Pollution Questions in English

(C) $D.D.T.$ (Dichlorodiphenyltrichloroethane) is a non-biodegradable,persistent organic pollutant.
Due to the process of biological magnification (biomagnification),the concentration of $D.D.T.$ increases as it moves up the trophic levels in a food chain.
In an aquatic food chain,the sequence is: Phytoplankton $\rightarrow$ Zooplankton $\rightarrow$ Small fish (e.g.,Eel) $\rightarrow$ Large fish/Crustaceans (e.g.,Crab) $\rightarrow$ Fish-eating birds (e.g.,Sea gull).
Since the sea gull occupies the highest trophic level in this list,it will accumulate the highest concentration of $D.D.T.$ in its body tissues.

(D) Biomagnification refers to the increase in the concentration of non-biodegradable pollutants (such as $DDT$ or mercury) at successive trophic levels in a food chain.
This occurs because the toxic substance accumulated by an organism cannot be metabolized or excreted,and thus passes on to the next higher trophic level in a higher concentration.

(B) The intensity of sound is measured in decibels $(dB)$.
Normal conversation typically occurs at an intensity level ranging between $40$ and $60 dB$.
Sounds above $80 dB$ are considered to be noise pollution and can cause hearing damage over prolonged exposure.

(A) $CO$ (carbon monoxide) is the most poisonous among the given options.
In human beings,carbon monoxide causes headaches,dizziness,and difficulty in breathing.
Haemoglobin has a significantly greater affinity for $CO$ than for oxygen.
It binds with haemoglobin to form carboxyhaemoglobin $(Hb.CO)$,which is much more stable than oxyhaemoglobin.
This reduces the oxygen-carrying capacity of the blood,leading to hypoxia and potentially death.

(B) The effect of pollution is first observed on the green vegetation of an area. Plants are highly sensitive to atmospheric pollutants like $SO_2$,$NO_x$,and ozone. They act as bio-indicators because they show visible symptoms of damage,such as chlorosis,necrosis,or stunted growth,long before other organisms in the ecosystem exhibit significant stress. Therefore,green vegetation serves as the primary indicator of environmental pollution.

(D) Large green plants are planted in high noise pollution zones because they have the capacity to absorb sound waves. These green plants,used for checking noise pollution,are known as green mufflers.

(D) Positive soil pollution refers to the addition of undesirable substances to the soil that degrade its quality.
$A$. Excessive use of fertilizers adds chemicals like nitrates and phosphates,which alter soil chemistry.
$B$. Addition of industrial,agricultural,or domestic wastes introduces pollutants into the soil.
$C$. Reduction in soil productivity is a consequence of these pollutants.
Since all these factors contribute to the contamination of soil,the correct answer is $D$.

(B) Carbon monoxide $(CO)$ is considered a primary and major air pollutant.
It is a colorless,odorless,and tasteless gas produced by the incomplete combustion of carbon-containing fuels such as gasoline,natural gas,oil,coal,and wood.
$CO$ is highly toxic to humans and animals because it binds to hemoglobin in the blood more effectively than oxygen,reducing the oxygen-carrying capacity of the blood.

(B) Pollution refers to the introduction of harmful substances into the environment,which negatively impacts the natural processes of ecosystems.
Ecological balance is the state of dynamic equilibrium within a community of organisms in which genetic,species,and ecosystem diversity remain relatively stable.
Pollution disrupts this equilibrium by altering the physical,chemical,or biological characteristics of the environment,thereby affecting the survival and interactions of living organisms.
Therefore,the correct answer is $(b)$ Ecological balance.

(A) sound level in the range of $70-90$ decibels $(dB)$ is classified as very loud.
This level of noise is typically experienced in environments such as heavy traffic on highways or busy urban areas.
Prolonged exposure to sound levels in this range can lead to auditory fatigue or potential hearing damage.

(D) Cadmium is a toxic heavy metal. When it accumulates in the human body,particularly in the liver,kidneys,and thyroid,it leads to a painful condition known as Itai-itai disease (also known as ouch-ouch disease). This disease is characterized by severe bone pain and softening of the bones (osteomalacia).

(B) Biological 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 serves as a standard measure of the degree of water pollution caused by organic matter.
The higher the $BOD$ value,the greater the amount of organic pollution in the water body.

(D) Pesticides are chemical substances used to control pests,including insects,weeds,and fungi.
When these chemicals are applied to soil,they do not only target the intended pests but also kill beneficial soil microorganisms and non-target plants.
This disruption of the soil ecosystem negatively impacts the food chain and food web,as these organisms are primary producers or essential decomposers in the ecosystem.
Therefore,pesticides are the soil pollutants that significantly affect the food chain and food web.

