particles, are
tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to particles and the gas together.
Sources of particulate matter can be manmade or natural. Some particulates occur naturally, originating from
volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as
the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant
amounts of aerosols. Increased levels of fine particles in the air are linked to health hazards such as heart
disease, altered lung function and lung cancer.
 Chlorofluorocarbons (CFCs) - harmful to the ozone layer emitted from products currently banned from
use.
 Ammonia (NH3) - emitted from agricultural processes. Ammonia is a compound with the formula NH3. It
is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to
the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers.
Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceuticals.
Although in wide use, ammonia is both caustic and hazardous.
 Radioactive pollutants - produced by nuclear explosions, war explosives, and natural processes such as
the radioactive decay of radon.
Secondary pollutants include:
Photochemical smog –
Smog is a kind of air pollution; the word "smog" is combination of smoke and fog. Classic smog results from
large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. Modern smog
does not usually come from coal but from vehicular and industrial emissions that are acted on in the
atmosphere by sunlight to form secondary pollutants that also combine with the primary emissions to form
photochemical smog.
 Ground level ozone (O3) formed from NOx and VOCs. Ozone (O3) is a key constituent of the troposphere
(it is also an important constituent of certain regions of the stratosphere commonly known as the Ozone
layer). Photochemical and chemical reactions involving it drive many of the chemical processes that occur in
the atmosphere by day and by night. At abnormally high concentrations brought about by human activities
(largely the combustion of fossil fuel), it is a pollutant, and a constituent of smog.
 Peroxyacetyl nitrate (PAN) - The best known member of a class of photochemical oxidizing agents
known as the peroxyacyl nitrates. The peroxyacyl nitrates are formed when ozone reacts
with hydrocarbons such as those found in unburned petroleum. They are commonly found
in photochemical smog. The peroyxacyl nitrates attack plants, causing spotting and discoloration of leaves,
destruction of flowers, reduction in fruit production and seed formation, and death of the plant. They also
cause red, itchy, runny eyes and irritated throats in humans. Cardiac and respiratory conditions, such
as emphysema and chronic bronchitis, may result from long-term exposure to the peroxyacyl nitrates.
Air Pollution Effects:
1. Reduced lung functioning
2. Irritation of eyes, nose, mouth and throat
3. Asthma attacks
4. Respiratory symptoms such as coughing and wheezing
5. Increased respiratory disease such as bronchitis
6. Reduced energy levels
7. Headaches and dizziness
Disruption of endocrine, reproductive and immune systems
Neurobehavioral disorders
Cardiovascular problems
Cancer
Premature death
Effects of Air- Pollution on Animals:
 Acid rain (formed in the air) destroys fish life in lakes and streams
 Excessive ultraviolet radiation coming from the sun through the ozone layer in the upper atmosphere
which is eroded by some air pollutants, may cause skin cancer in wildlife
 Ozone in the lower atmosphere may damage lung tissues of animals
Effects of Air- Pollution on Plants:
 Leaf Damage
 Chemicals such as sulfur dioxide, ozone, fluorides and peroxyacyl nitrate damage the leaves of plants
cause’s changes in the colors of leaf tissue, which may turn white, brown or yellow.
 Nitrogen dioxide, a byproduct of combustion from car engines or open fires, can slow the growth of
plants, carbon monoxide is less benign. This component of car exhaust is poisonous to humans and will
stunt the growth of plants.
 Fluorides absorbed by leaves are conducted towards the margins of broad leaves (grapes) and to the tips of
monocotyledonous leaves (gladiolus). Little injury takes place at the site of absorption, whereas the
margins or the tips of the leaves build up injurious concentrations
 Large quantities of ammonia into the atmosphere for brief periods of time and cause severe injury to
vegetation in the immediate vicinity.
 Sulfur dioxide enters the leaves mainly through the stomata (microscopic openings) and the resultant
injury is classified as either acute or chronic. The colour of the necrotic area can vary from a light tan or
near white to an orange-red or brown depending on the time of year, the plant species affected and weather
conditions.
 Ozone symptoms characteristically occur on the upper surface of affected leaves and appear as a flecking,
bronzing or bleaching of the leaf tissues.
Air pollution controlling methods
 Emission Control Equipments
Emission control equipments are of two types.
a. Gaseous control equipments
b. Particulate control equipments
The different kinds of methods and equipments of emission control are shown in Fig.3.1.
Fig.3.1 Different types of emission control equipment
1. Gravitational Settling Chambers
In this type of equipments, the particulate-laden gas is
allowed to enter an enlarged area with a particular
velocity. Inside the chamber, the velocity of the gas is
reduced due to the enlarged portion. The gravitation force
makes the dust particles to deposit at bottom of the
hopper portion and makes clean gas.
Fig. Gravitational Settling chamber
These types of gravitational settling chambers are generally used to remove large particles of size about
50mm from gas streams.
Merits:
1. Simple in design, construction and operation
2. Very less initial cost
3. Low operating cost
Demerits:
1. Requirement of space for installation is more
2. Less efficiency for particles of size smaller than 50 µm.
2. Cyclone Separators
A cyclone separator consists of an inlet,
cylindrical shell, conical base and hopper. The dust-
laden gas is allowed to enter tangentially in the inlet.
A centrifugal force is generated by spinning the gas
stream. The magnitude of centrifugal force generated
on the gas stream depends on the cyclone diameter,
mass of the particle and velocity of gas within the
cyclone. This centrifugal force throws the particulates
on the walls of cyclone which separates the particulate
matters from the particulate laden gas. The cleaned air
goes upward and the dust particles are collected at the
bottom of the hopper.
Fig.. Cyclone-Clean air
Merits
1. More effective than the gravitational settling chambers in the removal of much smaller particles.
2. Relatively inexpensive
3. Operative cost is less.
4. Handle large volume of gases at temperatures up to 98°C.
3. Fabric Filters (or) Bag Filters
These are the oldest equipments adopted for removal
of particulate matters from industrial gases. In this
type of filters, woven or non-woven fabrics are used to
filter the particulate-laden gases. Efficiency of the
fabric filters is about 99% and it can able to remove
particles as small as 0.1 µm. Filter bags are generally
of tubular shape or envelope shape. The type of fabric
is decided based on temperature of the gas and the
corrosiveness or abrasiveness of the particles.
Fig. Fabric filter
The bag houses consist of a group of bag (or fabric) filters suspended from an overhead support. The dust
laden gas is allowed at the bottom of the bag house. The gas stream is allowed to pass through the bags. The
dust particles are trapped at the fabric surface and the clean air is collected at the top. This accumulated dust
particles are collected at the bottom of the bag house as solid waste. The bags are cleaned either by
mechanical shakers or by reverse air.
Merits
 High collection efficiency up to 99%.
 Broad range of particles is collected by the fabric
filters.
 Large volume of gases at relatively high speeds may
be cleaned.
 Particles are collected in dry state.
 Particles up to 0.lp.m are collected by the fabric
filters.
Demerits
 The possibility of explosion or fire is more in a
bag house.
 Requires more space for installation of bag
house.
 Size of the bag house unit is large.
 The construction cost is high.
