Air Pollution

Unit-4

Syllabus

• Air Pollution, Composition of Air, Structure of atmosphere, Ambient air quality standards, Classification of air pollutants, Sources of common air pollutants like SPM, SO2, NOX, Natural and anthropogenic Sources, and its effects.

Air Pollution

• Definition:- Air pollution is define as • “ Excessive concentration of foreign matter in

air, which adversely affects the well being of individuals or causes damage to the property”.

Composition of Air

Atmosphere and its Structure

• Atmosphere:- The gaseous layer surrounding the earth is known as atmosphere.

• The atmosphere is the life supporting mantle, surrounding the earth.

• The atmosphere surrounds the earth up to 700 km, atmosphere is subdivided as

• Troposphere:- ( 0 To 12 Km) Contains 75 % of the gases in the atmosphere. This is where we live and weather occurs.

• Stratosphere:- (12 – 50 Km) this layer contains ozone layer. Ozone acts as a shield for the earth’s surface. It absorbs ultraviolet radiations from the sun. This causes temperature increase in the upper part of the layer.

• Mesosphere:- ( 50 to 80 Km) This is the coldest region of the atmosphere. This layer protects the earth from meteoroid. They burn up in this area.

• Thermosphere:- ( 80 Km and above) The air is very thin in this region. Thermosphere means “Heat Sphere”. The temperature is very high in this region

• This layer contains:-• (a) Ionosphere:-This is the lower part of the

thermosphere. It extends from 80 Km – 550 Km. This layer generally helps in radio communication.

• (b) Exosphere:- The upper part of the thermosphere. It extends from 550 km and above. Air is very thin here this is the area where satellite orbits the earth.

Structure of Atmosphere

Ambient air Quality Standards

Pollutant Time Weighted Average

Concentration in Ambient Air

Industrial Area Residential, Rural and other Sensitive Area

Sulphur Dioxide (SO2) Annual 24 hours

80 µg/m3 120 µg/m3

60 µg/m3 80 µg/m3

15 µg/m3 30 µg/m3

Oxides of Nitrogen (NO2)

Annual 24 hours

80 µg/m3 120 µg/m3

60 µg/m3 80 µg/m3

15 µg/m3 30 µg/m3

Suspended Particulate Matter (SPM)

Annual 24 hours

360 µg/m3 500 µg/m3

140 µg/m3 200 µg/m3

70 µg/m3 100 µg/m3

Respirable ** Particulate Matter (RPM)

Annual

24 hours

120 µg/m3

150 µg/m3

60 µg/m3 100 µg/m3

50 µg/m3 75 µg/m3

Lead (pb) Annual 24 hours

1.0 µg/m3 1.5 µg/m3

0.75 µg/m3 1.00 µg/m3

0.50 µg/m3 0.75 µg/m3

Carbon Monoxide(CO)

8 hours 1 hour

5.0 µg/m3 10.0 µg/m3

2.0 µg/m3 4.0 µg/m3

1.0 µg/m3 2.0 µg/m3

* Ministry of Environment and Forests, Government of India notification,1994** Particle size less than 10 µm

Major Sources of Air Pollution

• 1) Natural Sources:- The natural sources of air pollution are volcanic eruptions, releasing of poisonous gases like SO2 ( Sulfur dioxide), Hydrogen sulphide (H2S), Carbon Monoxide(CO), Forest fires, natural organic and inorganic decays, Pollen grains, wind blown dust, among them pollen grain are important because it causes allergic reactions in individuals.

Anthropogenic sources

• (a) Rapid Industrialization:- The Industries such as pulp and paper, chemical, metallurgical plants, refineries are responsible for air pollution, the most common pollutants are CO2, SO2, CO, NO, H2S etc.

• (b) Transportation:- Automobile exhausts release smoke. The smoke is a result of incomplete combustion of carbonaceous matter. The common pollutants are CO ( Carbon Monoxide), CO2, and Hydrocarbons.

• (c) Burning of Fossil fuels and fires:- The conventional sources of energy are wood, coal, and fossil fuels. The byproducts of fossil fuels is nothing but poisonous gases such as CO, CH4 (methane), SO2, and NOX.