(B) The correct answer is $B$.
Hydrogen $(H_2)$ is a clean gas and is not considered a pollutant.
Sulphur dioxide $(SO_2)$ and Carbon monoxide $(CO)$ are primary air pollutants that cause respiratory issues and environmental damage.
While Carbon dioxide $(CO_2)$ is a greenhouse gas,it is a natural component of the atmosphere. It is not classified as a pollutant at normal concentrations; however,its excessive concentration leads to global warming and the greenhouse effect.

(C) Water blooms are caused by the excessive growth of planktonic algae in water bodies.
This phenomenon is primarily triggered by the enrichment of water with nutrients like nitrogen and phosphorus,often originating from sewage or agricultural runoff,a process known as eutrophication.
While the algae bloom itself produces oxygen during the day,the subsequent death and decomposition of this massive amount of organic matter by microorganisms consume large quantities of dissolved oxygen.
This leads to a severe depletion of $O_2$ levels,which is detrimental to aquatic animals.
Therefore,while water blooms are a direct result of excessive nutrient availability (eutrophication),the most critical ecological consequence that affects the lake's survival is the resulting oxygen deficiency.

(A) The correct answer is $A$.
$CO$ (Carbon monoxide) is released due to the incomplete combustion of petroleum products.
Automobiles are responsible for the production of approximately $74\%$ of the total man-made $CO$ in the atmosphere,making it the most significant pollutant released in terms of quantity from vehicular exhaust.

(D) The noise level in a quiet office environment is typically measured at approximately $60 \text{ dB}$.
This level is considered moderate and is consistent with standard office equipment and human conversation levels.

(B) Nitrogen oxides $(NO_x)$ emitted from automobiles and power plants react in the atmosphere to form fine particulate matter and secondary pollutants. These nitrogen oxides,along with sulfur dioxide $(SO_2)$,are primary precursors to acid rain. When these gases are converted into acids (nitric acid and sulfuric acid) and settle on the Earth's surface in the absence of precipitation,it is known as dry acid deposition. Therefore,nitrogen oxides are a significant source of dry acid deposition.

(C) When domestic sewage rich in organic waste enters a lake,it leads to eutrophication.
Microorganisms like bacteria decompose this organic matter,which requires a large amount of dissolved oxygen.
This process significantly reduces the Biological Oxygen Demand $(BOD)$ and depletes the dissolved oxygen levels in the water.
As a result,aquatic organisms,especially fish,die due to the lack of oxygen (asphyxiation).

(B) Minamata disease is a neurological syndrome caused by severe mercury poisoning.
It was first discovered in Minamata City,Japan,in $1956$.
The disease occurred due to the consumption of fish and shellfish contaminated with methylmercury,which was discharged into the Minamata Bay by a local chemical factory.
Mercury is a persistent pollutant that bioaccumulates in the food chain,leading to high concentrations in aquatic organisms.

(D) Bio-magnification refers to the increase in concentration of non-biodegradable substances (like $DDT$ or mercury) at successive trophic levels in 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.
As a result, the concentration of the pollutant increases as it moves up the food chain, which can have harmful effects on top-level consumers.

(B) The Bhopal gas tragedy occurred on the night of $2-3$ December $1984$ at the Union Carbide India Limited $(UCIL)$ pesticide plant in Bhopal.
Methyl isocyanate $(MIC)$ gas leaked from the storage tank due to the ingress of water into the tank.
This reaction between methyl isocyanate and water is highly exothermic,which led to a rapid increase in pressure and temperature,causing the tank to rupture and release the toxic gas into the atmosphere.

(B) Acid rain is caused by the atmospheric emission of sulfur dioxide $(SO_2)$ and nitrogen oxides ($NO_x$,specifically $NO_2$).
These gases react with water vapor,oxygen,and other chemicals in the atmosphere to form sulfuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$.
When these acids fall to the ground with precipitation,it is known as acid rain,which has a $pH$ lower than $5.6$.

(C) Eutrophication is the natural or artificial enrichment of a water body, such as a $Lake$ or pond, with nutrients like nitrogen and phosphorus.
This process leads to excessive growth of algae and aquatic plants, which eventually depletes the dissolved oxygen levels in the water, causing the death of aquatic organisms.
Therefore, $Eutrophication$ is a phenomenon primarily observed in aquatic ecosystems like $Lakes$.

(C) Biological amplification (biomagnification) refers to the increase in concentration of non-biodegradable substances at successive trophic levels in a food chain.
Since these substances cannot be metabolized or excreted by organisms,they accumulate in the fatty tissues.
Heavy metals (like mercury),pesticides (like $DDT$),and non-biodegradable chemicals are classic examples of pollutants that undergo biomagnification.
Therefore,organisms at the higher trophic levels,such as top predators,are most severely affected.