4. Electrostatic Precipitator (ESP)
Fig. Electrostatic Precipitator
In this type of equipments, two electrodes are used to separate the dust particles from a gas stream. The
gas stream is allowed to pass between the two electrode wires (which are called as discharge
electrodes). The electrical charge is imparted to the particles through a high-voltage direct-current
corona. The high-voltage field ionizes the gas molecules in the air stream and makes the particulate
matters with negative charge. The negatively charged particles are attracted by the positively charged
electrodes which are called as collectors. The charge of the particles is neutralized at the moment of
collection, and they can be removed from the collectors by rapping, washing.
Merits
• Efficiency is 99% or more.
• More suitable for wide range of particle sizes.
• Sub-micron particles can also be collected.
 Can handle large volumes of gas from 25 to 1000 m3
sec.
• Can operate continuously with little maintenance. Can be used to collect acid or tar mists.
Demerits
 High initial installation cost.
 Require more space.
 Require more power.
 More surface area is required for obtaining high efficiency.
Wet collectors (or) Scrubbers
Wet precipitation is the basic principle of wet scrubbers in which particles in the atmosphere are removed
by nature.
The basic functions of these are to make contact between the particulates and the scrubbing liquid, usually
water.
The major types of wet scrubbers are
(i) Spray towers
(ii) Centrifugal scrubbers
(iii) Venturi scrubbers and
(iv) Packed bed columns
Among the above types of wet scrubbers, each type has its unique applicability. Spray towers are the
simplest types of wet scrubbers. They are low energy scrubbers and that can be used to remove particles of
size 5 to 10 m. Venturi scrubbers are of high energy scrubbers and they can be effective in removal of
particles of size smaller than 3 µm.
Fig..Spray towers
In the spray tower the air stream with particles is introduced at the bottom. The Polluted gas flows upward.
Water is introduced at the top by means of spray nozzles.
By inertial impaction and interception the particulate matters are entrained by then molecules. The water
with particles is collected at the bottom and disposed.
The efficiency of a spray tower depends on the velocity of water,size of spray droplet size, velocity of gas,
quantity of water and gas introduced and trajectories. Efficiency increases with decreasing diameter of
water droplet and increasing droplet quantity
Merits
These are very much effective in simultaneous removal of gases and Particulates. Effective in wide
range of loading.
Requirement of space is very less compared to dry collectors.
Lesser chance of explosion of dust-air mixtures.
 Corrosive gases may be neutralized by proper choice of scrubbing liquid,
 Temperature is reduced at the exhaust.
Demerits
Energy cost is relatively higher than the dry collectors.
 Disposal of the wastewater is the main demerit of this type and requires treatment.
Possibility of corrosion is more.
 Less efficiency in collection of very smaller particles.
3. Soil pollution
Soil pollution
Soil pollution is defined as, “contamination of soil by human and natural activities which may cause
harmful effect on living organisms”.
Composition of soil is listed below:
COMPONENT %
Organic mineral matter ---- 45%
Organic matter -----05%
Soil water ----25 %
Soil air ---- 25 %
SOURCES OF SOIL POLLUTION
Soil pollution mainly occurs due to the following:
1. Industrial wastes
2. Urban wastes
3. Agricultural practices
4. Radioactive pollutants
5. Biological agents
Industrial wastes – Disposal of Industrial wastes is the major problem for soil pollution Sources: Industrial
pollutants are mainly discharged from various origins such as pulp and paper mills, chemical fertilizers, oil
refineries, sugar factories, tanneries, textiles, steel, distilleries, fertilizers, pesticides, coal and mineral
mining industries, drugs, glass, cement, petroleum and engineering industries etc. Effect: These pollutants
affect and alter the chemical and biological properties of soil. As a result, hazardous chemicals can enter
into human food chain from the soil or water, disturb the biochemical process and finally lead to serious
effects on living organisms.
Urban wastes – Urban wastes comprise of both commercial and domestic wastes consisting of dried sludge
and sewage. All the urban solid wastes are commonly referred to as refuse. Constituents of urban refuse:
This refuse consists of garbage and rubbish materials like plastics, glasses, metallic cans, fibres, paper,
rubbers, street sweepings, fuel residues, leaves, containers, abandoned vehicles and other discarded
manufactured products. Urban domestic wastes though disposed off separately from industrial wastes, can
still be dangerous. This happens because they are not easily degraded.
Agricultural practices – Modern agricultural practices pollute the soil to a large extent. With the
advancing agro-technology, huge quantities of fertilizers, pesticides, herbicides and weedicides are added to
increase the crop yield. Apart from these farm wastes, manure, slurry, debris, soil erosion containing mostly
inorganic chemicals are reported to cause soil pollution
Radioactive pollutants/ - Radioactive substances resulting from explosions of nuclear testing laboratories
and industries giving rise to nuclear dust radioactive wastes, penetrate the soil and accumulate giving rise to
land/soil pollution.
Ex: 1. Radio nuclides of Radium, Thorium, Uranium, isotopes of Potassium (K-40) and Carbon (C-14) are
commonly found in soil, rock, water and air.
2. Explosion of hydrogen weapons and cosmic radiations include neutron, proton reactions by which
Nitrogen (N-15) produces C-14. This C-14 participates in Carbon metabolism of plants which is then into
animals and human beings.
3. Radioactive waste contains several radio nuclides such as Strontium90, Iodine129, Cesium-137 and
isotopes of Iron which are most injurious. Strontium get deposited in bones and tissues instead of calcium.
4. Nuclear reactors produce waste containing Ruthenium-106, Iodine-131, Barium140, Cesium-144 and
Lanthanum-140 along with primary nuclides Sr-90 with a half life 28 years and Cs-137 with a half life 30
years. Rain water carries Sr-90 and Cs-137 to be deposited on the soil where they are held firmly with the
soil particles by electrostatic forces. All the radio nuclides deposited on the soil emit gamma radiations.
Biological agents – Soil gets a large amount of human, animal and bird excreta which constitute a major
source of land pollution by biological agents.
Ex: 1. Heavy application of manures and digested sludge can cause serious damage to plants within a few
years
Effects of soil pollution
Effect on Health of Humans: Considering how soil is the reason we are able to sustain ourselves, the
contamination of it has major consequences on our health. Crops and plants grown on polluted soil absorb
much of the pollution and then pass these on to us. This could explain the sudden surge in small and
terminal illnesses.
Long term exposure to such soil can affect the genetic make-up of the body, causing congenital illnesses
and chronic health problems that cannot be cured easily. In fact, it can sicken the livestock to a
considerable extent and cause food poisoning over a long period of time. The soil pollution can even lead
to widespread famines if the plants are unable to grow in it.
Effect on Growth of Plants: The ecological balance of any system gets affected due to the widespread
contamination of the soil. Most plants are unable to adapt when the chemistry of the soil changes so
radically in a short period of time. Fungi and bacteria found in the soil that bind it together begin to
decline, which creates an additional problem of soil erosion.
The fertility slowly diminishes, making land unsuitable for agriculture and any local vegetation to
survive. The soil pollution causes large tracts of land to become hazardous to health. Unlike deserts,
which are suitable for its native vegetation, such land cannot support most forms of life.
Decreased Soil Fertility: The toxic chemicals present in the soil can decrease soil fertility and therefore
decrease in the soil yield. The contaminated soil is then used to produce fruits and vegetables which lacks
quality nutrients and may contain some poisonous substance to cause serious health problems in people
consuming them.
Toxic Dust: The emission of toxic and foul gases from landfills pollutes the environment and causes
serious effects on health of some people. The unpleasant smell causes inconvenience to other people.
