Pollution Questions in English

(D) Quantitative pollutants are those substances which are already present in the environment,but are termed as pollutants when their concentration (quantity) increases in the environment.
For example,$CO_{2}$ is naturally present in the environment,but its concentration increases due to human activities like burning fossil fuels,which makes it a quantitative pollutant.

(A) Stone leprosy is a phenomenon caused by the reaction of atmospheric pollutants like $SO_{2}$ and $H_{2}SO_{4}$ with calcium carbonate $(CaCO_{3})$ present in marble and red sandstone.
These pollutants react with the stone to form calcium sulphate $(CaSO_{4})$,which is powdery and leads to the yellowing and flaking of the stone surface,a condition known as stone leprosy.
The Taj Mahal is affected by $SO_{2}$ emissions,historically linked to the Mathura refinery,while the Red Fort is affected by $SO_{2}$ from coal burning in nearby railway yards.

(C) Compressed Natural Gas $(CNG)$ is a fuel gas made of petrol which is compressed to a high pressure.
Its primary component is methane $(CH_4)$, which typically makes up $80-90\%$ of the gas.
It is considered a cleaner fuel compared to petrol and diesel because it produces fewer pollutants upon combustion.

(A) An electrostatic precipitator is a device used to remove particulate matter from industrial exhaust gases.
It works by charging the dust particles electrically and then collecting them on oppositely charged plates.
This technology is highly efficient and can remove over $99\;\%$ of the particulate matter present in the exhaust.

(B) Catalytic converters are fitted into automobiles for reducing emission of poisonous gases. They use expensive metals like platinum-palladium and rhodium as catalysts. As the exhaust passes through the catalytic converter,unburnt hydrocarbons are converted into $CO_2$ and $H_2O$,$CO$ is converted into $CO_2$,and $NO_x$ is converted into $N_2$ gas. Motor vehicles equipped with catalytic converter should use unleaded petrol because lead in the petrol inactivates the catalyst.

(C) Eutrophication is the natural aging of a lake by nutrient enrichment of its water.
When this process is accelerated by human activities such as the discharge of effluents from industries and homes,it is called cultural or accelerated eutrophication.
The primary contaminants responsible for this nutrient enrichment are phosphates and nitrates,which act as plant nutrients and stimulate excessive growth of algae and aquatic plants.

(C) Euro-$II$ emission norms were implemented to control the levels of pollutants in vehicle exhaust.
Specifically,these norms aimed to reduce the content of sulphur and aromatic hydrocarbons in fuels to minimize air pollution.

(C) The phenomenon of increase in concentration of non-biodegradable pollutants at successive trophic levels is called biomagnification.
In an aquatic food chain,the concentration of $DDT$ increases as it moves up the trophic levels:
$1$. Water: $0.003 \; ppb$
$2$. Phytoplanktons: $0.04 \; ppm$
$3$. Small fish: $0.5 \; ppm$
$4$. Large fish: $2 \; ppm$
$5$. Fish-eating birds: $25 \; ppm$
Therefore,the maximum concentration is observed in fish-eating birds.

(B) Snow blindness is a condition caused by the high intensity of $UV-B$ radiation.
When $UV-B$ radiation is absorbed by the cornea,it causes inflammation of the cornea,a condition known as snow blindness.
This is particularly common in high-altitude regions where snow reflects $UV-B$ rays,increasing exposure.

(B) Thermal pollution refers to the degradation of water quality by any process that changes ambient water temperature.
Coal-based power plants use water for cooling purposes in their condensers.
After passing through the condensers,this water becomes heated and is discharged back into the water bodies,leading to a significant increase in the temperature of the receiving water,which is known as thermal pollution.

(D) Lead is considered the most hazardous pollutant in automobile exhaust.
It interferes with haem synthesis,oxygen transport,and glucose metabolism.
Exposure to lead can cause severe health issues such as anaemia,vomiting,convulsions,and neurological disorders like madness.

