Air Pollutions

Presentation outline

• Introduction• Structure of Atmosphere • Definition of Air Pollution• Source of Air Pollution • Classification of Air Pollution• Effect of Air Pollution• Control of Air Pollution

What does the atmosphere do for us?

• Obviously everyone has to breathe. We need oxygen to keep our bodies working. Just try holding your breath for a few seconds and see what happens. People are not the only ones who need oxygen; all kinds of animals need it too. Without the atmosphere we would all quickly die. But that's not the only thing the atmosphere does for us.

Benefits of Atmosphere

• A RADIATION SHIELD• SECURITY BLANKET• WEATHERING THE STORMS

Atmosphere as a Resource• Atmospheric

Composition– Nitrogen 78.08%– Oxygen 20.95%– Argon 0.93%– Carbon dioxide 0.04%

Structure of Atmosphere

• The Atmosphere is divided into layers according to major changes in temperature. Gravity pushes the layers of air down on the earth's surface

• 99% of the total mass of the atmosphere is below 32 kilometres.

Structure of Atmosphere

Name of part Height From Earth surface in km

Temperature in c

Troposphere 00-11 15 to (-55)

Stratosphere 11-50 (-2) to (-55)

Mesosphere 50-85 (-2) to (-90)

Thermosphere 85-100 (-90) to (-1200)

Layer of Atmosphere

Air Pollution

• Chemicals added to the atmosphere by natural events or human activities in high enough concentrations to be harmful that’s call Air Pollution .

• Possibly one of the most important characteristics of air pollutants is their trans-boundary nature - they can easily travel and affect the areas far away from their points of origination.

Source of Air pollution

Natural pollution• volcanoes, fumaroles

and hot springs • decay from marshes,

bogs • increase ozone due to

thunder storms, fires.

Man made pollution• Stationary sources -

those that are fixed in location.

• Mobile sources - those that move while polluting, e.g. trucks, cars, busses etc

Classification of air pollution

• Classification based on origin of air pollution• Gaseous Air Pollutants• Air borne Particules as Air Polluants

Classification based on origin of air pollution

• Primary air pollutants are the ones that are emitted directly into the atmosphere by the sources (such as power-generating plants).

• Secondary air pollutants are the ones that are formed as a result of reactions between primary pollutants and other elements in the atmosphere, such as ozone.

Gaseous Air Pollution

• There pollutions are in gaseous state at normal temperature and pressure.

• Common gas pollutants are– COX

– SOX

– Nox

–O3

SO2 Sulphur Dioxide

• Colourless gas with penetrating and pungent odour

• produced mainly when coal and fuel oil are burned

• present in power plant exhaust

• narrows the airway, causing sneezing and shortness of breath, especially in those with asthma

S + O2 SO2

2 SO2 + O2 2SO3

SO3 + H2O H2SO4

CO-Carbon Monoxide

• colorless, odorless, tasteless, non irritating gas

• produced when carbon does not burn in fossil fuels, ie incomplete combustion.

• Commonly present in automobile exhaust• CO is very dangerous asphyxiant and its high

levels are fatal to human life.

NOx-Nitrogen Dioxide

• reddish, brown gas• produced when nitric oxide combines with

oxygen in the atmosphere• present in car exhaust and power plants

N2 + 2O2 2NO2

4NO2+2H2O+O2 4HNO3

HYDROCARBONS

• Hydrocarbons are compounds that have carbon and hydrogen

• Benzene, methane, etc are common hydrocarbon pollutants.

• The major sources are automobile and industrial exhaust..

• Benzene: colorless, flammable liquid pollutant have carcinogenic property…

• Methane is common green house gas .. It produce by naturally along with human activities.

Air borne Particules as Air Pollution

• Solid particles between 1 and 100 μm (micrometres) in diameter are called dust particles, while solid particles less than 1 μm in diameter are called fumes, or smoke.