Changes in Soil Structure: The death of many soil organisms (e.g. earthworms) in the soil can lead to
alteration in soil structure. Apart from that, it could also force other predators to move to other places in
search of food
Control measures of soil pollution:
1. Soil erosion can be controlled by a variety of forestry and farm practices. Ex: Planting trees on barren
slopes Contour cultivation and strip cropping may be practiced instead of shifting cultivation Terracing and
building diversion channels may be undertaken. Reducing deforestation and substituting chemical manures
by animal wastes also helps arrest soil erosion in the long term.
2. Proper dumping of unwanted materials: Excess wastes by man and animals pose a disposal problem.
Open dumping is the most commonly practiced technique. Nowadays, controlled tipping is followed for
solid waste disposal. The surface so obtained is used for housing or sports field.
3. Production of natural fertilizers: Bio-pesticides should be used in place of toxic chemical pesticides.
Organic fertilizers should be used in place of synthesized chemical fertilizers. Ex: Organic wastes in animal
dung may be used to prepare compost manure instead of throwing them wastefully and polluting the soil.
4. Proper hygienic condition: People should be trained regarding sanitary habits. Ex: Lavatories should be
equipped with quick and effective disposal methods.
5. Public awareness: Informal and formal public awareness programs should be imparted to educate people
on health hazards by environmental education. Ex: Mass media, Educational institutions and voluntary
agencies can achieve this.
6. Recycling and Reuse of wastes: To minimize soil pollution, the wastes such as paper, plastics, metals,
glasses, organics, petroleum products and industrial effluents etc should be recycled and reused. Ex:
Industrial wastes should be properly treated at source. Integrated waste treatment methods should be
adopted.
7. Ban on Toxic chemicals: Ban should be imposed on chemicals and pesticides like DDT, BHC, etc which
are fatal to plants and animals. Nuclear explosions and improper disposal of radioactive wastes should be
banned.
Marine pollution
Definition
Marine pollution can be defined as the introduction of substances to the marine environment directly or
indirectly by man resulting in adverse effects sushi hazards to human health, obstruction of marine
activities, and lowering the quality of sea water
The main sources of marine pollution are
i. Rivers, which bring pollutants from their drainage basins,
ii. Catchment area i.e. coastline where human settlements in the form of hotels, industry, agricultural,
practices have been established, and
iii. Oil drilling and shipment.
Sources of marine pollution
According to International Maritime Organization (IMO), the different sources contributing marine
pollution are
1. Land based sources
2. Air based sources
3. Maritime transportation
4. Dumping of wastes
5. Offshore production
Land based sources
Storm water: Urban runoff, or storm water, is more difficult to control. Storm water drains collect and
channel the water from all non-porous surfaces, such as pavements and tarred roads, within a catchment.
Storm water flow depends on rainfall, and the first flows following a dry spell often contain high levels of
pollutants, such as heavy metals (particularly lead), oil residues, nutrients (nitrogen and phosphorus), and
pathogenic (disease causing) micro-organisms, such as viruses, bacteria and protozoa, from faecal
material.
Rivers: Rivers carry to the sea water containing contaminants such as nutrients and pesticides from
agricultural runoff, fecal pollution resulting from poor sanitation, and industrial discharges. Soil erosion,
partly a result of poor catchment management, can cause increased water turbidity and siltation of
estuaries.
2 Air based sources-
Air based sources of marine pollution are referred to all the types of industrial activities that create air
pollution which eventually drifts over and falls onto marine waters.
a. Disposal of oil during the normal cleaning process.
b. Accidental spill of oil.
c. Disposal of garbage generated by the crews of marine vessels (the navy, fishing fleets, pleasure boaters
etc.).
3 Eutrophication - Disposal of effluent with more nitrogen and phosphorus causes 'eutrophication' (over
fertilization), which may cause algal blooms. These blooms can discolor the water, clog fish gills, or even
be toxic. Microbial breakdown of dead algae can cause deficiency of oxygen.
4 Pesticides-Pesticides such as DDT (Dichlorodiphenyltrichloroethane) and other persistent chemicals
accumulate in the fatty tissue of animals. These chemicals can cause reproductive failure in marine
mammals and birds.
5 Plastics - Plastic is the dangerous solid waste. Plastic is not biodegradable and therefore affects the
oceans for long periods of time. Plastics kill many marine animals. Turtles, for example, often swallow
floating plastic bags, mistaking them for jelly- fish. Animals are often strangled when they become
entangled with plastic debris.
6 Radioactive wastes-Any leakage or failure of radioactive wastes containers, which are used to dispose
low level radioactive wastes in deep sea, causes more effects that could be devastating.
 Prevention of marine pollution
Following are some of the preventive measures of marine pollution.
a.Careful handling of oil and petroleum products.
b.Ban ocean dumping of sludge and hazardous dredged materials.
c.Dispose fully treated municipal and industrial wastes.
d.Regulate coastal development.
e.Hygienic and aesthetic maintenance of recreational beaches.
f. Controlled use of pesticides and chemicals in agricultural activities in delta' portions.
g.Separate sewage and storm water lines.
h.Protect sensitive areas from development, oil drilling, and oil shipping.
i. Provide double hulls for oil tankers.
j. Ban on dumping of radioactive wastes.
Sources and Effects of Marine Pollution
Type Primary Source/Cause Effect
Nutrients Runoff approximately 50% sewage,
50% from forestry, farming, and other
land use. Also airborne nitrogen oxides
from power plants, cars etc.
Feed algal blooms in coastal waters.
Decomposing algae depletes water of
oxygen, killing other marine life. Can spur
algal blooms (red tides), releasing toxins that
can kill fish and poison people.
Sediments Erosion from mining, forestry,
farming, and other land-use; coastal
dredging and mining
Cloud water; impede photosynthesis below
surface waters. Clog gills of fish. Smother
and bury coastal ecosystems. Carry toxins
and excess nutrients.
Pathogens Sewage,livestock. Contaminate coastalswimming areas and
seafood, spreading cholera, typhoid and
other diseases.
Alien Species Several thousand per day transported in
ballast water; also spread through
canals linking bodies of water and
fishery enhancement projects.
Outcompete native species and reduce
biological diversity. Introduce new marine
diseases. Associated with increased
incidence of red tides and other algal
blooms. Problem in major ports.
Persistent Toxins
(PCBs,Heavy
metals, DDT
etc.)
Industrial discharge; wastewater
discharge from cities; pesticides from
farms, forests,home use etc.; seepage
from landfills.
Poison or cause disease in coastalmarine
life, especially near major cities or industry.
Contaminate seafood. Fat-soluble toxins that
bio-accumulate in predators can cause
disease and reproductive failure.
Oil 46% from cars,heavy machinery,
industry, other land-based sources;
32% from oil tanker operations and
other shipping; 13% from accidents at
sea; also offshore oil drilling and
natural seepage.
Low level contamination can kill larvae and
cause disease in marine life. Oil slicks kill
marine life, especially in coastalhabitats.
Tar balls from coagulated oil litter beaches
and coastalhabitat. Oil pollution is down
60% from 1981.
Plastics Fishing nets; cargo and cruise ships;
beach litter; wastes from plastics
industry and landfills.
Discard fishing gear continues to catch fish.