(B) . Acid rain is primarily caused by the emission of sulphur dioxide $(SO_2)$ and nitrogen oxides ($NO_x$,including $NO_2$) into the atmosphere.
These gases are released in large quantities due to the burning of fossil fuels in industries and vehicles.
When these gases react with water vapor in the atmosphere,they form sulphuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$.
These acids then fall to the earth along with rain,resulting in acid rain,which is harmful to aquatic life,soil,and buildings.

(C) Minamata disease is a neurological syndrome caused by severe mercury poisoning.
It was first discovered in Minamata City,Japan,in $1956$.
It is caused by the release of industrial wastewater containing methylmercury into the sea,which then bioaccumulates in fish and shellfish.
When humans consume these contaminated aquatic organisms,they develop the disease.

(B) Minamata disease is a neurological syndrome caused by severe mercury poisoning. It was first discovered in Minamata city,Japan,in $1956$. The disease was caused by the release of methylmercury in the industrial wastewater from the Chisso Corporation's chemical factory. This mercury bioaccumulated in shellfish and fish in Minamata Bay,which were then consumed by the local human population and animals. Cats,dogs,and pigs were observed to be affected by the disease due to the consumption of contaminated fish. Rabbits,however,were not part of the food chain involving the contaminated marine life in the bay and thus remained free from the disease.

(C) Eutrophication is the natural or artificial enrichment of a water body with nutrients,such as nitrogen and phosphorus.
This nutrient enrichment leads to excessive growth of algae and other aquatic plants,often referred to as an algal bloom.
While this supports the dense growth of specific organisms,it consumes dissolved oxygen,leading to the death of other aquatic life and a significant decrease in overall species diversity.

(B) Water bloom is a phenomenon caused by the excessive growth of planktonic algae or cyanobacteria in water bodies,which leads to the discoloration of the water. Among the given options,Blue-green algae (Cyanobacteria) are the primary organisms responsible for forming water blooms in eutrophic water bodies. Therefore,the correct option is $B$.

(C) Fluoride pollution,when present in excess in drinking water,primarily affects the teeth and bones.
This condition is known as fluorosis.
In teeth,it causes dental fluorosis,which is characterized by the mottling of tooth enamel.
Therefore,the correct option is $C$.

(A) The presence of excess fluoride in drinking water leads to a condition known as dental fluorosis,which is characterized by the mottling or staining of teeth.
Fluoride is beneficial in small amounts for the prevention of dental caries,but concentrations exceeding $1.5 \text{ ppm}$ can cause skeletal and dental fluorosis.
Therefore,the correct option is $A$.

(B) $D.D.T.$ (Dichlorodiphenyltrichloroethane) was the first modern synthetic insecticide developed in the $1940s$. It became the most widely used pesticide globally for controlling agricultural pests and disease-carrying insects like mosquitoes. Although its use is now restricted or banned in many countries due to its persistence in the environment and bioaccumulation,it remains historically the most common pesticide.

(C) Aldrin is a well-known organochlorine insecticide,which is a type of chlorinated hydrocarbon.
Malathion is an organophosphate insecticide.
Pyrethrum is a natural insecticide derived from chrysanthemum flowers.
Carbamates are a class of insecticides derived from carbamic acid.

(A) $DDT$ stands for Dichlorodiphenyltrichloroethane. It is a synthetic chemical compound that belongs to the class of organochlorines. It was widely used as an insecticide due to its effectiveness in controlling pests,but it is now banned in many countries due to its persistence in the environment and bioaccumulation in the food chain.

(B) $DDT$ (Dichlorodiphenyltrichloroethane) is a persistent organic pollutant.
It is highly lipophilic,meaning it has high fat solubility.
Because it is not easily metabolized or excreted by organisms,it accumulates in the fatty tissues.
As it moves up the trophic levels in a food chain,the concentration of $DDT$ increases,a process known as biomagnification.

(A) The Bhopal gas tragedy,which occurred on the night of $2-3$ December $1984$,was a major industrial disaster.
It was caused by the accidental leakage of a highly toxic gas called Methyl isocyanate $(CH_3NCO)$ from the Union Carbide India Limited $(UCIL)$ pesticide plant in Bhopal,Madhya Pradesh.
This gas is extremely reactive and toxic,leading to thousands of immediate deaths and long-term health issues for the survivors.
Therefore,the correct option is $A$.

(C) $D.D.T.$ stands for Dichlorodiphenyltrichloroethane.
It is a synthetic chemical compound belonging to the class of organochlorines.
It was widely used as an insecticide due to its effectiveness in controlling pests,but it is now largely banned or restricted in many countries due to its persistence in the environment and bioaccumulation in the food chain.

