Air Pollution and Its Control Questions in English

(D) The harmful effect of air pollutants depends on several factors:
$1$. Concentration of the pollutant: The higher the concentration of the pollutant,the more severe its harmful effect.
$2$. Duration of exposure: The longer the duration of exposure to the pollutant,the more significant the damage caused.
$3$. Type of organism: Different organisms exhibit varying levels of sensitivity and resistance to specific air pollutants.
Therefore,all the mentioned factors influence the harmful effects of air pollutants. The correct option is $D$.

(A) Thermal power plants burn fossil fuels like coal to generate electricity.
This combustion process releases large amounts of particulate matter,sulfur dioxide $(SO_2)$,nitrogen oxides $(NO_x)$,and carbon dioxide $(CO_2)$ into the atmosphere.
These emissions are major contributors to air pollution,acid rain,and the greenhouse effect.
Therefore,thermal power plants are primarily responsible for air pollution.

(A) scrubber is a pollution control device used to remove harmful gases,particularly sulfur dioxide $(SO_2)$,from industrial exhaust streams. In a scrubber,the exhaust is passed through a spray of water or lime $(Ca(OH)_2)$. The lime reacts with the sulfur dioxide to form calcium sulfate or calcium sulfite,which can be removed as a sludge. Therefore,the correct option is $A$.

(C) According to the Central Pollution Control Board $(CPCB)$,particulate matter of size $2.5 \ \mu m$ or less in diameter (known as $PM_{2.5}$) is responsible for causing the greatest harm to human health.
These fine particulates can be inhaled deep into the lungs and can cause respiratory problems,inflammation,and damage to the lungs,and they can even enter the bloodstream.

(B) An electrostatic precipitator is a device used to remove particulate matter,such as dust and smoke,from industrial exhaust gases.
It consists of electrode wires that are maintained at several thousand volts,which produce a corona that releases electrons.
These electrons attach to dust particles,giving them a negative charge.
The collecting plates are grounded and attract the charged dust particles,effectively removing them from the gas stream.

(D) The Air (Prevention and Control of Pollution) Act was enacted in the year $1981$ to provide for the prevention,control,and abatement of air pollution in India.
It was later amended in $1987$ to include noise as an air pollutant.

(A) $CNG$ stands for Compressed Natural Gas.
It is a cleaner fuel compared to petrol and diesel,as it burns more efficiently and produces fewer pollutants,making it an environmentally friendly alternative for vehicles.

(B) An electrostatic precipitator is a device used to remove particulate matter from the exhaust gases of industrial plants,such as thermal power plants.
It works by charging the dust particles electrically and then collecting them on plates of opposite charge.
This technology is highly efficient and can remove over $99 \%$ of the particulate matter present in the exhaust.

(B) The given figure represents a scrubber,which is a device used to remove harmful gases like sulfur dioxide $(SO_2)$ from industrial exhaust.
In a scrubber,the exhaust is passed through a spray of water or lime $(Ca(OH)_2)$.
The water or lime solution reacts with the sulfur dioxide to neutralize it,thereby preventing it from being released into the atmosphere.

(D) The Air (Prevention and Control of Pollution) Act was enacted in $1981$ and was amended in $1987$ to include noise as an air pollutant.
Noise is defined as an undesired high level of sound,which can cause psychological and physiological damage to humans.

(B) Automobiles burn petroleum inefficiently,contributing significantly to air pollution. Automobile exhaust contains various pollutants,including hydrocarbons,carbon monoxide,nitrogen oxides,and lead. Lead,specifically in the form of tetraethyl lead $Pb(C_2H_5)_4$ or tetramethyl lead $Pb(CH_3)_4$,was historically added to gasoline as an anti-knock agent. It is considered the most hazardous metal pollutant because it interferes with oxygen and glucose metabolism,inhibits haeme synthesis,and causes severe damage to vital organs in the human body.

(B) The correct answer is $SO_{2}$.
$A$ scrubber is a pollution control device used to remove harmful gases,particularly sulphur dioxide $(SO_{2})$,from industrial exhaust streams.
In a scrubber,the exhaust gas is passed through a spray of water or a lime solution,which reacts with the acidic gases to neutralize and remove them before the air is released into the atmosphere.

(C) The Mathura-based petroleum refinery poses a significant threat to the Taj Mahal in Agra and other monuments in the Fatehpur Sikri complex.
Petroleum or oil refineries are major sources of gaseous pollutants,primarily releasing $SO_{2}$ and $NO_{x}$.
These gases ($SO_{2}$ and $NO_{x}$) mix with atmospheric moisture to form acids like $HNO_{3}$ and $H_{2}SO_{4}$.
These acids react with the marble $(CaCO_{3})$ of the Taj Mahal,causing corrosion and yellowing,a process often referred to as 'stone leprosy'.

(D) $CO_2$ is normally not considered an air pollutant because it is a natural component of the atmosphere and is essential for photosynthesis in plants.
However,its concentration has increased significantly due to large-scale deforestation and the combustion of fossil fuels.
While high concentrations of $CO_2$ contribute to global warming,it is not classified as a primary pollutant in the same category as $SO_2$ or nitrogen oxides.

(B) scrubber is used to remove gases like sulphur dioxide $(SO_2)$ and ammonia $(NH_3)$ from industrial exhaust.
In a wet scrubber,the exhaust air is passed through a spray of water or a chemical solution like lime $(Ca(OH)_2)$.
The pollutants dissolve in the spray or react with the chemical,thereby cleaning the air before it is released into the atmosphere.