Other plastic debris entangles marine life or
is mistaken for food. Plastics litter beaches
and coasts and may persist for 200 to 400
years.
Radioactive
substances
Discarded nuclear submarine and
military waste; atmospheric fallout;
also industrial wastes.
Hot spots of radio activity. Can enter food
chain and cause disease in marine life.
Concentrate in top predators and shellfish,
which are eaten by people.
Thermal Cooling water from power plants and
industrial sites
Kill off corals and other temperature
sensitive sedentary species. Displace other
marine life.
Noise Supertankers, other large vessels and
machinery
Can be heard thousands of kilometers away
under water. May stress and disrupt marine
life.

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LIC PRIVATISATION its a bane or boon.pptx
 

Unit ii environmntl polltn

  • 1. Unit – ii Environmental Pollution 1.Water Pollution  Introduction: Water is the essential element that makes life on Earth possible. Without water there would be no life. About 97% of the total water available on Earth is found in the oceans and is too salty for drinking or irrigation. The remaining 3% is fresh water. Of this, 2.997% is locked in ice caps or glaciers. Thus, only 0.003% of the Earth's total volume of water is easily available to us as" soil moisture, groundwater, water vapor and the water in lakes, streams, rivers and wetlands. Definition: Water pollution can be defined as alteration in physical, chemical or biological characteristics of water making it unsuitable for designated use in its natural state.  Sources of water pollution: Pollution of water can be caused by point sources or non-point sources.  Point sources are specific sites near water which directly discharge effluents into them. Major point sources of water pollution are industries, power plants, underground coal mines, offshore oil wells etc.  Non-point sources is not at any particular site, rather, these sources are scattered, which individually or collectively pollute water. Surface run-off from agricultural fields, overflowing small drains, rain water sweeping roads and fields, atmospheric deposition etc. are the non-point sources of water pollution. Types of water pollutions Ground water pollution: there are a number of potential sources of ground water pollution. Septic tanks, industry (textile, chemical, and tanneries), deep well injection, mining etc. are mainly responsible for ground water pollution, which is irreversible. Ground water pollution with arsenic, fluoride and nitrate are posing serious health hazards. Surface water pollution: The major sources of surface water pollution are: 1. Sewage: Pouring the drains and sewers in fresh water bodies causes water pollution. The problem is severe in cities. 2. Industrial effluents: Industrial wastes containing toxic chemicals, acids, alkalis, metallic salts, phenols, cyanides, ammonia, radioactive substances, etc. are sources of water pollution. They also cause thermal (heat) pollution of water. 3. Synthetic detergents: Synthetic detergents used in washing and cleaning produce foam and pollute water. 4. Agrochemicals: Agrochemicals like fertilizers (containing nitrates and phosphates) and pesticides (insecticides, fungicides, herbicides etc.) washed by rain-water and surface run-off pollute water. 5. Oil: Oil spillage into sea-water during drilling and shipment pollute it. 6. Waste heat: Waste heat from industrial discharges increases the temperature of water bodies and affects distribution and survival of sensitive species. Nutrient Water pollution:
  • 2. Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters, in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth. Excess nitrates and phosphorus encourage the growth of aquatic plants and algae. Nutrient-boosted algae growth leads to massive algae blooms, visible as a bright green, foul smelling sheen on the water’s surface. Some of the algae making up the blooms produce toxins that are dangerous to fish, wildlife, and humans. The blooms eventually die off, and their decomposition consumes a lot of dissolved oxygen, leaving waters with low oxygen concentrations. Invertebrates and fish are killed when oxygen levels dip too low.  Effects of water pollution 1. Presence of the many infectious agents causes many diseases. The different types of organisms and the water borne diseases are given below in Table Table: Water Borne Diseases Vs Responsible Organisms 2. Change in colour of water affects the usage of water and growth of plants and organisms in water. 3. The oxygen demanding wastes such as animal manure and plant residues deplete the dissolved oxygen content of water which is harmful to the aquatic lives. 4. The inorganic substances present in water causes many damages to the water. a. Makes the water unfit for drinking and other purposes. b. Corrosion of metals exposed to such waters. c. Causes skin cancers, damages to spinal, CNS, liver and kidneys. d. Reduces crop yield 5. Growth of aquatic plants and fishes are affected by the presence of acids, alkalies and toxic substances. 6. Oil and other lubricants affect the self purification of the stream or water body. 7. The organic chemicals such as detergents, pesticides, plastics, oil and gasoline present in the water damages the CNS and causes birth defects and genetic disorders. Also these are harmful to the lives of aquatic ecosystem. 8. Enrichment of nutrients (Eutrophication) from surrounding watershed affects the penetration of light through the water, causing damage to the characteristics of water and aquatic life. 9. Dumping of solid wastes resulting surface water as well as ground water pollution. 10. Disposal of coolant water used in industries increase the temperature of the surface water. This affects the solubility of oxygen in water and aquatic ecosystem. 11. More amounts of nitrates in water due to the application of artificial fertilizer in agricultural lands can cause methemoglobinemia known as blue baby. Also it decreases the oxygen carrying capacity of the blood in the body. 12. Oil spills or leaks from underground storage tanks on land are affecting a large area in a very short time.oil spills at sea decrease the oxygen level in the water and cause more harm to the marine planktons and creatures living in the sea 13. Run-off from farms, backyards, and golf courses contain pesticides such as DDT that in turn contaminate the water. 14. Leachates from landfill sites are another major contaminating source. It damages the ecosystems health and reproductivity of wildlife. Groundwater is susceptible to contamination, as pesticides are mobile in the soil. 16. Presence of radioactive materials such as iodine, radon, cesium, uranium and thorium and its isotopes
  • 3. causes genetic disorders, birth defects and certain cancers. 17. The chlorinated organic pesticides like dieldrin, aldrin and DDT are hazardous mainly due to their concentration in the food chain. They have high stability, low vapour pressure and very low solubility in water. As a result of biological magnification (accumulation of concentration from one level to another level of food chain), these are harmful to the mammals in longer term effects. 18. The presences of sediments (soil and silt) cause the following damages. a. Fills lakes and reservoirs b. Obstructs shipping channel c. Clogs hydroelectric turbines d. Affects photosynthesis of aquatic plants e. Disturbs the aquatic food chain f. Carries pesticides, bacteria and harmful substances to the receiving water body. g. Makes the water unsuitable for bathing, swimming, boating and other recreational uses.  Control of Water Pollution It is easy to reduce water pollution from point sources by legislation. However, due to absence of denied strategies it becomes difficult to prevent water pollution from non-point sources. The following points may help in reducing water pollution from non-point sources. (i) Judicious use of agrochemicals like pesticides and fertilizers which will reduce their surface run-off and leaching. Avoid use of these on sloped lands. (ii) Use of nitrogen fixing plants to supplement the use of fertilizers. (iii)Adopting integrated pest management to reduce reliance on pesticides. (iv) Prevent run-off of manure. Divert such run-off to basin for settlement. The nutrient rich water can be used as fertilizer in the fields. (v) Separate drainage of sewage and rain water should be provided to prevent overflow of sewage with rainwater. (vi) Planting trees would reduce pollution by sediments and will also prevent soil erosion. For controlling water pollution from point sources, treatment of waste water is essential before being discharged. Parameters which are considered for reduction in such water are-Total solids, biological oxygen demand (BOD), chemical oxygen demand (COD), nitrates and phosphates, oil and grease, toxic metals etc. Wastewaters should be properly treated by primary and secondary treatments to reduce the BOD, COD levels up to the permissible levels for discharge. Advanced treatment for removal of nitrates and phosphates will prevent eutrophication. Before the discharge of wastewater, it should be disinfected to kill the disease-causing organisms like bacteria. Proper chlorination should-be done to prevent the formation of chlorinated hydrocarbons or-disinfection should be done by ozone or ultraviolet radiations. 2. Noise pollution Introduction Noise may not seem as harmful as the contamination of air or water, but it is a pollution problem that affects human health and can contribute to a general deterioration of environmental quality. The unpleasant and unwanted sound is called noise. It is not a substance that can accumulate in the environment like most other pollutants. Sound is measured in a unit called the 'decibel' (dB). Sound can propagate through a medium like air, liquid or solid. Sound wave is a pressure perturbation in the medium through which sound travels. Sound pressure alternately causes compression and rarefaction. The number of compressions and rarefactions of the molecules of the medium (for example air) in a unit time is described as frequency. It is expressed in Hertz (Hz) and is equal to the number of cycles per second.