(A) The major source of noise pollution worldwide is the transport system. For example,a jet plane taking off generates $150 \; dB$ or more of sound,which significantly contributes to environmental noise levels.

(B) In a polluted lake,the presence of organic matter increases the activity of microorganisms,which consume more oxygen for decomposition. This leads to a high Biochemical Oxygen Demand $(BOD)$. Consequently,the amount of Dissolved Oxygen $(DO)$ in the water decreases significantly.

(D) Catalytic converters are fitted into automobiles to reduce emission of poisonous gases. These converters contain expensive metals like platinum,palladium,and rhodium as catalysts. As the exhaust passes through the catalytic converter,unburnt hydrocarbons are oxidized into $CO_2$ and $H_2O$,while carbon monoxide $(CO)$ is oxidized into $CO_2$ and nitric oxide $(NO)$ is reduced to nitrogen gas $(N_2)$.

(B) Black foot disease is a severe peripheral vascular disease that causes gangrene in the feet.
It is primarily caused by chronic exposure to high concentrations of Arsenic in drinking water.
Arsenic contamination in groundwater is a major environmental health issue.

(A) Carbon monoxide $(CO)$ is a colorless,odorless gas that is highly toxic to animals and humans because it binds to hemoglobin in the blood with an affinity about $200$ to $250$ times greater than oxygen,forming carboxyhemoglobin. This prevents the blood from carrying oxygen to tissues,leading to hypoxia. However,plants do not possess hemoglobin or similar oxygen-transport systems,and they are generally unaffected by $CO$ at concentrations typically found in the environment.

(C) $NO_x$ (nitrogen oxides) are primary pollutants that contribute to the formation of secondary pollutants like ozone and peroxyacetyl nitrate $(PAN)$,lead to acid rain through the formation of nitric acid,and are key precursors in the formation of photochemical smog. Pheophytization is the process where chlorophyll loses its central magnesium ion to become pheophytin,typically due to acidic conditions or heavy metal stress,but it is not a direct environmental impact caused by $NO_x$ emissions.

(D) Air pollution is primarily controlled by devices such as scrubbers and electrostatic precipitators.
Scrubbers are used to remove gases like $SO_2$ from industrial exhaust.
Electrostatic precipitators are highly efficient devices used to remove particulate matter from industrial exhaust.
Effluent treatment is related to water pollution control,not air pollution.

(B) Acoustic zoning is a planning strategy used to manage and control noise levels in different areas. It involves designating specific zones (such as residential,commercial,or industrial) based on their tolerance to noise,thereby mitigating the impact of noise pollution on human health and the environment.

(A) Acid rain is primarily composed of sulfuric acid and nitric acid.
It causes necrosis (death of plant tissues) by damaging the leaf surface and disrupting metabolic processes.
It also causes the acidification of the leaf environment,which leads to the replacement of the central magnesium ion in chlorophyll-$a$ with hydrogen ions,converting it into phaeophytin,thereby reducing photosynthetic efficiency.
$PAN$ (Peroxyacetyl nitrate) is a secondary pollutant formed by the photochemical reaction of nitrogen oxides and hydrocarbons in the presence of sunlight,not by acid rain.
Therefore,statements $(a)$ and $(b)$ are correct.

(C) Acid rain lowers the $pH$ of the water body,which inhibits the growth of most green algae and sensitive aquatic organisms. Therefore,an increase in the growth of green algae is not an effect of acid rain; rather,it is a decrease.

(B) Ozone $(O_3)$ is a gas that plays a dual role in the atmosphere.
In the stratosphere,it forms the ozone layer,which absorbs harmful ultraviolet $(UV)$ radiation from the sun,thus acting as a protectant for living organisms.
In the troposphere,however,ozone is a secondary pollutant formed by the reaction of nitrogen oxides $(NO_x)$ and volatile organic compounds $(VOCs)$ in the presence of sunlight,where it acts as a harmful chemical pollutant.

