Pollution Questions in English

(A) Chemical agents,such as synthetic fertilizers and pesticides,have several disadvantages:
$1$. Toxicity: Many chemicals are toxic and can cause health issues in humans and animals upon exposure.
$2$. Environmental Pollution: Excessive use of chemicals leads to the contamination of air,water,and soil,affecting overall ecosystem health.
$3$. Soil Degradation: Weedicides and other chemicals can accumulate in the soil,altering its $pH$ balance and reducing long-term fertility,while also harming non-target organisms.
Therefore,all three statements ($I, II,$ and $III$) correctly describe the disadvantages of chemical agents.

(B) $BOD$ stands for Biochemical Oxygen Demand. It represents the amount of dissolved oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria. Therefore,a greater $BOD$ indicates that there is a higher amount of organic matter present,which leads to a greater consumption of dissolved oxygen,thereby decreasing the oxygen content of the water.

(A) Carbon monoxide $(CO)$ is a major air pollutant.
It is highly toxic because it has a much higher affinity for haemoglobin than oxygen $(O_2)$.
When inhaled,$CO$ binds with haemoglobin to form carboxyhaemoglobin,which is a stable compound.
This prevents haemoglobin from binding with oxygen,thereby reducing the oxygen-carrying capacity of the blood,leading to hypoxia and potentially fatal poisoning.

(A) Biomagnification (or biological magnification) refers to the increase in concentration of non-degradable pollutants (such as heavy metals like mercury or pesticides like $DDT$) at successive trophic levels of a food chain.
This occurs because a toxic substance accumulated by an organism cannot be metabolized or excreted,and is thus passed on to the next higher trophic level in higher concentrations.
Eutrophication is the process of nutrient enrichment in water bodies,which leads to excessive growth of algae and depletion of dissolved oxygen.

(D) Pesticides are chemical substances used to repel,kill,or control weeds,pathogens,and other pests.
When these chemicals accumulate in the soil,they act as pollutants.
They can kill beneficial soil microorganisms and non-target plants,thereby disrupting the balance of the food chain and food web.

(B) Noise pollution is a physical form of pollution that affects the receiver directly.
$dB$ (decibel) is a standard abbreviation used for the quantitative expression of the intensity of sound or noise.

(C) Acid rain is the result of $SO_2$ and $NO_2$ pollution in the atmosphere.
When these gases react with water vapor in the atmosphere,$SO_2$ leads to the formation of sulfuric acid $(H_2SO_4)$ and $NO_2$ leads to the formation of nitric acid $(HNO_3)$.
Both of these are strong acids that lower the $pH$ of rainwater,causing it to become acidic.

(D) Air pollution has significant detrimental effects on all living organisms and the climate.
Statement $I$ is correct because air pollutants cause injury to all living organisms by interfering with their physiological processes.
Statement $II$ is correct because pollutants like $SO_2$ and $O_3$ reduce the growth and yield of crops and can lead to the premature death of plants by damaging leaves and inhibiting photosynthesis.
Statement $III$ is correct because air pollutants such as particulate matter,$NO_2$,and $SO_2$ cause respiratory diseases like bronchitis,lung cancer,and emphysema in humans and animals.
Therefore,all three statements are correct.

(C) Lichens,such as $Usnea$,are widely recognized as bioindicators of air pollution. They are extremely sensitive to atmospheric pollutants,especially sulfur dioxide $(SO_{2})$. In areas with high levels of $SO_{2}$,lichens fail to grow,making their presence or absence a reliable indicator of air quality.

(A) Minamata is a disease caused by the biomagnification of heavy metals,specifically mercury $(Hg)$.
When mercury is released into water bodies,it enters the food chain and accumulates in higher concentrations at higher trophic levels.
Consumption of contaminated fish leads to mercury poisoning in humans,which affects the nervous system and various physiological functions.