  • 4. There is a wide range of sound pressures, which encounter human ear. Increase in sound pressure does not invoke linear response of human ear. A meaningful logarithmic scale has been devised. The noise measurements are expressed as Sound Pressure Level (SPL) .It is expressed as a dimensionless unit, decibel (dB). Decibel scale is a measure of loudness. Noise can affect human ear because of its loudness and frequency (pitch).  The Central Pollution Control Board (CPCB) Standards The Central Pollution Control Board (CPCB) committee has recommended permissible noise levels for different locations Table: Noise standards by CPCB  Characteristics of Noise  Sound pressure  Frequency  Duration  Time of the day  Location  Intermittency  Source of Noise Pollution There are several sources of noise pollution that contribute to both indoor and outdoor noise pollution. Household sources These includes Food mixer, Vacuum cleaner, Washing machines and driers, Air conditioner and TV’S Social Events Place of worship, Disco’s, Parties, Political meetings and place where people sell goods with loudspeaker Commercial and Industrial Activities These include Printing press, construction sites and manufacturing industries. Examples Bulldozers, motors, drilling machines, dump trucks, pavement breakers etc. Transportation These include road traffic noise, Aircraft noise and noise from railroads Effects of Noise pollution Noise pollution affects both health and behavior. Unwanted sound (noise) can damage physiological health. Noise pollution can cause hypertension, high stress levels, hearing loss, sleep disturbances, and other harmful effects. Interferes with man's communication- In a noisy area communication is severely affected.  Hearing damage: Noise can cause temporary or permanent hearing loss. (NITTS-Noise induced temporary threshold shift means (temporary deafness) NIPTS- Noise induced permanent threshold shift- (Permanent deafness) ) It depends on intensity and duration of sound level. Auditory sensitivity is reduced with noise level of over 90 dB sound for more than a few minutes.  Physiological and Psychological changes: Continuous exposure to noise affects the functioning of various systems of the body. It may result in hypertension, insomnia (sleeplessness), gastro-intestinal
  • 5. and digestive disorders, peptic ulcers, blood pressure changes, behavioral changes, emotional changes etc.  Control of Noise Pollution a. Reduction in sources of noise: Sources of noise pollution like heavy vehicles and old vehicles may not be allowed to play in the populated areas. b. Noise making machines should be kept in containers with J sound absorbing media. The noise path will be in interrupted! and will not reach the workers. c. Proper oiling will reduce the noise from the machinery. d. Use of sound absorbing silencers: Silencers can reduce noise j by absorbing sound. For this purpose various types of fibrous ! Material could be used. e. Planting more trees having broad leaves. f. Through Law: Legislation can ensure that sound production is minimized at various social functions. Unnecessary horn blowing should be restricted especially in vehicle-congested areas. 3. Air pollution Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damages the natural environment, into the atmosphere. The atmosphere is a complex, dynamic natural gaseous system that is essential to support life on planet Earth. An air pollutant is known as a substance in the air that can cause harm to humans and the environment. Pollutants can be in the form of solid particles, liquid droplets, or gases. In addition, they may be natural or man-made. Source of air pollution: Sources of air pollution refer to the various locations, activities or factors which are responsible for the releasing of pollutants in the atmosphere. These sources can be classified into two major categories which are:  Anthropogenic sources (human activity) mostly related to burning different kinds of fuel. "Stationary Sources" include smoke stacks of power plants, manufacturing facilities (factories) and waste incinerators, as well as furnaces and other types of fuel-burning heating devices "Mobile Sources" include motor vehicles, marine vessels, aircraft and the effect of sound etc. Chemicals, dust and controlled burn practices in agriculture and forestry management. Controlled or prescribed burning is a technique sometimes used in forest management, farming, prairie restoration or greenhouse gas abatement. Fire is a natural part of both forest and grassland ecology and controlled fire can be a tool for foresters. Controlled burning stimulates the germination of some desirable forest trees, thus renewing the forest. Fumes from paint, hair spray, varnish, aerosol sprays and other solvents Waste deposition in landfills, which generate methane. Methane is not toxic; however, it is highly flammable and may form explosive mixtures with air. Methane is also asphyxia and may displace oxygen in an enclosed space. Asphyxia or suffocation may result if the oxygen concentration is reduced to below 19.5% by displacement  Natural sources Dust from natural sources, usually large areas of land with little or no vegetation. Methane, emitted by the digestion of food by animals, for example cattle. Radon gas from radioactive decay within the Earth's crust. Radon is a colorless, odorless, naturally occurring, radioactive noble gas that is formed from the decay of radium. It is considered to be a health
  • 6. hazard Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the basement and it is the second most frequent cause of lung cancer, after cigarette smoking. Smoke and carbon monoxide from wildfires. Volcanic activity, which produce sulfur, chlorine, and ash particulates. Classification of Air pollutants: Pollutants can be classified as either primary or secondary. Usually, Primary pollutants are substances directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone - one of the many secondary pollutants that make up photochemical smog. Note that some pollutants may be both primary and secondary: that is, they are both emitted directly and formed from other primary pollutants. Primary pollutants Primary pollutants produced by human activity include: Sulfur oxides (SOx) – Sulfur dioxide, a chemical compound with the formula SO2 produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus causes acid rain. Inhalation narrows the airway, causing wheezing and shortness of breath, especially in those with asthma. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.  Nitrogen oxides (NOx) – Among oxides of nitrogen, especially nitrogen dioxide is emitted from high temperature combustion. It can be seen as the brown haze dome above or plume downwind of cities. Nitrogen dioxide is the chemical compound with the formula NO2. This reddish-brown toxic gas has a characteristic sharp, biting odor which affects lungs and causes wheezing; increases chance of respiratory infection  Carbon monoxide - is a colorless, odorless, non-irritating but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide. It deprives body of Oxygen causing headaches, fatigue, and impaired vision. Inhalation of carbon monoxide causes serious impact on respiratory, cardiac and neural systems.  Carbon dioxide (CO2) - a greenhouse gas emitted from combustion but is also a gas vital to living organisms. It is a natural gas in the atmosphere. Upon increasing in concentration leads to increase of earth’s average temperature causing global warming.  Volatile organic compounds - VOCs are an important outdoor air pollutant. They are often divided into the separate categories of methane (CH4) and non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhance global warming. Other hydrocarbon VOCs are also significant greenhouse gases via their role in creating ozone and in prolonging the life of methane in the atmosphere, although the effect varies depending on local air quality. Within the NMVOCs, the aromatic compounds benzene, toluene and xylene are suspected carcinogens and may lead to leukemia through prolonged exposure. 1, 3-butadiene is another dangerous compound which is often associated with industrial uses.
