Pollution Questions in English

(C) When irrigation is practiced for a long period without proper drainage,the water evaporates,leaving behind salts in the soil. This process leads to the accumulation of salts in the top layer of the soil,a condition known as soil salinity. This is a significant environmental issue in agricultural practices.

(B) The aquatic plant $Eichhornia$ $crassipes$, commonly known as water hyacinth, was introduced into India from America for its beautiful flowers and leaf shape.
It is an invasive species that grows rapidly in water bodies, causing clogging of waterways and depletion of dissolved oxygen, which leads to the death of fishes and other aquatic organisms.
It is often referred to as the 'Terror of Bengal' due to its uncontrollable growth in the water bodies of West Bengal.
Therefore, the correct option is $B$.

(A) Acid rain is primarily caused by the emission of sulfur dioxide $(SO_2)$ and nitrogen oxides ($NO_x$,specifically $NO_2$) into the atmosphere.
These gases are released in large quantities during the combustion of fossil fuels (like coal and petroleum) in power plants,vehicles,and industries.
When these gases react with water vapor,oxygen,and other chemicals in the atmosphere,they form sulfuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$,which then fall to the ground as acid rain.

(B) pollutant is defined as a substance or energy introduced into the environment that has undesired effects,or adversely affects the usefulness of a resource.
$CO$ (Carbon monoxide),hydrocarbons,and $SO_2$ (Sulfur dioxide) are primary air pollutants that cause significant harm to human health and the environment.
$CO_2$ (Carbon dioxide) is a natural component of the atmosphere and is essential for photosynthesis in plants. While it is a greenhouse gas contributing to global warming at high concentrations,it is not classified as a pollutant in the same sense as toxic gases like $CO$ or $SO_2$ in standard biological and environmental contexts.

(C) Automobiles are a major source of air pollution.
Among the heavy metals released,$Lead$ $(Pb)$ is considered one of the most harmful pollutants.
It is added to gasoline as an anti-knocking agent.
When fuel is burned,$Lead$ is released into the atmosphere,which can cause serious health issues,including neurological damage,especially in children.
Therefore,the correct option is $C$.

(B) According to the World Health Organization $(WHO)$ and environmental standards,noise levels above $80 \, dB$ are considered harmful to human health.
Prolonged exposure to noise levels exceeding $80 \, dB$ can lead to hearing impairment,stress,and other physiological issues.
Therefore,$80 \, dB$ is the threshold level for noise pollution.

(D) The Taj Mahal is primarily threatened by acid rain,which is caused by the high concentration of sulfur dioxide $(SO_2)$ in the atmosphere.
Sulfur dioxide is released from industrial activities,particularly from the Mathura oil refinery.
When $SO_2$ reacts with moisture in the air,it forms sulfuric acid,which leads to the corrosion of the marble,a process often referred to as 'marble cancer'.

(B) Minamata disease is a neurological syndrome caused by severe mercury poisoning. It was first discovered in Minamata City,Kumamoto Prefecture,Japan,in $1956$. The disease was caused by the release of methylmercury in the industrial wastewater from the Chisso Corporation's chemical factory. This highly toxic chemical bioaccumulated in shellfish and fish in Minamata Bay,which were then eaten by the local human population and animals. Cats in the area were severely affected,exhibiting symptoms like convulsions and erratic behavior,which led to the term 'dancing cat fever'. Pigs and dogs were also affected. However,rabbits were not reported to be affected by the disease in this specific ecological context.

(D) Phosphate pollution in water bodies is primarily caused by the discharge of untreated or partially treated sewage and the runoff from agricultural fields where phosphate-rich fertilizers are used.
These sources contribute to eutrophication,which leads to excessive growth of algae and depletion of dissolved oxygen in the water.

(C) Carbon monoxide $(CO)$ is a major air pollutant.
It has a much higher affinity for hemoglobin than oxygen $(O_2)$.
When $CO$ is inhaled,it binds to hemoglobin to form carboxyhemoglobin,which is a stable compound.
This prevents hemoglobin from binding with oxygen,thereby reducing the oxygen-carrying capacity of the blood and leading to hypoxia.

