AIR
POLLUTION
What is Air Pollution?
There are a certain percentage of gases present in the
atmosphere. An increase or decrease in the composition of these gases is
harmful to survival.
Types of Air Pollutants
There are two types of air pollutants:
Primary Pollutants
The pollutants that directly cause air pollution are known
as primary pollutants. Sulphur-dioxide emitted from factories is a primary
pollutant.
Secondary Pollutants
The pollutants formed by the intermingling and reaction of
primary pollutants are known as secondary pollutants. Smog, formed by the
intermingling of smoke and fog, is a secondary pollutant.
Causes of Air Pollution
Following are the important causes of air pollution:
1.
Burning of Fossil Fuels
The combustion of fossil
fuels emits a large amount of sulphur dioxide. Carbon monoxide
released by incomplete combustion of fossil fuels also results in air
pollution.
2.
Automobiles
The gases emitted from vehicles such as jeeps, trucks,
cars, buses, etc. pollute the environment. These are the major sources of
greenhouse gases and also result in diseases among individuals.
3.
Agricultural Activities
Ammonia is one of the most hazardous gases emitted during
agricultural activities. The insecticides, pesticides and fertilizers emit
harmful chemicals in the atmosphere and contaminate it.
4.
Factories and Industries
Factories and industries are the main source of carbon
monoxide, organic compounds, hydrocarbons, and chemicals. These are released
into the air degrading its quality.
5.
Mining Activities
In the mining process, the minerals below the earth are
extracted using large equipments. The dust and chemicals released during the
process not only pollute the air but also deteriorate the health of the workers
and people living in the nearby areas.
6.
Domestic Sources
The household cleaning products and paints contain toxic
chemicals that are released in the air. The smell from the newly painted walls
is the smell of the chemicals present in the paints. It not only pollutes the
air but also affects breathing.
Effects of Air Pollution
The hazardous effects of air pollution on the environment
include:
·
Diseases
Air pollution has resulted in several respiratory disorders
and heart diseases among humans. The cases of lung cancer have increased in the
last few decades. Children living near polluted areas are more prone to
pneumonia and asthma. Many people die every year due to the direct or indirect
effects of air pollution.
·
Global Warming
Due to the emission of greenhouse gases, there is an
imbalance in the gaseous composition of the air. This has led to an increase in
the temperature of the earth. This increase in earth’s temperature is known
as global warming. This has resulted in the
melting of glaciers and an increase in sea levels. Many areas are submerged
under water.
·
Acid Rain
The burning of fossil fuels releases harmful gases such as
nitrogen oxides and sulphur oxides in the air. The water droplets combine with
these pollutants resulting in the deposition of acid rain which is composed of
sulphuric acid and nitric acid which damages human, animal and plant life.
·
Ozone Layer Depletion
The release of chlorofluorocarbons, halons, and
hydrochlorofluorocarbons in the atmosphere is the major cause of depletion of
ozone layer. The depleting ozone layer does not prevent the harmful ultraviolet
rays coming from the sun and causes skin diseases and eye problems among
individuals.
Effect on Animals
The air pollutants suspend on the water bodies and affect
the aquatic life. Pollution also compels the animals to leave their habitat and
shift to a new place and responsible for the extinction of animal species.
Air Pollution Control
Following are the measures one should adopt to control air
pollution:
a.
Avoid Using Vehicles
People should avoid using vehicles for shorter distances.
Rather they should prefer public modes of transport to travel from one place to
another. This not only prevents pollution but also conserves energy.
b.
Energy Conservation
A large number of fossil fuels are burnt to generate
electricity. Therefore, do not forget to switch off the electrical appliances
when not in use. Thus, you can save the environment at the individual level.
Use of energy-efficient devices such CFLs also controls pollution to a greater
level.
c.
Use of Clean Energy Resources
The use of solar, wind and geothermal energies reduce air
pollution at a larger level. Various countries including India have implemented
the use of these resources as a step towards a cleaner environment.
Other air pollution
control measures include:
- By
minimizing and reducing the use of fire and fire products.
- Since
industrial emissions are one of the major causes of air pollution, the
pollutants can be controlled or treated at the source itself to reduce its
effects. For example, if the reactions of a certain raw material yield a
pollutant, then the raw materials can be substituted with other less
polluting materials.
- Fuel
substitution is another way of controlling air pollution. In many parts of
India, petrol and diesel are being replaced by CNG – Compressed Natural
Gas fuelled vehicles. These are mostly adopted by vehicles that aren’t
fully operating with ideal emission engines.
- Although
there are many practices in India which focus on repairing the quality of
air, most of them are either forgotten or not being enforced properly.
There are still a lot of vehicles on roads which haven’t been tested for
vehicle emissions.
