Chemistry PARTICULATE POLLUTANTS

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PARTICULATE POLLUTANTS

`text(Particulate matter)` :

(i) It is the non-gaseous matter in the atmosphere.

(ii) It consists of soot, dust, mist, fibres, fly ash, fur, spores, pollen grains etc.

(iii) It is of two types settleable (larger than `10``mu``m`) and suspended (less than `10``mu``m`)

(iv) SPM (suspended particulate matter) is classified into `3` categories -

(a) Aerosols (less than `1``mu``m`)

(b) Dust (solid particles with more than `1``mu``m` diameter)

(c) Mist (liquid particles with more than `1``mu``m` diameter)

(v) It is added in the atmosphere by burning of fuels.

(i) It is the non-gaseous matter in the atmosphere.

(ii) It consists of soot, dust, mist, fibres, fly ash, fur, spores, pollen grains etc.

(iii) It is of two types settleable (larger than `10``mu``m`) and suspended (less than `10``mu``m`)

(iv) SPM (suspended particulate matter) is classified into `3` categories -

(a) Aerosols (less than `1``mu``m`)

(b) Dust (solid particles with more than `1``mu``m` diameter)

(c) Mist (liquid particles with more than `1``mu``m` diameter)

(v) It is added in the atmosphere by burning of fuels.

`text(Aerosols)` :

(i) These are chemicals released in the air with force in the form of mist or vapour by jet planes.

(ii) Aerosols contain `text[CFC (chlorofluorocarbons)]` which destroy ozone layer in the stratosphere. This permitting some more harmful U.V. radiations to reach the earth surface.

(iii) U.V. radiations cause skin cancer and increases mutation rates.

(iv) Ozone acts as preventive shield against the U.V. rays.

(v) Freons are several CFMS (chlorofluoromethanes) released into troposphere where they dissociates and release free chlorine that causes depletion of ozone.

(vi) Freon or CFC also used in refrigerator, air conditioners and in making plastic foams.

(i) These are chemicals released in the air with force in the form of mist or vapour by jet planes.

(ii) Aerosols contain `text[CFC (chlorofluorocarbons)]` which destroy ozone layer in the stratosphere. This permitting some more harmful U.V. radiations to reach the earth surface.

(iii) U.V. radiations cause skin cancer and increases mutation rates.

(iv) Ozone acts as preventive shield against the U.V. rays.

(v) Freons are several CFMS (chlorofluoromethanes) released into troposphere where they dissociates and release free chlorine that causes depletion of ozone.

(vi) Freon or CFC also used in refrigerator, air conditioners and in making plastic foams.

`text(Smog)` :

(i) The term smog was coined by Des Voeux.

(ii) It is produced by the combination of smoke and fog.

(iii) It causes silvering/glazing and necrosis in plants, allergies and asthma/bronchitis in human.

(iv) Smog is of two types :

(a) `text(Classical or London smog or sulphurous smog)` - It occurs at low temperature and contains `H_2S`, `SO_2`, smoke and dust particles. It was first observed in winter months at London in 1905. It is formed due to domestic and industrial combustion of coal.

(b) `text(Photochemical smog or Los Angeles smog)` - It was first observed in the mid day at Los Angeles in 1943. The cause of this smog was thought to be due to combustion of petroleum in automobiles.

Photo chemical smog occurs at high temperature over cities and towns. It is formed by the reaction of two air pollutants nitrogen oxides (mainly `NO_2`) and hydrocarbons (`HC`) that react with one another in the presence of `U.V.` radiations of sun light to produce ozone (`O_3`) and PAN (peroxy acetyl nitrate) which constitute the photochemical smog.

`text(Nitrogen oxides)` `+ text(Hydrocarbons)` `undersettext(of sunlight) oversettext(U.V. radiation) rightarrow` `text(PAN) + text(Ozone)`

Ozone and PAN are commonly referred to as oxidants.

Breathing ozone affects the respiratory and nervous system, resulting in headache, respiratory distress and exhaustion. It also causes irritation in eyes and asthma. The ozone is known to destroy crops of potato, alfalfa and spinach to the extent of `50%`. It also damages leaves of tobacco, tomato and pine as also the grape fruits. Besides, the PAN also blocks Hill reaction of photosynthesis.

(i) The term smog was coined by Des Voeux.

(ii) It is produced by the combination of smoke and fog.

(iii) It causes silvering/glazing and necrosis in plants, allergies and asthma/bronchitis in human.

(iv) Smog is of two types :

(a) `text(Classical or London smog or sulphurous smog)` - It occurs at low temperature and contains `H_2S`, `SO_2`, smoke and dust particles. It was first observed in winter months at London in 1905. It is formed due to domestic and industrial combustion of coal.

(b) `text(Photochemical smog or Los Angeles smog)` - It was first observed in the mid day at Los Angeles in 1943. The cause of this smog was thought to be due to combustion of petroleum in automobiles.

Photo chemical smog occurs at high temperature over cities and towns. It is formed by the reaction of two air pollutants nitrogen oxides (mainly `NO_2`) and hydrocarbons (`HC`) that react with one another in the presence of `U.V.` radiations of sun light to produce ozone (`O_3`) and PAN (peroxy acetyl nitrate) which constitute the photochemical smog.

`text(Nitrogen oxides)` `+ text(Hydrocarbons)` `undersettext(of sunlight) oversettext(U.V. radiation) rightarrow` `text(PAN) + text(Ozone)`

Ozone and PAN are commonly referred to as oxidants.

Breathing ozone affects the respiratory and nervous system, resulting in headache, respiratory distress and exhaustion. It also causes irritation in eyes and asthma. The ozone is known to destroy crops of potato, alfalfa and spinach to the extent of `50%`. It also damages leaves of tobacco, tomato and pine as also the grape fruits. Besides, the PAN also blocks Hill reaction of photosynthesis.

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