  • 7.  Particulate matter - Particulates alternatively referred to as particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to particles and the gas together. Sources of particulate matter can be manmade or natural. Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer.  Chlorofluorocarbons (CFCs) - harmful to the ozone layer emitted from products currently banned from use.  Ammonia (NH3) - emitted from agricultural processes. Ammonia is a compound with the formula NH3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceuticals. Although in wide use, ammonia is both caustic and hazardous.  Radioactive pollutants - produced by nuclear explosions, war explosives, and natural processes such as the radioactive decay of radon. Secondary pollutants include: Photochemical smog – Smog is a kind of air pollution; the word "smog" is combination of smoke and fog. Classic smog results from large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. Modern smog does not usually come from coal but from vehicular and industrial emissions that are acted on in the atmosphere by sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.  Ground level ozone (O3) formed from NOx and VOCs. Ozone (O3) is a key constituent of the troposphere (it is also an important constituent of certain regions of the stratosphere commonly known as the Ozone layer). Photochemical and chemical reactions involving it drive many of the chemical processes that occur in the atmosphere by day and by night. At abnormally high concentrations brought about by human activities (largely the combustion of fossil fuel), it is a pollutant, and a constituent of smog.  Peroxyacetyl nitrate (PAN) - The best known member of a class of photochemical oxidizing agents known as the peroxyacyl nitrates. The peroxyacyl nitrates are formed when ozone reacts with hydrocarbons such as those found in unburned petroleum. They are commonly found in photochemical smog. The peroyxacyl nitrates attack plants, causing spotting and discoloration of leaves, destruction of flowers, reduction in fruit production and seed formation, and death of the plant. They also cause red, itchy, runny eyes and irritated throats in humans. Cardiac and respiratory conditions, such as emphysema and chronic bronchitis, may result from long-term exposure to the peroxyacyl nitrates. Air Pollution Effects: 1. Reduced lung functioning 2. Irritation of eyes, nose, mouth and throat 3. Asthma attacks 4. Respiratory symptoms such as coughing and wheezing 5. Increased respiratory disease such as bronchitis 6. Reduced energy levels 7. Headaches and dizziness Disruption of endocrine, reproductive and immune systems Neurobehavioral disorders Cardiovascular problems Cancer
  • 8. Premature death Effects of Air- Pollution on Animals:  Acid rain (formed in the air) destroys fish life in lakes and streams  Excessive ultraviolet radiation coming from the sun through the ozone layer in the upper atmosphere which is eroded by some air pollutants, may cause skin cancer in wildlife  Ozone in the lower atmosphere may damage lung tissues of animals Effects of Air- Pollution on Plants:  Leaf Damage  Chemicals such as sulfur dioxide, ozone, fluorides and peroxyacyl nitrate damage the leaves of plants cause’s changes in the colors of leaf tissue, which may turn white, brown or yellow.  Nitrogen dioxide, a byproduct of combustion from car engines or open fires, can slow the growth of plants, carbon monoxide is less benign. This component of car exhaust is poisonous to humans and will stunt the growth of plants.  Fluorides absorbed by leaves are conducted towards the margins of broad leaves (grapes) and to the tips of monocotyledonous leaves (gladiolus). Little injury takes place at the site of absorption, whereas the margins or the tips of the leaves build up injurious concentrations  Large quantities of ammonia into the atmosphere for brief periods of time and cause severe injury to vegetation in the immediate vicinity.  Sulfur dioxide enters the leaves mainly through the stomata (microscopic openings) and the resultant injury is classified as either acute or chronic. The colour of the necrotic area can vary from a light tan or near white to an orange-red or brown depending on the time of year, the plant species affected and weather conditions.  Ozone symptoms characteristically occur on the upper surface of affected leaves and appear as a flecking, bronzing or bleaching of the leaf tissues. Air pollution controlling methods  Emission Control Equipments Emission control equipments are of two types. a. Gaseous control equipments b. Particulate control equipments The different kinds of methods and equipments of emission control are shown in Fig.3.1. Fig.3.1 Different types of emission control equipment 1. Gravitational Settling Chambers In this type of equipments, the particulate-laden gas is allowed to enter an enlarged area with a particular velocity. Inside the chamber, the velocity of the gas is
  • 9. reduced due to the enlarged portion. The gravitation force makes the dust particles to deposit at bottom of the hopper portion and makes clean gas. Fig. Gravitational Settling chamber These types of gravitational settling chambers are generally used to remove large particles of size about 50mm from gas streams. Merits: 1. Simple in design, construction and operation 2. Very less initial cost 3. Low operating cost Demerits: 1. Requirement of space for installation is more 2. Less efficiency for particles of size smaller than 50 µm. 2. Cyclone Separators A cyclone separator consists of an inlet, cylindrical shell, conical base and hopper. The dust- laden gas is allowed to enter tangentially in the inlet. A centrifugal force is generated by spinning the gas stream. The magnitude of centrifugal force generated on the gas stream depends on the cyclone diameter, mass of the particle and velocity of gas within the cyclone. This centrifugal force throws the particulates on the walls of cyclone which separates the particulate matters from the particulate laden gas. The cleaned air goes upward and the dust particles are collected at the bottom of the hopper. Fig.. Cyclone-Clean air Merits 1. More effective than the gravitational settling chambers in the removal of much smaller particles. 2. Relatively inexpensive 3. Operative cost is less. 4. Handle large volume of gases at temperatures up to 98°C. 3. Fabric Filters (or) Bag Filters These are the oldest equipments adopted for removal of particulate matters from industrial gases. In this type of filters, woven or non-woven fabrics are used to filter the particulate-laden gases. Efficiency of the fabric filters is about 99% and it can able to remove particles as small as 0.1 µm. Filter bags are generally of tubular shape or envelope shape. The type of fabric is decided based on temperature of the gas and the corrosiveness or abrasiveness of the particles.