(B) The correct statement is $B$.
Excessive use of chemical fertilizers leads to nutrient runoff into nearby water bodies,causing eutrophication,which results in algal blooms and depletion of dissolved oxygen.
Option $A$ is incorrect because maize can be grown using organic farming methods.
Option $C$ is incorrect because while both are nitrogen fixers,$Azotobacter$ is a free-living bacterium,whereas $Rhizobium$ forms symbiotic associations in root nodules.
Option $D$ is incorrect because while $Anabaena$ and $Nostoc$ are important for nitrogen fixation and organic matter addition,they are not primarily known for mobilizing phosphate and potassium; that role is typically associated with phosphate-solubilizing bacteria $(PSB)$ like $Bacillus$ or $Pseudomonas$.

(D) The Government of India has been actively promoting the Ethanol Blended Petrol $(EBP)$ program to reduce dependency on imported crude oil and to promote environmental sustainability.
Initially,the target was set for $10\%$ blending,but the government has since advanced its roadmap for $20\%$ ethanol blending in petrol (known as $E20$ fuel) to be achieved by the year $2025-26$.
Therefore,among the given options,$20\%$ represents the current policy target for ethanol blending in India.

(A) Photochemical smog is formed by the reaction of sunlight with nitrogen oxides $(NO_x)$ and volatile organic compounds $(VOCs)$.
It typically contains ozone $(O_3)$,nitrogen oxides $(NO_x)$,and peroxyacetyl nitrates $(PAN)$.
Carbon dioxide $(CO_2)$ is a greenhouse gas and a product of combustion,but it is not a constituent of photochemical smog.
Therefore,the correct answer is $A$.

(D) Disinfectants are substances used to kill or inhibit the growth of microorganisms in water to make it safe for drinking.
Chlorine $(Cl_2)$,Ozone $(O_3)$,and Chloramine $(NH_2Cl)$ are widely used as chemical disinfectants in water treatment plants because they effectively eliminate pathogens.
$Phenyl$ (a mixture of phenols and other compounds) is primarily used as a household cleaner and disinfectant for surfaces,floors,and drains.
It is toxic if ingested and is not suitable or approved for use as a disinfectant in drinking water.

(C) Domestic sewage is rich in organic waste,which acts as a nutrient source for algae and bacteria.
$1$. The excessive growth of algae,known as algal bloom,occurs due to the high nutrient content (eutrophication).
$2$. As these algae die,decomposers (bacteria) consume the dissolved oxygen in the water to break down the organic matter.
$3$. This leads to a severe depletion of dissolved oxygen $(DO)$ in the water body.
$4$. Consequently,aquatic organisms like fish die due to asphyxiation (lack of oxygen).

(B) 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 degree of water pollution caused by organic matter.
Greater the $BOD$ of waste water,more is its polluting potential.

(A) $CO$ (Carbon Monoxide) is a poisonous gas that binds to hemoglobin in the blood to form carboxyhemoglobin.
This compound is much more stable than oxyhemoglobin,which reduces the oxygen-carrying capacity of the blood,leading to hypoxia and potentially death.

(C) According to the Central Pollution Control Board $(CPCB)$,particulate matter of size $2.5 \mu m$ or less in diameter (commonly referred to 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 breathing and respiratory symptoms,irritation,inflammations,and damage to the lungs and premature deaths.

(B) The intensity of sound is measured in decibels $(dB)$.
According to environmental standards and biological studies,the sound level of a normal conversation typically ranges between $30$ and $60$ $dB$.
- $10-20$ $dB$ represents a very quiet environment (like a whisper).
- $70-90$ $dB$ represents loud noise (like traffic or a loud factory).
- $120-150$ $dB$ represents extremely high noise levels that can cause permanent hearing damage.
Therefore,the correct range for normal conversation is $30-60$ $dB$.

(B) Biomagnification refers to the increase in concentration of non-biodegradable substances at successive trophic levels in a food chain.
$DDT$ (Dichlorodiphenyltrichloroethane) is a persistent organic pollutant.
It is highly lipid-soluble (fat-soluble),which allows it to accumulate in the fatty tissues of organisms.
Because it is not easily metabolized or excreted,it gets stored in the body fat and is passed on to the next higher trophic level in increasing concentrations.

(D) The 'Blue Baby' syndrome,also known as methemoglobinemia,is a condition caused by the presence of high levels of nitrates in drinking water.
When infants consume water with high nitrate content,the nitrates are converted into nitrites in their digestive system.
These nitrites react with hemoglobin in the blood to form methemoglobin,which has a reduced capacity to carry oxygen.
This leads to a decrease in oxygen supply to the body tissues,causing the skin to appear bluish,hence the term 'Blue Baby' syndrome.