(D) scrubber is an air pollution control device used to remove harmful gases,such as sulphur dioxide $(SO_2)$,from industrial exhaust emissions.
Statement $I$ is correct: Scrubbers are specifically designed to remove acidic gases like sulphur dioxide from industrial flue gases.
Statement $II$ is correct: In a wet scrubber,the exhaust gas is passed through a spray of water or an alkaline solution,such as lime $(Ca(OH)_2)$.
Statement $III$ is correct: Water acts as a solvent to dissolve certain gases,while lime reacts chemically with sulphur dioxide to form a precipitate of calcium sulphate $(CaSO_4)$ or calcium sulphide $(CaSO_3)$,which can then be removed from the system.
Therefore,all three statements are correct.

(C) To control air pollution in Delhi, the $Supreme Court$ of India issued directives to switch all public transport buses to $Compressed Natural Gas$ $(CNG)$. This transition was mandated to be completed by the end of the year $2002$. Therefore, $A = \text{compressed natural gas}$, $B = 2002$, and $C = \text{Supreme Court}$.

(C) In Delhi, the Supreme Court of India passed an order to switch the entire fleet of public transport, specifically buses, to run on $CNG$ $(Compressed Natural Gas)$ by the end of $2002$ to combat the severe air pollution levels.

(C) scrubber is a device used to remove harmful gases from industrial exhaust. It works by spraying water or lime through the exhaust stream. In this process,sulfur dioxide $(SO_2)$ reacts with the lime or water to form a precipitate,thereby removing it from the flue gas before it is released into the atmosphere.

(B) Factories release highly toxic gases and particulate matter.
Tall chimneys are recommended to release these pollutants at a higher altitude in the atmosphere,which helps in reducing the concentration of pollutants at the ground level.
Additionally,these chimneys are often equipped with electrostatic precipitators,which act as emission control units to remove dust and soot particles from the flue gases before they are released into the environment.

(B) An $Electrostatic$ $Precipitator$ is the most widely used device to remove particulate matter from the exhaust of thermal power plants.
It works by charging the dust particles electrically and then collecting them on grounded plates.
It can remove over $99\%$ of the particulate matter present in the exhaust.

(D) Air pollution has detrimental effects on all living organisms.
$1$. It affects plants by reducing their growth,yield,and causing premature death of leaves.
$2$. It affects animals (including humans) by causing respiratory issues,cardiovascular diseases,and other health complications.
$3$. Lichens are highly sensitive indicators of air pollution,especially $SO_2$,and they disappear from polluted areas.
Therefore,air pollution causes damage to plants,animals,and lichens.

(D) The harmful effects of air pollution are not uniform and depend on several factors:
$1$. $Concentration$ $of$ $pollutants$: Higher concentrations generally lead to more severe toxic effects.
$2$. $Organism$: Different species or individuals have varying levels of sensitivity to specific pollutants.
$3$. $Duration$ $of$ $exposure$: The length of time an organism is exposed to the pollutant significantly influences the extent of damage caused.
Therefore, all these factors determine the overall impact of air pollution.

(B) The given diagram represents a Scrubber,which is used to remove gases like sulfur dioxide $(SO_2)$ from industrial exhaust.
In a scrubber,the exhaust is passed through a spray of water or lime to remove harmful gases.
Therefore,it is used to clean impure air.

(D) Pollutants from vehicles can be reduced by several methods:
$1$. Catalytic converters: These contain expensive metals like platinum,palladium,and rhodium as catalysts. They convert unburnt hydrocarbons into $CO_2$ and $H_2O$,and carbon monoxide $(CO)$ and nitric oxide $(NO)$ into less harmful $CO_2$ and $N_2$ gas.
$2$. Proper maintenance: Regular servicing of vehicles ensures efficient combustion of fuel,thereby reducing the emission of harmful pollutants.
$3$. Lead-free fuel: Using unleaded petrol or diesel prevents the release of lead into the atmosphere,which is a toxic heavy metal that can damage catalytic converters and cause health issues.

(A) The Air (Prevention and Control of Pollution) Act was enacted in India in the year $1981$ to combat air pollution.
Later,in the year $1987$,this Act was amended to include noise as an air pollutant,recognizing the harmful effects of noise on human health and the environment.
Therefore,the correct sequence of years is $1981$ and $1987$.

(A) $CNG$ stands for Compressed Natural Gas.
It is a cleaner fuel compared to petrol and diesel,as it burns most efficiently and produces very little unburnt residue.
It is widely used as an alternative fuel for vehicles to reduce air pollution.

(B) According to the $NCERT$ textbook,the implementation of measures to control air pollution in Delhi,such as switching to Compressed Natural Gas $(CNG)$ for public transport,led to a significant reduction in the levels of sulfur dioxide $(SO_2)$ between $1997$ and $2002$.

(A) An electrostatic precipitator is a device used to remove particulate matter from industrial exhaust gases.
In the given diagram:
$P$ represents the negatively charged wire,which creates a corona discharge.
$Q$ represents the dust particles that get charged as they pass through the electric field.
$R$ represents the discharged corona (or the corona discharge region) around the wire.
Therefore,the correct sequence is $P$ = Negatively charged wire,$Q$ = Dust particles,$R$ = Discharged corona.