  • 10. Fig. Fabric filter The bag houses consist of a group of bag (or fabric) filters suspended from an overhead support. The dust laden gas is allowed at the bottom of the bag house. The gas stream is allowed to pass through the bags. The dust particles are trapped at the fabric surface and the clean air is collected at the top. This accumulated dust particles are collected at the bottom of the bag house as solid waste. The bags are cleaned either by mechanical shakers or by reverse air. Merits  High collection efficiency up to 99%.  Broad range of particles is collected by the fabric filters.  Large volume of gases at relatively high speeds may be cleaned.  Particles are collected in dry state.  Particles up to 0.lp.m are collected by the fabric filters. Demerits  The possibility of explosion or fire is more in a bag house.  Requires more space for installation of bag house.  Size of the bag house unit is large.  The construction cost is high. 4. Electrostatic Precipitator (ESP) Fig. Electrostatic Precipitator In this type of equipments, two electrodes are used to separate the dust particles from a gas stream. The gas stream is allowed to pass between the two electrode wires (which are called as discharge electrodes). The electrical charge is imparted to the particles through a high-voltage direct-current corona. The high-voltage field ionizes the gas molecules in the air stream and makes the particulate matters with negative charge. The negatively charged particles are attracted by the positively charged
  • 11. electrodes which are called as collectors. The charge of the particles is neutralized at the moment of collection, and they can be removed from the collectors by rapping, washing. Merits • Efficiency is 99% or more. • More suitable for wide range of particle sizes. • Sub-micron particles can also be collected.  Can handle large volumes of gas from 25 to 1000 m3 sec. • Can operate continuously with little maintenance. Can be used to collect acid or tar mists. Demerits  High initial installation cost.  Require more space.  Require more power.  More surface area is required for obtaining high efficiency. Wet collectors (or) Scrubbers Wet precipitation is the basic principle of wet scrubbers in which particles in the atmosphere are removed by nature. The basic functions of these are to make contact between the particulates and the scrubbing liquid, usually water. The major types of wet scrubbers are (i) Spray towers (ii) Centrifugal scrubbers (iii) Venturi scrubbers and (iv) Packed bed columns Among the above types of wet scrubbers, each type has its unique applicability. Spray towers are the simplest types of wet scrubbers. They are low energy scrubbers and that can be used to remove particles of size 5 to 10 m. Venturi scrubbers are of high energy scrubbers and they can be effective in removal of particles of size smaller than 3 µm. Fig..Spray towers
  • 12. In the spray tower the air stream with particles is introduced at the bottom. The Polluted gas flows upward. Water is introduced at the top by means of spray nozzles. By inertial impaction and interception the particulate matters are entrained by then molecules. The water with particles is collected at the bottom and disposed. The efficiency of a spray tower depends on the velocity of water,size of spray droplet size, velocity of gas, quantity of water and gas introduced and trajectories. Efficiency increases with decreasing diameter of water droplet and increasing droplet quantity Merits These are very much effective in simultaneous removal of gases and Particulates. Effective in wide range of loading. Requirement of space is very less compared to dry collectors. Lesser chance of explosion of dust-air mixtures.  Corrosive gases may be neutralized by proper choice of scrubbing liquid,  Temperature is reduced at the exhaust. Demerits Energy cost is relatively higher than the dry collectors.  Disposal of the wastewater is the main demerit of this type and requires treatment. Possibility of corrosion is more.  Less efficiency in collection of very smaller particles. 3. Soil pollution Soil pollution Soil pollution is defined as, “contamination of soil by human and natural activities which may cause harmful effect on living organisms”. Composition of soil is listed below: COMPONENT % Organic mineral matter ---- 45% Organic matter -----05% Soil water ----25 % Soil air ---- 25 % SOURCES OF SOIL POLLUTION Soil pollution mainly occurs due to the following: 1. Industrial wastes 2. Urban wastes 3. Agricultural practices 4. Radioactive pollutants 5. Biological agents Industrial wastes – Disposal of Industrial wastes is the major problem for soil pollution Sources: Industrial pollutants are mainly discharged from various origins such as pulp and paper mills, chemical fertilizers, oil refineries, sugar factories, tanneries, textiles, steel, distilleries, fertilizers, pesticides, coal and mineral
  • 13. mining industries, drugs, glass, cement, petroleum and engineering industries etc. Effect: These pollutants affect and alter the chemical and biological properties of soil. As a result, hazardous chemicals can enter into human food chain from the soil or water, disturb the biochemical process and finally lead to serious effects on living organisms. Urban wastes – Urban wastes comprise of both commercial and domestic wastes consisting of dried sludge and sewage. All the urban solid wastes are commonly referred to as refuse. Constituents of urban refuse: This refuse consists of garbage and rubbish materials like plastics, glasses, metallic cans, fibres, paper, rubbers, street sweepings, fuel residues, leaves, containers, abandoned vehicles and other discarded manufactured products. Urban domestic wastes though disposed off separately from industrial wastes, can still be dangerous. This happens because they are not easily degraded. Agricultural practices – Modern agricultural practices pollute the soil to a large extent. With the advancing agro-technology, huge quantities of fertilizers, pesticides, herbicides and weedicides are added to increase the crop yield. Apart from these farm wastes, manure, slurry, debris, soil erosion containing mostly inorganic chemicals are reported to cause soil pollution Radioactive pollutants/ - Radioactive substances resulting from explosions of nuclear testing laboratories and industries giving rise to nuclear dust radioactive wastes, penetrate the soil and accumulate giving rise to land/soil pollution. Ex: 1. Radio nuclides of Radium, Thorium, Uranium, isotopes of Potassium (K-40) and Carbon (C-14) are commonly found in soil, rock, water and air. 2. Explosion of hydrogen weapons and cosmic radiations include neutron, proton reactions by which Nitrogen (N-15) produces C-14. This C-14 participates in Carbon metabolism of plants which is then into animals and human beings. 3. Radioactive waste contains several radio nuclides such as Strontium90, Iodine129, Cesium-137 and isotopes of Iron which are most injurious. Strontium get deposited in bones and tissues instead of calcium. 4. Nuclear reactors produce waste containing Ruthenium-106, Iodine-131, Barium140, Cesium-144 and Lanthanum-140 along with primary nuclides Sr-90 with a half life 28 years and Cs-137 with a half life 30 years. Rain water carries Sr-90 and Cs-137 to be deposited on the soil where they are held firmly with the soil particles by electrostatic forces. All the radio nuclides deposited on the soil emit gamma radiations. Biological agents – Soil gets a large amount of human, animal and bird excreta which constitute a major source of land pollution by biological agents. Ex: 1. Heavy application of manures and digested sludge can cause serious damage to plants within a few years Effects of soil pollution Effect on Health of Humans: Considering how soil is the reason we are able to sustain ourselves, the contamination of it has major consequences on our health. Crops and plants grown on polluted soil absorb much of the pollution and then pass these on to us. This could explain the sudden surge in small and terminal illnesses.