• (d) Deforestation:- The balance of O2 and CO2 is maintained in the nature by the vegetation. The deforestation by man for his own needs has disturbed the balance of CO2 and O2, Concentration.

• (e) Increase in Population:- an increase in population leads to global warming and emission of green house gases. It also contributes to losses in forest cover and loss of wild life.

• (f) Agriculture activities:- Various pesticides and insecticides are used for agricultural purposes. Thus they cause air pollution.

• (g) Radioactive fallout:- Nuclear reaction, nuclear weapon testing contributes towards Nuclear pollution. Nuclear Pollutants are very harmful to man, animals and vegetations.

Classification of air pollutants

• Air pollutants are broadly classified as• (a) According to origin• (b) According to chemical composition• (c) According to State of matter.

According to Origin

• Air Pollutants can be classified as• (a) Primary Pollutants• (b) Secondary Pollutants• Primary Pollutants:- Primary pollutants are

those which are directly emitted from identifiable source

• These pollutants are emitted directly to the atmosphere.

• Ex:- (a) Particulate matter(b) Oxides of Sulphur(c) Oxides of Nitrogen(d) Carbon Monoxide(e) Radioactive Compounds

• Secondary air pollutants:- Secondary air pollutants are those which are produced in the air by the reaction of two or more primary pollutants.

• Ex:-• Ozone• Formaldehyde• Photochemical smog• Peroxy acetyl nitrate (PAN)

According to Chemical Composition

• All the air pollutants are classified as• (a) organic pollutants• (b) In organic pollutants• (a) Organic Pollutants:- Organic Pollutants contain

carbon and hydrogen. • Ex:- • Hydro Carbon• Aldehyde and Ketones• Alcohols• Organic Sulphur compounds

• Inorganic Pollutants:- Inorganic compounds mainly includes

• (a) Carbon monoxide (CO)• (b) Carbon dioxide (CO2)• (c)Carbonates• (d) Oxides of sulphur, nitrogen• (e) Ozone

According to State of Matter

• Air pollutants according to state of matter are classified as

• (a) Natural Contaminants• (b) Particulate matter• (c) Gases and vapours

Natural Contaminants

• The air contaminants which are produced from natural sources are called natural contaminants

• Eg. Pollen grains are emitted from weeds, grasses and trees

• This pollen grains are irritating to some individuals

• Size of pollen grains = 10 to 50 (µ)

Particulate matter• These may be liquid or solid. The

particulate matter are identified as aggregates which are larger than 0.002 µ but smaller than 500 µ

• (a) Dust (1 To 10,000 µ) : Small solid particles resulting from break up of large masses through processes such as crushing, grinding or blasting.

• (b) Smoke ( 0.5 To 1 µ) Consist of finely divided solid particles produced by incomplete combustion of organic particles such as coal, wood, or tobacco.

• Mist:- These are liquid particles formed by condensation of vapor

• Fog (1 to 40 µ ):- High concentration of mist is called as fog. It is dispersion of liquid particles in air.

• Fumes ( 0.03 to 0.3 µ ):- Fine solid particles formed by the condensation of vapors of solid material. The fumes are generally emit from melting operations.

• Ash ( 1 to 1000 µ ):- fine, noncombustible particles are known as fly ash.

• Spray (10 to 1000 µ):- Liquid particles formed by automation

Gases And Vapors

• (a) Carbon Monoxide:- (CO) This is an odorless, tasteless and colorless gas formed due to incomplete combustion of carbonaceous matter. The sources of carbon monoxide are motor vehicles, burning of fossil fuel and industrial processes.

• (b) Oxides of Sulphur:- They Include 4 different gaseous compounds such as Sulfur monoxide ( SO), Sulfur dioxide ( SO2), Sulphur trioxide ( SO3) and sulphur tetra oxide (SO4).

• Sulphur dioxide is a colorless, non flammable gas with suffocating odor.

Oxides of Nitrogen

• Oxides of Nitrogen Include 4 gaseous compound:- Nitric oxide ( NO), Nitrogen dioxide (NO2), Nitrous Oxide (N) Nitrogen penta oxide (N2O5)

• In air pollution, Nitric oxide (NO) and Nitrogen dioxide are of prime concern.The sources of this pollutants are Industrial

Processes, automobile exhausts.