(A) $DDT$ (Dichlorodiphenyltrichloroethane) is a synthetic organochlorine chemical compound.
It is highly stable and resistant to environmental degradation by microorganisms.
Because it cannot be broken down easily by natural biological processes,it accumulates in the environment and in the tissues of living organisms,a process known as biomagnification.
Therefore,it is classified as a non-biodegradable pollutant.

(B) The intensity of sound is measured in decibels $(dB)$.
$A$ normal conversation typically occurs at a sound level ranging between $30$ and $60\,dB$.
- $0-20\,dB$ represents very faint sounds like whispering or rustling leaves.
- $70-90\,dB$ represents loud sounds like heavy traffic or a lawnmower.
- $120-150\,dB$ represents extremely loud,painful sounds like a jet engine or a rock concert.
Therefore,the correct range for a normal conversation is $30-60\,dB$.

(B) $BOD$ stands for Biochemical Oxygen Demand.
It is defined as the amount of dissolved oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
Therefore,it represents the amount of $O_2$ required by aerobic microorganisms to decompose the organic matter present in a water sample.
Thus,option $B$ is the correct answer.

(C) Stonefly nymphs are highly sensitive to water pollution and low dissolved oxygen levels. They serve as biological indicators of clean,well-oxygenated water. Therefore,their presence indicates good water quality,and they are typically absent in polluted water bodies. In contrast,organisms like water hyacinth and certain blue-green algae thrive in nutrient-rich,polluted water.

(D) Fluoride pollution,when present in drinking water at concentrations higher than $1.5 \ ppm$,primarily affects the skeletal system and teeth. This condition is known as fluorosis. In teeth,it causes dental fluorosis,which leads to mottling or discoloration of the enamel. Therefore,the correct option is $D$.

(D) The Bhopal gas tragedy,which occurred on the night of December $2-3, 1984$,was caused by the accidental release of methyl isocyanate $(MIC)$ gas from the Union Carbide pesticide plant.
$MIC$ is highly reactive with water. When water entered the storage tank,it triggered an exothermic reaction that produced a large amount of heat and pressure,causing the tank to rupture and release the toxic gas into the atmosphere.

(B) Lead $(Pb)$ is a toxic heavy metal that can accumulate in the human body.
According to medical and environmental health standards,a blood lead level of $30 \mu g / 100 \ ml$ is considered the warning concentration,above which it can cause significant health issues such as neurological damage,anemia,and developmental delays.
Therefore,the correct option is $B$.

(D) Chlorine,Ozone,and Chloramine are commonly used as disinfectants for the purification of drinking water to kill pathogens and ensure safety. Phenyl is a disinfectant used primarily for cleaning floors and surfaces,but it is toxic and not suitable for the purification of drinking water.

(D) The Central Pollution Control Board $(CPCB)$ has established standards for the discharge of municipal and industrial wastewater into natural water bodies.
For water bodies that receive municipal waste,the $CPCB$ prescribes that the Biochemical Oxygen Demand $(BOD)$ should be less than $3.0\,ppm$ (parts per million) to ensure the water quality remains suitable for aquatic life and human use.
Therefore,the correct option is $D$.

(B) Electrostatic precipitators are highly efficient devices used in thermal power plants to remove particulate matter from the exhaust gases.
They can remove over $99\%$ of the particulate matter present in the exhaust from a thermal power plant.
$SPM$ stands for Suspended Particulate Matter,which includes dust,soot,and other fine particles.
Therefore,electrostatic precipitators are primarily used to control $SPM$.

(B) Biological indicators are organisms that provide information about the quality of the environment.
$Stonefly$ nymphs are highly sensitive to low oxygen levels and pollution; therefore,their presence indicates clean,well-oxygenated water.
Conversely,$Bloodworms$,$Sewage$ $fungus$,and $Sludge$ $worms$ (like $Tubifex$) are tolerant of high organic pollution and low oxygen levels,making them indicators of polluted water.
Thus,$Stonefly$ is not an indicator of water pollution,but rather an indicator of clean water.

(C) $BOD$ 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.
When sewage is discharged into a river,it contains a large amount of organic matter,which serves as food for microorganisms.
As these microorganisms decompose the organic matter,they consume a significant amount of dissolved oxygen,leading to an increase in the $BOD$ value.
Therefore,a high $BOD$ value is a direct indicator of water pollution caused by sewage.