(A) Biodegradable pollutants are substances that can be broken down into simpler,harmless components by the action of microorganisms like bacteria and fungi.
Sewage is organic waste that is easily decomposed by microbial action.
In contrast,plastic,polythene,and $DDT$ are non-biodegradable pollutants that persist in the environment for a long time.

(C) Air pollutants reduce the growth and yield of crops.
They also cause premature death of plants.
Therefore,both $(a)$ and $(b)$ are correct effects of air pollution on plants.

(B) Eutrophication is a natural state in many lakes and ponds that have a rich supply of nutrients.
This leads to the decomposition of organic matter by bacteria and other decomposers through the process of anaerobic respiration.
Anaerobic respiration in the absence of oxygen produces gases like hydrogen sulfide $(H_2S)$ and methane $(CH_4)$,which cause a foul smell in the water bodies.

(D) Biomagnification refers to the increase in concentration of non-biodegradable substances (like $DDT$,mercury,etc.) at successive trophic levels in a food chain.
Since these substances are fat-soluble and cannot be metabolized or excreted,they accumulate in the fatty tissues of organisms.
As energy and matter move up the food chain,the concentration of these toxic substances increases significantly.
Therefore,the highest concentration of these pollutants is found in the top carnivores (or tertiary consumers) of the food chain.

(D) Hydroelectric power plants are considered a clean source of energy and do not cause significant pollution.
Thermal power plants cause air pollution by releasing fly ash,$SO_2$,hydrocarbons,and other gases.
Automobiles contribute to air pollution by emitting $CO$,hydrocarbons,$SPM$ (Suspended Particulate Matter),and other gases.
Radioactive power plants pose risks of radioactive waste and thermal pollution.

(D) Industries such as petroleum,paper manufacturing,and metal extraction and processing release wastewater containing heavy metals. These heavy metals include mercury $(Hg)$,cadmium $(Cd)$,copper $(Cu)$,and lead $(Pb)$,which are highly toxic to aquatic life and humans.

(A) Primary air pollutants are those that are emitted directly from a source into the atmosphere.
Examples include $NO$,$NO_{2}$,and $VOCs$ (Volatile Organic Compounds).
Secondary air pollutants are formed in the atmosphere through chemical reactions between primary pollutants and other atmospheric components.
$O_{3}$ (Ozone) and $PAN$ (Peroxyacetyl nitrate) are examples of secondary pollutants.
Therefore,among the given options,only $VOCs$ are primary pollutants.

(B) The correct answer is $80 \, dB$.
Noise is defined as an unwanted,high-level sound that causes discomfort or harm.
It is a physical form of pollution that directly affects the receiver.
According to environmental standards,sound levels reaching or exceeding $80 \, dB$ are considered hazardous and are classified as noise pollution.

(B) Fly ash is a light airborne particulate matter.
It is primarily produced as a byproduct of coal-based thermal power plants.
It should be removed from flue gases using wet scrubbers or electrostatic precipitators and can be effectively used in the construction industry as a building material.
Insectivorous plants are specialized plants that trap insects to fulfill their nitrogen requirements,for example,$Drosera$.
Orchid plants are typically epiphytes that grow on other plants for physical support without deriving nutrients from them.

(D) Mercury pollution leads to the accumulation of methylmercury in aquatic food chains,which causes Minamata disease. The following table summarizes the diseases caused by various pollutants:

Disease	Caused by
Minamata disease	Mercury
Black foot disease	Arsenic
Itai-itai disease	Cadmium
Skeletal fluorosis	Fluoride
Blue-baby syndrome	Nitrate

(D) Acid rain results from air pollution by oxides of nitrogen $(NO_{x})$ and sulfur $(SO_{x})$. These gases react with water to form acids.
$SO_{2} + H_{2}O \rightarrow H_{2}SO_{3}$
$SO_{3} + H_{2}O \rightarrow H_{2}SO_{4}$
$N_{2}O_{5} + H_{2}O \rightarrow 2HNO_{3}$
When the $pH$ of rain is below $5.6$,it is termed as acid rain.