  • 14. Long term exposure to such soil can affect the genetic make-up of the body, causing congenital illnesses and chronic health problems that cannot be cured easily. In fact, it can sicken the livestock to a considerable extent and cause food poisoning over a long period of time. The soil pollution can even lead to widespread famines if the plants are unable to grow in it. Effect on Growth of Plants: The ecological balance of any system gets affected due to the widespread contamination of the soil. Most plants are unable to adapt when the chemistry of the soil changes so radically in a short period of time. Fungi and bacteria found in the soil that bind it together begin to decline, which creates an additional problem of soil erosion. The fertility slowly diminishes, making land unsuitable for agriculture and any local vegetation to survive. The soil pollution causes large tracts of land to become hazardous to health. Unlike deserts, which are suitable for its native vegetation, such land cannot support most forms of life. Decreased Soil Fertility: The toxic chemicals present in the soil can decrease soil fertility and therefore decrease in the soil yield. The contaminated soil is then used to produce fruits and vegetables which lacks quality nutrients and may contain some poisonous substance to cause serious health problems in people consuming them. Toxic Dust: The emission of toxic and foul gases from landfills pollutes the environment and causes serious effects on health of some people. The unpleasant smell causes inconvenience to other people. Changes in Soil Structure: The death of many soil organisms (e.g. earthworms) in the soil can lead to alteration in soil structure. Apart from that, it could also force other predators to move to other places in search of food Control measures of soil pollution: 1. Soil erosion can be controlled by a variety of forestry and farm practices. Ex: Planting trees on barren slopes Contour cultivation and strip cropping may be practiced instead of shifting cultivation Terracing and building diversion channels may be undertaken. Reducing deforestation and substituting chemical manures by animal wastes also helps arrest soil erosion in the long term. 2. Proper dumping of unwanted materials: Excess wastes by man and animals pose a disposal problem. Open dumping is the most commonly practiced technique. Nowadays, controlled tipping is followed for solid waste disposal. The surface so obtained is used for housing or sports field. 3. Production of natural fertilizers: Bio-pesticides should be used in place of toxic chemical pesticides. Organic fertilizers should be used in place of synthesized chemical fertilizers. Ex: Organic wastes in animal dung may be used to prepare compost manure instead of throwing them wastefully and polluting the soil. 4. Proper hygienic condition: People should be trained regarding sanitary habits. Ex: Lavatories should be equipped with quick and effective disposal methods. 5. Public awareness: Informal and formal public awareness programs should be imparted to educate people on health hazards by environmental education. Ex: Mass media, Educational institutions and voluntary agencies can achieve this. 6. Recycling and Reuse of wastes: To minimize soil pollution, the wastes such as paper, plastics, metals, glasses, organics, petroleum products and industrial effluents etc should be recycled and reused. Ex:
  • 15. Industrial wastes should be properly treated at source. Integrated waste treatment methods should be adopted. 7. Ban on Toxic chemicals: Ban should be imposed on chemicals and pesticides like DDT, BHC, etc which are fatal to plants and animals. Nuclear explosions and improper disposal of radioactive wastes should be banned. Marine pollution Definition Marine pollution can be defined as the introduction of substances to the marine environment directly or indirectly by man resulting in adverse effects sushi hazards to human health, obstruction of marine activities, and lowering the quality of sea water The main sources of marine pollution are i. Rivers, which bring pollutants from their drainage basins, ii. Catchment area i.e. coastline where human settlements in the form of hotels, industry, agricultural, practices have been established, and iii. Oil drilling and shipment. Sources of marine pollution According to International Maritime Organization (IMO), the different sources contributing marine pollution are 1. Land based sources 2. Air based sources 3. Maritime transportation 4. Dumping of wastes 5. Offshore production Land based sources Storm water: Urban runoff, or storm water, is more difficult to control. Storm water drains collect and channel the water from all non-porous surfaces, such as pavements and tarred roads, within a catchment. Storm water flow depends on rainfall, and the first flows following a dry spell often contain high levels of pollutants, such as heavy metals (particularly lead), oil residues, nutrients (nitrogen and phosphorus), and pathogenic (disease causing) micro-organisms, such as viruses, bacteria and protozoa, from faecal material. Rivers: Rivers carry to the sea water containing contaminants such as nutrients and pesticides from agricultural runoff, fecal pollution resulting from poor sanitation, and industrial discharges. Soil erosion, partly a result of poor catchment management, can cause increased water turbidity and siltation of estuaries. 2 Air based sources- Air based sources of marine pollution are referred to all the types of industrial activities that create air pollution which eventually drifts over and falls onto marine waters. a. Disposal of oil during the normal cleaning process.
  • 16. b. Accidental spill of oil. c. Disposal of garbage generated by the crews of marine vessels (the navy, fishing fleets, pleasure boaters etc.). 3 Eutrophication - Disposal of effluent with more nitrogen and phosphorus causes 'eutrophication' (over fertilization), which may cause algal blooms. These blooms can discolor the water, clog fish gills, or even be toxic. Microbial breakdown of dead algae can cause deficiency of oxygen. 4 Pesticides-Pesticides such as DDT (Dichlorodiphenyltrichloroethane) and other persistent chemicals accumulate in the fatty tissue of animals. These chemicals can cause reproductive failure in marine mammals and birds. 5 Plastics - Plastic is the dangerous solid waste. Plastic is not biodegradable and therefore affects the oceans for long periods of time. Plastics kill many marine animals. Turtles, for example, often swallow floating plastic bags, mistaking them for jelly- fish. Animals are often strangled when they become entangled with plastic debris. 6 Radioactive wastes-Any leakage or failure of radioactive wastes containers, which are used to dispose low level radioactive wastes in deep sea, causes more effects that could be devastating.  Prevention of marine pollution Following are some of the preventive measures of marine pollution. a.Careful handling of oil and petroleum products. b.Ban ocean dumping of sludge and hazardous dredged materials. c.Dispose fully treated municipal and industrial wastes. d.Regulate coastal development. e.Hygienic and aesthetic maintenance of recreational beaches. f. Controlled use of pesticides and chemicals in agricultural activities in delta' portions. g.Separate sewage and storm water lines. h.Protect sensitive areas from development, oil drilling, and oil shipping. i. Provide double hulls for oil tankers. j. Ban on dumping of radioactive wastes. Sources and Effects of Marine Pollution Type Primary Source/Cause Effect Nutrients Runoff approximately 50% sewage, 50% from forestry, farming, and other land use. Also airborne nitrogen oxides from power plants, cars etc. Feed algal blooms in coastal waters. Decomposing algae depletes water of oxygen, killing other marine life. Can spur algal blooms (red tides), releasing toxins that can kill fish and poison people. Sediments Erosion from mining, forestry, farming, and other land-use; coastal dredging and mining Cloud water; impede photosynthesis below surface waters. Clog gills of fish. Smother and bury coastal ecosystems. Carry toxins and excess nutrients.
  • 17. Pathogens Sewage,livestock. Contaminate coastalswimming areas and seafood, spreading cholera, typhoid and other diseases. Alien Species Several thousand per day transported in ballast water; also spread through canals linking bodies of water and fishery enhancement projects. Outcompete native species and reduce biological diversity. Introduce new marine diseases. Associated with increased incidence of red tides and other algal blooms. Problem in major ports. Persistent Toxins (PCBs,Heavy metals, DDT etc.) Industrial discharge; wastewater discharge from cities; pesticides from farms, forests,home use etc.; seepage from landfills. Poison or cause disease in coastalmarine life, especially near major cities or industry. Contaminate seafood. Fat-soluble toxins that bio-accumulate in predators can cause disease and reproductive failure. Oil 46% from cars,heavy machinery, industry, other land-based sources; 32% from oil tanker operations and other shipping; 13% from accidents at sea; also offshore oil drilling and natural seepage. Low level contamination can kill larvae and cause disease in marine life. Oil slicks kill marine life, especially in coastalhabitats. Tar balls from coagulated oil litter beaches and coastalhabitat. Oil pollution is down 60% from 1981. Plastics Fishing nets; cargo and cruise ships; beach litter; wastes from plastics industry and landfills. Discard fishing gear continues to catch fish. Other plastic debris entangles marine life or is mistaken for food. Plastics litter beaches and coasts and may persist for 200 to 400 years. Radioactive substances Discarded nuclear submarine and military waste; atmospheric fallout; also industrial wastes. Hot spots of radio activity. Can enter food chain and cause disease in marine life. Concentrate in top predators and shellfish, which are eaten by people. Thermal Cooling water from power plants and industrial sites Kill off corals and other temperature sensitive sedentary species. Displace other marine life. Noise Supertankers, other large vessels and machinery Can be heard thousands of kilometers away under water. May stress and disrupt marine life.