(B) The symbol $dB$ stands for $decibel$.
It is a logarithmic unit used to express the ratio of two values of a physical quantity,often power or intensity.
In the context of environmental issues,$dB$ is used to measure the intensity of sound or noise pollution.
Therefore,it represents a particular pollutant,specifically noise pollution.

(A) Biochemical Oxygen Demand $(BOD)$ 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 standard test used to measure the amount of biodegradable organic matter present in water bodies or sewage.
Greater $BOD$ indicates higher pollution levels because more oxygen is required by microorganisms to decompose the organic waste.
Therefore,$BOD$ is a key indicator of water quality and organic pollution.

(D) $DDT$ (Dichlorodiphenyltrichloroethane) is a persistent organic pollutant that undergoes biomagnification in the food chain.
In birds,high concentrations of $DDT$ interfere with calcium metabolism.
This interference leads to the thinning of eggshells.
Consequently,the eggshells break prematurely during incubation,preventing the eggs from hatching and leading to a significant decline in the bird population.

(A) scrubber is a device used in chemical factories and power plants to remove harmful gases from industrial exhaust streams.
Specifically,it is used to remove gases like $SO_2$ (sulfur dioxide) by spraying water or lime through the exhaust,which reacts with the gas to neutralize it.
Particulate matter is typically removed using electrostatic precipitators or filter bags,not scrubbers.

(A) Eutrophication is the process of nutrient enrichment (especially nitrogen and phosphorus) in water bodies,which promotes excessive growth of algae (algal bloom).
As these algae die,their decomposition by microorganisms consumes a large amount of dissolved oxygen in the water.
This leads to a significant decrease in the biological oxygen demand $(BOD)$ and dissolved oxygen levels,causing aquatic organisms like fish to die due to suffocation (lack of oxygen).

(B) Acid rain is primarily caused by the emission of sulfur dioxide $(SO_2)$ and nitrogen oxides $(NO_2)$ into the atmosphere.
These gases react with water vapor,oxygen,and other chemicals in the atmosphere to form sulfuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$.
These acids then fall to the ground with rain,snow,or fog,resulting in acid rain,which has a $pH$ lower than $5.6$.

(A) The phenomenon where the concentration of non-biodegradable pollutants (toxicants) increases at each successive trophic level in a food chain is known as $Biomagnification$. This occurs because the 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.

(B) When a lake is saturated with organic waste,it leads to a process called eutrophication.
Microorganisms decompose this organic matter,which requires a significant amount of dissolved oxygen.
This leads to a sharp decrease in the $BOD$ (Biochemical Oxygen Demand) levels,causing the dissolved oxygen content in the water to drop drastically.
As a result,aquatic life,particularly fish,cannot survive due to the lack of oxygen and eventually die.

(D) The phenomenon where toxic substances like $DDT$ increase in concentration at each successive trophic level is known as biomagnification.
In an aquatic food chain,$DDT$ enters the water and is absorbed by phytoplankton $(0.003 \ ppb)$.
It then moves to zooplankton,small fish,and large fish,with concentrations increasing significantly.
Finally,it reaches the highest concentration in fish-eating birds (top carnivores) due to their position at the end of the food chain,where it can reach levels as high as $25 \ ppm$.

(C) Aerosols are fine solid particles or liquid droplets suspended in the air.
$1$. They are known to be harmful to human health as they can cause respiratory issues.
$2$. Aerosols can alter rainfall and monsoon patterns by affecting cloud formation and solar radiation.
$3$. They have a negative impact on agricultural land by reducing sunlight reaching crops and potentially causing acid rain.
$4$. Therefore,the statement that they increase agricultural productivity is false,as they generally reduce crop yields.

(C) Primary pollutants are emitted directly from sources,such as $SO_2$,$CO$,and $CO_2$.
Secondary pollutants are formed in the atmosphere through chemical reactions between primary pollutants and other atmospheric components.
$O_3$ (Ozone) in the troposphere is a classic example of a secondary pollutant,formed by the reaction of nitrogen oxides and volatile organic compounds in the presence of sunlight.