- Another
way of controlling air pollution caused by industries is to modify and
maintain existing equipments so that the emission of pollutants is
minimized.
- Sometimes
controlling pollutants at the source is not possible. In that case, we can
have process control equipment to control the pollution.
- A
very effective way of controlling air pollution is by diluting the air
pollutants.
- The
last and the best way of reducing the ill effects of air pollution is tree
plantation. Plants and trees reduce a large number of pollutants in the
air. Ideally, planting trees in areas of high pollution levels will be
extremely effective.
FORMATION AND
DEPLETION OF OZONE
The ozone layer is a region in the earth’s stratosphere that
contains high concentrations of ozone and protects the earth from the harmful
ultraviolet radiations of the sun.”
Ozone Layer Depletion
“Ozone layer depletion is the gradual thinning
of the earth’s ozone layer in the upper atmosphere caused due tho release
of chemical compounds containing gaseous bromine or chlorine from
industries or other human activities.”
Ozone layer
depletion is the thinning of the ozone layer present in the atmosphere. This
happens when the chlorine and bromine atoms in the atmosphere come in contact
with ozone and destroy the ozone molecules. One chlorine can destroy 100,000
molecules of ozone. It is destroyed more quickly than it is created.
The
ozone-depleting substances that contain chlorine include chlorofluorocarbon,
carbon tetrachloride, hydrochlorofluorocarbons, and methyl chloroform. Chlorofluorocarbons
are the most abundant ozone-depleting substance. It is only when the chlorine
atom reacts with some other molecule, it does not react with ozone.
Montreal Protocol was proposed in 1987 to
stop the use, production and import of ozone-depleting substances and minimise
their concentration in the atmosphere to protect the ozone layer of the earth.
Causes of Ozone Layer Depletion
The ozone layer depletion is a major
concern and is associated with a number of factors. The main causes responsible
for the depletion of the ozone layer are listed below:
·
Chlorofluorocarbons
Chlorofluorocarbons or the CFC are the
main cause of ozone layer depletion. These are released by soaps, solvents,
spray aerosols, refrigerators, air-conditioners, etc.
The molecules of chlorofluorocarbons in
the stratosphere are broken down by the ultraviolet radiations and release
chlorine atoms. These atoms react with ozone and destroy it.
·
Unregulated Rocket
Launches
Researches say that the unregulated launching
of rockets result in much more depletion of ozone layer than the CFCs do. If
not controlled, this might result in a huge loss of the ozone layer by the year
2050.
·
Nitrogenous Compounds
The nitrogenous compounds such as NO2, NO,
N2O are highly responsible for the depletion of the ozone layer.
·
Natural Causes
The ozone layer has been found to be
depleted by certain natural processes such as Sun-spots and stratospheric
winds. But it does not cause more than 1-2% of the ozone layer depletion.
The volcanic eruptions are also
responsible for the depletion of ozone layer.
Ozone Depleting Substances (ODS)
“Ozone depleting substances are the substances such
as chlorofluorocarbons, halons, carbon tetrachloride, hydrofluorocarbons, etc.
that are responsible for the depletion of ozone layer.”
Following is the list of some of the main
ozone depleting substances and the sources from where they are released:
Ozone-Depleting
Substances
|
Sources
|
Chlorofluorocarbons
(CFCs)
|
Refrigerators,
air-conditioners, solvents, dry-cleaning agents, etc.
|
Halons
|
Fire-extinguishers
|
Carbon
tetrachloride
|
Fire
extinguishers, solvents
|
Methyl
chloroform
|
Adhesives,
aerosols
|
Hydrofluorocarbons
|
Solvent
cleaning, fire extinguishers, solvent cleaning
|
Effects of Ozone Layer Depletion
The depletion of ozone layer has harmful
effects on the environment. Let us see the major effects of ozone layer
depletion on man and environment.
Effects
on Human Health
The humans will be directly exposed to the
harmful ultraviolet radiations of the sun due to the depletion of ozone layer.
This might result in serious health issues among humans such as skin
diseases, cancer, sunburns, cataract, quick ageing,
and weekend immune system.
Effects
on Animals
Direct exposure to ultraviolet radiations
leads to skin and eye cancer in animals.
Effects
on the Environment
Strong ultraviolet rays may lead to
minimal growth, flowering and photosynthesis in plants. The forests also have
to bear the harmful effects of the ultraviolet rays.
Effects
on Marine Life
Planktons are greatly affected by the
exposure to harmful ultraviolet rays. These are higher in the aquatic food
chain. If the planktons are destroyed the organisms present in the lower food
chain are also affected.
Solutions to Ozone Layer Depletion
The depletion of ozone layer is a serious
issue and various programmes had been launched by the government of various
countries to prevent it. But, steps should be taken at the individual level as
well to prevent the depletion of ozone layer.