Hydrocarbon

• Organic compounds containing only carbon and hydrogen are classified as Hydrocarbons.

• They are of 2 types.• (a) Aliphatic hydrocarbon• (b) Aromatic hydrocarbon• Hydrocarbon present in the atmosphere in the

atmosphere from both natural and man made sources.

• The major sources of hydrocarbon is burning of gasoline and industrial processes.

Effects of some common air pollutants

• 1) Particulate Matter:- • Effects on human:-• The pollutants of size less than 1 µ causes lung

damage• Asbestos fibers causes cancer• Lead from automobile exhaust affects brain• It causes several respiratory diseases• Silica , arsenic, dust causes cancer

• Effects on plants:-• Deposition of particulate matter containing

toxic metals affects the growth of plants• The particulate matter after deposition on

plant leaves block stomata opening of plants and reduce plant growth.

• The particulate matter with acid rain, reduces pH of the soil which makes the infertile.

• Effect on Material:• The particulate matter causes damage to

building• The corrosion is enhanced• It causes cracks and fading of pointed surface• Particulates accumulate on the soil and

reduces fertility of soil.

Carbon Monoxide

• Effects on humans:- • The high concentration of CO can cause death• The combination of CO and hemoglobin leads to the

formation of carboxylhaemoglobin (COHb) reduces the oxygen carrying capacity of blood.

• At concentration of 100 ppm people experience dizziness and headache.

• The cigarette smoke contains 400 to 450 ppm CO the percentage of COHb in blood of cigarette smokers increases with increase in smoking.

• At concentration of 750 ppm of CO it will cause death.

• Effects on plants:-• CO reduces nitrogen fixing capacity of

bacteria. Which affects the plant growth.• High concentration of causes leaf drops,

reduces the size of leaf and ageing• Effects on materials:-• Carbon monoxide appears to have no

detrimental effect on materials.

Oxides of Sulphur

• Effects on human health:-• It causes irritation of eyes and respiratory

tracts.• Increase in SO2 concentration in the

atmosphere, may lead to lung cancer• SO2 may obstruct breathing

• SO2 leads to the formation of H2 SO4 which is 20 times more irritant than SO2

• Effects on Plants:-• The low concentration for long period may

cause discoloration of leaves• SO2 affects the growth of plants• At high concentration the leaf tissues gets

damaged.• H2SO4 is extremely toxic to plants and soil

fertility.

• Effects on materials:-• The sulphuric acid will attack building

materials containing carbonates. This will form CaSO4 the CaSO4 gets easily washed away leaving discolored surface

• Paper absorb SO2 causing the paper to become brittle

• Leather looses the strength and flexibility.

Oxides of Nitrogen

• Effects on Human Health: nitric Oxide reduces the Oxygen carrying capacity of blood.

• Nitrogen dioxide causes irritation of lungs• High level of NOx causes pneumonia, lung

cancer, oxygen deficiency.• NOx causes irritation of respiratory system,

nervous system and digestive tracts.• NOx is extremely dangerous to human health.

• Effects on vegetation:- • NO2 and primary pollutants can damage plant

tissues• High concentration of NO Causes Damage to

leaves.• Secondary Pollutants such as smog, O3 may

damage the vegetation• Effects on materials:-• Nitric acid causes corrosion to metal surface• NO2 fades the color of clothes

• NO2 causes cracking of rubber

Hydrocarbon

• Effects on human health:-• Aromatic hydrocarbon may lead to cancer• Inhalation of hydrocarbon causes irritation of

respiratory tract.• Methane creates narcotic effects on human

beings• Most of the hydrocarbon are carcinogenic to

lungs

• Effects on Vegetation:-• HC affects plant growth• Discoloration of leaves• Effects on Materials:-• It causes discoloration of materials• Material becomes less elastic and more brittle.

Notations

• parts-per-million (ppm) 10–6, parts-per-billion (ppb) 10–9, and parts-per-trillion (ppt) 10–12 level

Prevent Air Pollution