(A) $BOD$ (Biochemical Oxygen Demand) 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.
Greater $BOD$ indicates a higher concentration of organic pollutants in the water,which requires more oxygen for decomposition.
Therefore,a higher $BOD$ value directly correlates to a higher polluting potential of the waste water.
Thus,the correct statement is that the greater the $BOD$ of waste water,the more is its polluting potential.

(B) Blue baby disease,also known as methaemoglobinaemia,is caused by the high concentration of nitrates in drinking water,often resulting from the heavy use of nitrogen-rich fertilizers in agricultural areas.
When nitrates are ingested,they are converted into nitrites,which react with haemoglobin to form methaemoglobin.
Methaemoglobin cannot bind oxygen effectively,leading to tissue hypoxia and a characteristic bluish tint to the skin.

(A) $BOD$ stands for Biochemical Oxygen Demand.
It is a measure of the amount of dissolved oxygen required by aerobic microorganisms to decompose the organic matter present in a given volume of water.
If the $BOD$ of waste water is high,it indicates that there is a large amount of organic matter present,which requires more oxygen for decomposition.
Therefore,a higher $BOD$ value directly correlates with a higher polluting potential of the waste water.

(D) $DDT$ residues are rapidly passed through the food chain causing biomagnification because $DDT$ is soluble in lipids (lipo-soluble).
Biomagnification,also known as bioamplification or biological magnification,is the increase in the concentration of a substance,such as the pesticide $DDT$,that occurs in a food chain as a consequence of:
• Persistence (slow to be broken down by environmental processes).
• Food chain energetics.
• Low (or non-existent) rate of internal degradation/excretion of the substance,which is often due to its water-insolubility and high lipid solubility,allowing it to accumulate in the fatty tissues of organisms.

(B) The solubility of gases in liquids is inversely proportional to temperature.
As the temperature of a liquid increases,the kinetic energy of the gas molecules increases,causing them to escape from the liquid phase more easily.
Since lake $A$ has a higher temperature than lake $B$,the solubility of oxygen in lake $A$ will be lower.
Conversely,lake $B$,having a lower temperature,will have a higher rate of oxygen dissolution compared to lake $A$.

(A) The Government of India,through a new auto fuel policy,has laid out a roadmap to cut down vehicular pollution in Indian cities.
According to the Euro $II$ norms,sulphur content must be controlled at $350\, ppm$ in diesel and $150\, ppm$ in petrol to reduce harmful emissions.

(C) The Assertion is correct because high-intensity noise pollution near airports causes various health issues like stress,sleep disturbance,and hearing impairment.
The Reason is incorrect because the sound level of jet aeroplanes typically ranges between $140 \, dB$ to $150 \, dB$,not exceeding $160 \, dB$. While $150 \, dB$ is extremely high and harmful,the specific value mentioned in the reason is factually inaccurate.

(C) The Assertion is correct because organochlorine pesticides are indeed organic compounds containing chlorine atoms.
The Reason is incorrect because $Fenitrothion$ is an organophosphate pesticide,not an organochlorine pesticide.
Organochlorine pesticides,such as $DDT$,are persistent organic pollutants that accumulate in the food chain (biomagnification).
Therefore,the correct choice is $C$.

(B) The Assertion is correct because diesel vehicles are a major source of suspended particulate matter $(SPM)$,which is harmful to human health.
The Reason is also correct because catalytic converters are used in automobiles to reduce the emission of poisonous gases like carbon monoxide $(CO)$ and nitrogen oxides $(NO_x)$ by converting them into less harmful gases like carbon dioxide $(CO_2)$ and nitrogen $(N_2)$.
However,catalytic converters are ineffective at reducing the emission of $SPM$ (particulate matter).
Therefore,while both statements are true,the Reason does not explain why $SPM$ is released by diesel vehicles.

(D) Pollution is defined as an undesirable change in the physical,chemical,or biological characteristics of air,water,and land that causes harmful effects on living organisms.
Pollution can be natural or anthropogenic (man-made). Natural sources of pollution include volcanic eruptions,forest fires,and soil erosion.
Therefore,the Assertion $(A)$ is incorrect because pollution is not always caused by human activities.
Contamination refers to the presence of harmful substances or organisms in an environment,whereas pollution implies that these substances cause adverse effects on the ecosystem.
Thus,pollution is distinct from contamination,making the Reason $(R)$ incorrect.
Since both the Assertion and the Reason are incorrect,the correct option is $(D)$.