(D) Eutrophication is the process of nutrient enrichment in water bodies,which leads to the excessive growth of algae (like $BGA$ or Blue-Green Algae).
This excessive growth leads to the depletion of dissolved oxygen $(DO)$ as aerobic bacteria decompose the organic matter.
Consequently,the death of submerged organisms occurs due to the lack of oxygen.
Finally,the $COD$ (Chemical Oxygen Demand) increases because more oxygen is required to oxidize the increased amount of organic matter present in the water.

(A) The release of phosphates and nitrates into water bodies acts as a fertilizer for aquatic plants and algae. This process is known as nutrient enrichment or eutrophication. As a result,it leads to an excessive increase in algal growth,often referred to as an algal bloom.

(B) Spraying of pesticides is an example of diffuse water pollution.
Diffuse water pollution,also known as non-point source pollution,occurs when pollutants are carried into water bodies through runoff from large areas such as agricultural fields,rather than from a single,identifiable pipe or source.

(C) non-point source of water pollution refers to pollution that comes from many diffuse sources rather than a single,identifiable location.
Agricultural runoff is a classic example of a non-point source because it involves the washing away of fertilizers,pesticides,and sediments from large areas of farmland into water bodies during rainfall or irrigation.
In contrast,sewage outlets and factory effluents are considered point sources because they discharge pollutants from a specific,identifiable pipe or location.

(A) Oil slick refers to a layer of oil floating on the surface of water. When fishes come in contact with this oil,it enters their respiratory system and causes clogging of gills. This prevents the exchange of gases,leading to suffocation and mass scale death of fishes.

(B) Prolonged water logging in agricultural fields prevents the diffusion of oxygen into the soil,leading to poor aeration. Furthermore,as water evaporates,it leaves behind dissolved salts,which accumulate in the topsoil over time,leading to high salinity. This process is a common cause of soil degradation in irrigated lands.

(B) Blue-baby syndrome,also known as methemoglobinemia,is caused by the presence of high levels of nitrates in drinking water,which is a form of soil and water pollution. When ingested,these nitrates are converted into nitrites,which combine with haemoglobin to form methaemoglobin. This reduces the oxygen-carrying capacity of the blood,leading to a bluish discoloration of the skin.

(C) $Euro-II$ norms were specifically implemented to reduce the content of sulphur and aromatic compounds in fuels,not $CO$.
$CO$ (carbon monoxide) is a product of incomplete combustion,but the primary goal of $Euro-II$ was to lower sulphur content to $350 \ ppm$ in diesel and $150 \ ppm$ in petrol.
Therefore,the Assertion is incorrect because it misidentifies the target pollutants of the $Euro-II$ norms.
However,the Reason statement is factually correct in its description of the harmful effects of these pollutants (reduced visibility due to smog and carboxyhemoglobin formation due to $CO$).
Thus,the correct choice is that the Assertion is incorrect,but the Reason is correct.

(A) Eutrophication is the natural or accelerated enrichment of water bodies by nutrients like nitrates and phosphates,which makes the water body highly fertile.
This increase in nutrient content promotes the excessive growth of planktonic algae,known as algal blooms.
These blooms impart a distinct color to the water bodies and cause deterioration of water quality and fish mortality.
Therefore,both the Assertion and the Reason are correct,and the Reason provides the correct explanation for the Assertion.

(A) Biomagnification refers to the increase in concentration of toxic substances at successive trophic levels.
$DDT$ accumulates in the bodies of birds and interferes with calcium metabolism.
This interference leads to the thinning of eggshells,which causes them to break prematurely before the embryo is fully developed.
Consequently,this leads to a decline in the bird population.
Therefore,both the Assertion and the Reason are correct,and the Reason is the correct explanation of the Assertion.