Following are some of the points that
would help in preventing this problem at a global level:
Avoid
Using Pesticides
Natural methods should be implemented to
get rid of pests and weeds instead of using chemicals. One can use eco-friendly
chemicals to remove the pests or remove the weeds manually.
Minimise
the Use of Vehicles
The vehicles emit a large amount of greenhouse gases that lead to global
warming as well as ozone depletion. Therefore, the use of vehicles should be
minimised as much as possible.
Use
Eco-friendly Cleaning Products
Most of the cleaning products have
chlorine and bromine releasing chemicals that find way into the atmosphere and
affect the ozone layer. These should be substituted with natural products to
protect the environment.
The
Use of Nitrous Oxide should be Prohibited
The government should take actions and
prohibit the use of harmful nitrous oxide that is adversely affecting the ozone
layer. The people should be made aware of the harmful effects of nitrous oxide
and the products emitting the gas so that its use is minimised at the
individual level as well.
GREENHOUSE EFFECT
“Greenhouse
effect is the process by which radiations from the sun are absorbed by the
greenhouse gases and not reflected back into space and increase
the surface temperature of the earth causing global warming.
The major contributors to the greenhouses gases are
factories, automobiles, deforestation, etc. The increased number of factories and
automobiles increases the amount of these gases in the atmosphere. The
greenhouse gases never let the radiations to escape from the earth and increase
the surface temperature of the earth. This then leads to global warming.
Causes of Greenhouse Effect
The major causes of the greenhouse effect
are:
·
Burning of Fossil Fuels
Fossil fuels are an important part of our
lives. They are widely used in transportation and to produce electricity.
Burning of fossil fuels releases carbon dioxide. With the increase in
population, the utilization of fossil fuels had increased. This has led to an
increase in the release of greenhouse gases in the atmosphere.
·
Deforestation
Plants and trees take in carbon dioxide
and release oxygen. Due to the cutting of trees, there is an inconsiderable
increase in the greenhouse gases which increases the earth’s temperature.
·
Farming
Nitrous oxide used in fertilizers is one
of the contributors to greenhouse effect in the atmosphere.
·
Industrial Waste and Landfills
The industries and factories produce
harmful gases which are released in the atmosphere.Landfills also release
carbon dioxide and methane that adds to the greenhouse gases.
Effects of Greenhouse Effect
The main effects of increased greenhouse
gases are:
1. Global Warming
It is the phenomenon of a gradual increase
in the average temperature of the Earth’s atmosphere. The main cause for this
environmental issue is the increased volumes of greenhouse gases such as carbon
dioxide and methane released by the burning of fossil fuels, emissions from the
vehicles, industries and other human activities.
2. Depletion of Ozone Layer
Ozone Layer protects the earth from
harmful ultraviolet rays from the sun. It is found in the upper regions of the
stratosphere. The depletion of the ozone layer results in the entry of
the harmful UV rays to the earth’s surface that might lead to skin cancer
and can also change the climate drastically.
The major cause of this phenomenon is the
accumulation of natural greenhouse gases including chlorofluorocarbons, carbon
dioxide, methane, etc.
3. Smog and Air Pollution
Smog is formed by the combination of smoke
and fog. It can be caused both by natural means and man-made activities.
In general, smog is generally formed by
the accumulation of more greenhouse gases including nitrogen and sulfur
oxides. The major contributors to the formation of smog are the automobile and
industrial emissions, agricultural fires, natural forest fires and the reaction
of these chemicals among themselves.
4. Acidification of Water Bodies
Increase in the total amount of greenhouse
gases in the air has turned most of the world’s water bodies acidic. The
greenhouse gases mix with the rainwater and fall as acid rain. This leads to
the acidification of water bodies.
Also, the rainwater carries the
contaminants along with it and fall into the river, streams and lakes thereby
causing their acidification.
GLOBAL WARMING
“Global
warming is a gradual increase in the earth’s temperature generally due to the
greenhouse effect caused by increased levels of carbon dioxide, CFCs, and other
pollutants. “
Causes of Global Warming
Following are the major causes of global
warming:
Man-made Causes of Global Warming
·
Deforestation
Plants are the main source of oxygen. They
take in carbon dioxide and release oxygen thereby maintaining environmental
balance. The forests are being depleted for many domestic and commercial
purposes. This has led to an environmental imbalance thereby giving rise to
global warming.
·
Use of Vehicles
The use of vehicles even for very short
distances results into various gaseous emissions. Vehicles burn fossil fuels
which emit a large amount of carbon dioxide and other toxins into the
atmosphere resulting in a temperature increase.