Effect of air Pollution

• Health of Human and other Animals• Greenhouse effect • Acid Rain• Ozone Departing

Health of Human and other Animals

• People facing problem like skin cancer , problem in eye(to watch) etc.

• Children who live in high ozone areas are more likely to develop asthma.

Greenhouse effect

• Carbon dioxide and other gases allow light to pass , but trap heat in the atmosphere much like glass in greenhouse traps heat.

• This greenhouse effect is thought to be responsible for global warming.

• Global warming is increase in the average temperature of the atmosphere

Greenhouse effect

Impact of Global warming• Temperature extremes • Rise in sea level • Injuries from storms, coastal flooding • Interruption of power supply, contamination

of drinking water • Drought • Food shortages due to shift in agricultural

food production

Impact of Global warming

• Air pollution ( made worse by warming) • Asthma, bronchitis, emphysema

complications • Strain on public health systems • Increased need due to population

migrations • Unable to contain spread of infectious

diseases

Acid Rain

• The term "acid rain" is commonly used to mean the deposition of acidic components in rain

Acid Rain• its pH being about 5.6, because carbon dioxide

and water in the air react together to form carbonic acid, a weak acid.• H2O + CO2 → H2CO3(aq)

• The main sources of these pollutants are vehicles and industrial and power-generating plants.

Acid rain reaction

• SO2 + water vapor + ozone H2SO4

• NO + sunlight + O2 NO2 + various

• atmospheric gases HNO3

Acid rain - causes

• The principal cause of acid rain is sulfur- and nitrogen compounds from human sources, such as electricity generation, factories and motor vehicles. Coal power plants are one of the most polluting.

Process

Effects of Acid Rain

• Acidify lakes• leaches metals out of rocks and soil• kill fish, plants

Ozone depletion

• The stratosphere contains the ozone shield, a layer of ozone (O3) in the stratosphere, 50 km above the ground.

Hazards of UV radiation

• Hazards of UV radiation include increased mutation rate, which can lead to skin cancer and cataracts, depression of the immune system, impaired crop and tree growth, and the death of plankton.

Health effects of Ozone depletion

• By the UV radiation, 75 million cases of cataracts and 300,000 more cases of skin cancer every year.

Ozone Hole above Antarctica• During the 1980s scientists discovered a

"hole" in the ozone over Antarctica. • By the 1990s atmospheric scientists had

detected an annual loss of 40-50% of the ozone above Antarctica, which produced an ozone hole every spring.

• One CFC molecule can destroy 100,000 ozone molecules.

Control of Air Pollutants

Methods of air pollution control can be divided into two categories: •THE CONTROL OF PARTICULATE EMISSIONS •THE CONTROL OF GASEOUS EMISSIONS

THE CONTROL OF PARTICULATE EMISSIONS

• The term particulate refers to tiny particles of matter such as smoke, soot, and dust that are released during industrial, agricultural, or other activities.

• Particulate matter can be control by using following devices

Gravitational Settling Chamber

• Like settling basins in water and waste water treatment, settling chambers provide enlarged areas to minimize horizontal velocities of air flow thus allow time for gravity to carry the particle to the floor.

Filtration• Filters consist of porous structure

composed of granular or fibrous material which tends to retain the particulate matter as the carrier gas passes through the voids of the filter.

• The dust is collected on the inside of the bag surface and the filtered gas is discharged to the atmosphere

• 99% efficient

Wet Scrubbers• spray systems where fine

water droplets are sprayed at high velocity at right angles to the emerging gas

• relatively low efficiencies (80-90%) and is usually employed as a pre-cleaner to remove particles larger than 5m

General solutions:

• switch from coal to cleaner fuels - use natural gas

• reduce energy use, improve energy efficiency • burn less coal, use lower sulfur coals. Coal

gasification • After burning the SO2 can be cleaned out by

scrubbing• Give education about control of air pollution.

Bibliography

• Google• Wikipedia• Tropical-Rainforest-Animals.com• ScienceTerrific.com• Environmental Studies By Snehal Popli

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