(C) Cadmium $(Cd)$ poisoning leads to itai-itai (ouch-ouch) disease.
Cadmium consumption causes diarrhea,bone deformation,kidney damage,retarded growth,and $CNS$ injury.
Mercury $(Hg)$ poisoning causes Minamata disease.
Lead $(Pb)$ consumption causes damage to the liver,heart,and kidney,and reduces hemoglobin formation.
Black-foot disease is caused by chronic exposure to arsenic $(As)$.

(C) Noise is defined as an undesired,high-level sound. It is a physical form of pollution that affects the receiver directly. Noise or pollutant sound is generally considered to have a value of $80 \ dB$ or above.

(B) Acid rain is primarily caused by the emission of nitrogen oxides $(NO_{x})$,sulphur dioxide $(SO_{2})$,and other pollutants like hydrogen chloride $(HCl)$ from thermal power plants,industries,and automobiles. These gases react with water vapor in the atmosphere to form acids. Methane $(CH_{4})$ is a greenhouse gas that contributes to global warming but is not a primary cause of acid rain.

(A) $BOD$ stands for Biological Oxygen Demand.
It refers to the amount of dissolved oxygen required by aerobic microorganisms to break down the organic matter present in a given volume of water at a specific temperature over a specified time period.

(C) brief exposure to an extremely high sound level of $150 \, dB$ or more,such as that generated by the takeoff of a jet plane or rocket,can cause immediate physical damage to the eardrums.
This damage to the eardrums often leads to a permanent impairment of hearing ability,which is clinically referred to as deafness.
Therefore,both the physical damage to the eardrums and the resulting deafness are consequences of such intense noise exposure.

(B) Secondary air pollutants are not emitted directly into the atmosphere. They are formed by chemical reactions between primary pollutants (like nitrogen oxides and hydrocarbons) in the presence of sunlight. Smog is a classic example of a secondary pollutant,as it is formed through complex photochemical reactions in the atmosphere.

(D) Peroxyacetyl nitrate $(PAN)$ is a secondary pollutant.
It is formed by the photochemical reaction between nitrogen oxides $(NO_{x})$ and hydrocarbons $(HC)$ in the presence of sunlight.
Therefore,the correct combination is $III$ and $IV$.

(D) Bad ozone is formed in the troposphere,which is the lowest layer of the atmosphere. It is a pollutant that is harmful to plants and animals. In contrast,'good' ozone is formed in the stratosphere and acts as a protective shield by absorbing harmful $UV$ radiation from the sun.

(A) In big cities,the primary sources of atmospheric pollution are automobile exhausts and industrial smoke. These sources release significant amounts of $CO$ (Carbon monoxide) and oxides of sulphur $(SO_x)$,which are considered the major atmospheric pollutants.

(B) Phosphates are major components of many fertilizers and detergents,which primarily cause water and soil pollution through eutrophication. In contrast,pollen from plants,carbon monoxide $(CO)$,and hydrocarbons are well-known air pollutants that degrade air quality and affect human health.

(A) At the cellular level,$SO_{2}$ pollution destroys all membrane systems. In cases of intense exposure to $SO_{2}$,there is bleaching of leaf pigments due to the conversion of chlorophyll-$a$ to phaeophytin-$a$. Thus,$SO_{2}$ exposure significantly impacts plant productivity. $SO_{2}$ pollution is a primary cause of acid rain,which is damaging the marble of the Taj Mahal. Mosses and lichens are highly sensitive indicators of $SO_{2}$ pollution.

(A) As the exhaust emission passes through the catalytic converter,nitric oxide splits into nitrogen and oxygen. Carbon monoxide is oxidized to carbon dioxide,and unburnt hydrocarbons are completely burnt (oxidized) into $CO_{2}$ and $H_{2}O$.