(C) The Electrostatic Precipitator $(ESP)$ is a highly efficient device that can remove over $99\;\%$ of particulate matter present in the exhaust from a thermal power plant.
In an $ESP$,the electrode wires are maintained at several thousand volts,which produce a corona that releases electrons.
These electrons attach to dust particles,giving them a net negative charge.
The collecting plates (anodes) are grounded and attract the charged dust particles.
Therefore,the Reason is incorrect because the particles are given a negative charge,not a positive charge,and the collecting plates are grounded to attract these negatively charged particles.

(A) High concentration of atmospheric $SO_2$ acts as a pollutant that causes damage to plant tissues.
$SO_2$ reacts with chlorophyll $a$ and replaces the central magnesium $(Mg)$ ion,converting it into phaeophytin.
This process,known as pheophytinization,leads to the degradation of chlorophyll,thereby reducing the photosynthetic efficiency and primary productivity of the plant.
Therefore,both the Assertion and the Reason are correct,and the Reason is the correct explanation of the Assertion.

(C) $PAN$ (Peroxyacetyl nitrate) is a secondary pollutant because it is not emitted directly into the atmosphere but is formed through chemical reactions between primary pollutants.
$PAN$ is formed by the photochemical reaction of nitrogen oxides $(NO_x)$ and hydrocarbons in the presence of sunlight (photochemical smog).
Since the Reason states that $PAN$ is formed in the absence of light,the Reason is incorrect.
Therefore,the Assertion is correct,but the Reason is incorrect.

(A) The Taj Mahal is primarily composed of marble,which is $CaCO_3$ (calcium carbonate).
$SO_2$ emissions from the Mathura refinery react with atmospheric moisture to form $H_2SO_4$ (sulphuric acid),leading to acid rain.
This acid reacts with the calcium carbonate of the monument: $CaCO_3 + H_2SO_4 \longrightarrow CaSO_4 + H_2O + CO_2$.
The resulting calcium sulphate $(CaSO_4)$ is a powdery,unstable substance that causes the marble to corrode and lose its luster,leading to the destruction of the monument.
Therefore,both the Assertion and the Reason are correct,and the Reason provides the correct explanation for the Assertion.

(N/A)

Biodegradable pollutants	Non-biodegradable pollutants
$(1)$ These are pollutants that are decomposed or degraded by microbial action.	$(1)$ These are pollutants that are not decomposed by microbial action.
$(2)$ They show relatively rapid degradation.	$(2)$ They are degraded very slowly.
$(3)$ They generally do not accumulate in the environment.	$(3)$ They often accumulate in the environment.
$(4)$ They can be used to produce useful products like manure,compost,and biogas. Examples: Garbage,sewage,livestock waste.	$(4)$ Only a few of them can be recycled; others are not manageable. Examples: $DDT$,$BHC$,plastics,polythene,cans,glass,etc.

(N/A)

Primary Pollutant	Secondary Pollutant
$(1)$ These pollutants are emitted directly into the environment from a source.	$(1)$ These pollutants are formed through the interaction of primary pollutants with other atmospheric constituents.
$(2)$ They persist in the same form in which they are released into the environment.	$(2)$ They are typically formed through photochemical reactions in the atmosphere.
$(3)$ They are generally less potent than secondary pollutants.	$(3)$ They are often more potent than primary pollutants due to synergistic effects.

(N/A)

Wet Deposition	Dry Deposition
$(1)$ It refers to the removal of acidic pollutants from the atmosphere through precipitation such as rain,fog,and snow.	$(1)$ It refers to the process where acidic gases and particulate matter settle onto surfaces from the atmosphere in the absence of precipitation.
$(2)$ It involves the incorporation of pollutants into water droplets before they reach the ground.	$(2)$ It involves the direct deposition of pollutants onto surfaces like soil,vegetation,and buildings via wind and gravity.

(N/A)

Brown air	Grey air
$(1)$ It is a reddish-brown haze primarily containing nitrogen oxides $(NO_x)$.	$(1)$ It is a grey-coloured haze primarily formed of $SO_2$,particulate matter,and smoke,often referred to as classical smog.
$(2)$ It occurs under intense solar conditions,leading to photochemical smog.	$(2)$ It occurs under less intense solar conditions,often associated with industrial pollution.