(A) Excess of nitrates in drinking water is harmful to human health and can be fatal for infants. Excessive use of fertilizers often leads to the accumulation of nitrates in water sources. In infants, excess nitrate reacts with haemoglobin to form non-functional methaemoglobin, which impairs oxygen transport in the blood. This condition is clinically termed as methaemoglobinemia or $blue \text{ } baby \text{ } syndrome$. This disease can damage the respiratory and vascular systems and may lead to severe suffocation.

(A) $BOD$ (Biochemical Oxygen Demand) 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.
The greater the $BOD$ of waste water,the more is its polluting potential.
Therefore,$BOD$ is used as a measure of the amount of organic matter (pollutants) present in water.
Since the Reason explains why $BOD$ is used as a measure of pollution,both statements are correct and the Reason is the correct explanation of the Assertion.

(N/A) Algal bloom:
Algal bloom refers to an excessive increase in the population of algae or blue-green algae in a water body,which causes the water to become discolored. This process leads to a significant increase in the biological oxygen demand $(BOD)$,which depletes dissolved oxygen,ultimately resulting in the death of fishes and other aquatic organisms.
Red-tides:
Red tides are caused by the rapid multiplication of red dinoflagellates,such as $Gonyaulax$. Due to their massive numbers,the sea surface appears red in color. These organisms release large amounts of toxins into the water,which can be lethal to a large number of marine animals,including fishes.

(N/A) $BOD$ stands for Biochemical Oxygen Demand. It is a measure of the amount of dissolved oxygen required by aerobic microorganisms to decompose the organic matter present in a given volume of water. It serves as an indicator of the level of organic pollution in water bodies; higher $BOD$ indicates higher pollution.

(N/A) Greenhouse gases: The greenhouse effect refers to an overall increase in the average temperature of the Earth due to the presence of greenhouse gases. Greenhouse gases mainly consist of carbon dioxide,methane,and water vapour. When solar radiations reach the Earth,some of these radiations are absorbed. These absorbed radiations are released back into the atmosphere. These radiations are trapped by the greenhouse gases present in the atmosphere. This helps in keeping our planet warm and thus,helps in human survival. However,an increase in the amount of greenhouse gases can lead to an excessive increase in the Earth's temperature,thereby causing global warming.
$(b)$ Catalytic converter: Catalytic converters are devices fitted in automobiles to reduce vehicular pollution. These devices contain expensive metals such as platinum,palladium,and rhodium that act as catalysts. As the vehicular discharge passes through the catalytic converter,the unburnt hydrocarbons present in it get converted into carbon dioxide and water. Carbon monoxide and nitric oxide released by catalytic converters are converted into carbon dioxide and nitrogen gas (respectively).
$(c)$ Ultraviolet $B$: Ultraviolet $B$ is an electromagnetic radiation which has a shorter wavelength than visible light. It is a harmful radiation that comes from sunlight and penetrates through the ozone hole onto the Earth's surface. It induces many health hazards in humans. $UV-B$ damages $DNA$ and activates the process of skin ageing. It also causes skin darkening and skin cancer. High levels of $UV-B$ cause corneal cataract in human beings.

(N/A) Pollution is defined as any undesirable change in the physical,chemical,or biological characteristics of air,land,water,or soil that harmfully affects human life,industrial processes,living conditions,and cultural assets.
The primary causes of pollution include:
$1$. Industrial Activities: Release of toxic chemicals,heavy metals,and particulate matter into the atmosphere and water bodies.
$2$. Vehicular Emissions: Combustion of fossil fuels in automobiles releases gases like $CO$,$CO_2$,$NO_x$,and hydrocarbons.
$3$. Agricultural Practices: Excessive use of chemical fertilizers,pesticides,and herbicides leads to soil degradation and water eutrophication.
$4$. Waste Disposal: Improper management of solid waste,including plastic and electronic waste,leads to land and water pollution.
$5$. Deforestation: Removal of trees reduces the natural capacity of the environment to filter pollutants,leading to increased $CO_2$ levels.