(D) Hydrogen sulphide $(H_2S)$ is a toxic gas that acts as a respiratory irritant.
Exposure to $H_2S$ can lead to various health issues,including nausea,irritation of the eyes,and irritation of the throat.
Therefore,all the listed symptoms are caused by hydrogen sulphide exposure.

(B) The Central Pollution Control Board $(CPCB)$ has established guidelines for the discharge of industrial and municipal wastewater into natural surface water bodies.
According to these standards, the Biochemical Oxygen Demand $(BOD)$ of the discharged wastewater must be less than $10 \, ppm$ to prevent excessive pollution and maintain the health of aquatic ecosystems.

(B) $DDT$ (Dichlorodiphenyltrichloroethane) is a persistent organic pollutant that undergoes biomagnification. In birds,high concentrations of $DDT$ interfere with calcium metabolism. This leads to the thinning of the eggshells. Consequently,these thin-shelled eggs break prematurely during incubation,resulting in a significant decline in the bird population because many of the eggs laid did not hatch.

(D) Carbon monoxide $(CO)$ is a highly toxic gas that binds to hemoglobin in the blood with an affinity much higher than that of oxygen,forming carboxyhemoglobin.
This process reduces the oxygen-carrying capacity of the blood,leading to various physiological symptoms.
Specifically,exposure to $CO$ results in:
$(I)$ Giddiness (dizziness)
$(II)$ Headache
$(III)$ Decreased vision
$(IV)$ Cardiovascular malfunction
$(V)$ Asphyxia (suffocation due to lack of oxygen)
Therefore,all the listed statements are correct.

(A) Photochemical smog is an oxidizing type of air pollution that occurs in warm,dry,and sunny climates.
It is formed by the action of sunlight on nitrogen oxides $(NO_x)$ and volatile organic compounds (hydrocarbons) emitted by automobiles and factories.
The primary components of photochemical smog include ozone $(O_3)$,peroxyacetyl nitrate $(PAN)$,and various nitrogen oxides $(NO_x)$.

(A) Reptiles and birds are typically secondary or tertiary consumers in an ecosystem.
$DDT$ (Dichlorodiphenyltrichloroethane) is a non-biodegradable chemical pollutant that undergoes biomagnification,leading to higher concentrations in higher trophic levels.
In birds,$DDT$ interferes with calcium metabolism,causing thinning of eggshells,which leads to premature breaking and a decline in population.
Therefore,$DDT$ is the primary cause for the decline in their populations.

(C) The effect of pollution is observed first on green vegetation. This is because plants are primary producers and are directly exposed to atmospheric pollutants,such as sulfur dioxide $(SO_2)$,nitrogen oxides $(NO_x)$,and particulate matter. These pollutants interfere with photosynthesis,stomatal function,and overall plant metabolism,leading to visible damage such as chlorosis,necrosis,and stunted growth before affecting higher trophic levels.

(D) Primary pollutants are those that enter the air directly from their source,$e.g.,$ $NO_{2}, Br_{2}, Cl_{2}, CO, DDT$,etc.
Secondary pollutants are formed from the interaction of primary pollutants with atmospheric constituents. For example,nitrogen oxides react with atmospheric moisture (water vapour) to form $HNO_{3}$,which contributes to acid rain.

(A) Statement $I$ is correct: Algal blooms are caused by the excessive growth of planktonic (free-floating) algae, which impart a distinct colour to the water bodies.
Statement $II$ is correct: These blooms produce toxins that are harmful to aquatic life, leading to fish mortality and the deterioration of water quality.
Statement $III$ is incorrect in the context of 'algal blooms': While Water hyacinth $(Eichhornia \text{ crassipes})$ is indeed known as the 'Terror of Bengal' and is a problematic aquatic weed, it is a macrophyte, not an alga. Therefore, it is not responsible for 'algal blooms'.
Thus, only statements $I$ and $II$ are correct regarding algal blooms.