(N/A)

$BOD$	$COD$
$(1)$ $BOD$ stands for Biochemical Oxygen Demand.	$(1)$ $COD$ stands for Chemical Oxygen Demand.
$(2)$ It is a test used to measure the concentration of biodegradable organic matter present in a water sample.	$(2)$ It is a test used to indirectly measure the total amount of organic compounds (both biodegradable and non-biodegradable) in water.
$(3)$ Micro-organisms such as bacteria are used as biological oxidizing agents.	$(3)$ Strong chemical oxidants such as potassium dichromate are used.

(B) Catalytic converters contain expensive metals such as platinum,palladium,and rhodium which act as catalysts to reduce the emission of poisonous gases like carbon monoxide and nitrogen oxides.
Lead present in petrol acts as a catalyst poison.
It binds to the active sites of these metals,thereby inactivating them and rendering the catalytic converter ineffective.
Therefore,the use of unleaded petrol is recommended for vehicles equipped with catalytic converters.

(B) Thermal pollution is harmful for aquatic animals for several reasons:
$1$. Warm water holds less dissolved oxygen compared to cold water,leading to suffocation of aquatic life.
$2$. Abrupt changes in water temperature cause 'thermal shock',which can be fatal to fishes and other organisms.
$3$. Increased temperature accelerates the metabolic rate of organisms due to increased enzymatic activity,leading to higher oxygen demand.
$4$. Higher temperatures can create anaerobic conditions in deep waters,which promotes the growth of harmful bacteria.

(B) Increased concentration of $DDT$ in the body of birds interferes with calcium metabolism.
This disruption leads to the thinning of eggshells.
As a result,the eggshells break prematurely before the embryo reaches maturity,leading to a decline in bird populations.

(B) In West Bengal,groundwater is contaminated with $Arsenic$.
Chronic exposure to $Arsenic$ leads to a condition known as black foot disease.
This disease causes severe damage to the blood vessels of the lower limbs.
Eventually,it leads to progressive gangrene.

(A) The correct matches are as follows:
$(1)$ Mercury $(Hg)$ causes abdominal pain and haemolysis $(1-d)$.
$(2)$ Lead $(Pb)$ causes anaemia and convulsions $(2-e)$.
$(3)$ Arsenic $(As)$ causes hyperkeratosis and liver cirrhosis $(3-b)$.
$(4)$ Cadmium $(Cd)$ causes bone deformation (itai-itai disease) and testicular atrophy $(4-c)$.
Therefore,the correct sequence is $1-d, 2-e, 3-b, 4-c$.

(B) The correct matches are as follows:
$(1)$ Electrostatic precipitator: It is used to remove over $99\%$ of particulate matter present in the exhaust from a thermal power plant. Thus,$(1-c)$.
$(2)$ Scrubber: It is used to remove harmful gases like sulfur dioxide $(SO_2)$ from industrial exhaust by passing it through a spray of water or lime. Thus,$(2-a)$.
$(3)$ Catalytic converter: These are fitted into automobiles for reducing the emission of poisonous gases. They convert unburnt hydrocarbons into $CO_2$ and $H_2O$,and carbon monoxide and nitric oxide into $CO_2$ and $N_2$ gas. Thus,$(3-b)$.
Therefore,the correct sequence is $(1-c, 2-a, 3-b)$.

(N/A) Noise is defined as an undesired or unpleasant sound that is detrimental to human health. It is a form of environmental pollution that can cause stress,hearing impairment,and other physiological or psychological issues.

(B) $BOD$ stands for Biochemical Oxygen Demand.
It refers to the amount of dissolved oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
It is a measure of the organic pollutant load in water bodies.

(N/A) $DDT$ is a non-biodegradable pollutant. It undergoes biological magnification (biomagnification) at different trophic levels. It enters the food chain from water,accumulates in phytoplankton,then passes to fish,and finally reaches high concentrations in predatory birds.