·
Chlorofluorocarbon
With the excessive use of air conditioners
and refrigerators, humans have been adding CFCs into the environment which
affects the atmospheric ozone layer. The ozone layer protects the earth surface
from the harmful ultraviolet rays emitted by the sun. The CFCs has led to ozone layer depletion making way for the
ultraviolet rays, thereby increasing the temperature of the earth.
·
Industrial Development
With the advent of industrialization, the
temperature of the earth has been increasing rapidly. The harmful emissions
from the factories add to the increasing temperature of the earth.
·
Agriculture
Various farming activities produce carbon
dioxide and methane gas. These add to the greenhouse gases in the atmosphere
and increase the temperature of the earth.
·
Overpopulation
Increase in population means more people
breathing. This leads to an increase in the level of carbon dioxide, the
primary gas causing global warming, in the atmosphere.
Natural Causes of Global Warming
·
Volcanoes
Volcanoes are one of the largest natural
contributors to global warming. The ash and smoke emitted during volcanic eruptions
goes out into the atmosphere and affects the climate.
·
Water Vapour
Water vapour is a kind of greenhouse gas.
Due to the increase in earth’s temperature more water gets evaporated from the
water bodies and stays in the atmosphere adding to global warming.
·
Forest Blazes
Forest blazes or forest fires emit a large
amount of carbon-containing smoke. These gases are released into the atmosphere
and increase the earth’s temperature resulting in global warming.
Effects of Global Warming
Following are the major effects of global
warming:
1. Rise in Temperature
Global warming has led to an incredible
increase in earth’s temperature. Since 1880, the earth’s temperature has
increased by 1.4 degrees. This has resulted in an increase in melting of
glaciers which have led to an increase in the sea levels. This could have
devastating effects on coastal regions.
2. Threat to the Ecosystem
Global warming has affected the coral
reefs that can lead to a loss of plant and animal lives. Increase in global
temperatures has made the fragility of coral reefs even worse.
3. Climate Change
Global warming has led to a change in
climatic conditions. There are droughts at some places and floods at some. This
climatic imbalance is the result of global warming.
4. Spread of Diseases
Global warming leads to a change in the
patterns of heat and humidity. This has led to the movement of mosquitoes that
carry and spread diseases.
5. Decrease in the Human Population
Due to an increase in floods, tsunamis and
other natural calamities, the population of humans tend to decrease. Also, the
spread of diseases leads to a decrease in the human population.
6. Loss of Natural Habitat
A global shift in the climate leads to the
loss of habitats of several plants and animals. In this case, the animals need
to migrate from their natural and many of them even get extinct. This is yet
another major impact of global warming on biodiversity.
Mitigation
of Global warming
Mitigating global warming is
about reducing the release of greenhouse gas emissions that are warming our
planet. Mitigation strategies include retrofitting buildings to make them more
energy efficient; adopting renewable
energy sources like solar, wind and small hydro; helping cities develop more
sustainable transport such as bus rapid transit, electric
vehicles, and biofuels; and promoting more sustainable uses of land and
forests.
PHOTOCHEMICAL SMOG
Photochemical smog is formed due to the
reaction of sunlight with nitrogen oxides and hydrocarbons. Formaldehyde,
nitric oxide, ozone, PAN, acrolein are the main components of photochemical
smog. The steps involved in the formation of photochemical smog are:
Hydrocarbons and nitrogen dioxide are released into the atmosphere as a
result of burning of fossil fuels. Due to high concentrations of these
pollutants, they react with sunlight. The reactions proceed as shown below:
NO2 →hγ
NO + O
(Nitrogen di
oxide) (Nitric oxide)
O
+ O2 ↔
O3
O3
+ NO →
NO2 + O2
Since, NO2 and
O3 are oxidizing
agents, they react with the unburnt hydrocarbons to produce acrolein, PAN and
formaldehyde.
Effects of
photochemical smog
·
Both ozone and
PAN and cause eye irritation while nitric oxide (derived from NO2) is responsible
for throat and nose irritation.
·
At higher levels,
this type of smog can also cause headaches, throat dryness, chest pain and
other respiratory ailments.
ACID RAIN
Oxides of nitrogen (NO2,
NO) and sulphur (SO2 and SO3) which are formed due to the burning of coal,
automobile fuel and other fossil fuels, form nitric acid (HNO3) and sulphuric
acid (H2SO4) by reacting with water in the presence of atmospheric oxygen. This
results in ‘Acid rain’.
Effects of Acid rain
·
Acid rain causes damage to the plants, agriculture and crops.
·
It also causes respiratory problems in humans.
·
Acid rain damages buildings and structures made
of metal and stone. Limestone is a major constituent used in various monuments
and statues like Taj Mahal in India.
·
Acid rain when reacting with limestone causes
loss of colour and lustre of monuments, resulting in their disfiguration.
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