(D) $CNG$ (Compressed Natural Gas) is considered a superior fuel compared to petrol or diesel for the following reasons:
$(i)$ It burns most efficiently,leaving almost no unburnt residue.
$(ii)$ It is more cost-effective (cheaper) than petrol or diesel.
$(iii)$ It produces significantly less pollution.
$(iv)$ It cannot be siphoned off by thieves,unlike liquid fuels.
$(v)$ It cannot be adulterated easily,ensuring fuel quality.
Therefore,all three statements ($I, II,$ and $III$) are correct.

(D) Delhi has the highest number of vehicles in India,leading to severe air pollution. To address this,the Supreme Court directed the government to implement several measures to reduce vehicular pollution:
$1.$ Phasing out of old vehicles.
$2.$ Use of unleaded petrol.
$3.$ Use of low-sulphur petrol and diesel.
$4.$ Use of catalytic converters in vehicles to reduce toxic emissions.
$5.$ Applying stringent pollution level norms (such as Euro $II$ norms).
$6.$ Switching public transport from diesel/petrol to $CNG$ (Compressed Natural Gas).
Since all the listed statements ($I$ to $VI$) are correct measures taken by the government,the correct option is $D$.

(B) Manganese $(Mn)$ is a heavy metal that acts as a water pollutant. Exposure to high levels of $Mn$ in humans can lead to various health issues,including sterility,eye diseases,memory loss,and vision impairment.

(A) Based on the provided flow chart of water pollutants:
$1$. $A$ represents Domestic sewage,which is a primary source of water pollution containing suspended,colloidal,and dissolved materials.
$2$. $B$ represents Thermal (hot) waste water,which is a physical pollutant often released from industries.
$3$. $C$ represents Organic compounds,such as phenols and dyes,which are classified under chemical pollutants.
$4$. $D$ represents Inorganic compounds,such as heavy metals (e.g.,$Pb, Cd, Hg, Cu$),which are also classified under chemical pollutants.
Therefore,the correct identification is $A-$Domestic sewage,$B-$Thermal (hot) waste water,$C-$Organic compounds,$D-$Inorganic compounds.

(A) According to the Central Pollution Control Board $(CPCB)$,particulate matter with a diameter of $2.5$ micrometers or less $(PM\, 2.5)$ is responsible for causing the greatest harm to human health.
These fine particulates can be inhaled deep into the lungs,causing breathing and respiratory symptoms,irritation,inflammation,and damage to the lungs,and may even lead to premature death.

(D) Catalytic converters are fitted into automobiles to reduce the emission of poisonous gases like $NO_x$ and $CO$.
They contain expensive metals such as platinum,palladium,and rhodium which act as catalysts.
As exhaust gases pass through the catalytic converter,the following reactions occur:
$1.$ Unburnt hydrocarbons are oxidized into $CO_2$ and $H_2O$.
$2.$ Carbon monoxide $(CO)$ is oxidized into carbon dioxide $(CO_2)$.
$3.$ Nitric oxide $(NO)$ is reduced into nitrogen gas $(N_2)$ and oxygen $(O_2)$.
Vehicles fitted with catalytic converters must use unleaded petrol because lead present in leaded petrol causes the inactivation (poisoning) of the catalyst,rendering the converter ineffective. Therefore,all four statements are correct.

(D) An Electrostatic Precipitator $(ESP)$ is an electrical device used to remove over $99\, \%$ of particulate matter present in the exhaust from thermal power plants.
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 net negative charge.
Collecting plates are grounded and attract the charged dust particles.
Therefore,all three statements ($I, II,$ and $III$) are correct.

(B) scrubber is used to remove gases like sulfur dioxide from industrial exhaust. In the given diagram:
$A$ represents the entry of dirty air containing pollutants.
$B$ represents the exit of clean air after the scrubbing process.
$C$ represents the water or lime spray used to wash out the pollutants.
$D$ represents the particulate matter or waste collected at the bottom.
Therefore,the correct identification is $A-$Dirty air,$B-$Clean air,$C-$Water line spray,$D-$Particulate matter.